This document summarizes observations of SDSS1133, an unusual transient object offset from the center of a nearby dwarf galaxy. SDSS1133 has been detected in observations spanning 63 years, and exhibits broad emission lines and strong variability. While initially classified as a supernova due to its non-detection in 2005, more recent observations over the past decade show it has rebrightened over a magnitude and displays properties consistent with both an active galactic nucleus and luminous blue variable star eruptions. Its nature remains ambiguous between an extreme example of pre-supernova mass loss or a potential candidate for a recoiling supermassive black hole.
Detection of solar_like_oscillations_in_relies_of_the_milk_way_asteroseismolo...Sérgio Sacani
Asteroseismic constraints on K giants make it possible to infer radii, masses and ages of tens
of thousands of field stars. Tests against independent estimates of these properties are however
scarce, especially in the metal-poor regime. Here, we report the detection of solar-like
oscillations in 8 stars belonging to the red-giant branch and red-horizontal branch of the globular
cluster M4. The detections were made in photometric observations from the K2 Mission
during its Campaign 2. Making use of independent constraints on the distance, we estimate
masses of the 8 stars by utilising different combinations of seismic and non-seismic inputs.
When introducing a correction to the Δν scaling relation as suggested by stellar models, for
RGB stars we find excellent agreement with the expected masses from isochrone fitting, and
with a distance modulus derived using independent methods. The offset with respect to independent
masses is lower, or comparable with, the uncertainties on the average RGB mass
(4 − 10%, depending on the combination of constraints used). Our results lend confidence to
asteroseismic masses in the metal poor regime. We note that a larger sample will be needed
to allow more stringent tests to be made of systematic uncertainties in all the observables
(both seismic and non-seismic), and to explore the properties of RHB stars, and of different
populations in the cluster.
We present deep optical images of the Large and Small Magellanic Clouds (LMC and SMC) using
a low cost telephoto lens with a wide field of view to explore stellar substructure in the outskirts
of the stellar disk of the LMC (r < 10 degrees from the center). These data have higher resolution
than existing star count maps, and highlight the existence of stellar arcs and multiple spiral arms in
the northern periphery, with no comparable counterparts in the South. We compare these data to
detailed simulations of the LMC disk outskirts, following interactions with its low mass companion,
the SMC. We consider interaction in isolation and with the inclusion of the Milky Way tidal field.
The simulations are used to assess the origin of the northern structures, including also the low density
stellar arc recently identified in the DES data by Mackey et al. (2015) at ∼ 15 degrees. We conclude
that repeated close interactions with the SMC are primarily responsible for the asymmetric stellar
structures seen in the periphery of the LMC. The orientation and density of these arcs can be used to
constrain the LMC’s interaction history with and impact parameter of the SMC. More generally, we
find that such asymmetric structures should be ubiquitous about pairs of dwarfs and can persist for
1-2 Gyr even after the secondary merges entirely with the primary. As such, the lack of a companion
around a Magellanic Irregular does not disprove the hypothesis that their asymmetric structures are
driven by dwarf-dwarf interactions.
PROBING FOR EVIDENCE OF PLUMES ON EUROPA WITH HST/STISSérgio Sacani
Roth et al. (2014a) reported evidence for plumes of water venting from a southern high latitude
region on Europa – spectroscopic detection of off-limb line emission from the dissociation
products of water. Here, we present Hubble Space Telescope (HST) direct images of Europa in
the far ultraviolet (FUV) as it transited the smooth face of Jupiter, in order to measure absorption
from gas or aerosols beyond the Europa limb. Out of ten observations we found three in which
plume activity could be implicated. Two show statistically significant features at latitudes similar
to Roth et al., and the third, at a more equatorial location. We consider potential systematic
effects that might influence the statistical analysis and create artifacts, and are unable to find any
that can definitively explain the features, although there are reasons to be cautious. If the
apparent absorption features are real, the magnitude of implied outgassing is similar to that of the
Roth et al. feature, however the apparent activity appears more frequently in our data.
Artigo descreve a descoberta dos astrônomos de 4 imagens de uma supernova geradas pelo efeito de lente gravitacional e formando o raro padrão da Cruz de Einstein.
Detection of solar_like_oscillations_in_relies_of_the_milk_way_asteroseismolo...Sérgio Sacani
Asteroseismic constraints on K giants make it possible to infer radii, masses and ages of tens
of thousands of field stars. Tests against independent estimates of these properties are however
scarce, especially in the metal-poor regime. Here, we report the detection of solar-like
oscillations in 8 stars belonging to the red-giant branch and red-horizontal branch of the globular
cluster M4. The detections were made in photometric observations from the K2 Mission
during its Campaign 2. Making use of independent constraints on the distance, we estimate
masses of the 8 stars by utilising different combinations of seismic and non-seismic inputs.
When introducing a correction to the Δν scaling relation as suggested by stellar models, for
RGB stars we find excellent agreement with the expected masses from isochrone fitting, and
with a distance modulus derived using independent methods. The offset with respect to independent
masses is lower, or comparable with, the uncertainties on the average RGB mass
(4 − 10%, depending on the combination of constraints used). Our results lend confidence to
asteroseismic masses in the metal poor regime. We note that a larger sample will be needed
to allow more stringent tests to be made of systematic uncertainties in all the observables
(both seismic and non-seismic), and to explore the properties of RHB stars, and of different
populations in the cluster.
We present deep optical images of the Large and Small Magellanic Clouds (LMC and SMC) using
a low cost telephoto lens with a wide field of view to explore stellar substructure in the outskirts
of the stellar disk of the LMC (r < 10 degrees from the center). These data have higher resolution
than existing star count maps, and highlight the existence of stellar arcs and multiple spiral arms in
the northern periphery, with no comparable counterparts in the South. We compare these data to
detailed simulations of the LMC disk outskirts, following interactions with its low mass companion,
the SMC. We consider interaction in isolation and with the inclusion of the Milky Way tidal field.
The simulations are used to assess the origin of the northern structures, including also the low density
stellar arc recently identified in the DES data by Mackey et al. (2015) at ∼ 15 degrees. We conclude
that repeated close interactions with the SMC are primarily responsible for the asymmetric stellar
structures seen in the periphery of the LMC. The orientation and density of these arcs can be used to
constrain the LMC’s interaction history with and impact parameter of the SMC. More generally, we
find that such asymmetric structures should be ubiquitous about pairs of dwarfs and can persist for
1-2 Gyr even after the secondary merges entirely with the primary. As such, the lack of a companion
around a Magellanic Irregular does not disprove the hypothesis that their asymmetric structures are
driven by dwarf-dwarf interactions.
PROBING FOR EVIDENCE OF PLUMES ON EUROPA WITH HST/STISSérgio Sacani
Roth et al. (2014a) reported evidence for plumes of water venting from a southern high latitude
region on Europa – spectroscopic detection of off-limb line emission from the dissociation
products of water. Here, we present Hubble Space Telescope (HST) direct images of Europa in
the far ultraviolet (FUV) as it transited the smooth face of Jupiter, in order to measure absorption
from gas or aerosols beyond the Europa limb. Out of ten observations we found three in which
plume activity could be implicated. Two show statistically significant features at latitudes similar
to Roth et al., and the third, at a more equatorial location. We consider potential systematic
effects that might influence the statistical analysis and create artifacts, and are unable to find any
that can definitively explain the features, although there are reasons to be cautious. If the
apparent absorption features are real, the magnitude of implied outgassing is similar to that of the
Roth et al. feature, however the apparent activity appears more frequently in our data.
Artigo descreve a descoberta dos astrônomos de 4 imagens de uma supernova geradas pelo efeito de lente gravitacional e formando o raro padrão da Cruz de Einstein.
Flaring from the_supermassive_black_hole_in_mrk335_studied_with_swift_and_nustarSérgio Sacani
Os comportamentos estranhos e desconcertantes dos buracos negros tornam-se cada dia menos misteriosos, com as novas observações feitas com as missões Swift e NuSTAR da NASA. Os dois telescópios espaciais registraram um buraco negro supermassivo no meio de uma gigantesca explosão de luz de raio-X, ajudando os astrônomos a tentarem resolver um grande quebra-cabeça: Como os buracos negros supermassivos emitem flares?
Os resultados sugerem que os buracos negros supermassivos emitem flares de raios-X, quando suas coroas circundantes, fontes de partículas extremamente energéticas, são atiradas ou lançadas para fora dos buracos negros.
“Essa é a primeira vez que nós somos capazes de linkar o lançamento da coroa com uma flare”, disse Dan Wilkins, da Universidade de Saint Mary em Halifax, no Canadá e principal autor do artigo que descreve os resultados na revista Monthly Notices of The Royal Astronomical Society. “Isso nos ajudará a entender como os buracos negros supermassivos alimentam alguns dos objetos mais brilhantes do universo”.
Os buracos negros supermassivos não emitem luz por si só, mas eles as vezes são circundados por discos de material quente e brilhante. A gravidade do buraco negro puxa o gás ao redor, aquecendo esse material e fazendo com que ele brilhe com diferentes tipos de luz. Outra fonte da radiação perto do buraco negro é a coroa. As coroas são feitas de partículas altamente energéticas que geram luz de raio-X, mas os detalhes sobre sua aparência, ou como elas se formam, ainda não são claros.
First identification of_direct_collapse_black_holes_candidates_in_the_early_u...Sérgio Sacani
The first black hole seeds, formed when the Universe was younger than ⇠ 500Myr, are recognized
to play an important role for the growth of early (z ⇠ 7) super-massive black holes.
While progresses have been made in understanding their formation and growth, their observational
signatures remain largely unexplored. As a result, no detection of such sources has been
confirmed so far. Supported by numerical simulations, we present a novel photometric method
to identify black hole seed candidates in deep multi-wavelength surveys.We predict that these
highly-obscured sources are characterized by a steep spectrum in the infrared (1.6−4.5μm),
i.e. by very red colors. The method selects the only 2 objects with a robust X-ray detection
found in the CANDELS/GOODS-S survey with a photometric redshift z & 6. Fitting their
infrared spectra only with a stellar component would require unrealistic star formation rates
(& 2000M# yr−1). To date, the selected objects represent the most promising black hole seed
candidates, possibly formed via the direct collapse black hole scenario, with predicted mass
> 105M#. While this result is based on the best photometric observations of high-z sources
available to date, additional progress is expected from spectroscopic and deeper X-ray data.
Upcoming observatories, like the JWST, will greatly expand the scope of this work.
A highly magnetized twin-jet base pinpoints a supermassive black holeSérgio Sacani
Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical
models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could
be the case for NGC1052, to launch these jets. This requires magnetic fields on the order of 103 G to 104 G. We imaged the vicinity
of the SMBH of the AGN NGC1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is
smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the
magnetic field at 1 Schwarzschild radius to lie between 200 G and 8:3 104 G consistent with Blandford & Znajek models.
We present spectroscopic observations of the nearby dwarf galaxy AGC 198691. This object is part
of the Survey of H I in Extremely Low-Mass Dwarfs (SHIELD) project, which is a multi-wavelength
study of galaxies with H I masses in the range of 106-107:2 M discovered by the ALFALFA survey.
We have obtained spectra of the lone H II region in AGC 198691 with the new high-throughput
KPNO Ohio State Multi-Object Spectrograph (KOSMOS) on the Mayall 4-m as well as with the Blue
Channel spectrograph on the MMT 6.5-m telescope. These observations enable the measurement of the
temperature-sensitive [O III]4363 line and hence the determination of a \direct" oxygen abundance
for AGC 198691. We nd this system to be an extremely metal-decient (XMD) system with an
oxygen abundance of 12+log(O/H) = 7.02 0.03, making AGC 198691 the lowest-abundance starforming
galaxy known in the local universe. Two of the ve lowest-abundance galaxies known have
been discovered by the ALFALFA blind H I survey; this high yield of XMD galaxies represents a
paradigm shift in the search for extremely metal-poor galaxies.
On some structural_features_of_the_metagalaxySérgio Sacani
Progress in a group of investigations designed
to discover some of the structural details in individual galaxies and in the
Metagalaxy is reported in the following pages.
(a) The first section is concerned with the distribution of cluster-type
Cepheids in high galactic latitude. To the 169 already known in latitudes,
greater than or equal to ± 20o
, the systematic variable star programme carried
on at Harvard has added 312, mostly fainter than magnitude 13-0. With
allowance for absorption and for uncertainties yet remaining in the mean
absolute magnitude of these stars, the thickness of the Milky Way, so far
as this type of star is concerned, is not less than twenty-five kiloparsecs ;
he extent of the Milky Way in its own plane, by the same criterion, is more
than thirty kiloparsecs, perhaps much more.
(b) The extent of the Milky Way in the anti-centre quadrant is considered
on the basis of classical and cluster-type Cepheids ; provisionally
it is found that the galactic system reaches to a distance of at least ten
kiloparsecs in longitude 150o
.
(r) More than six hundred new variables have been found in the Large
Magellanic Cloud and measured for position, ranges and median magnitudes ;
the frequency of periods is not unlike that for the classical Cepheids in the
galactic system ; the light curves also are comparable in all details. The
Magellanic Cepheids, like the galactic classical Cepheids, are concentrated
in regions of high star-density.
(d) Further study of the period-luminosity relation in the Large Magellanic
Cloud permits its revision and strengthening for the Cepheids of
highest absolute magnitude. An observed deviation from the relation
that had previously been found for the Small Cloud is probably to be
attributed to scale error in the magnitude system. No seriously disturbing
Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of
1011.5 K. Relativistic boosting can increase its observed value, but apparent brightness temperatures
much in excess of 1013 K are inaccessible using ground-based very long baseline interferometry (VLBI)
at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission
RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as
small as 26 µas (2.7 light months) and brightness temperature in excess of 1013 K. These measurements
challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive
black holes and require a much higher Doppler factor than what is determined from jet apparent
kinematics.
Keywords: galaxies: active — galaxies: jets — radio continuum: galaxies — techniques: interferometric
— quasars: individual (3C 273)
Detection of lyman_alpha_emission_from_a_triply_imaged_z_6_85_galaxy_behind_m...Sérgio Sacani
We report the detection of Ly emission at 9538A
in the Keck/DEIMOS and HST WFC3
G102 grism data from a triply-imaged galaxy at z = 6:846 0:001 behind galaxy cluster MACS
J2129.4 0741. Combining the emission line wavelength with broadband photometry, line ratio upper
limits, and lens modeling, we rule out the scenario that this emission line is [O II] at z = 1:57. After
accounting for magnication, we calculate the weighted average of the intrinsic Ly luminosity to be
1:31042 erg s 1 and Ly equivalent width to be 7415A. Its intrinsic UV absolute magnitude at
1600A
is 18:60:2 mag and stellar mass (1:50:3)107 M, making it one of the faintest (intrinsic
LUV 0:14 L
UV) galaxies with Ly detection at z 7 to date. Its stellar mass is in the typical range
for the galaxies thought to dominate the reionization photon budget at z & 7; the inferred Ly escape
fraction is high (& 10%), which could be common for sub-L z & 7 galaxies with Ly emission. This
galaxy oers a glimpse of the galaxy population that is thought to drive reionization, and it shows
that gravitational lensing is an important avenue to probe the sub-L galaxy population.
We discovered two transient events in the Kepler eld with light curves that strongly suggest they
are type II-P supernovae. Using the fast cadence of the Kepler observations we precisely estimate
the rise time to maximum for KSN2011a and KSN2011d as 10.50:4 and 13.30:4 rest-frame days
respectively. Based on ts to idealized analytic models, we nd the progenitor radius of KSN2011a
(28020 R) to be signicantly smaller than that for KSN2011d (49020 R) but both have similar
explosion energies of 2.00:3 1051 erg.
The rising light curve of KSN2011d is an excellent match to that predicted by simple models of
exploding red supergiants (RSG). However, the early rise of KSN2011a is faster than the models
predict possibly due to the supernova shockwave moving into pre-existing wind or mass-loss from the
RSG. A mass loss rate of 10 4 M yr 1 from the RSG can explain the fast rise without impacting
the optical
ux at maximum light or the shape of the post-maximum light curve.
No shock breakout emission is seen in KSN2011a, but this is likely due to the circumstellar inter-
action suspected in the fast rising light curve. The early light curve of KSN2011d does show excess
emission consistent with model predictions of a shock breakout. This is the rst optical detection of
a shock breakout from a type II-P supernova.
Artigo da Science Express apresentando os últimos resultados da sonda Rosetta que mostram que a água presente no cometa 67P/C-G tem uma razão de deutério/hidrogênio, três vezes maior do que aquela encontrada nos oceanos da Terra, isso faz com que volte com força total o debate sobre de onde a água dos nossos oceanos se originou.
Flaring from the_supermassive_black_hole_in_mrk335_studied_with_swift_and_nustarSérgio Sacani
Os comportamentos estranhos e desconcertantes dos buracos negros tornam-se cada dia menos misteriosos, com as novas observações feitas com as missões Swift e NuSTAR da NASA. Os dois telescópios espaciais registraram um buraco negro supermassivo no meio de uma gigantesca explosão de luz de raio-X, ajudando os astrônomos a tentarem resolver um grande quebra-cabeça: Como os buracos negros supermassivos emitem flares?
Os resultados sugerem que os buracos negros supermassivos emitem flares de raios-X, quando suas coroas circundantes, fontes de partículas extremamente energéticas, são atiradas ou lançadas para fora dos buracos negros.
“Essa é a primeira vez que nós somos capazes de linkar o lançamento da coroa com uma flare”, disse Dan Wilkins, da Universidade de Saint Mary em Halifax, no Canadá e principal autor do artigo que descreve os resultados na revista Monthly Notices of The Royal Astronomical Society. “Isso nos ajudará a entender como os buracos negros supermassivos alimentam alguns dos objetos mais brilhantes do universo”.
Os buracos negros supermassivos não emitem luz por si só, mas eles as vezes são circundados por discos de material quente e brilhante. A gravidade do buraco negro puxa o gás ao redor, aquecendo esse material e fazendo com que ele brilhe com diferentes tipos de luz. Outra fonte da radiação perto do buraco negro é a coroa. As coroas são feitas de partículas altamente energéticas que geram luz de raio-X, mas os detalhes sobre sua aparência, ou como elas se formam, ainda não são claros.
First identification of_direct_collapse_black_holes_candidates_in_the_early_u...Sérgio Sacani
The first black hole seeds, formed when the Universe was younger than ⇠ 500Myr, are recognized
to play an important role for the growth of early (z ⇠ 7) super-massive black holes.
While progresses have been made in understanding their formation and growth, their observational
signatures remain largely unexplored. As a result, no detection of such sources has been
confirmed so far. Supported by numerical simulations, we present a novel photometric method
to identify black hole seed candidates in deep multi-wavelength surveys.We predict that these
highly-obscured sources are characterized by a steep spectrum in the infrared (1.6−4.5μm),
i.e. by very red colors. The method selects the only 2 objects with a robust X-ray detection
found in the CANDELS/GOODS-S survey with a photometric redshift z & 6. Fitting their
infrared spectra only with a stellar component would require unrealistic star formation rates
(& 2000M# yr−1). To date, the selected objects represent the most promising black hole seed
candidates, possibly formed via the direct collapse black hole scenario, with predicted mass
> 105M#. While this result is based on the best photometric observations of high-z sources
available to date, additional progress is expected from spectroscopic and deeper X-ray data.
Upcoming observatories, like the JWST, will greatly expand the scope of this work.
A highly magnetized twin-jet base pinpoints a supermassive black holeSérgio Sacani
Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical
models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could
be the case for NGC1052, to launch these jets. This requires magnetic fields on the order of 103 G to 104 G. We imaged the vicinity
of the SMBH of the AGN NGC1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is
smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the
magnetic field at 1 Schwarzschild radius to lie between 200 G and 8:3 104 G consistent with Blandford & Znajek models.
We present spectroscopic observations of the nearby dwarf galaxy AGC 198691. This object is part
of the Survey of H I in Extremely Low-Mass Dwarfs (SHIELD) project, which is a multi-wavelength
study of galaxies with H I masses in the range of 106-107:2 M discovered by the ALFALFA survey.
We have obtained spectra of the lone H II region in AGC 198691 with the new high-throughput
KPNO Ohio State Multi-Object Spectrograph (KOSMOS) on the Mayall 4-m as well as with the Blue
Channel spectrograph on the MMT 6.5-m telescope. These observations enable the measurement of the
temperature-sensitive [O III]4363 line and hence the determination of a \direct" oxygen abundance
for AGC 198691. We nd this system to be an extremely metal-decient (XMD) system with an
oxygen abundance of 12+log(O/H) = 7.02 0.03, making AGC 198691 the lowest-abundance starforming
galaxy known in the local universe. Two of the ve lowest-abundance galaxies known have
been discovered by the ALFALFA blind H I survey; this high yield of XMD galaxies represents a
paradigm shift in the search for extremely metal-poor galaxies.
On some structural_features_of_the_metagalaxySérgio Sacani
Progress in a group of investigations designed
to discover some of the structural details in individual galaxies and in the
Metagalaxy is reported in the following pages.
(a) The first section is concerned with the distribution of cluster-type
Cepheids in high galactic latitude. To the 169 already known in latitudes,
greater than or equal to ± 20o
, the systematic variable star programme carried
on at Harvard has added 312, mostly fainter than magnitude 13-0. With
allowance for absorption and for uncertainties yet remaining in the mean
absolute magnitude of these stars, the thickness of the Milky Way, so far
as this type of star is concerned, is not less than twenty-five kiloparsecs ;
he extent of the Milky Way in its own plane, by the same criterion, is more
than thirty kiloparsecs, perhaps much more.
(b) The extent of the Milky Way in the anti-centre quadrant is considered
on the basis of classical and cluster-type Cepheids ; provisionally
it is found that the galactic system reaches to a distance of at least ten
kiloparsecs in longitude 150o
.
(r) More than six hundred new variables have been found in the Large
Magellanic Cloud and measured for position, ranges and median magnitudes ;
the frequency of periods is not unlike that for the classical Cepheids in the
galactic system ; the light curves also are comparable in all details. The
Magellanic Cepheids, like the galactic classical Cepheids, are concentrated
in regions of high star-density.
(d) Further study of the period-luminosity relation in the Large Magellanic
Cloud permits its revision and strengthening for the Cepheids of
highest absolute magnitude. An observed deviation from the relation
that had previously been found for the Small Cloud is probably to be
attributed to scale error in the magnitude system. No seriously disturbing
Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of
1011.5 K. Relativistic boosting can increase its observed value, but apparent brightness temperatures
much in excess of 1013 K are inaccessible using ground-based very long baseline interferometry (VLBI)
at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission
RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as
small as 26 µas (2.7 light months) and brightness temperature in excess of 1013 K. These measurements
challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive
black holes and require a much higher Doppler factor than what is determined from jet apparent
kinematics.
Keywords: galaxies: active — galaxies: jets — radio continuum: galaxies — techniques: interferometric
— quasars: individual (3C 273)
Detection of lyman_alpha_emission_from_a_triply_imaged_z_6_85_galaxy_behind_m...Sérgio Sacani
We report the detection of Ly emission at 9538A
in the Keck/DEIMOS and HST WFC3
G102 grism data from a triply-imaged galaxy at z = 6:846 0:001 behind galaxy cluster MACS
J2129.4 0741. Combining the emission line wavelength with broadband photometry, line ratio upper
limits, and lens modeling, we rule out the scenario that this emission line is [O II] at z = 1:57. After
accounting for magnication, we calculate the weighted average of the intrinsic Ly luminosity to be
1:31042 erg s 1 and Ly equivalent width to be 7415A. Its intrinsic UV absolute magnitude at
1600A
is 18:60:2 mag and stellar mass (1:50:3)107 M, making it one of the faintest (intrinsic
LUV 0:14 L
UV) galaxies with Ly detection at z 7 to date. Its stellar mass is in the typical range
for the galaxies thought to dominate the reionization photon budget at z & 7; the inferred Ly escape
fraction is high (& 10%), which could be common for sub-L z & 7 galaxies with Ly emission. This
galaxy oers a glimpse of the galaxy population that is thought to drive reionization, and it shows
that gravitational lensing is an important avenue to probe the sub-L galaxy population.
We discovered two transient events in the Kepler eld with light curves that strongly suggest they
are type II-P supernovae. Using the fast cadence of the Kepler observations we precisely estimate
the rise time to maximum for KSN2011a and KSN2011d as 10.50:4 and 13.30:4 rest-frame days
respectively. Based on ts to idealized analytic models, we nd the progenitor radius of KSN2011a
(28020 R) to be signicantly smaller than that for KSN2011d (49020 R) but both have similar
explosion energies of 2.00:3 1051 erg.
The rising light curve of KSN2011d is an excellent match to that predicted by simple models of
exploding red supergiants (RSG). However, the early rise of KSN2011a is faster than the models
predict possibly due to the supernova shockwave moving into pre-existing wind or mass-loss from the
RSG. A mass loss rate of 10 4 M yr 1 from the RSG can explain the fast rise without impacting
the optical
ux at maximum light or the shape of the post-maximum light curve.
No shock breakout emission is seen in KSN2011a, but this is likely due to the circumstellar inter-
action suspected in the fast rising light curve. The early light curve of KSN2011d does show excess
emission consistent with model predictions of a shock breakout. This is the rst optical detection of
a shock breakout from a type II-P supernova.
Artigo da Science Express apresentando os últimos resultados da sonda Rosetta que mostram que a água presente no cometa 67P/C-G tem uma razão de deutério/hidrogênio, três vezes maior do que aquela encontrada nos oceanos da Terra, isso faz com que volte com força total o debate sobre de onde a água dos nossos oceanos se originou.
Validation of twelve_small_kepler_transiting_planets_in_the_habitable_zoneSérgio Sacani
Artigo descreve a análise dos mais novos exoplanetas descobertos pela missão Kepler, incluindo o Kepler-438b, o exoplaneta mais parecido com a Terra já descoberto até o momento.
Multi dimensional simulations_of_the_expanding_supernova_remnant_of_sn1987_aSérgio Sacani
Artigo descreve as mais novas simulações computacionais realizadas para se poder entender o funcionamento e a origem da remanescente de supernova SN1987A.
Um dos artigos da edição especial da revista Science, mostrando as alterações nas propriedades do cometa Churyumov-Gerasimenko, à medida que ele se aproxima do Sol.
Chandra deep observation_of_xdcpj004402033_a_massive_galaxy_cluster_at_z_1_5Sérgio Sacani
Artigo apresenta os resultados obtidos pelo Chandra ao medir com precisão a massa do mais massivo aglomerado de galáxias do universo distante, o Aglomerado Gioiello.
Artigo descreve a descoberta de um sistema de anéis 200 vezes maior do que o sistema de anéis de Saturno num exoplaneta orbitando a jovem estrela J1407
Investigating Coronal Holes and CMEs as Sources of Brightness Depletion Detec...Sérgio Sacani
The Parker Solar Probe (PSP) mission provides a unique opportunity to observe the solar corona from distances
below 20 R☉. In this work, we utilize white light images from the Wide-field Imager for Solar PRobe aboard the
PSP from solar encounters 10 through 13 to examine the causes of brightness depletions of the corona during the
rapid transit of PSP through the perihelia of its orbit. We analyze the effect of (1) coronal holes (CHs) and (2)
energetic coronal mass ejection (CME) events on the observed brightness of the images. We speculate on the
causes of the brightness depletions, ascribing them to the evacuation of (1) free electrons (reduced K-corona) and
(2) interplanetary dust (reduced F-corona). In particular, we show that (1) the presence of CHs in all of the orbits is
directly correlated with the depletion of the global white light emission recorded, and (2) a huge CME event in
encounter 13 caused a very deep depletion in its wake that removed the electron content as well as some of the
interplanetary dust.
The xmm newton-view_of_the_central_degrees_of_the_milk_waySérgio Sacani
Novas imagens do Observatório de Raios-X XMM-Newton da ESA revelaram alguns dos processos mais intensos que acontecem no coração da nossa Via Láctea.
As fontes brilhantes e pontuais que se destacam por toda imagem indicam os sistemas estelares binários onde uma das estrelas atingiu o final de sua vida, desenvolvendo para um objeto compacto e denso – uma estrela de nêutrons ou um buraco negro.
A região central da Via Láctea também contém jovens estrelas e aglomerados estelares e algumas dessas fontes são visíveis como pontos brancos e vermelhos brilhando na imagem, que se espalha por 1000 anos-luz.
A maior parte da ação ocorre no centro, onde nuvens difusas de gás estão sendo cavadas por ventos poderosos soprados por estrelas jovens, bem como por supernovas.
The most luminous_galaxies_discovered_by_wiseSérgio Sacani
Artigo descreve estudo feito por astrônomos e com a ajuda da sonda WISE da NASA para identificar as galáxias do tipo ELIRGs, entre elas a mais luminosa galáxia do universo, com um buraco negro gigantesco em seu interior e localizada a cerca de 12.8 bilhões de anos de distância da Terra.
The puzzling source_in_ngc6388_a_possible_planetary_tidal_disruption_eventSérgio Sacani
Artigo descreve a descoberta da destruição de um planeta ao passar próximo a uma estrela do tipo anã branca presente dentro do aglomerado globular de estrelas NGC 6388. Para isso os astrônomos utilizaram um arsenal de telescópios.
AT2023fhn (the Finch): a Luminous Fast Blue Optical Transient at a large offs...Sérgio Sacani
Luminous Fast Blue Optical Transients (LFBOTs) - the prototypical example being AT 2018cow - are a rare class of events
whose origins are poorly understood. They are characterised by rapid evolution, featureless blue spectra at early times, and
luminous X-ray and radio emission. LFBOTs thus far have been found exclusively at small projected offsets from star-forming
host galaxies. We present Hubble Space Telescope, Gemini, Chandra and Very Large Array observations of a new LFBOT,
AT 2023fhn. The Hubble Space Telescope data reveal a large offset (> 3.5 half-light radii) from the two closest galaxies, both
at redshift 𝑧 ∼ 0.24. The location of AT 2023fhn is in stark contrast with previous events, and demonstrates that LFBOTs can
occur in a range of galactic environments.
Fleeting Small-scale Surface Magnetic Fields Build the Quiet-Sun CoronaSérgio Sacani
Arch-like loop structures filled with million Kelvin hot plasma form the building blocks of the quiet-Sun corona.
Both high-resolution observations and magnetoconvection simulations show the ubiquitous presence of magnetic
fields on the solar surface on small spatial scales of ∼100 km. However, the question of how exactly these quietSun coronal loops originate from the photosphere and how the magnetic energy from the surface is channeled to
heat the overlying atmosphere is a long-standing puzzle. Here we report high-resolution photospheric magnetic
field and coronal data acquired during the second science perihelion of Solar Orbiter that reveal a highly dynamic
magnetic landscape underlying the observed quiet-Sun corona. We found that coronal loops often connect to
surface regions that harbor fleeting weaker, mixed-polarity magnetic field patches structured on small spatial
scales, and that coronal disturbances could emerge from these areas. We suggest that weaker magnetic fields with
fluxes as low as 1015 Mx and/or those that evolve on timescales less than 5 minutes are crucial to understanding
the coronal structuring and dynamics.
Observational constraints on mergers creating magnetism in massive starsSérgio Sacani
Massive stars (those ≥8 solar masses at birth) have radiative envelopes that cannot sustain the dynamos that produce magnetic fields in lower mass stars. Despite this, ∼7% of massive stars have observed magnetic fields. We use multi-epoch interferometric and spectroscopic observations to characterise a magnetic binary system formed of two massive stars. We find that only one star of the binary is magnetic. Using the non-magnetic star as an independent reference clock to estimate the age of the system, we show that the magnetic star appears younger than its companion. The system properties, and a surrounding bipolar nebula, can be reproduced by a model in which this system was originally a triple within which two of the stars merged, producing the magnetic massive star. Thus, our results provide observational evidence that magnetic fields form in at least some massive stars through stellar mergers.
Radio imaging obserations_of_psr_j1023_0038_in_an_lmxb_stateSérgio Sacani
Uma estrela super densa formada depois da explosão de uma supernova está expelindo poderosos jatos de material no espaço, sugerem pesquisas recentes.
Num estudo publicado no dia 6 de Agosto de 2015, uma equipe de cientistas na Austrália e na Holanda descobriram poderosos jatos sendo expelidos de uma sistema estelar duplo conhecido como PSR J1023+0038.
Pensava-se anteriormente que os únicos objetos no universo capazes de formar jatos poderosos eram os buracos negros.
O sistema PSR J1023+0038 contém uma estrela extremamente densa que os astrônomos chamam de estrela de nêutrons, numa órbita próxima com uma estrela normal.
Ela foi identificada primeiro como uma estrela de nêutrons em 2009, mas foi somente quando a equipe de pesquisa observou a estrela com o rádio telescópio Very Large Array nos EUA em 2013 e 2014 que eles perceberam que a estrela estava produzindo jatos mais fortes do que se esperava.
Os astrônomos James Miller-Jones, do International Centre for Radio Astronomy Research (ICRAR), disse que as estrelas de nêutrons podem ser pensadas como cadáveres estelares.
“Elas são formadas quando uma estrela massiva esgota todo o seu combustível e vira uma supernova, e as partes centrais da estrela colapsam sobre sua própria gravidade”, disse ele.
“Essas coisas tem normalmente entre uma vez e meia a massa do Sol e somente entre 10 a 15 km de diâmetro, de modo que são extremamente densas”.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
X-rays from a Central “Exhaust Vent” of the Galactic Center ChimneySérgio Sacani
Using deep archival observations from the Chandra X-ray Observatory, we present an analysis of
linear X-ray-emitting features located within the southern portion of the Galactic center chimney,
and oriented orthogonal to the Galactic plane, centered at coordinates l = 0.08◦
, b = −1.42◦
. The
surface brightness and hardness ratio patterns are suggestive of a cylindrical morphology which may
have been produced by a plasma outflow channel extending from the Galactic center. Our fits of the
feature’s spectra favor a complex two-component model consisting of thermal and recombining plasma
components, possibly a sign of shock compression or heating of the interstellar medium by outflowing
material. Assuming a recombining plasma scenario, we further estimate the cooling timescale of this
plasma to be on the order of a few hundred to thousands of years, leading us to speculate that a
sequence of accretion events onto the Galactic Black Hole may be a plausible quasi-continuous energy
source to sustain the observed morphology
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
PRESENTATION ABOUT PRINCIPLE OF COSMATIC EVALUATION
Sdss1133 an unsually_perssitent_transient_in_a_nearby_dwarf_galaxy
1. Mon. Not. R. Astron. Soc. 000, 1–?? (0000) Printed 19 November 2014 (MN LATEX style file v2.2)
SDSS1133: An Unusually Persistent Transient in a Nearby Dwarf
Galaxy
Michael Koss1;2?, Laura Blecha3;4, Richard Mushotzky3, Chao Ling Hung2, Sylvain
Veilleux3, Benny Trakhtenbrot1;5, Kevin Schawinski1, Daniel Stern6, Nathan Smith7,
Yanxia Li2, Allison Man8, Alexei V. Filippenko9, Jon C. Mauerhan7, Kris Stanek10, and
David Sanders2
1Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich, Switzerland
2Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
3Astronomy Department, University of Maryland, College Park, MD, USA
4Einstein Fellow
5Zwicky Fellow
6Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, MS 169-506, Pasadena, CA 91109, USA
7Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA
8Dark Cosmology Center, University of Copenhagen, Copenhagen, Denmark
9Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
10Department of Astronomy, The Ohio State University, Columbus, Ohio 43210, USA
19 November 2014
ABSTRACT
While performing a survey to detect recoiling supermassive black holes, we have identified
an unusual source having a projected offset of 800 pc from a nearby dwarf galaxy. The object,
SDSS J113323.97+550415.8, exhibits broad emission lines and strong variability. While orig-inally
classified as a supernova (SN) because of its nondetection in 2005, we detect it in recent
and past observations over 63 yr and find over a magnitude of rebrightening in the last 2 years.
Using high-resolution adaptive optics observations, we constrain the source emission region
to be . 12 pc and find a disturbed host-galaxy morphology indicative of recent merger activ-ity.
Observations taken over more than a decade show narrow [O III] lines, constant ultraviolet
emission, broad Balmer lines, a constant putative black hole mass over a decade of observa-tions
despite changes in the continuum, and optical emission-line diagnostics consistent with
an active galactic nucleus (AGN). However, the optical spectra exhibit blueshifted absorption,
and eventually narrow Fe II and [Ca II] emission, each of which is rarely found in AGN spec-tra.
While this peculiar source displays many of the observational properties expected of a
potential black hole recoil candidate, some of the properties could also be explained by a lu-minous
blue variable star (LBV) erupting for decades since 1950, followed by a Type IIn SN
in 2001. Interpreted as an LBV followed by a SN analogous to SN 2009ip, the multi-decade
LBV eruptions would be the longest ever observed, and the broad H emission would be the
most luminous ever observed at late times ( 10 yr), larger than that of unusually luminous
supernovae such as SN 1988Z, suggesting one of the most extreme episodes of pre-SN mass
loss ever discovered.
Key words: black holes— galaxies: active — luminous blue variables— supernovae
1 INTRODUCTION
The coalescence of binary supermassive black holes (SMBHs) in
galaxy mergers is thought to constitute the strongest source of
gravitational waves (GW; Merritt Milosavljevi´c 2005). Theory
suggests that these waves carry momentum, causing the merged
? E-mail: mkoss@phys.ethz.ch
black hole (BH) to experience a velocity recoil or kick that dis-places
it from the center of its host galaxy (Peres 1962; Beken-stein
1973; Thorne Braginskii 1976). Numerical simulations of
SMBH mergers have found, surprisingly, that GW recoil kicks may
be quite large, up to 5000 kms1 (Campanelli et al. 2006;
Lousto Zlochower 2011). Consequently, a merged SMBH may
even be ejected from its host galaxy.
An active galactic nucleus (AGN) ejected from the center of a
galaxy should be able to carry along its accretion disk as well as
c
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arXiv:1401.6798v2 [astro-ph.GA] 18 Nov 2014
2. 2 M. Koss et al.
the broad-line region, resulting in an AGN spatially offset from
its host galaxy and/or an AGN with broad emission lines offset
in velocity (Madau Quataert 2004; Komossa Merritt 2008;
Blecha Loeb 2008). Recoiling AGNs with offsets 1 kpc
may have lifetimes up to tens of Myr for a fairly wide range in
kick speeds, and velocity-offset AGNs may have similar lifetimes
(Blecha et al. 2011, 2013). Thus far, several candidate recoiling
SMBHs have been found via spatial offsets, though none has been
confirmed (see Komossa 2012, for a review). The disturbed galaxy
CXOC J100043.1+020637 (or CID-42) contains a candidate recoil-ing
AGN offset by 2.5 kpc from the galactic center (Civano et al.
2010, 2012). However, in order for the recoiling AGN to produce
narrow-line emission, it must be observed very quickly after the
kick while it still inhabits a dense gaseous region. Another recoil
candidate found by Jonker et al. (2010) consists of an X-ray source
offset by 3 kpc from the center of an apparently undisturbed spiral
galaxy, but this could also be explained as an ultraluminous X-ray
source (ULX) associated with an accreting intermediate-mass black
hole (IMBH) in a massive, young stellar cluster, or perhaps a very
luminous Type IIn supernova (SN IIn; see Filippenko 1997, for a
review).
These recoiling kicks have significant implications for mod-els
of SMBH and galaxy coevolution (Volonteri 2007; Sijacki et al.
2011; Blecha et al. 2011). A hitherto unknown low-redshift pop-ulation
of SMBH mergers in dwarf galaxies could have profound
implications for gravitational wave detectors. Although the SMBH
occupation fraction in dwarf galaxies is uncertain, their shallower
potential wells greatly increase the possibility of detecting gravita-tional
wave kicks; nearly every major SMBH merger would result
in a substantial displacement of the remnant SMBH. While current
detectors, like the advanced Laser Interferometer Gravitational-
Wave Observatory or Pulsar Timing Arrays, are more sensitive to
stellar-mass BHs or the most massive SMBHs (Sesana 2013), fu-ture
space-based detectors such as the proposed Laser Interferome-ter
Space Antenna would be more sensitive to lower-mass SMBHs
( 105–106 M
3. ), making this mass range found in dwarf galaxies
an important population for study.
Particularly at low bolometric luminosities (Lbol 6 1043
erg s1 ), some Type II supernovae (SNe) can be a source of im-posters
for AGNs (Filippenko 1989) and recoiling SMBHs, espe-cially
when the broad-line emission lasts for decades. Some SNe
are also preceded by strong winds and nonterminal eruptions sim-ilar
to those of luminous blue variables (LBVs) such as Carinae
(Smith et al. 2011). There is also evidence that LBV eruptions can
be followed by SNe IIn (Gal-Yam et al. 2007;Mauerhan et al. 2013;
Ofek et al. 2014), with narrow as well as broader Balmer emission
lines that can persist for decades (Smith et al. 2008a; Kiewe et al.
2012), sometimes with an appearance similar to that of broad-line
AGNs. SNe IIn occur in a dense circumstellar medium (CSM) cre-ated
by pre-SN mass loss, and the narrow hydrogen lines are pro-duced
by photoionization of the dense winds irradiated by X-rays
from the region behind the forward shock (Chevalier Fransson
1994). (The broader lines arise when the SN ejecta interact directly
with the CSM.) Type IIn SNe can even produce forests of narrow
coronal lines such as [O III] (e.g., SN 2005ip; Smith et al. 2009).
Our study focuses on an enigmatic point source, SDSS
J113323.97+550415.8 (hereafter SDSS1133), having a projected
offset of 800 pc (5.800) from the center of a nearby dwarf galaxy,
Mrk 177 (UGC 239), and with broad-line emission observed by the
Sloan Digital Sky Survey (SDSS) in 2003. SDSS1133 was men-tioned
as a possible case of a quasar having a noncosmological
redshift because of its broad Balmer lines but very low luminos-ity
(Lopez-Corredoira Gutierrez 2005). In a study of narrow-line
Seyfert 1 galaxies, Zhou et al. (2006) classified SDSS1133 as a
SN because of its nondetection in data obtained in January 2005
with the 2.16 m telescope at the Beijing Observatory. This SN clas-sification
was also applied by Reines et al. (2013) based on the
SDSS spectra using the automated SN detection code of Graur
Maoz (2013). Finally, SDSS1133 was listed as a possible “Voorw-erp”
candidate for a giant ionized cloud (Keel et al. 2012).
To better understand this unusual source, we obtained new op-tical
spectra, adaptive optics (AO) images, and ultraviolet (UV) and
X-ray observations of it.We also analyzed archival images, finding
that the object is detected over a time span of 63 yr. The host galaxy,
Mrk 177, is at a distance of 28.9 Mpc (distance modulus 32.3 mag;
Tully 1994). We use this redshift-independent distance indicator
for the subsequent analysis of SDSS1133 and Mrk 177. At this dis-tance,
100 corresponds to 140 pc. Galactic foreground extinction is
very low, AV = 0:03 mag (Schlafly Finkbeiner 2011).
2 OBSERVATIONS AND DATA ANALYSIS
2.1 Imaging
We use archival optical SDSS images from 2001 December 18 and
2002 April 1 (UT dates are used throughout this paper), as well as
111 griz images taken over 26 nights from Pan-STARRS1 (PS1)
between 2010 March and 2014 March. Additionally, we have pho-tographic
Digital Sky Survey (DSS) plates from the POSS I and II
surveys, with 100 pixel1 sampling and a limiting magnitude of 21
and 22.5, respectively. The 1994 observation, with the IIIaJ emul-sion
and GG395 filter, is comparable to the g filter. The 1950 plate
from the POSS-I O survey uses the 103aO emulsion with a re-sponse
between u and g. The 1999 observation is with the IIIaF
emulsion, similar to the i band. Example images can be found in
Figure 1.
We measure the photometry of SDSS1133 (Fig. 2–3) using
a two-dimensional surface brightness fitting program, GALFIT
(Peng et al. 2002). We fit a 500 region around SDSS1133, using a
point-spread function (PSF) model for the source light and a linear
model based on radial distance to model contamination from Mrk
177. The PSF model position is allowed to vary across the image
region. PSF models from the SDSS and PS1 data are used for the
image convolution. For the PSF model in DSS images, we use a me-dian
of 5 nearby, bright, unsaturated stars. The DSS imaging scale
is in photographic density, which is nonlinear with intensity. Thus,
the increase in contamination from the galaxy causes the source
intensity to be underestimated. To correct for this nonlinearity in
DSS images, we measure SDSS PSF magnitudes of 5 nearby un-saturated
stars with varying brightnesses to calculate the magnitude
of SDSS1133 in the DSS plates.
We fit the positions of 5 bright, unsaturated stars common to
each of the images for source astrometry, using the 2001 SDSS as-trometry
as the reference.We find no significant difference between
SDSS and PS1 astrometry. For the DSS images, the declination off-sets
are 0:200 with respect to the SDSS astrometry, while we find
right-ascension offsets of 100 in the 1950 DSS image and 0.600 in
the 1994 image.
We also estimate photometry from SDSS spectra taken in
March 2003 using PYSYNPHOT, which determines the flux in the
spectra as measured by different photometric filters. We convert
from spectra filter magnitudes to PSF magnitudes using the off-set
between fibermag and PSF magnitudes from the original SDSS
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0000 RAS, MNRAS 000, 1–??
4. SDSS1133+5504: An Unusually Persistent Transient in a Nearby Dwarf Galaxy 3
images. Finally, we include as an upper limit an observation in Jan-uary
2005 using the 2.16-m telescope of the Beijing Observatory
which failed to detect the source within 3 mag of the 2002 SDSS
observation (Zhou et al. 2006).
We obtained AO images on 2013 June 16 with the NIRC2
instrument on the Keck-2 10-m telescope equipped with the wide
camera, which has a 4000 field of view (FOV) and 40 mas pixel1
(Fig. 4). In this observation, we used a 3-point dither pattern for
6 min in the J and Kp filters, as well as 12 min in the Pa
6. filter covers the redshift of SDSS1133 and Mrk 177
(z = 0:007845). An image of the AO tip-tilt star is used for PSF
estimation (Fig. 5) and photometric calibration based on measured
2MASS magnitudes in J and Kp.
The Swift satellite observed SDSS1133 as a Target of Opportu-nity
(ToO) program on 2013 August 26, 27, and 28 for 3.5, 3.8, and
11.2 ks, respectively, with its X-Ray Telescope (XRT) in Photon
Counting mode (PC mode) and the UV-Optical Telescope (UVOT)
with the UVW1 near-UV filter. The total exposure time was 18.5
ks. X-ray data were reduced with the task XRTPIPELINE (version
0.12.6). Source and background photons were extracted with XS-ELECT
(version 2.4b), from circles with radii of 4700 and 20000,
respectively, in the 0.3–10 keV band. For PSF photometry with
UVOT, we use a nearby star with known magnitudes scaled to the
brightness of SDSS1133.
2.2 Optical Spectroscopy
We use optical spectra from a variety of telescopes for this study
of SDSS1133 (Fig. 6–8). SDSS spectra were taken in 2003 March,
456 days after the object had diminished in brightness about 2.5
mag from its peak in 2001 December. SDSS1133 was targeted as
part of the ugri-selected quasar survey because of its AGN-like
colors.
SDSS1133 was also observed with the University of Hawaii
2.2 m telescope and the SuperNova Integral Field Spectrograph
(SNIFS) on 1–4 May 2013 for a total duration of 160 min. SNIFS is
an optical integral field unit (IFU) spectrograph with blue (3000–
5200 A° ) and red (5200–9500 A° ) channels having a resolution of
360 kms1 . The SNIFS reduction pipeline SNURP was used for
wavelength calibration, spectro-spatial flatfielding, cosmic ray re-moval,
and flux calibration (Aldering et al. 2006). A sky image was
taken after each source image and subtracted from each IFU ob-servation.
Flux corrections were applied each night based on the
standard star Feige 34. In order to estimate the amount of narrow-line
contamination from Mrk 177 at the position of SDSS1133 in
the SDSS spectrum, we placed an aperture at the same radial dis-tance
from Mrk 177, but to the northeast of SDSS1133 with the
same aperture size as the SDSS fiber (300).
We used the DEIMOS spectrograph on the Keck-II telescope
to obtain a 10 min spectrum (range 4730–9840 A° ) of the object and
the galaxy nucleus (200 slit, PA = 137.5) with a 600 lines mm1
grating on 2013 December 13. Finally, we used the MMT to ob-serve
SDSS1133 on 2014 January 3 (100 slit, PA = 137.5); the
spectrum spans 3700–8926 A° .
We fit the spectra using an extensible spectroscopic analy-sis
toolkit for astronomy, PYSPECKIT, which uses a Levenberg-
Marquardt algorithm for fitting. We adopt a power-law fit to model
the continuum and Gaussian components to model the emission
lines. All narrow-line widths were fixed to the best fit of the [O III]
5007 line. We fit the spectra of H using a narrow component
based on the [O III] 5007 line along with a broad component. Ad-ditionally,
some AGNs have broad Balmer lines that are poorly fit
with a single Gaussian component, so we fit H and H
7. with two
broad components (broad and very broad) when it is statistically
significant based on the reduced 2. Fitting the H
8. line is more
complicated because of Fe II lines on the red wing as well as [O III]
4959 on the red wing; we therefore use the H
9. fitting procedure
following the code described by Trakhtenbrot Netzer (2012). To
measure the full width at half-maximum intensity (FWHM) of the
broad component of the Balmer lines, we first subtract the narrow-line
component. Finally, we fit a separate broad component to each
of the calcium near-infrared (NIR) triplet (8498, 8452, 8662)
lines and to O I 8446. The luminosities of the narrow lines and
their velocity offsets from Mrk 177 can be found in Table 2.
3 RESULTS
3.1 X-ray, UV, Optical, and NIR Emission
Imaging from multiple time periods can differentiate an AGN from
a SN; the latter typically fade quickly, and they rapidly become red-der
in color. Using images from the DSS, SDSS, and the PS1 survey
(Fig. 1) along with synthetic photometry from the observed spec-tra,
we measure the g mag of SDSS1133 between 1950 and 2013
(Fig. 2).We find that SDSS1133 brightened in 2001 and 2002 com-pared
to 1950 and 1993, and it shows variable brightening and dim-ming
between 2010 and 2013. A nondetection in a 2MASS image
on 2000 January 10, in the NIR, suggests that significant bright-ening
happened sometime between 2000 January 10 and the first
SDSS image on 2001 December 18. SDSS1133 was detected in the
near-UV at 10:7 mag AB in 2004 and at 10:9 mag AB in 2013
by the GALEX and Swift satellites (respectively), 2 yr and 12 yr af-ter
peak brightness (assumed to be the first SDSS observation on
2001 December 18). Over the last 12 yr, the optical and UV colors
of SDSS1133 have remained relatively constant (Fig. 2, right) and
consistent with those of quasars (Richards et al. 2001).
High-resolution imaging at the . 20 pc scale is critical for
differentiating between an ongoing merger of two galaxies and a
post-merger recoiling SMBH that has left its host-galaxy nucleus
behind.We imaged a 4000 region around SDSS1133 in the NIR Pa
10. and Kp filters using AO with the Near Infrared Camera 2 (NIRC2)
instrument on the Keck-II telescope (Fig. 4). The images reveal an
unresolved point source at spatial scales of . 12 (Kp) and . 22 pc
(Pa
11. ) coincident with the location of SDSS1133. SDSS1133 shows
average colors (g i 0:3 to 0.2 mag) constant within the un-certainties
from 2002 through 2014. This color is consistent with
nearby (z 0:1) SDSS quasars (Richards et al. 2001). Addition-ally,
the iAB KVega color of SDSS1133 is 2.5 mag, in agreement
with results for low-redshift quasars (Peth et al. 2011) and much
redder than the stellar locus (i K 1 mag). While red colors
can be found in SNe because of dust formation, these colors often
evolve with time.
NIR images trace the old stellar population and the bulk of
the stellar mass. Those of SDSS1133 exhibit a disturbed morphol-ogy
and a double-nucleus structure with a separation of 60 pc. The
Kp absolute magnitudes of the nuclei are 14:1 and 14:2, in the
range of dwarf-galaxy nuclei or very young, massive star clusters
(Forbes et al. 2008). Radial profiles of SDSS1133 and the tip-tilt
star used in each observation are shown in Figure 5. The radial pro-files
of the nuclei in Kp and Pa
12. are consistent with the stellar
profiles of the tip-tilt stars, suggesting no extended emission.
With the Swift XRT at 0.3–10 keV, 7:6 3:4 background-subtracted
counts were detected, corresponding to a signal-to-noise
c
0000 RAS, MNRAS 000, 1–??
13. 4 M. Koss et al.
RA (J2000)
Dec (J2000)
1950
1.32
1.28
1.24
1.20
1.16
1.12
1.08
1.04
1.00
RA (J2000)
Dec (J2000)
1994
1.28
1.24
1.20
1.16
1.12
1.08
1.04
1.00
RA (J2000)
Dec (J2000)
1.245
1.230
1.215
1.200
1.185
1.170
1.155
1.140
1999-IR 1.125
RA (J2000)
Dec (J2000)
2001
360
330
300
270
240
210
180
150
120
90
RA (J2000)
Dec (J2000)
2002
360
330
300
270
240
210
180
150
120
90
RA (J2000)
Dec (J2000)
105
90
75
60
45
30
2010 15
RA (J2000)
Dec (J2000)
2013-UV
1.76
1.68
1.60
1.52
1.44
1.36
1.28
1.20
1.12
RA (J2000)
Dec (J2000)
105
90
75
60
45
30
2013 15
Figure 1. Images of the host galaxy Mrk 177 and SDSS1133, 2500 wide and displayed with an arcsinh scale representing photographic density or CCD counts.
The 1950 and 1994 images are from blue DSS plates, the 1999 image is from an IR DSS plate, and the 2001–2013 data are g-band images from the SDSS and
PS1. A dashed green circle of 200 radius is drawn for SDSS1133 based on positions in the 2001 SDSS observation. A 3-pixel unsharp mask has been applied
to the DSS and UV images because of their lower resolution and pixel sampling.
16.3
17.3
mg (mag)
18.3
19.3
20.3
1950 1995 2000 2005 2010 2015
Year
−16
−15
−14
−13
−12
−11
Mg (mag)
DSS
SDSS
SDSS spec
PS1
MMT spec
21.3
2002 2004 2006 2008 2010 2012 2014
Year
0.8
0.6
0.4
0.2
0.0
g − i (mag)
−0.2
−0.4
SDSS
SDSS spec
PS1
MMT spec
Figure 2. Left: Measured g magnitudes for SDSS1133 over the last 63 yr from DSS photographic plates, the SDSS, and PS1. The vertical dashed line indicates
a time gap. The blue DSS filter magnitudes have been converted to g magnitudes based on the SDSS colors. The 2005 observation represents an upper limit.
We also included lower-quality synthetic photometry taken from the SDSS and MMT spectroscopy in time periods where higher-quality photometry was not
available. Right: Measured g i colors of SDSS1133 since its peak brightness in 2001. Photometry is from the SDSS and PS1 during 2010–2014. We also
included lower-quality synthetic photometry taken from the SDSS and MMT spectroscopy in time periods where higher quality photometry was not available.
The grey shaded region indicates average colors of nearby (z 0:1) SDSS quasars (Richards et al. 2001).
ratio (S/N) of 2.2 and a net count rate of (4:1 1:8) 104
counts s1. The marginal Swift X-ray detection cannot distinguish
between the AGN and SN scenarios. Assuming a power-law in-dex
of 1.9, representative of an AGN, the luminosity is 1:5 1039
erg s1 in the 0.3–10 keV band.
3.2 Spectral Shape, Narrow-Line Diagnostics, Broad-Line
Emission
We measure the amount of narrow-line emission detected in
SDSS1133, the nucleus of the host galaxy Mrk 177, and at a po-sition
the same radial distance from the nucleus of Mrk 177 as
SDSS1133 (Mrk 177 IFU-offset) using the IFU image; the latter
allows us to determine the expected level of narrow-line contam-ination
in SDSS1133 from Mrk 177. All line offsets are from the
wavelength of [O III] 5007 in Mrk 177 at z = 0:007845. The
measured line offset of the narrow lines in SDSS1133 and the host
galaxy, Mrk 177, is redshifted by a small amount (269 kms1 ),
while Mrk 177 IFU-offset is blueshifted by a small amount (18
12 kms1 ). The narrow-line FWHMs of SDSS1133 and Mrk
177 are consistent with the SDSS instrumental resolution (150
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0000 RAS, MNRAS 000, 1–??
14. SDSS1133+5504: An Unusually Persistent Transient in a Nearby Dwarf Galaxy 5
−16
−15
−14
−13
2002 2004 2006 2008 2010 2012 2014
Date
−12
M (mag)
NUV-1.5
g
r
i
z
J
Kp
16.3
17.3
m (mag)
18.3
19.3
20.3
Figure 3. Photometry of SDSS1133 since its peak brightness in 2001 in AB mag. Optical observations (griz) are shown for the first year in 2001–2002 from
the SDSS (filled squares), an upper limit from the Beijing observatory in 2005 (arrow), and finally observations from PS1 in 2010–2014 (filled circles). Error
bars are typically smaller than symbols. We have also included lower-quality synthetic photometry taken from the SDSS and MMT (stars) in time periods
where higher quality photometry was not available. NIR AO observations from NIRC2 are shown as triangles. NUV GALEX and Swift UVOT data are shown
as purple crosses and have been offset by 1.5 mag.
kms1 ). The FWHM of Mrk 177 IFU-offset is consistent with
the spectral resolution of the IFU (360 kms1 ).
We apply AGN emission-line diagnostics (e.g., Kewley et al.
2006; Veilleux Osterbrock 1987) to the [N II]/H, [S II]/H,
[O I]/H narrow lines of SDSS1133 and Mrk 177 (Fig. 6). The
host galaxy, Mrk 177, is classified as an H II region in all diagnos-tics.
SDSS1133 is classified as a Seyfert with the [S II] and [O I]
diagnostics in 2003 SDSS spectra.
We find that the [N II] luminosity of the narrow-line emission
found in SDSS1133 in 2003 and 2013 is consistent with that of Mrk
177 IFU-offset. However, the [O III], H
15. , H, and [O II] lines are
significantly stronger than in Mrk 177 IFU-offset. This is confirmed
by the two-dimensional images, which show that the emission lines
are above the continuum level of SDSS1133 and Mrk 177. By 2013,
the [O III] luminosity decreased.
A plot of the H
16. spectral region can be found in Figure 7. We
see that the 2013 Keck spectrum exhibits narrow Fe II emission,
less-broad H
17. emission (2020 kms1 vs. 2530 kms1 ), lower
luminosity, weaker continuum emission, and a lower intensity ratio
of [O III] to H
18. compared to the 2003 spectrum. Examining H
in 2013 (Fig. 8), we find wider broad H emission (1390kms1
vs. 1660 kms1 ) and lower luminosity than in 2003. Assuming
SDSS1133 is an AGN, we fit the H
20. ) 6:0, 6.0, and 6.2 in
2003, 2013, and 2014, respectively. Like all single-epoch (“virial”)
MBH determinations, these estimated values have uncertainties of
about 0.5 dex (Shen 2013), suggesting that the measured SMBH
masses are constant within the uncertainties.
A plot of the broad Balmer lines smoothed to the same reso-lution
and offset to the same continuum can be found in Figure 9.
There is evidence of blueshifted absorption in the H
22. emission
dropped by 10–20% between 2003 and 2013–2014, whereas the to-tal
broad H emission dropped by 65–70%. The broad H/H
23. in-tensity
ratio is 13 in 2003 and 5 in 2013–2014. The Balmer decre-ment
in 2003 for the broad hydrogen lines is considerably larger
than the recombination value, suggesting that the broad emission
originates in very dense gas or suffers higher extinction. Finally,
the change in blueshifted absorption, which is different in 2003
than in 2013–2014, may cause variation in the broad-line emission
and Balmer decrement.
A feature associated with the broad-line region in 1/3 of
quasars (Netzer 1990) and some SNe is broad emission in the Ca II
NIR triplet (8498, 8452, 8662) and O I 8446 (Fig. 10). In 2003,
we find the FWHM of these lines to be 630–650 kms1 , signif-icantly
higher than that of the narrow-line region, and offset by
117 36 kms1 for the Ca II triplet and 210 52 kms1 for
O I. The 2013 Keck spectrum exhibits narrower Ca II emission of
270 kms1 . Fits to [Fe II] 7155 and [Ca II] 7291, 7324 show
that no emission lines are detected in 2003, whereas the 2013 Keck
spectrum exhibits strong, narrow emission consistent with the in-strumental
resolution (220 kms1 ).
We fit the spectrum blueward of 5000 °A
and find a best fit for
a possible nonthermal power-law AGN contribution (p) of p =
0:92 0:27 in 2003 (SDSS) and p = 0:42 0:21 in 2013 (Keck).
3.3 Host Galaxy
SDSS1133 is located in Mrk 177, a nearby blue compact dwarf
galaxy with peculiar morphology (Petrosian et al. 2007). The 5.800
separation between SDSS1133 and the center of Mrk 177 corre-sponds
to a projected physical distance of 0.81 kpc. Given the ob-served
magnitude of g = 15:69 (SDSS), the galaxy absolute mag-nitude
is Mg = 16:6, comparable to that of the Small Magel-lanic
Cloud. The center of the host galaxy was also observed spec-troscopically
by SDSS, resulting in a measurement of the oxygen
abundance, 12 + log(O/H) = 8.58, somewhat oxygen-rich given its
brightness, but still on the SDSS mass-metallicity relation from
Tremonti et al. (2004). In the host galaxy, Mrk 177, we measure
the Ca II NIR triplet absorption lines to be within 3 10 kms1
of the redshift derived from the [O III] emission line.
We can also measure the star-formation rate (SFR) based on
GALEX observations of Mrk 177 taken in 2004. Because of the low
spatial resolution of GALEX, we are unable to completely rule out
c
0000 RAS, MNRAS 000, 1–??
25. Filter
100 pc
130
120
110
100
90
80
70
60
1140 1150 1160 1170 1180 1190
PIXEL
840
830
820
810
800
790
PIXEL
Mrk 177-Nucleus
Kp Filter
100 pc
440
400
360
320
280
240
200
160
120
Figure 4. AO images of SDSS1133 and Mrk 177. The image is centered on Mrk 177 with a spatial scale of 40 mas pixel1 and displayed with an arcsinh scale
in CCD counts. Top left: 1200 wide Kp image. The FWHM of SDSS1133 is consistent with the PSF image (FWHM = 0:0800), corresponding to point-like
emission at a scale of 12 pc. Top right: 1200 wide Pa
26. image. The FWHM of SDSS1133 is consistent with the PSF image (FWHM = 0:1500) corresponding to
point-like emission at a scale of 22 pc. Bottom: 2.400 Kp zoomed-in image of the nuclear region of Mrk 177 showing signs of morphological disruption and
two nuclei.
the possibility of contamination by SDSS1133, but we measure a
SFR of 0.05 M
27. yr1 based on Kennicutt (1998).
4 DISCUSSION
Table 3 summarizes the unusual properties of SDSS1133. Given its
long observed lifetime, luminosity, and highly variable behavior,
SDSS1133 is peculiar among AGNs, as well as among SNe, tidal
disruption flares, ULXs, and other stellar phenomena. In the follow-ing
sections, we discuss possible source scenarios for SDSS1133
in more detail. An LBV followed by a SN, or a recoiling SMBH,
are the most likely scenarios, while a ULX, tidal flare, or tidally
stripped AGN are disfavored by the observations. Finally, we dis-cuss
the frequency of other events like SDSS1133.
4.1 LBV Outburst, or LBV Outburst Followed by a SN
SDSS1133 is a source with an optical absolute magnitude of 13:5
(which could either be constant or caught serendipitously erupting
in 1950, 1994, and 1999) followed by a brief, luminous transient
in 2001/2002 that reached 16 mag and slowly faded to 13 mag.
The value 13:5 mag exceeds the classical Eddington limit for a
100 M
28. star. The peak brightness of 16 is unprecedented for an
LBV eruption, though there is still some debate about whether SN
2009ip and SN 1961V, both reaching nearly 18 mag in the opti-cal,
were extreme Carinae-like events or core-collapse SNe (see
also Kochanek et al. 2010; Smith et al. 2011; Van Dyk Matheson
2012). The closest LBV is Car, which had a Great Eruption in
the mid-19th century that was 13:0 mag from 1843 to 1855,
with some uncertainty from the historical records and estimated ex-tinction
(Smith Frew 2011). Broad-line emission is also found in
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0000 RAS, MNRAS 000, 1–??
29. SDSS1133+5504: An Unusually Persistent Transient in a Nearby Dwarf Galaxy 7
1.0
0.8
0.6
0.4
0.2
0.00 0.05 0.10 0.15 0.20 0.25 0.30
Distance from center (arcsec)
0.0
Flux (normalized with peak flux)
SDSS1133 Pab
SDSS1133 Kp
Tip Tilt Pab
Tip Tilt Kp
Figure 5. AO radial profiles of SDSS1133 (solid line) and the tip-tilt star (dashed line) used for PSF estimation in each observation. 0.100 corresponds to a
physical scale of 14 pc. The radial profiles of theKp (FWHM = 0:0800) and Pa
30. (FWHM = 0:1500) of SDSS1133 images are consistent with the stellar profiles
of the tip-tilt stars.
1.5
1.0
0.5
0.0
−0.5
−2.0 −1.5 −1.0 −0.5 0.0 0.5 1.0
log [NII]/H
−1.0
log [OIII]/H
33. SDSS1133-2003
Mrk 177 Nucl.
Mrk 177 Offset
SDSS1133-2013
SDSS1133-2014
HII
Seyfert
LINER
Figure 6. Optical diagnostic diagrams [N II]/H, [S II]/H, and [O I]/H vs. [O III]/H
34. (e.g., Kewley et al. 2006) for SDSS1133 and the host galaxy Mrk
177 from the SDSS spectra. Lines indicate the approximate separation between H II regions, composite regions, Seyfert AGNs, and LINER AGNs.
blue compact dwarfs (Izotov et al. 2007) because of stellar winds
around young massive stars (Izotov et al. 2007, 2012) in regions
of active star formation. However, stellar winds are ruled out for
SDSS1133 since the H luminosity of 0:7 1040 erg s1 is too
large. A superbubble produced by multiple SNe is ruled out by the
small spatial scale of the emission, 12 pc. As we discuss be-low,
an LBV followed by a SN is a more likely scenario given the
features of the recent optical spectra.
Late-time observations of interacting SNe provide critical in-formation
about the nature and mass-loss history of massive stars
immediately before core collapse. The redshifted portion of the
H and H
35. lines has become suppressed over the last decade,
and the reddest individual peak has diminished in luminosity be-tween
2003 and 2013. This could be dust in the post-shock medium
that is obscuring emission from ejecta components in the receding
hemisphere of the explosion (e.g., SN 2006jc; Smith et al. 2008b).
The Type IIn SN 1998S (Mauerhan Smith 2012) does exhibit
[O I], [O II], and [O III] emission 14 yr after outburst. Several SNe
show ongoing broad emission as the fast SN ejecta cross the re-verse
shock behind the SN/CSM interface (e.g., SNe 1980K, 1993J,
1970G, and 1957D; Milisavljevic et al. 2012). Finally, the appear-ance
of late-time narrow [Fe II] and [Ca II] in the 2013 spectra has
been found in other SNe (e.g., SN 1992H; Filippenko 1997).
We can make a conservative order-of-magnitude estimate of
the total bolometric luminosity of SDSS1133 over 12 yr based on
the observed UV, optical, and NIR observations (2200–24,000 A° )
to test whether it violates the total expected energy from a SN. To
do this, we assume that the spectral energy distribution (SED) of
SDSS1133 follows the last UV observation in 2013, the 2014MMT
optical spectrum (3675–8850 A° ), and the J and Kp Keck measure-ments.
We interpolate between the unobserved regions in the range
2200–24,000 A° . We assume that the SED follows the dashed lines
in the g-band light curve in Figure 2 and obtain a total energy of
1:7 1050 ergs. This is probably a lower limit since we exclude
the far-UV and X-ray emission, and the bolometric correction is
larger at earlier times because of the greater amounts of UV and X-ray
emission. The largest amount of emission from a SN explosion
thus far has been from SN 2003ma, with an integrated bolomet-ric
luminosity of 4 1051 ergs. While the integrated bolometric
luminosity of SN 2003ma was a factor of 20 higher than for
SDSS1133, the peak emission of SN 2003ma was MR = 21:5
mag, about 150 times brighter than SDSS1133.
The eruptive LBV and SN hypothesis has several issues that
make SDSS1133 one of the most unusual LBV/SN candidates. The
51 yr putative eruptive LBV phase before the SN (whose peak
brightness was in 2001) is the longest observed before a SN explo-sion.
The luminous broad H emission requires interaction with
a very dense CSM linked to an extreme amount of mass loss by
the LBV. A plot of H emission from SDSS1133 as a function of
time after peak magnitude can be found in Figure 11, as compared
with the other most luminous SNe observed at late times. In 2013,
SDSS1133 shows little decrease in H compared to other known
SNe, and it has more luminous late-time H emission than even
extreme cases like SN 1988Z (Aretxaga et al. 1999). Additionally,
c
0000 RAS, MNRAS 000, 1–??
37. region of SDSS1133 from 2003 (SDSS, left), 2013 (Keck, middle), and 2014 (MMT, right). The 2013 and 2014 spectra show
narrow Fe II emission, weaker continuum emission, and a lower ratio of [O III] to H
38. compared to the 2003 spectrum.
6300 6400 6500 6600 6700 6800
Wavelength (°A
)
2.0
1.5
1.0
0.5
0.0
Flux (10−15erg/s/cm2/°A)
SDSS-2003
[NII]6549°A
[NII]6585°A
[OI]6300°A
[SII]6718°A
[SII]6732°A
H
6300 6400 6500 6600 6700 6800
Wavelength (°A
)
2.0
1.5
1.0
0.5
0.0
Flux (10−15erg/s/cm2/°A)
Keck-2013
[NII]6549°A
[NII]6585°A
[OI]6300°A
[SII]6718°A
[SII]6732°A
H
6300 6400 6500 6600 6700 6800
Wavelength (°A
)
2.0
1.5
1.0
0.5
0.0
Flux (10−15erg/s/cm2/°A)
MMT-2014
[NII]6549°A
[NII]6585°A
[OI]6300°A
[SII]6718°A
[SII]6732°A
H
Figure 8. H region of SDSS1133 from 2003 (SDSS, left), 2013 (Keck, middle), and 2014 (MMT, right). A power-law continuum has been subtracted from
the spectra. Black lines indicate the observed spectra, blue lines are model components, and red lines represent the summed model spectra. Emission lines are
shown at the redshift of the host galaxy Mrk 177.
UV emission in SNe typically drops by several magnitudes in tens
of days, while the UV emission of SDSS1133 exhibits no change
when observed between 2004 by GALEX and 2013 by Swift. Strong
UV emission is unexpected because SNe have line blanketing, and
LBV eruptions usually form much dust. A possible explanation is
a cluster of O-type stars or an H II region that is not detected in
the NIR images. However, the NIR AO Pa
39. observations should
directly trace the gas ionized by young, massive stars. In this case,
the flux would be overestimated, which would reduce the pre-SN
flux and the late-time fading. On the other hand, an H II region
seems unlikely given the 22 pc resolution of AO in Pa
40. and the
change in narrow-line emission between 2003 and 2013. Finally,
additional monitoring is required to understand whether the light
curve is consistent with a monotonic decrease expected from a SN.
If the variability is confirmed to be nonmonotonic, showing very
significant rebrightening, scenarios for SDSS1133 with a LBV and
SN origin will be severely constrained.
4.2 An AGN
4.2.1 Recoiling Black Hole
While the SMBH occupation fraction in dwarf galaxies is only be-ginning
to be constrained (e.g., Reines et al. 2013), any SMBH
mergers that occur as a result of dwarf-dwarf mergers could pro-duce
a substantially offset recoiling AGN. This is because dwarf
galaxies have low escape speeds, and thus even low-velocity recoil
kicks may displace a SMBH from the galactic nucleus. If we as-sume
that the potential of Mrk 177 is dominated by a dark-matter
halo with an NFW profile (Navarro et al. 1996b) for its spatial mass
distribution of dark matter and a halo to stellar mass ratio of 30,
then for the inferred stellar mass of 108:55 M
41. , a reasonable guess
for the central escape speed is 170–200 km s1. The recent spec-tra
have a broad H component consistent with little or no velocity
offset; thus, in the recoiling AGN scenario we can assume that ei-ther
the recoil kick was directed largely in the transverse direction
or that the AGN is on a bound orbit near turnaround.
While high-velocity kicks ( 1000kms1 ) are expected to
be quite rare, GW recoil velocities of 100–200 km s1 should be
relatively common. Lousto et al. (2012) calculate that, even if the
progenitor SMBH spins are mostly aligned prior to their merger
(thus reducing the kick speed), 100–200 km s1 kicks should be
produced in 21–28% of SMBH mergers (assuming a cosmologi-cally
motivated distribution of SMBH mass ratios). These would
correspond to bound or marginally unbound recoil kicks. An addi-tional
12–13% of such mergers should result in recoil velocities of
200–300 km s1, which would leave the recoiling AGN unbound
from its host.
The accretion rate onto a recoiling AGN should decrease
monotonically with time as its accretion disk diffuses outward (un-less
the SMBH encounters a fresh fuel supply). Thus, even if the
SMBH was accreting at the Eddington limit at the time of the kick,
its accretion rate may be only a few percent of Eddington by the
time it is observed as an offset AGN, several Myr later. This is con-sistent
with the low AGN luminosity observed for SDSS1133. Note
that typical offset AGN lifetimes are a few to a few tens of Myr
(Blecha et al. 2011), consistent with the inferred travel time for a
SMBH from the center of Mrk 177 to the current offset (0.8 kpc)
of SDSS1133, and allowing for some deceleration. Furthermore, if
the recoiling SMBH is on a bound orbit, it may be able to replen-
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0000 RAS, MNRAS 000, 1–??
42. SDSS1133+5504: An Unusually Persistent Transient in a Nearby Dwarf Galaxy 9
−10000 −5000 0 5000 10000
Velocity (km s−1)
10−1
Flux Arbitrary
SDSS Mar-2003
Keck Dec-2013
MMT Jan-2014
100
−10000 −5000 0 5000 10000
Velocity (km s−1)
10−1
Flux Arbitrary
SDSS Mar-2003
Keck Dec-2013
MMT Jan-2014
Figure 9. Broad-line region of SDSS1133 in H
43. (left) and H (right) from SDSS in 2003, Keck in 2013, and the MMT in 2014. The spectra have been
smoothed to the same spectral resolution, offset to the same continuum level, and plotted on a log scale in the ordinate. There is evidence of blueshifed
absorption in the H
44. and H regions at 3000 to 8000 kms1 in almost all of the spectra except the 2003 SDSS spectra. The total broad H
45. emission
dropped by 10–20% between 2003 and 2013–2014, whereas the total broad H emission dropped by 65–70%.
0.08
0.06
0.04
0.02
8400 8450 8500 8550 8600 8650 8700 8750
rest [°A]
0.00
]
F [(10−15 erg/s/cm2/°A
SDSS-2003
0.08
0.06
0.04
0.02
8400 8450 8500 8550 8600 8650 8700 8750
rest [°A]
0.00
]
F [(10−15 erg/s/cm2/°A
Keck-2013
0.10
0.08
0.06
0.04
0.02
0.00
7100 7150 7200 7250 7300 7350
rest [°A
]
−0.02
]
F [(10−15 erg/s/cm2/°A
SDSS-2003
0.10
0.08
0.06
0.04
0.02
0.00
7100 7150 7200 7250 7300 7350
rest [°A]
−0.02
]
F [(10−15 erg/s/cm2/°A
Keck-2013
Figure 10. Calcium near-IR triplet region of SDSS1133 as observed in 2003 (left) and 2013 (middle left), showing line fits to O I 8446 and Ca II 8498,
8452, 8662. The 2003 spectra shows broader emission. Fits to [Fe II] 7155 and [Ca II] 7291, 7324 in 2003 (middle right) and 2013 (right) are also shown.
No emission lines are detected in 2003, whereas the 2013 spectrum exhibits strong, narrow emission consistent with the resolution of the instrument (220
kms1 ).
ish its fuel supply on subsequent passages through the galaxy, thus
extending its offset AGN lifetime (Blecha et al. 2011).
While the expected properties of recoiling AGNs are poorly
understood, SDSS1133 does show many features similar to ob-served
broad-line AGN and those expected for recoiling AGNs,
including the following: (1) point-like emission for 63 yr that is
on very small scales of . 12 pc, (2) broad Fe II emission is seen in
almost all Type-1 AGN spectra, (3) broad Ca II NIR triplet emis-sion
is found in 1/3 of quasars (Netzer 1990), (4) a blue power-law
continuum with no detected stellar absorption lines from the
host-galaxy nucleus, (5) some narrow-line optical emission-line di-agnostics
consistent with an AGN, (6) a SMBH mass measurement
that remains constant within the uncertainties over a decade, de-spite
changes in the continuum, (7) variability with dimming and
rebrightening, (8) lack of significant color evolution, (9) relatively
constant UV luminosity, and (10) H luminosity consistent with
a low-mass SMBH accreting at a typical rate of a few percent of
LEdd.
Since the majority ( 80–100%) of AGNs are variable
(MacLeod 2012), and less luminous AGNs tend to be more vari-able
(Desjardins et al. 2007), one might expect SDSS1133 to show
high variability. However, the drop in brightness of SDSS1133 be-tween
the last SDSS image on 2002 April 1 and the SDSS spectra
taken on 2003 March 9, over a period of about a year, is quite large
at 2.2–2.9 mag. While this sharp a change has been observed in
a few AGNs (e.g., Gaskell 2006), the large variability and strong
late-time UV emission are more consistent with tidal flares.
As an AGN, the rapid drop in luminosity between 2002 and
2003, the narrow [Fe II] lines, and the presence of [Ca II] 7291,
7324 emission are difficult to understand. The [Ca II] lines are
rarely seen in AGNs because dust grains are presumed to suppress
the Ca II emission through the substantial Ca depletion (Ferland
1993). While found in some AGNs such as I Zw 1 (Phillips 1976),
the feature is rare among AGN spectra.
The total broad H luminosity of 0:7 1040 erg s1 would
make this a very low luminosity AGN, with a predicted bolometric
luminosity of 1042 erg s1 (Greene Ho 2007) and an Edding-ton
ratio of 0.02. Thus, this object is similar in its gross properties to
many of the very low luminosity AGNs recently discovered, which
have inferred BH masses in the 105–106 M
46. range (Reines et al.
2013).
Finally, in a variant of the recoiling AGN scenario, the ex-treme
variability of SDSS1133 could arise from the tidal disrup-tion
of a star by the recoiling BH. This would result in a short-lived,
luminous flare from the accretion of the stellar debris. Tidal
disruption events are bright in the X-rays, UV, and sometimes op-tical
(Komossa 2002; Gezari et al. 2006). For low-mass SMBHs
such as SDSS1133, the flare is expected to be super-Eddington,
with an estimated duration of 2–5 yr (Ulmer 1999). Stellar tidal
disruptions by recoiling SMBHs may contribute a small but non-
c
0000 RAS, MNRAS 000, 1–??
47. 10 M. Koss et al.
0 1000 2000 3000 4000 5000 6000
Epoch (Days)
1042
1041
1040
1039
1038
1037
H Luminosity (erg/s)
SDSS1133
1980K
1988Z
1993J
1998S
Figure 11. H emission from SDSS1133 compared to the most luminous late-time SNe from the literature (Aretxaga et al. 1999; Mauerhan Smith 2012;
Chandra et al. 2009). SDSS1133 displays a very flat profile along with the brightest late-time H ever seen, even including very luminous SNe such as SN
1988Z.
negligible fraction to the total rate of tidal disruptions by SMBHs
(Komossa Merritt 2008; Stone Loeb 2012).
Because SDSS1133 is detected over 63 yr, with roughly con-stant
luminosity and broad-line emission over the past decade, this
scenario requires the SMBH to have a reservoir of gas persisting be-fore
and after the event, which produces continuous AGN emission.
Since the 2003 spectrum does not show any distinct features ex-pected
from tidal disruption flares (e.g., Strubbe Quataert 2011),
we conclude that any such flare must have faded in 2 yr from
observed peak brightness. This, combined with the small decline
in brightness during the 104 days between the 2001 and 2002 ob-servations,
argues against the tidal disruption scenario. More fun-damentally,
this scenario requires an additional rare event (a tidal
disruption flare) in a highly unusual object, namely a recoiling BH
in a dwarf galaxy.
4.2.2 An Infalling Tidally Stripped Dwarf or ULX?
It is theoretically possible that Mrk 177 is observed in an ear-lier
stage of merging, such that SDSS1133 originated in a satel-lite
galaxy falling into the host galaxy. In this case, the center of
the host galaxy could contain its own, relatively quiescent SMBH.
The AO images in the Kp and Pa
48. bands both show an unresolved
point source at the location of SDSS1133 down to spatial scales of
12 pc and 22 pc, respectively. This is consistent with a recoiling
AGN that has left its host galaxy behind. If instead SDSS1133 is
an infalling dwarf galaxy, then it must have been tidally stripped
at radii 12 pc, a strong constraint. Numerical models suggest
that repeated strong tidal encounters with a much more massive
host can remove more than 99% of the total initial mass of a satel-lite
galaxy (e.g., Pe˜narrubia et al. 2008). However, the only galaxy
near SDSS1133 is Mrk 177, a dwarf galaxy with insufficient mass
to be responsible for such extreme tidal stripping of a fellow dwarf
companion.
When an SMBH is present, its sphere of influence sets an up-per
limit on the amount of stripping; even strong tidal encounters
will be ineffective at removing mass where the SMBH dominates
the gravitational potential. Making the first-order assumption that
the dwarf galaxy followed the observed SMBH-bulge scaling re-lations
prior to stripping, our SMBH mass estimate of 106:0 M
49. for SDSS1133 implies a stellar velocity dispersion of 60 km s1
(Tremaine et al. 2002). Using the standard definition for the size
of the SMBH sphere of influence, rin
= GMBH=2
, we find
rin
1 pc. This implies that the SMBH sphere of influence is
likely to be unresolved, such that a tidal dwarf remnant stripped to
within a few times rin
cannot be ruled out. Note that extrapolation
from the SMBH-bulge scaling relations (H¨aring Rix 2004) im-plies
a progenitor galaxy for SDSS1133 larger than Mrk 177. How-ever,
the value of inferred from Tremaine et al. (2002) is likely
an upper limit. Tidal stripping and stellar feedback can decrease
the velocity dispersion (e.g., Pe˜narrubia et al. 2009; Navarro et al.
1996a; Zolotov et al. 2012), and the progenitor may also have been
somewhat less massive. All of these would yield a larger radius of
influence. Specifically, a factor of 4 decrease in velocity dispersion
from the above estimates would imply that the SMBH sphere of
influence is at least marginally resolvable (rin
7–19 pc). There-fore,
the tidal stripping scenario is very strongly constrained by the
need for both an unidentified massive galaxy to strip the SDSS1133
progenitor and for a compact, unresolvable SMBH sphere of influ-ence.
In contrast, a recoiling SMBH ejected from a spherical
stellar distribution will only retain stars within a radius r
(=vk)2 rin
. For a Bahcall-Wolf profile normalized such that
M(r rin
) = 2MBH (Bahcall Wolf 1976), a kick of 200
km s1 would only allow the inner 0.003 pc of the stellar cusp,
or a few thousand M
50. , to remain bound to the SMBH. Thus, in
the recoil scenario the stellar cusp would not be resolved under any
circumstances.
Interpreting SDSS1133 as a ULX, it is either accreting ambi-ent
gas (i.e., indistinguishable from an AGN discussed in previous
scenarios) or accreting from a stellar companion (which is unten-able
for our large inferred BH mass 106 M
51. ). The most extreme
ULX is HLX-1 (ESO 243-49), with LX = 2 1042 erg s1 and
a BH mass of (3–300) 103 M
52. (Farrell et al. 2009), making it
the most convincing example of an IMBH. This BH mass is sig-nificantly
lower than that inferred for SDSS1133. HLX-1 is offset
from its host-galaxy center by 3 kpc (in projection), and may
reside in a tidally stripped dwarf galaxy that is merging with the
host galaxy (e.g., Mapelli et al. 2012). In principle, the AGN in
SDSS1133 could have a similar origin, such that its host galaxy
was tidally stripped long ago, but the point-like AO observations
and lack of nearby massive galaxies place strong constraints against
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0000 RAS, MNRAS 000, 1–??
53. SDSS1133+5504: An Unusually Persistent Transient in a Nearby Dwarf Galaxy 11
this. If SDSS1133 were a ULX, it would be the first ever to be ob-served
with broad Balmer lines (Roberts et al. 2011). Given the
inferred BH mass of SDSS1133, as a ULX it is extremely X-ray
weak, with a 2–10 keV to V -band flux ratio of 100; this is be-low
that of most ULXs, though some in their low states such as
M101-ULX1 and M81-ULX1 have observed ratios similar to this
(Tao et al. 2012).
4.3 Frequency of Objects like SDSS1133
A survey of all 3579 low-redshift (z 0:3) broad emission-line
objects ( 1000 kms1 FWHM; Stern Laor 2012) found only
two objects offset from the host-galaxy nucleus: SDSS1133 along
with a very close dual AGN Mrk 739 (Koss et al. 2011). The low
frequency of detections of spatially offset broad-line sources found
in the SDSS quasar survey (1/3579, 0:1%) does not exclude the
possibility of a significant population. The small physical separa-tion
of 800 pc found for SDSS1133 can only be resolved at very low
redshift with the imaging of the SDSS (at z 0:03, 1.300 800
pc). The broad-line luminosity of SDSS1133 is among the weakest
dozen of the SDSS sample, and at the current reduced brightness
of SDSS1133 it would be too faint for the survey (Richards et al.
2004). Future space-based surveys such as Euclid andWFIRST
will obtain high-resolution images with precision astrometry of
large areas of the sky, enabling them to probe the nuclear regions
of nearby galaxies for offset point sources. Both have IR grisms
as part of their wide-field surveys to cover broad AGN lines in the
NIR such as the Paschen lines.
5 CONCLUSION
SDSS1133 has many observed properties consistent with a recoil-ing
AGN, but it also has some properties that favor interpretation
of this source as an eruptive luminous blue variable star outburst-ing
for decades followed by a Type IIn SN. SDSS1133 would be
the longest LBV eruption ever observed and have a much greater
late-time H luminosity than even extreme events like SN 1988Z.
SDSS1133 has recently undergone a 1 mag rebrightening in PS1
images, suggesting that the coming years will be critical to un-derstand
the true nature of this source. Future high spatial reso-lution
and high sensitivity UV, X-ray, and radio observations of
SDSS1133 are critical for constraining the source nature. In the
UV, the measurement of strong N V 1240 and (especially) broad
C IV 1550 emission would decisively favor the AGN interpre-tation.
Additionally, high-resolution UV images could determine
whether the strong UV emission and prominent narrow-line emis-sion
in [O I], [O II], and [O III] is produced by a compact H II
region or a young star cluster not seen in the NIR AO image. High-sensitivity
X-ray observations could differentiate between softer
thermal X-ray emission from a SN shock and an AGN power law.
ACKNOWLEDGMENTS
We are grateful to Jessica Lu and Aaron Barth for useful discus-sion
and suggestions. We thank Neil Gehrels and the Swift team
for approving and executing a ToO observation. M.K. and K.S. ac-knowledge
support from Swiss National Science Foundation (NSF)
grant PP00P2 138979/1. M.K. also acknowledges support for this
work provided by the National Aeronautics and Space Adminis-tration
(NASA) through Chandra Award Number AR3-14010X is-sued
by the Chandra X-ray Observatory Center, which is operated
by the Smithsonian Astrophysical Observatory for and on behalf
of NASA under contract NAS8-03060. Support for L.B. was pro-vided
by NASA through the Einstein Fellowship Program, grant
PF2-130093. A.V.F. received generous financial assistance from
Gary and Cynthia Bengier, the Christopher R. Redlich Fund, the
Richard and Rhoda Goldman Fund, the TABASGO Foundation,
and NSF grant AST-1211916. The work of D.S. was carried out at
Jet Propulsion Laboratory, California Institute of Technology, un-der
a contract with NASA.
Some of the data presented herein were obtained at the W.
M. Keck Observatory, which is operated as a scientific partner-ship
among the California Institute of Technology, the Univer-sity
of California, and NASA; the Observatory was made possi-ble
by the generous financial support of the W. M. Keck Founda-tion.
Data reported here were obtained in part at the MMT Ob-servatory,
a joint facility of the University of Arizona and the
Smithsonian Institution. Funding for the SDSS and SDSS-II has
been provided by the Alfred P. Sloan Foundation, the Participat-ing
Institutions, the NSF, the U.S. Department of Energy, NASA,
the Japanese Monbukagakusho, the Max Planck Society, and the
Higher Education Funding Council for England. The SDSS web-site
is http://www.sdss.org/. The PS1 data have been made possible
through contributions of the Institute for Astronomy, the Univer-sity
of Hawaii, the Pan-STARRS1 Project Office, the Max-Planck
Society and its participating institutes, the Max Planck Institute
for Astronomy (Heidelberg) and the Max Planck Institute for Ex-traterrestrial
Physics (Garching), The Johns Hopkins University,
Durham University, the University of Edinburgh, Queen’s Uni-versity
Belfast, the Harvard-Smithsonian Center for Astrophysics,
the Las Cumbres Observatory Global Telescope Network Incorpo-rated,
the National Central University of Taiwan, the Space Tele-scope
Science Institute, NASA under grant NNX08AR22G issued
through the Planetary Science Division of the NASA Science Mis-sion
Directorate, the NSF under grant AST-1238877, the University
of Maryland, and Eotvos Lorand University (ELTE).
This research made use of the NASA/IPAC Extragalactic
Database (NED) which is operated by the Jet Propulsion Labora-tory,
California Institute of Technology, under contract with NASA.
It also employed Astropy, a community-developed core Python
package for Astronomy (Astropy Collaboration, 2013). Moreover,
it used APLpy, an open-source plotting package for Python hosted
at http://aplpy.github.com.
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Table 1. Photometry
Filter a Mag b Mag err c Date Telescope d e
103aO 18.6 0.7 1950-03-20 DSS1 1
IIIaJ 18.4 0.40 1994-04-14 DSS2 1
IIIaF 18.8 0.50 1999-04-25 DSS2 1
u 16.28 0.08 2001-12-18 SDSS 1
u 16.75 0.08 2002-04-01 SDSS 1
g 16.41 0.04 2001-12-18 SDSS 1
g 16.40 0.04 2002-04-01 SDSS 1
g 18.7 0.18 2003-03-09 SDSSspec 1
i 16.48 0.04 2001-12-18 SDSS 1
i 16.40 0.04 2002-04-01 SDSS 1
i 18.65 0.05 2003-03-09 SDSSspec 1
r 16.26 0.04 2001-12-18 SDSS 1
r 16.31 0.04 2002-04-01 SDSS 1
r 18.28 0.06 2003-03-09 SDSSspec 1
z 16.45 0.04 2001-12-18 SDSS 1
z 16.34 0.04 2002-04-01 SDSS 1
z 18.49 0.08 2003-03-09 SDSSspec 1
NUV 21.62 0.40 2004-03-06 GALEX 1
g 19.4 0.0 2005-01-01 Beijing 1
g 19.58 0.01 2010-03-17 PS1 4
g 19.68 0.05 2011-03-12 PS1 8
g 20.18 0.01 2012-02-22 PS1 2
g 19.38 0.07 2013-01-16 PS1 8
r 19.02 0.03 2010-03-13 PS1 4
r 19.37 0.01 2011-03-12 PS1 4
r 19.91 0.04 2012-02-22 PS1 4
r 19.31 0.06 2012-12-27 PS1 4
r 19.49 0.02 2013-02-09 PS1 8
r 19.02 0.03 2014-03-24 PS1 4
i 19.48 0.03 2010-03-03 PS1 4
i 19.5 0.03 2011-03-14 PS1 4
i 20.12 0.03 2012-02-11 PS1 4
i 19.62 0.04 2013-01-27 PS1 4
i 19.48 0.03 2014-03-16 PS1 4
z 19.43 0.07 2010-02-27 PS1 8
z 19.72 0.03 2010-05-18 PS1 8
z 19.57 0.01 2010-12-25 PS1 4
z 19.73 0.10 2011-01-22 PS1 4
z 19.82 0.01 2011-05-11 PS1 4
z 20.11 0.12 2012-02-09 PS1 4
z 19.82 0.02 2012-04-10 PS1 4
z 19.48 0.02 2013-01-03 PS1 4
z 19.32 0.05 2014-01-20 PS1 1
J 19.02 0.18 2013-06-16 NIRC2 1
Kp 18.92 0.16 2013-06-16 NIRC2 1
uvw1 21.41 0.30 2013-08-27 SWIFT 1
g 19.19 0.20 2014-01-04 MMTspec 1
a Specific filter used for image. The 103aO, IIIaJ, and IIIaF designations refer to plates from the DSS.
b All magnitudes are listed as AB mag.
c Uncertainty from photometric zero point and uncertainty in measuring photometry with GALFIT. For synthetic photometry
from spectra, the uncertainty includes the conversion from aperture to PSF magnitudes.
d MMTspec and SDSSspec indicate synthetic photometry; all of the other observations were from imaging.
e Number of observations taken at separate times within 1 week of the first observation. For PS1 several observations are
often taken within a week; we have measured the weighted mean of these separate observations.
c
0000 RAS, MNRAS 000, 1–??
57. SDSS1133+5504: An Unusually Persistent Transient in a Nearby Dwarf Galaxy 15
Table 2. Emission-Line Properties
Namea Line Offset b FWHM c Luminosity d Date
(kms1 ) (kms1 ) (1036 erg s1 )
Narrow Lines
SDSS1133 H
63. -186 360 10335 2013
Mrk 177 [O III] 5007 0 150 1884 2003
Mrk 177-IFU offset [O III] 5007 -186 360 6925 2013
Mrk 177 [O I] 6300 0 150 265 2003
Mrk 177-IFU offset [O I] 6300 -186 360 63 2013
Mrk 177 H 0 150 3325 2003
Mrk 177-IFU offset H -186 360 12717 2013
Mrk 177 [N II] 6583 0 150 865 2003
Mrk 177-IFU offset [N II] 6583 -186 360 258 2013
Mrk 177 [S II] 6716 0 150 865 2003
Mrk 177-IFU offset [S II] 6716 -186 360 2711 2013
Mrk 177 [S II] 6731 0 150 635 2003
Mrk 177-IFU offset [S II] 6731 -186 360 2211 2013
a Name of spectrum. Mrk 177 and SDSS1133 are from the SDSS. Mrk 177 IFU-offset is taken using the SNIFS IFU at the
same radial offset from the nucleus of Mrk 177 as SDSS1133 (but in the opposite direction) and with the same aperture size.
SDSS1133-IFU is taken of SDSS1133 with Mrk 177 IFU-offset subtracted, leaving only the broad lines to fit.
b Offset from the measured [O III] line in Mrk 177.
c All of the narrow lines measured were consistent with the instrumental resolution.
d Luminosity assuming a distance of 28.9 Mpc.
c
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64. 16 M. Koss et al.
Table 3. Source Properties
Propertya AGN LBV Outburst SNe
Bright ( 13 mag) optical emission for 51 yr Y Y
Optical drop of 2.2 mag in 1 year R Y Y
Peak optical mag of 16 Y Y
20 pc point-source emission Y Y Y
Constant UV emission for a decade Y
Constant g i color for a decade Y
Changing broad-line width Y Y
Broad H ( 1000 kms1 ) for a decade Y R
Broad-line Balmer decrement change R Y
Narrow [O III] emission Y R
Late-time narrow [Fe II] emission R R
Late-time narrow [Ca II] emission R R
P-Cygni blueshifted absorption R Y
i Kp color = 2.5 mag Y R
0.3–10 keV/H ratio 1 R Y
a R indicates rarely, Y indicates common, and blank indicates never
observed among this type of source.
c
0000 RAS, MNRAS 000, 1–??