This document describes observations of the pre-cataclysmic variable binary star system NN Serpentis using a CCD sensor. Light curve data of the system's apparent magnitude over time was collected, extracted from files, and calibrated. The light curve showed periodic fluctuations due to the orbit as well as a deep eclipse when the red dwarf passed in front of the white dwarf. By fitting a sine wave to the light curve, the orbital period was calculated to be 3.206 ± 0.023 hours. Additional parameters of the binary system were also determined from the observations and prior literature.
- Astrônomos descobriram que uma pequena estrela, do tamanho de Júpiter, possui uma tempestade muito parecida com a Grande Mancha Vermelha e que está ali, persistente por dois anos.
- Enquanto nos planetas, esse tipo de característica é normal, em estrelas essa é a melhor evidência encontrada até hoje.
- A estrela é chamada de W1906+40 e pertence a uma classe de objetos frios chamados de Anãs-L.
- Elas são consideradas estrelas pois fundem átomos e geram luz, como o Sol faz, enquanto que as anãs marrons são conhecidas como estrelas que falharam, pois elas não possuem o processo de fusão atômica em seu interior.
- Nesse novo estudo os astrônomos foram capazes de verificar as mudanças na atmosfera da estrela por dois anos. A técnica usada foi semelhante à de detecção de exoplanetas, analisando a curva de luz da estrela, que apresentava quedas, mas que não era por questão de planetas.
- Os astrônomos usaram o Spitzer e estudaram a luz infravermelha da estrela, que revelou uma gigantesca mancha escura que não era uma mancha magnética estelar, mas sim uma tempestade com um diâmetro equivalente ao de 3 Terras. O spitzer foi capaz de estudar camadas diferentes da atmosfera da estrela e esses dados junto com os dados do Kepler, revelaram com clareza a tempestade estelar.
- Futuras observações serão realizadas usando os dois equipamentos para tentar identificar esse tipo de tempestade em anãs marrons, por exemplo, e tentar descobrir se esse tipo de fenômeno é muito comum, ou é raro no universo.
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.
Evidence for reflected_lightfrom_the_most_eccentric_exoplanet_knownSérgio Sacani
Planets in highly eccentric orbits form a class of objects not seen within our Solar System. The most extreme case known amongst these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). We obtained CHIRON spectra to perform an independent estimation of the fundamental stellar parameters. New radial velocities from AAT and PARAS observations during periastron passage greatly improve our knowledge of the eccentric nature of the orbit. The combined analysis of our Keplerian orbital and Hipparcos astrometry show that the inclination of the planetary orbit is > 1.22◦, ruling out stellar masses for the companion. Our long-term robotic photometry show that the star is extremely stable over long timescales. Photometric monitoring of the star during predicted transit and periastron times using MOST rule out a transit of the planet and reveal evidence of phase variations during periastron. These possible photometric phase variations may be caused by reflected light from the planet’s atmosphere and the dramatic change in star–planet separation surrounding the periastron passage.
The characterization of_the_gamma_ray_signal_from_the_central_milk_way_a_comp...Sérgio Sacani
Past studies have identified a spatially extended excess of ∼1-3 GeV gamma rays from the region
surrounding the Galactic Center, consistent with the emission expected from annihilating dark
matter. We revisit and scrutinize this signal with the intention of further constraining its characteristics
and origin. By applying cuts to the Fermi event parameter CTBCORE, we suppress the tails
of the point spread function and generate high resolution gamma-ray maps, enabling us to more
easily separate the various gamma-ray components. Within these maps, we find the GeV excess
to be robust and highly statistically significant, with a spectrum, angular distribution, and overall
normalization that is in good agreement with that predicted by simple annihilating dark matter
models. For example, the signal is very well fit by a 36-51 GeV dark matter particle annihilating to
b
¯b with an annihilation cross section of σv = (1−3)×10−26 cm3
/s (normalized to a local dark matter
density of 0.4 GeV/cm3
). Furthermore, we confirm that the angular distribution of the excess is
approximately spherically symmetric and centered around the dynamical center of the Milky Way
(within ∼0.05◦
of Sgr A∗
), showing no sign of elongation along the Galactic Plane. The signal is
observed to extend to at least ' 10◦
from the Galactic Center, disfavoring the possibility that this
emission originates from millisecond pulsars.
We present long-baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of
the 870 m continuum emission from the nearest gas-rich protoplanetary disk, around TW Hya, that
trace millimeter-sized particles down to spatial scales as small as 1 AU (20 mas). These data reveal
a series of concentric ring-shaped substructures in the form of bright zones and narrow dark annuli
(1{6AU) with modest contrasts (5{30%). We associate these features with concentrations of solids
that have had their inward radial drift slowed or stopped, presumably at local gas pressure maxima.
No signicant non-axisymmetric structures are detected. Some of the observed features occur near
temperatures that may be associated with the condensation fronts of major volatile species, but the
relatively small brightness contrasts may also be a consequence of magnetized disk evolution (the
so-called zonal
ows). Other features, particularly a narrow dark annulus located only 1 AU from the
star, could indicate interactions between the disk and young planets. These data signal that ordered
substructures on AU scales can be common, fundamental factors in disk evolution, and that high
resolution microwave imaging can help characterize them during the epoch of planet formation.
Keywords: protoplanetary disks | planet-disk interactions | stars: individual (TW Hydrae)
•Lunar laser telemetry consists in determining the round-trip travel time of the light between a transmitter on the Earth and a reflector on the Moon, which is an equivalent measurement of the distance between these two points
- Astrônomos descobriram que uma pequena estrela, do tamanho de Júpiter, possui uma tempestade muito parecida com a Grande Mancha Vermelha e que está ali, persistente por dois anos.
- Enquanto nos planetas, esse tipo de característica é normal, em estrelas essa é a melhor evidência encontrada até hoje.
- A estrela é chamada de W1906+40 e pertence a uma classe de objetos frios chamados de Anãs-L.
- Elas são consideradas estrelas pois fundem átomos e geram luz, como o Sol faz, enquanto que as anãs marrons são conhecidas como estrelas que falharam, pois elas não possuem o processo de fusão atômica em seu interior.
- Nesse novo estudo os astrônomos foram capazes de verificar as mudanças na atmosfera da estrela por dois anos. A técnica usada foi semelhante à de detecção de exoplanetas, analisando a curva de luz da estrela, que apresentava quedas, mas que não era por questão de planetas.
- Os astrônomos usaram o Spitzer e estudaram a luz infravermelha da estrela, que revelou uma gigantesca mancha escura que não era uma mancha magnética estelar, mas sim uma tempestade com um diâmetro equivalente ao de 3 Terras. O spitzer foi capaz de estudar camadas diferentes da atmosfera da estrela e esses dados junto com os dados do Kepler, revelaram com clareza a tempestade estelar.
- Futuras observações serão realizadas usando os dois equipamentos para tentar identificar esse tipo de tempestade em anãs marrons, por exemplo, e tentar descobrir se esse tipo de fenômeno é muito comum, ou é raro no universo.
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.
Evidence for reflected_lightfrom_the_most_eccentric_exoplanet_knownSérgio Sacani
Planets in highly eccentric orbits form a class of objects not seen within our Solar System. The most extreme case known amongst these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). We obtained CHIRON spectra to perform an independent estimation of the fundamental stellar parameters. New radial velocities from AAT and PARAS observations during periastron passage greatly improve our knowledge of the eccentric nature of the orbit. The combined analysis of our Keplerian orbital and Hipparcos astrometry show that the inclination of the planetary orbit is > 1.22◦, ruling out stellar masses for the companion. Our long-term robotic photometry show that the star is extremely stable over long timescales. Photometric monitoring of the star during predicted transit and periastron times using MOST rule out a transit of the planet and reveal evidence of phase variations during periastron. These possible photometric phase variations may be caused by reflected light from the planet’s atmosphere and the dramatic change in star–planet separation surrounding the periastron passage.
The characterization of_the_gamma_ray_signal_from_the_central_milk_way_a_comp...Sérgio Sacani
Past studies have identified a spatially extended excess of ∼1-3 GeV gamma rays from the region
surrounding the Galactic Center, consistent with the emission expected from annihilating dark
matter. We revisit and scrutinize this signal with the intention of further constraining its characteristics
and origin. By applying cuts to the Fermi event parameter CTBCORE, we suppress the tails
of the point spread function and generate high resolution gamma-ray maps, enabling us to more
easily separate the various gamma-ray components. Within these maps, we find the GeV excess
to be robust and highly statistically significant, with a spectrum, angular distribution, and overall
normalization that is in good agreement with that predicted by simple annihilating dark matter
models. For example, the signal is very well fit by a 36-51 GeV dark matter particle annihilating to
b
¯b with an annihilation cross section of σv = (1−3)×10−26 cm3
/s (normalized to a local dark matter
density of 0.4 GeV/cm3
). Furthermore, we confirm that the angular distribution of the excess is
approximately spherically symmetric and centered around the dynamical center of the Milky Way
(within ∼0.05◦
of Sgr A∗
), showing no sign of elongation along the Galactic Plane. The signal is
observed to extend to at least ' 10◦
from the Galactic Center, disfavoring the possibility that this
emission originates from millisecond pulsars.
We present long-baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of
the 870 m continuum emission from the nearest gas-rich protoplanetary disk, around TW Hya, that
trace millimeter-sized particles down to spatial scales as small as 1 AU (20 mas). These data reveal
a series of concentric ring-shaped substructures in the form of bright zones and narrow dark annuli
(1{6AU) with modest contrasts (5{30%). We associate these features with concentrations of solids
that have had their inward radial drift slowed or stopped, presumably at local gas pressure maxima.
No signicant non-axisymmetric structures are detected. Some of the observed features occur near
temperatures that may be associated with the condensation fronts of major volatile species, but the
relatively small brightness contrasts may also be a consequence of magnetized disk evolution (the
so-called zonal
ows). Other features, particularly a narrow dark annulus located only 1 AU from the
star, could indicate interactions between the disk and young planets. These data signal that ordered
substructures on AU scales can be common, fundamental factors in disk evolution, and that high
resolution microwave imaging can help characterize them during the epoch of planet formation.
Keywords: protoplanetary disks | planet-disk interactions | stars: individual (TW Hydrae)
•Lunar laser telemetry consists in determining the round-trip travel time of the light between a transmitter on the Earth and a reflector on the Moon, which is an equivalent measurement of the distance between these two points
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)
Periodic mass extinctions_and_the_planet_x_model_reconsideredSérgio Sacani
The 27 Myr periodicity in the fossil extinction record has been con-
firmed in modern data bases dating back 500 Myr, which is twice the time
interval of the original analysis from thirty years ago. The surprising regularity
of this period has been used to reject the Nemesis model. A second
model based on the sun’s vertical galactic oscillations has been challenged
on the basis of an inconsistency in period and phasing. The third astronomical
model originally proposed to explain the periodicity is the Planet
X model in which the period is associated with the perihelion precession
of the inclined orbit of a trans-Neptunian planet. Recently, and unrelated
to mass extinctions, a trans-Neptunian super-Earth planet has been proposed
to explain the observation that the inner Oort cloud objects Sedna
and 2012VP113 have perihelia that lie near the ecliptic plane. In this
Letter we reconsider the Planet X model in light of the confluence of the
modern palaeontological and outer solar system dynamical evidence.
Key Words: astrobiology - planets and satellites - Kuiper belt:
general - comets: general
Science with small telescopes - exoplanetsguest8aa6ebb
The search for extrasolar planets has become one of the most attractive problems in modern astrophysics. The biggest observatories in the world are involved in this task as well as little amateur instruments. There is also a huge variety of astronomical methods used for their investigation. Here I present the projects for searching for exoplanets by transit method and our observations of the planet WASP-2b. We observed a transit on 3/4 August 2008 with a 354 mm Schmidt-Cassegrain Celestron telescope and CCD SBIG STL 11000M camera. By precise photometry made using MaximDL software we obtained the light curve of the star system. Decrease of brightness by 0.02m is detected. Analyzing our data we estimate the radius of the planet and inclination of its orbit. Our results are in good correlation with the published information in literature.
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.
A magnetar-powered X-ray transient as the aftermath of a binary neutron-star ...Sérgio Sacani
Mergers of neutron stars are known to be associated with short γ-ray
bursts1–4
. If the neutron-star equation of state is sufficiently stiff
(that is, the pressure increases sharply as the density increases), at
least some such mergers will leave behind a supramassive or even a
stable neutron star that spins rapidly with a strong magnetic field5–8
(that is, a magnetar). Such a magnetar signature may have been
observed in the form of the X-ray plateau that follows up to half
of observed short γ-ray bursts9,10. However, it has been expected
that some X-ray transients powered by binary neutron-star mergers
may not be associated with a short γ-ray burst11,12. A fast X-ray
transient (CDF-S XT1) was recently found to be associated with a
faint host galaxy, the redshift of which is unknown13. Its X-ray and
host-galaxy properties allow several possible explanations including
a short γ-ray burst seen off-axis, a low-luminosity γ-ray burst at
high redshift, or a tidal disruption event involving an intermediatemass black hole and a white dwarf13. Here we report a second X-ray
transient, CDF-S XT2, that is associated with a galaxy at redshift
z = 0.738 (ref. 14). The measured light curve is fully consistent with
the X-ray transient being powered by a millisecond magnetar. More
intriguingly, CDF-S XT2 lies in the outskirts of its star-forming host
galaxy with a moderate offset from the galaxy centre, as short γ-ray
bursts often do15,16. The estimated event-rate density of similar
X-ray transients, when corrected to the local value, is consistent
with the event-rate density of binary neutron-star mergers that is
robustly inferred from the detection of the gravitational-wave event
GW170817.
KIC 9832227: Using Vulcan Data to Negate the 2022 Red Nova Merger PredictionSérgio Sacani
KIC 9832227 is a contact binary whose 11 hr orbital period is rapidly changing. Based on the apparent exponential decay of its period, the two stars were predicted to merge in early 2022 resulting in a rare red nova outburst. Fortunately KIC 9832227 was observed in 2003 as part of the NASA Ames pre-Kepler Vulcan Project to search for transiting exoplanets. We find that the Vulcan timing measurement does not agree with the previous exponential decay model. This led us to re- evaluate the other early epoch non-Kepler data sets, the Northern Sky Variability Survey (NSVS) and Wide Angle Search for Planets (WASP) survey. We find that the WASP times are in good agreement with the previous prediction, but the NSVS eclipse time differs by nearly an hour. The very large disagreement of the Vulcan and NSVS eclipse times with an exponentially decaying model forces us to reject the merger hypothesis. Although period variations are common in contact binaries, the physical cause of the period changes in KIC 9832227 remains unexplained; a third star scenario is unlikely. This study shows the data collected by the Vulcan photometer to be extremely valuable for extending the baseline for measurements of variable stars in the Kepler field.
Gaussian Orbital Determination of 1943 AnterosMatthew Li
Paper detailing the theory, methods, calculations, and results regarding the investigation of the orbit of asteroid 1943 Anteros through approximately six weeks of celestial observation and data collection.
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)
Periodic mass extinctions_and_the_planet_x_model_reconsideredSérgio Sacani
The 27 Myr periodicity in the fossil extinction record has been con-
firmed in modern data bases dating back 500 Myr, which is twice the time
interval of the original analysis from thirty years ago. The surprising regularity
of this period has been used to reject the Nemesis model. A second
model based on the sun’s vertical galactic oscillations has been challenged
on the basis of an inconsistency in period and phasing. The third astronomical
model originally proposed to explain the periodicity is the Planet
X model in which the period is associated with the perihelion precession
of the inclined orbit of a trans-Neptunian planet. Recently, and unrelated
to mass extinctions, a trans-Neptunian super-Earth planet has been proposed
to explain the observation that the inner Oort cloud objects Sedna
and 2012VP113 have perihelia that lie near the ecliptic plane. In this
Letter we reconsider the Planet X model in light of the confluence of the
modern palaeontological and outer solar system dynamical evidence.
Key Words: astrobiology - planets and satellites - Kuiper belt:
general - comets: general
Science with small telescopes - exoplanetsguest8aa6ebb
The search for extrasolar planets has become one of the most attractive problems in modern astrophysics. The biggest observatories in the world are involved in this task as well as little amateur instruments. There is also a huge variety of astronomical methods used for their investigation. Here I present the projects for searching for exoplanets by transit method and our observations of the planet WASP-2b. We observed a transit on 3/4 August 2008 with a 354 mm Schmidt-Cassegrain Celestron telescope and CCD SBIG STL 11000M camera. By precise photometry made using MaximDL software we obtained the light curve of the star system. Decrease of brightness by 0.02m is detected. Analyzing our data we estimate the radius of the planet and inclination of its orbit. Our results are in good correlation with the published information in literature.
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.
A magnetar-powered X-ray transient as the aftermath of a binary neutron-star ...Sérgio Sacani
Mergers of neutron stars are known to be associated with short γ-ray
bursts1–4
. If the neutron-star equation of state is sufficiently stiff
(that is, the pressure increases sharply as the density increases), at
least some such mergers will leave behind a supramassive or even a
stable neutron star that spins rapidly with a strong magnetic field5–8
(that is, a magnetar). Such a magnetar signature may have been
observed in the form of the X-ray plateau that follows up to half
of observed short γ-ray bursts9,10. However, it has been expected
that some X-ray transients powered by binary neutron-star mergers
may not be associated with a short γ-ray burst11,12. A fast X-ray
transient (CDF-S XT1) was recently found to be associated with a
faint host galaxy, the redshift of which is unknown13. Its X-ray and
host-galaxy properties allow several possible explanations including
a short γ-ray burst seen off-axis, a low-luminosity γ-ray burst at
high redshift, or a tidal disruption event involving an intermediatemass black hole and a white dwarf13. Here we report a second X-ray
transient, CDF-S XT2, that is associated with a galaxy at redshift
z = 0.738 (ref. 14). The measured light curve is fully consistent with
the X-ray transient being powered by a millisecond magnetar. More
intriguingly, CDF-S XT2 lies in the outskirts of its star-forming host
galaxy with a moderate offset from the galaxy centre, as short γ-ray
bursts often do15,16. The estimated event-rate density of similar
X-ray transients, when corrected to the local value, is consistent
with the event-rate density of binary neutron-star mergers that is
robustly inferred from the detection of the gravitational-wave event
GW170817.
KIC 9832227: Using Vulcan Data to Negate the 2022 Red Nova Merger PredictionSérgio Sacani
KIC 9832227 is a contact binary whose 11 hr orbital period is rapidly changing. Based on the apparent exponential decay of its period, the two stars were predicted to merge in early 2022 resulting in a rare red nova outburst. Fortunately KIC 9832227 was observed in 2003 as part of the NASA Ames pre-Kepler Vulcan Project to search for transiting exoplanets. We find that the Vulcan timing measurement does not agree with the previous exponential decay model. This led us to re- evaluate the other early epoch non-Kepler data sets, the Northern Sky Variability Survey (NSVS) and Wide Angle Search for Planets (WASP) survey. We find that the WASP times are in good agreement with the previous prediction, but the NSVS eclipse time differs by nearly an hour. The very large disagreement of the Vulcan and NSVS eclipse times with an exponentially decaying model forces us to reject the merger hypothesis. Although period variations are common in contact binaries, the physical cause of the period changes in KIC 9832227 remains unexplained; a third star scenario is unlikely. This study shows the data collected by the Vulcan photometer to be extremely valuable for extending the baseline for measurements of variable stars in the Kepler field.
Gaussian Orbital Determination of 1943 AnterosMatthew Li
Paper detailing the theory, methods, calculations, and results regarding the investigation of the orbit of asteroid 1943 Anteros through approximately six weeks of celestial observation and data collection.
ASTRONOMICAL OBJECTS DETECTION IN CELESTIAL BODIES USING COMPUTER VISION ALGO...csandit
Computer vision, astronomy, and astrophysics function quite productively together to the point where they are completely logical for each other. Out of computer vision algorithms the
progress of astronomy and astrophysics would have slowed down to reasonably a deadlock. The new researches and calculations can lead to more information as well as higher quality of data. Consequently, an organized view on planetary surfaces can change all in the long run. A new
discovery would be a puzzling complexity or a possible branching of paths, yet the quest to know more about the celestial bodies by dint of computer vision algorithms will continue. The detection of astronomical objects in celestial bodies is a challenging task. This paper presents
an implementation of how to detect astronomical objects in celestial bodies using computer vision algorithm with satisfactory performance. It also puts forward some observations linked
among computer vision, astronomy, and astrophysics.
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
The mass of_the_mars_sized_exoplanet_kepler_138_b_from_transit_timingSérgio Sacani
Artigo da revista Nature, descreve o trabalho de astrônomos para medir o tamanho e a massa de um exoplaneta parecido com Marte, além de caracterizar por completo o sistema planetário da estrela Kepler-138.
Mapping spiral structure on the far side of the Milky WaySérgio Sacani
Little is known about the portion of the Milky Way lying beyond the Galactic center at distances
of more than 9 kiloparsec from the Sun. These regions are opaque at optical wavelengths
because of absorption by interstellar dust, and distances are very large and hard to measure.
We report a direct trigonometric parallax distance of 20:4þ2:8
2:2 kiloparsec obtained with the Very
Long Baseline Array to a water maser source in a region of active star formation. These
measurements allow us to shed light on Galactic spiral structure by locating the ScutumCentaurus
spiral arm as it passes through the far side of the Milky Way and to validate a
kinematic method for determining distances in this region on the basis of transverse motions.
Eccentricity from transit_photometry_small_planets_in_kepler_multi_planet_sys...Sérgio Sacani
Artigo descreve estudo que mostra que a órbita dos exoplanetas terrestres são na sua maioria órbitas circulares, o que é bom para se procurar por vida e o que vem causando uma revolução no entendimento sobre os sistemas de exoplanteas.
1. Orbital Period of the Pre-Cataclysmic Variable: NN Serpentis
Carlos Osorio∗
(Physics 134L)
(Dated: June 3, 2016)
Abstract. A pre-cataclysmic variable is a binary star system consisting of a white dwarf and a
less massive star, whose separation is not small enough to allow mass transfer between them. These
systems possess some interesting characteristics, for which they are commonly a subject of study.
On this lab a pre-cataclysmic variable by the name of NN Serpentis (NN Ser) is observed using a
CCD sensor located at Las Cumbres Observatory Global Telescope Network in Goleta, California.
After the extraction of the data from FIT files into catalogues, and the isolation of the NN Ser
data points from these catalogues, the light curve for this binary system in the V-band filter was
successfully plotted. By then plotting a waveform to fit the data, the period of the orbit of such
system was calculated to be 3.206±0.023 hrs. This value, along with some others acquired from
the scientific literature, were used to find a total of 7 parameters defining the binary, including the
mass and radius of the red dwarf, as well as the separation between the two stars. The calculated
parameters were within the scope of the previously published values, thus rendering the observation
as successful.
CONTENTS
I. INTRODUCTION 1
A. Roche Geometry 1
B. NN Ser 2
II. METHOD 2
A. Data Acquisition 2
B. Data Extraction and Calibration 2
C. Graph Generation and Curve-Fitting 3
III. RESULTS 4
A. Orbital Angular Frequency and Eclipse
Duration 6
B. The NN Ser Orbit and the Reflection Effect 8
IV. CALCULATIONS 9
V. CONCLUSION 10
VI. CURRENT RESEARCH 10
VII. REFERENCES 11
I. INTRODUCTION
A. Roche Geometry
A closed binary system is a system of two stellar
objects (such as stars, or dwarfs) that orbit around
∗ Also at Physics Department, University of California Santa Bar-
bara; cosorio@umail.ucsb.edu
each other due to a gravitational attraction. Closed
binary systems also possess the trait of having other
significant, non-gravitational interactions taking place
between the two stellar objects (Warner et al., 1995).
Among the most diverse and commonly studied types
of closed binary systems are the cataclysmic variables.
These are binary systems composed of a white dwarf
and some other, less massive, type of star. These two
stellar objects are usually referred to as the primary
and secondary stars, respectively. Due to the small
separation between the two stars, and the high density
of the white dwarf, the secondary star of a cataclysmic
variable becomes highly distorted and is no longer
spherical, but instead has a tear-like shape pointing
towards the primary star. The geometry that dominates
this type of system is called Roche geometry.
If the stars are close enough so that the gravita-
tional attraction of the primary star at the radius of the
secondary is greater than that of the secondary itself,
the mass of the secondary star begins flowing into the
primary, creating an accretion disk around it. This
mass flow is the defining characteristic of a cataclysmic
variable. The maximum region a secondary star could
occupy, with still complete gravitational binding over
its material, is called the Roche lobe, and it is bounded
by the critical gravitational potential at which mass
transfer can happen.
2. 2
B. NN Ser
Now, if the secondary star of this type of binary
system does not fill its Roche lobe completely, no mass
transfer can happen between the stars, and the system
is said to be detached. This binary is what is commonly
referred to as a pre-cataclysmic variable. An example of
such a binary system is the NN Serpentis, located about
500 parsecs away from earth in the Serpens constellation.
First referenced in the Palomar-Green Survey in 1980,
and originally catalogued as PG 1550+131, the NN Ser
system has a Right Ascension of 15h 53m 31.051s and
a declination of +120◦
57’ 40.13” in FK5 coordinates
(Simbad, 2016). It is a pre-cataclyismic binary system
composed of a red dwarf of low mass and a white dwarf
of about half the mass of the sun. With an inclination
of almost 90◦
, and a primary star much smaller than its
companion, the NN Ser undergoes through deep periodic
eclipses (Parsons et al., 2010).
The purpose of this lab is to observe the NN
Serpentis system through a CCD sensor to obtain the
period at which the stars orbit each other. This result
will then be used, along with some published parameters,
to calculate the radius and mass of the stars, as well
as the separation between the dwarfs and the orbital
velocity of the red dwarf.
II. METHOD
A. Data Acquisition
The NN Ser binary system was observed using a CCD
sensor located at Las Cumbres Observatory Global Tele-
scope Network in Goleta, California. The observation
took place on May 8th
, 2014 at 6:05am and lasted for
about 4 hours until 10:04am of the same day. The data
acquired consisted of 331 FIT images, 303 of which were
taken with a V band pass filter, while the rest were taken
with a B-filter. All 331 images were obtained with an
exposure time of 30 seconds, and had an average of 47
seconds between recordings. Due to the small amount of
data collected with the B-filter, this data was not ren-
dered useful for any of the calculations involved, and was
thus disregarded.
B. Data Extraction and Calibration
After the data was collected, the following step was
to extract from the FIT images the information that
was needed to obtain the orbital period of the binary
system. For this we used SExtractor to get a catalogue
of each FIT file. These newly created cat files contained
the time of observation, the aperture magnitude and
isophotal flux of each star in the image with their
associated errors, and each stars’ right ascension and
declination.
Now, in order to isolate the information of the
NN Ser system from the rest of the data points in
the cat files, a python code was written that would
recognize and extract the data on this binary system
from within each of the files. To do this an algorithm
was implemented in which the program would select
from each file the data point with the closest right
ascension and declination to that of the NN Ser system.
This was done by finding the data point within each file
that had the minimum square difference with the NN
Ser’s coordinates, as given by the following formula;
d = (ra − RA)2 + (δ − D)2 (1)
In here d represents the total distance of each data
point to the NN Ser’s coordinates, ra and δ are the right
ascension and declination of each data point respectively,
and RA and D the constant coordinate values for the
NN Ser, as given in section 1B.
After secluding the data for the NN Ser from
the cat files, the next step was to calibrate the aperture
magnitudes obtained from the CCD sensor to represent
the apparent magnitude of the stars. To do so we chose
two stars from the fit files and compared their aperture
magnitudes to the apparent V-Tycho magnitudes given
to them in the Sky-Map.net catalogue. Before this,
however, the Tycho magnitudes given by Sky-Map were
converted to the standard Johnson-Cousins passband
magnitudes by using the conversion formulas provided
by Mamajek et al. (2002). The function used to signal
out these two stars from each cat file and compare
them to their Sky-Map values was the same as that
used above to extract the NN Ser data points. The
average of the differences between the data and Sky-Map
3. 3
V-magnitude values, for each cat file, was then added to
all the aperture magnitudes of the NN Ser data points
in their corresponding cat file in order to convert them
into calibrated apparent magnitudes.
C. Graph Generation and Curve-Fitting
The last stage was to plot the graphs of the data col-
lected, and, using an existing curve-fitting function from
Python, draw a line of best fit for the data. Matplotlib’s
pyplot object was used to create four graphs in total.
The first (Fig.1) was a plot of the NN Ser’s uncalibrated
V-magnitudes against time, with the second plot (Fig.2)
being the same but with calibrated magnitudes instead.
The third graph (Fig.3) was a plot of the isophotal flux
as a function of time. Finally, the fourth plot (Fig.4) was
a scaled version of the second graph, with a sine wave
plotted to fit the data points. For all of these plots, the
time of each data point was specified to be the mid-point
of the exposure time, that is, 15 seconds after the expo-
sure started. To get a curve to fit the third plot, scipy’s
curve fit function was used. For the function to work, a
sine wave function was created and given as argument,
as well as an initial guess for the sine wave’s parameters.
This function would then return the fitted parameters of
the curve, as well as the errors in calculating such pa-
rameters.
6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5
Time of Observation [hr.]
8.5
8.0
7.5
7.0
6.5
6.0
UncalibratedApertureMagnitude
Uncalibrated V-Magnitude Light Curve
FIG. 1. Plot of the aperture magnitude of NN Serpentis, taken from Las Cumbres Observatory Global Telescope Network, as
a function of time. This plot shows some evidence for a fluctuation of NN Ser’s apparent magnitude with time, as well as a dip
in magnitude around 8.7 hours that is characteristic of a deep eclipse.
4. 4
6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5
Time of Observation [hr.]
16.0
16.5
17.0
17.5
18.0
18.5
CalibratedApparentMagnitude V-Magnitude Light Curve
FIG. 2. Plot of the calibrated apparent magnitude of NN Serpentis as a function of time. This plot shows a significant increase
in resolution from the uncalibrated plot in Fig.1. We can now see more clearly the periodic fluctuation of the binary system’s
apparent magnitude. The dip in magnitude caused by the red dwarf eclipsing the white dwarf around 8.7 hours is also more
evident. There exist a number of outliers between 8 and 8.5 hours that indicate the visibility of the sky around that time might
have been affected due to weather.
III. RESULTS
The graphs discussed in the previous section are
plotted below. The results given by these graphs turned
out to be very interesting, and it is valuable to run them
down one by one. As stated before, Fig.1 shows the
uncalibrated V-magnitude light curve. At first glance
this graph does not seem to have a concrete periodic
oscillation. Although this plot does show sign of a rela-
tion between the V-magnitude of NN Ser with time, the
seemingly rough ends and uneven spacings between the
minimums give little hope for finding a fitting model to
calculate the period of the binary’s orbit. Nevertheless,
by calibrating the aperture magnitudes into apparent
ones, in the process mentioned in section 2.B above, this
apparent chaotic result turns into a smooth waveform,
whose sinusoidal appearance is hard to overlook (Fig.2).
Looking at this graph we don’t only see with clarity a
periodic oscillation of the apparent magnitude, but there
also appears to be a hole in the plot once the data points
get close to the waveform’s minimum. This gap on the
outline of the graph is not due to lack of measurements,
but is instead the outcome of what is called a primary
eclipse. Since the white dwarf of this binary system is
almost half the size of its companion, and the inclination
of the system relative to us is close to 90◦
, when the
red dwarf’s orbit passes in front of its primary star,
the light emitted by the latter is completely blocked.
5. 5
6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5
Time of Observation [hr.]
10.0
9.5
9.0
8.5
8.0
7.5
7.0
6.5
6.0
IsophotalFlux
Time dependece of Isophotal Flux
FIG. 3. Graph of the Isophotal Flux of NN Serpentis, captured with an exposure time of 30 seconds by a CCD sensor, and
plotted as a function of time. This plot strongly correlates with the plot of apparent magnitude in Fig.2 as is expected since
the magnitude of a system is just the integral of the flux density over the filter’s banpass range. We see once again sinusoidal
fluctuations of the signal, as well as strong evidence of a deep eclipse around 8.7 hours, and signs for bad weather conditions
between 8 and 8.5 hours.
Therefore, for those brief minutes, we receive only the
light from the red dwarf, whose low temperature makes
its apparent magnitude so high (and its brightness so
low) that the system becomes no longer visible in the
V-bandpass region for the CCD sensor used. Such a
drastic change of magnitude during the eclipse is why
this phenomenon is also termed as a deep eclipse. This
effect can also be witnessed in Fig.6, in which the binary
star appears to completely fade away from the FITs
image, as compared to a few moments before, in Fig.5,
in which it ws completely visible. The error bars of both
these diagrams were taken to be the aperture magnitude
errors recorded for the binary in the cat files.
The next graph (Fig.3) serves as a verification of
the effects seen in the light curve of Fig.2. In it, the
sinusoidal aspect of the binary’s signal, as well as the
primary eclipse’s dip in signal around 8.7 hrs can be
recognized almost immediately. Notice also the set of
outliers between 8 and 8.5 hours present in both of these
graphs. The appearance of this outliers is thought to
be due to bad weather conditions during this time that
may have clouded the sky, thus making some of the
measurements produced in this range appear as if they
were dimmer. It is no surprise that the flux diagram
seems so closely related to the the light curve of Fig.2,
6. 6
6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5
Time of Observation [hr.]
16.0
16.2
16.4
16.6
16.8
17.0
17.2
CalibratedApparentMagnitude V-Magnitude Light Curve
Best Fit Curve
FIG. 4. A scaled up version of the light curve shown in Fig.2. This plot also has a sine wave of the form A sin(ω×t+φ)+b plotted
to fit the data. The sine wave seems to fit the data very closely, and thus serves as a good model for the periodic oscillation of
the binary star’s magnitude. With this fit, the angular frequency of the orbit was determined to be ω = 1.960 ± 0.014 rad−1
,
and thus the period to be P = 3.21 ± 0.11 hrs. The duration of the eclipse was also calculated to be ∆t = 0.176 ± 0.025 hrs.
after all, the magnitude of a system is just the integral
of its flux density over the specified band range.
A. Orbital Angular Frequency and Eclipse
Duration
The last graph presented (Fig.4) is a zoomed in
version of Fig.2 with a sine wave plotted to fit the data.
As explained in the methods section, this was possible
by using scipy’s curve fit function in python. The curve
of best fit generated through this method coincides very
accurately with the data points, as we see that the
curve passes through most of the data points’ error bars.
It is thus safe to say that this curve can serve as an
accurate model of the NN Ser’s light curve, at least in
the short-term range. The form of this sinusoidal curve
was A sin(ωt + φ) + b, and through curve fit the best-fit
parameters were found to be those shown below in Table
1. More specifically, the final wave plotted on this graph
was V = 0.293 sin(1.960t + 3.21) + 16.538.
There are three important aspects of these cal-
culated parameters. First of all, the angular frequency
of the magnitude, and thus the angular velocity of
the system’s orbit was calculated to be 1.960±0.014
rads/hr. This value will later be used to find the orbital
period of the NN Ser binary. The amplitude of the wave
described above also tells us the change in magnitude of
7. 7
-500-
500
FIG. 5. FITs image of the NN Serpentis system. In this image we can clearly see the appearance of the binary system, along
with some neighbor stars.
the system as it completes the orbit. The analysis of this
result will be shown in the next section (3.B). Finally,
we see that the waveform is centered at a magnitude
of 16.538±0.004 which relates very closely to the calcu-
lated mean V-magnitude of 16.8 by Haefner et al. (1989).
From the curve fit function it was also possible
to obtain the variance of the best fit parameters calcu-
lated. These values were then square rooted to give the
standard deviation of each parameter, and thus used
as their respective errors. From this graph it was also
possible to obtain the duration of the secondary eclipse.
This was calculated as being the time difference between
the midpoints of both the last data point before the
magnitude dip and the first recording after it, and the
last exposure of this event and the first data point back
near the fitted waveform. This way, the duration of the
eclipse (∆t) was found to be around 10.56 ± 1.5 min,
which is very close to the value found by Haefner et al.
(1989) to be around 12 min. The error in the calculation
of this value takes into account the amount of time
between the observations of the transition from the
waveform magnitude to the eclipsed value.
8. 8
-500-
500
FIG. 6. FITs image of the NN Serpentis system during a primary eclipse. This image is centered around the same location
in space as Fig.5, but NN Serpentis does not appear to be visible. This is a clear indication of the large change in magnitude
this binary undergoes through whenever the red dwarf passes in front of its primary, in what is generally called a deep eclipse.
More over, this total eclipse gives evidence for the inclination of the system being close to 90◦
.
B. The NN Ser Orbit and the Reflection Effect
One last thing to make sense of from the light curves
plotted in Fig.2 and Fig.4 is the respective orbital mo-
tion of the stellar objects in the system, along with the
reasoning behind this periodic motion of the apparent
magnitudes. As stated a couple of times before, the
minimum point in the light curves, where the dip in
magnitude occurs, corresponds to the eclipse of the
white dwarf by the red dwarf. It is known that the orbit
of these two stars are circular and not eccentric since the
tidal interactions of a pre-cataclysmic variable eliminate
any initial eccentricity in the system’s orbit (Warner
et al., 1989). This effect is also visible in the light curves
plotted, as any eccentricity in the orbit would cause
there to be different time displacements in between
extrema. With this being said, it is quite obvious that
the moment in which the red dwarf is situated behind
the white dwarf, in what is called a secondary eclipse, is
exactly one half-period away from the primary eclipse.
9. 9
This result is seemingly contradicting at first
due to the fact that the brightness of the binary system
seems to increase when the red dwarf is covered. The
reason behind this increase in brightness when the white
dwarf is in front of the red dwarf is what is usually
referred to as the reflection effect. This a phenomenon
caused by the red dwarf’s absorption and re-emission
of the white dwarf’s radiation (Hellier et al., 2001).
Now, since the red dwarf is tidally locked to the white
dwarf due to tidal interactions (J. Horner et al., 2012),
there is only one side of the red dwarf the absorbs all
the incoming radiation from the white dwarf, making
that side significantly hotter than the rest of its mass.
Since in stellar objects higher temperatures mean higher
brightnesses (and thus lower magnitudes), the side of
the red dwarf facing the white dwarf has a substantially
brighter surface than the rest of its body. That being
said, when the white dwarf is in front of the red dwarf,
the secondary’s brightest surface is also pointing directly
at Earth, and so we receive both the light of the white
dwarf, and it’s companion’s highest brightness, thus
reaching a maximum in the light curve.
With this known, we return to the amplitude
calculated for the light curve’s fitted waveform in Fig.4.
This amplitude tells us the change in magnitude of
the system as it completes the orbit. The only thing
changing throughout these stars’ orbit, in terms of the
brightness emitted towards the earth, is the angle at
which we face the hottest and brightest region of the
red dwarf. Therefore, the amplitude of the fitted sine
wave (0.293 ± 0.006) gives us a relation between the
brightnesses of the red dwarfs’ faces, and thus a relation
between each sides temperature. Specifically, this result
tells us that the brightest and dimmest faces of the red
dwarf have a magnitude difference of twice the derived
amplitude (0.586 ± 0.012). Although this result will not
be fully explored in this paper, it should pose as an
interesting calculation for any future observations on the
system’s temperature distribution.
IV. CALCULATIONS
Now that the sinusoidal aspect of the NN Ser system
was modeled and used to find the angular frequency of
the orbit, it is time to use these results to find some
defining parameters of the system. Unfortunately there
are very few things that can be done with only the data
that was used for this lab. One of the few parameters
that can be calculated on its own is the period of the
orbit. For this, the following equation was used, with P
being the period in hrs:
P =
2π
ω
(2)
The result of this calculation, along with all the ones that
will follow, are displayed in Table 1.1 below. With a value
of approximately 3.21 hrs, the period calculated closely
approaches its published value of 3.12 hrs (Brinkworth
et al., 2006). Notice also that all of the derived values
below take into account the errors of their calculations.
The propagation of this error was done by using the un-
certainties’ ufloat function in python, which was checked
throughout to show accurate error values.
Parameters Other sources Derived % Error
ω(rads/hr) - 1.960±0.014 -
A(magnitude) - 0.293±0.006 -
b(magnitude) ∗
16.8 16.538±0.004 1.6
φ(rads) - 3.21±0.011 -
∆t(min) 12 10.56±1.5 12
M1(M ) 0.535±0.012 - -
M2(M ) 0.111±0.004 - -
R1(R ) 0.0211±0.0002 - -
R2(R ) 0.149±0.002 0.184±0.023 23.5
P(hrs) 3.12 3.206±0.023 2.9
i(◦
) 0.149±0.002 -
q(M2/M1) 0.207±0.006 - -
a(R ) 0.934±0.009 0.947±0.016 1.4
Vt(km/s) - 359±6 -
TABLE I. List of all the parameter values acquired from other
sources, as well as the ones derived in this lab. The percent-
age error of the derived values with the accepted ones is also
shown. All the published values were taken from Parson et al.
(2010) and ∗
Haefner et al. (1989)
For the following calculations, three parameter values
were extracted from the literature, to compute a total of
six parameters. The first two of the parameters taken
from Parsons et al. (2010) are the mass ratio of the stars
and the mass of the primary star. The former of these two
has a value of about 0.207, as shown in the table above
as q. This ratio, along with the white dwarfs mass, also
given above, was later on used to calculate the separation
of the two stars, a, by using Keppler’s third law in the
10. 10
following form:
a3
=
GP2
orbitM1(1 + q)
4π2
(3)
This equation gave a separation between stars of
0.947 ± 0.016R , whose accepted value of 0.934R falls
within its errors.
The next step taken was to use the newly ac-
quired values of the period and star separation in an
equation to obtain the tangential velocity of the red
dwarf, Vt, modeled as if it travelled around the whit
dwarf in a perfect circle. As explained before, due
to tidal interactions, the orbit of this pre-cataclysmic
variable is circular and this model renders as an accurate
description of the system’s orbit.
Vt =
2πa
P
(4)
The tangential velocity of the red dwarf taken this way
was found to be 359 ± 6km/s.
Now, assuming that the white dwarf is small enough,
as compared to the red dwarf and the separation between
them, that it can be taken to be as a dot, the equation
to find the radius of the red dwarf becomes:
R2 =
Vt × ∆t
2
(5)
From which we see that the secondary star has a radius
a little less than a fifth of that of the sun. Notice how
this is the calculation with the biggest percentage error
with 23.5%. The big errors involved in this calculation
are thought to be a result of all the approximations that
were used to acquire this value.
By checking once again at the parameter values
in Table 1, we can see how close the calculated values
were to the already published ones, with each of them
having a percentage error of less than 3%, with the
exception of the red dwarf’s radius.
V. CONCLUSION
In this lab we were able to use FIT data files of the
NN Serpentis pre-cataclysmic variable, taken by Las
Cumbres Observatory Global Telescope Network, to
plot the V-band light curve of this binary system. After
calibration of the magnitudes, and curve fitting using
Python, the sinusoidal aspect of this binary’s light curve
was exposed. From here, the orbital period of the two
stars, P, was calculated to be 3.206±0.023 hrs, differing
only by 2.9% from the published value. Through this
process, the mean V-magnitude of the system, b, and
the amplitude of the magnitude change for each periodic
oscillation, A, were able to be computed. The light
curves plotted were also used to determine the length
of the periodic deep eclipse caused by the red dwarf
on the white dwarf primary, found to be 10.56 ± 1.5
min. Finally, these results, along with some parameter
values taken from the scientific literature, were used to
calculate the radius (R2) and tangential velocity (Vt) of
the white dwarf, as well as the separation (a) between
the two stars in the system to be 0.184 ± 0.023 R ,
359 ± 6 km/s, and 0.947 ± 0.016 R , respectively. All of
the calculated parameters were within the scope of the
accepted values, and, with the exception of R2, they all
had percentage errors of less than 3%.
Due to the general low percentage error of the
derived values in this observation, this experiment can
be termed successful. Nonetheless, the lack of data in
other bandpass filters (apart from V), and the short
amount of time of the recordings, exerted a constraint on
the potential of this observation’s findings. This should
be taken into account when taking future observations.
Also, from the amplitude change (A) of the system,
a more detailed analysis can be done to calculate the
temeprature distribution of the red dwarf.
VI. CURRENT RESEARCH
Recent studies surrounding the NN Serpentis binary
system concern about the existence of a planetary sys-
tem in its orbit. This theory was proposed due to some
small variations in the binary’s orbital period, which
could be explained by the gravitational interaction with
planets orbiting it. The latest studies suggest that there
are two gas planets orbiting the pre-cataclysmic variable,
each with an orbit of 15.5 and 7.7 years, and a mass of
6.9MJup and 2.2MJup, respectively, where MJup repre-
sents Jupiter masses (Beuerman et al., 2010). Studying
such a system offers the opportunity to understand bet-
11. 11
ter the evolution and formation of planets and stars in a
pre-cataclysmic variable.
VII. REFERENCES
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Precataclysmic Binary with Very Deep Eclipses.”
Astronomy and Astrophysics 213.1-2 (1989): L15-18.
Web. 20 May 2016.
-Hellier, Coel. Cataclysmic Variable Stars: How and
Why They Vary. London: Springer, 2001. Print.
- Horner, J., R. A. Wittenmyer, T. C. Hinse, and C.
G. Tinney. ”A Detailed Investigation of the Proposed
NN Serpentis Planetary System.” Monthly Notices of
the Royal Astronomical Society 425.1 (2012): 749-56.
Web.
- Parsons, S. G., T. R. Marsh, C. M. Copperwheat,
V. S. Dhillon, S. P. Littlefair, B. T. Gnsicke, and R.
Hickman. ”Precise Mass and Radius Values for the
White Dwarf and Low Mass M Dwarf in the
Pre-cataclysmic Binary NN Serpentis.” Monthly
Notices of the Royal Astronomical Society 402.4
(2010): 2591-608. Web.
- Warner, Brian. Cataclysmic Variable Stars.
Cambridge: Cambridge UP, 1995. Print.
- Wilson, Miller, Africano, Goodrich, and Mahaffey.
”Photoelectric Photometry of Six Cataclysmic
Variable Stars.” Astronomy and Astrophysics
Supplement Series 66.3 (Dec. 1986): 323-30. Web.
20 May 2016..
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M. R. Schreiber, W. Kley, V. S. Dhillon, S. P.
Littlefair, C. M. Copperwheat, and J. J. Hermes.
”Two Planets Orbiting the Recently Formed
Post-common Envelope Binary NN Serpentis.”
Astronomy and Astrophysics AA 521 (2010): n. pag.
Web.
- Mamajek, Eric E., Michael R. Meyer, and James
Liebert. ”PostT Tauri Stars in the Nearest OB
Association.” The Astronomical Journal 124.3
(2002): 1670-694. Web.