This document reports on the first direct detection of the central star of the planetary nebula NGC 6302 using the Wide Field Camera 3 on the Hubble Space Telescope. Photometry of the central star was obtained in two narrowband filters, F469N and F673N, from which the reddening was estimated to be c=3.1, corresponding to AV=6.6 magnitudes of extinction. Comparison to evolutionary tracks suggests the central star has a temperature of around 200,000 K, luminosity of 2000 L☉, and the nebula is around 2,200 years old. The high extinction from dust in the nebula had previously prevented direct detection of the central star.
The stellar content_of_the_ring_in_ngc660Sérgio Sacani
The document summarizes the results of a stellar photometry study of the polar ring galaxy NGC 660 using archival Hubble Space Telescope images. Over 550 stars were resolved, including many blue and red supergiants belonging to the polar ring. Analysis of the color-magnitude diagram for polar ring stars showed they are best represented by isochrones with a metallicity of Z=0.008. Star formation in the polar ring appears to have been continuous, with the youngest detected stars having an age of about 7 million years.
This document summarizes a study that used optical, infrared, and submillimeter data to examine star formation in the region surrounding the IC 348 star cluster and the nearby Flying Ghost Nebula. The study identified 13 protostars driving protostellar outflows in the region, including HH 211 which had not previously been detected at visible wavelengths. The region surrounding the Flying Ghost Nebula shows ongoing star formation with outflows similar to other areas of moderate star formation in Perseus. A candidate bent jet was also found, which may have been ejected from a multiple star system near IC 348.
This document summarizes a study of the young star cluster IC 5146. Optical and near-infrared photometry were obtained for over 700 stars in the region, including around the illuminating stars BD +46°3474 and the embedded variable star BD +46°3471. Around 100 emission-line stars brighter than R=20.5 were found, most in IC 5146. Spectroscopy of 38 stars found an average extinction of AV=3.0 mag. The age distribution of the emission-line stars was estimated from theoretical isochrones to have a median age of around 1 Myr.
The central star_of_the_planetary_nebula_ngc_6537Sérgio Sacani
1) HST images of the planetary nebula NGC 6537 fail to detect its central star, placing an upper limit on its magnitude of fainter than 22.4.
2) This limit is used to derive a lower limit for the star's temperature of at least 500,000 K based on Zanstra temperature analysis.
3) The energy balance temperature method, which does not require direct observation of the star, yields a temperature consistent with 500,000 K, as does the ionization state of the nebula.
1. This document describes a multiwavelength campaign on the Seyfert 1 galaxy Mrk 509 using five satellites and two ground-based facilities.
2. The campaign aims to study several open questions about active galactic nuclei (AGN), including the location and physics of outflows from AGN, the nature of continuum emission, the geometry and physical state of the X-ray broad emission line region, and the Fe-K line complex.
3. The observations cover more than five decades in frequency, from 2 μm to 200 keV, and include a simultaneous set of deep XMM-Newton and INTEGRAL observations over seven weeks. This allows the authors to disentangle different components and study time variability
This document reports the discovery of the central star of the planetary nebula IC 4663, which exhibits spectral properties that mimic a nitrogen-rich Wolf-Rayet star of spectral type [WN3]. This makes it the first unambiguous case of a planetary nebula central star taking on the properties of a Wolf-Rayet star. The central star is dominated by broad helium and nitrogen emission lines. The surrounding nebula is definitively a planetary nebula based on its morphology and chemical abundances. The discovery provides evidence for an alternative evolutionary pathway for some hydrogen-deficient, helium-rich post-asymptotic giant branch stars.
Three newly discovered_globular_clusters_in_ngc6822Sérgio Sacani
This document describes the discovery of three new globular clusters in the Local Group dwarf irregular galaxy NGC 6822. The authors present optical photometry of the clusters from archival CFHT/Megacam data. Two clusters are luminous and compact, while the third is a lower luminosity diffuse cluster. The positions of the new clusters are consistent with the linear alignment of previously known clusters in NGC 6822. Studying globular cluster systems in dwarf galaxies provides insights into the formation of larger galaxies through accretion and mergers.
Creation of cosmic structure in the complex galaxy cluster merger abell 2744Sérgio Sacani
Abell 2744 is one of the most actively merging galaxy clusters known, appearing to have "dark", "ghost", "bullet", and "stripped" substructures of around 1014 solar masses each. The cluster shows a complex phenomenology that will challenge simulations to reproduce. The authors present a detailed strong lensing, weak lensing, and X-ray analysis of Abell 2744, identifying 34 strongly lensed images around the massive Southern core and producing the most detailed mass map to date. They find evidence that the Southern core and Northwestern substructure are post-merger systems similar to the Bullet Cluster viewed from an angle, and derive a new constraint on the self-interaction cross section of dark matter particles. They
The stellar content_of_the_ring_in_ngc660Sérgio Sacani
The document summarizes the results of a stellar photometry study of the polar ring galaxy NGC 660 using archival Hubble Space Telescope images. Over 550 stars were resolved, including many blue and red supergiants belonging to the polar ring. Analysis of the color-magnitude diagram for polar ring stars showed they are best represented by isochrones with a metallicity of Z=0.008. Star formation in the polar ring appears to have been continuous, with the youngest detected stars having an age of about 7 million years.
This document summarizes a study that used optical, infrared, and submillimeter data to examine star formation in the region surrounding the IC 348 star cluster and the nearby Flying Ghost Nebula. The study identified 13 protostars driving protostellar outflows in the region, including HH 211 which had not previously been detected at visible wavelengths. The region surrounding the Flying Ghost Nebula shows ongoing star formation with outflows similar to other areas of moderate star formation in Perseus. A candidate bent jet was also found, which may have been ejected from a multiple star system near IC 348.
This document summarizes a study of the young star cluster IC 5146. Optical and near-infrared photometry were obtained for over 700 stars in the region, including around the illuminating stars BD +46°3474 and the embedded variable star BD +46°3471. Around 100 emission-line stars brighter than R=20.5 were found, most in IC 5146. Spectroscopy of 38 stars found an average extinction of AV=3.0 mag. The age distribution of the emission-line stars was estimated from theoretical isochrones to have a median age of around 1 Myr.
The central star_of_the_planetary_nebula_ngc_6537Sérgio Sacani
1) HST images of the planetary nebula NGC 6537 fail to detect its central star, placing an upper limit on its magnitude of fainter than 22.4.
2) This limit is used to derive a lower limit for the star's temperature of at least 500,000 K based on Zanstra temperature analysis.
3) The energy balance temperature method, which does not require direct observation of the star, yields a temperature consistent with 500,000 K, as does the ionization state of the nebula.
1. This document describes a multiwavelength campaign on the Seyfert 1 galaxy Mrk 509 using five satellites and two ground-based facilities.
2. The campaign aims to study several open questions about active galactic nuclei (AGN), including the location and physics of outflows from AGN, the nature of continuum emission, the geometry and physical state of the X-ray broad emission line region, and the Fe-K line complex.
3. The observations cover more than five decades in frequency, from 2 μm to 200 keV, and include a simultaneous set of deep XMM-Newton and INTEGRAL observations over seven weeks. This allows the authors to disentangle different components and study time variability
This document reports the discovery of the central star of the planetary nebula IC 4663, which exhibits spectral properties that mimic a nitrogen-rich Wolf-Rayet star of spectral type [WN3]. This makes it the first unambiguous case of a planetary nebula central star taking on the properties of a Wolf-Rayet star. The central star is dominated by broad helium and nitrogen emission lines. The surrounding nebula is definitively a planetary nebula based on its morphology and chemical abundances. The discovery provides evidence for an alternative evolutionary pathway for some hydrogen-deficient, helium-rich post-asymptotic giant branch stars.
Three newly discovered_globular_clusters_in_ngc6822Sérgio Sacani
This document describes the discovery of three new globular clusters in the Local Group dwarf irregular galaxy NGC 6822. The authors present optical photometry of the clusters from archival CFHT/Megacam data. Two clusters are luminous and compact, while the third is a lower luminosity diffuse cluster. The positions of the new clusters are consistent with the linear alignment of previously known clusters in NGC 6822. Studying globular cluster systems in dwarf galaxies provides insights into the formation of larger galaxies through accretion and mergers.
Creation of cosmic structure in the complex galaxy cluster merger abell 2744Sérgio Sacani
Abell 2744 is one of the most actively merging galaxy clusters known, appearing to have "dark", "ghost", "bullet", and "stripped" substructures of around 1014 solar masses each. The cluster shows a complex phenomenology that will challenge simulations to reproduce. The authors present a detailed strong lensing, weak lensing, and X-ray analysis of Abell 2744, identifying 34 strongly lensed images around the massive Southern core and producing the most detailed mass map to date. They find evidence that the Southern core and Northwestern substructure are post-merger systems similar to the Bullet Cluster viewed from an angle, and derive a new constraint on the self-interaction cross section of dark matter particles. They
Stars and gas_in_the_very_large_interacting_galaxy_ngc6872Sérgio Sacani
This document summarizes observations of stars and gas in the interacting galaxy NGC 6872 using radio telescope data and numerical simulations. It finds:
1) NGC 6872 contains 1.4x1010 solar masses of atomic hydrogen gas distributed in an extended rotating disk.
2) Massive gas concentrations of about 109 solar masses are detected at the tips of both tidal tails and in the northern optical arm near a companion galaxy.
3) Simulations reproducing the galaxy's morphology, inner bar, tidal tail extent and thinness support a gravitational interaction scenario with a small nearby companion galaxy.
A possible carbonrich_interior_in_superearth_55_cancrieSérgio Sacani
1) The document analyzes the possibility that the interior of the super-Earth exoplanet 55 Cancri e could be carbon-rich rather than oxygen-rich.
2) Models that assume an oxygen-rich interior with iron, silicates, and a water envelope cannot fully explain 55 Cancri e's mass and radius measurements. However, a carbon-rich interior containing iron, silicon carbide, and/or carbon could explain the observations without needing a volatile envelope.
3) A carbon-rich interior for 55 Cancri e is plausible given the reported carbon-rich composition of its host star, though more data is needed on the star's elemental abundances and the planet's atmosphere.
A supermassive black_hole_in_a_ultra_compact_dwarf_galaxySérgio Sacani
Hubble e Gemini observam a galáxia ultra compacta M60-UCD1 e por meio de imagens e medidas de espectrometria descobrem buraco negro que representa 15% da massa da galáxia. Um buraco negro gigante em uma galáxia anã.
This study uses asteroseismology to reveal fast core rotation in red giant stars, finding that the cores rotate at least 10 times faster than the surface by analyzing rotational splitting of mixed modes. Mixed modes that probe the core show larger rotational splitting than modes dominated by the outer layers, indicating non-rigid rotation that increases towards the stellar interior. Models are able to reproduce the observations, confirming theoretical predictions of a steep rotational gradient within red giant cores.
The new approach provides practical considerations for selection of the elements and their isotopes suitable for cold fusion energy and minimization of the radioactive waste.
Dust production and_particle_acceleration_in_supernova_1987_a_revealed_with_almaSérgio Sacani
This document presents spatially resolved submillimeter observations of supernova remnant SN 1987A using the Atacama Large Millimeter/Submillimeter Array (ALMA). The observations reveal that at longer wavelengths (2.8 mm - 1.4 mm), the emission is from a torus associated with the supernova shock wave, while at shorter wavelengths (870 μm - 450 μm) the emission is dominated by the inner supernova ejecta. For the first time, the dust emission is unambiguously shown to originate from the inner ejecta rather than from the surrounding material, supporting theoretical models of significant dust production in supernovae. The observations also allow separation of synchrotron emission from shock-accelerated particles in
The identification of_93_day_periodic_photometric_variability_for_yso_ylw_16aSérgio Sacani
This study identifies a 93 day periodic photometric variability in the Class I young stellar object (YSO) YLW 16A in the Rho Ophiuchus star forming region. Light curve analysis reveals variations of ~0.5 magnitudes in the Ks band over this period. The authors propose a triple system model consisting of an inner binary with a 93 day period eclipsed by a warped circumbinary disk, with a tertiary companion at ~40 AU responsible for warping the disk. This model is similar to one previously proposed for another YSO, WL 4, and may indicate such triple systems with eclipsing disks are common around young stars. Understanding these systems can provide insights into stellar and planetary formation and evolution.
A mildly relativistic wide-angle outflow in the neutron-star merger event GW1...Sérgio Sacani
GW170817 was the first gravitational wave detection of a binary
neutron-star merger1
. It was accompanied by radiation across the
electromagnetic spectrum and localized2
to the galaxy NGC 4993
at a distance of 40 megaparsecs. It has been proposed that the
observed γ-ray, X-ray and radio emission is due to an ultrarelativistic
jet launched during the merger, directed away from
our line of sight3–6. The presence of such a jet is predicted from
models that posit neutron-star mergers as the central engines
that drive short hard γ-ray bursts7,8
. Here we report that the radio
light curve of GW170817 has no direct signature of an off-axis
jet afterglow. Although we cannot rule out the existence of a jet
pointing elsewhere, the observed γ-rays could not have originated
from such a jet. Instead, the radio data require a mildly relativistic
wide-angle outflow moving towards us. This outflow could be the
high-velocity tail of the neutron-rich material dynamically ejected
during the merger or a cocoon of material that breaks out when a
jet transfers its energy to the dynamical ejecta. The cocoon model
explains the radio light curve of GW170817 as well as the γ-rays
and X-rays (possibly also ultraviolet and optical emission)9–15, and
is therefore the model most consistent with the observational data.
Cocoons may be a ubiquitous phenomenon produced in neutronstar
mergers, giving rise to a heretofore unidentified population of
radio, ultraviolet, X-ray and γ-ray transients in the local Universe
Graphical 3D Modeling of Molecules and Nanostructures in Sub-nanometer Scale ...Stoyan Sarg Sargoytchev
The Basic Structures of Matter – Supergravitation Unified Theory (BSM-SG) reveals non-spherical shapes of the stable elementary particles, composed of two types of helical structures with opposite twisting. Proton and neutron have one and the same toroidal sub-structure, but the shape of proton is a twisted torus like the figure 8, while the neutron is a double folded. The shape of proton permits modulation of the space fabrics creating a positive E-field. At neutron such modulation is locked in the near field, so it is not detectable, but when in motion it creates a magnetic field. Due to it’s near E-field the neutron is stable over the proton, forming a deuteron. The electron is a different three body system with two intrinsic frequencies. Its structure and dynamic properties provide classical explanations of: Compton frequency, anomalous magnetic moment, spin and relativistic effect of mass increase. The near Coulomb field of the proton defines the trace of orbiting electron. The atomic nuclei are 3D compositions of protons and neutrons, kept by the attractive supergravitational forces, while balancing the repulsive forces between protons. The increase of number of protons reveals the build-up trend of the atomic nuclei showing a perfect match with the pattern of the Periodic Table. The features defining the valences and the angular restrictions of the chemical bonds are apparent. The rotational freedom of neutrons over protons is behind the nuclear magnetic moment. The BSM-SG atomic models are convenient for 3D graphical modeling of complex molecules and nanostructures with sub-nanometer resolution.
Theoretical Feasibility of Cold Fusion According to the BSM-SG Unified TheoryStoyan Sarg Sargoytchev
Report at 31 Annual Meeting of SSE, 2012
Advances in the field of cold fusion or LENR need a deeper understanding of the nuclear reactions and, more particularly, the possibility for modification of the Coulomb barrier. The treatise “Basic Structures of Matter – Supergravitation Unified Theory”, based on an alternative concept of the physical vacuum, suggests non spherical shapes of the protons and neutrons. Held by strong nuclear forces the non-spherical protons and neutrons form atomic nuclei as fractal three-dimensional structures. Such nuclear structures exhibit an excellent match to the pattern of Periodic Table, showing signatures of valences, and angular restrictions of the chemical bonds. The Coulomb barrier in these nuclear structures does not converge to a small size according to the Bohr nuclear model and it could be modified by some technical methods. The analysis of some cold fusion experiments, using BSM-SG model, resulted for practical and suggestions for other nuclear reactions.
Video-record: http://www.youtube.com/watch?v=S3gJp8rLHWg
A giant galaxy in the young Universe with a massive ringSérgio Sacani
In the local (redshift z ≈ 0) Universe, collisional ring galaxies make up only ~0.01% of galaxies1 and are formed by head-on galactic collisions that trigger radially propagating density waves2–4. These striking systems provide key snapshots for dissecting galactic disks and are studied extensively in the local Universe5–9. However, not much is known about distant (z > 0.1) collisional rings10–14. Here we present a detailed study of a ring galaxy at a look-back time of 10.8 Gyr (z = 2.19). Compared with our Milky Way, this galaxy has a similar stellar mass, but has a stellar half-light radius that is 1.5–2.2 times larger and is forming stars 50 times faster. The extended, dif- fuse stellar light outside the star-forming ring, combined with a radial velocity on the ring and an intruder galaxy nearby, provides evidence for this galaxy hosting a collisional ring. If the ring is secularly evolved15,16, the implied large bar in a giant disk would be inconsistent with the current understand- ing of the earliest formation of barred spirals17–21. Contrary to previous predictions10–12, this work suggests that massive col- lisional rings were as rare 11 Gyr ago as they are today. Our discovery offers a unique pathway for studying density waves in young galaxies, as well as constraining the cosmic evolution of spiral disks and galaxy groups.
Confirmation of the_planetary_microlensing_signal_and_star_and_planet_mass_de...Sérgio Sacani
This document summarizes follow-up Hubble Space Telescope observations of the planetary microlensing event OGLE-2005-BLG-169. The HST observations confirm the relative proper motion between the source and lens stars predicted by the planetary signal in the original light curve. This provides the first confirmation of a planetary microlensing signal. The HST observations also measure the brightness of the planetary host star, allowing a precise determination of the planet and host star masses as well as their projected separation. Combined with measurements from Keck adaptive optics, the HST observations confirm the identification of the lens star and characterization of the planetary system.
1) The document reports on optical spectroscopic monitoring of the ultraluminous X-ray source M 101 ULX-1.
2) Analysis revealed the companion is a Wolf-Rayet star in an 8.2 day orbit around a black hole with a minimum mass of 5 solar masses.
3) M 101 ULX-1 has an exceptionally soft X-ray spectrum that violates expectations for accretion onto stellar-mass black holes, challenging current models of ultraluminous X-ray sources.
Detection of magnetic_fields_in_both_b_type_components_of_epsilon_lupi_system...Sérgio Sacani
Uma equipe de astrônomos detectou um chamado campo magnético fóssil em ambos os componentes de um sistema estelar binário, chamado de Epsilon Lupi.
Epsilon Lupi, também conhecida como HD 136504, é uma estrela binária brilhante, localizada na constelação do hemisfério sul de Lupus.
O par de estrelas está localizado a aproximadamente 500 anos-luz de distância da Terra, e cada estrela tem entre 7 e 8 vezes a massa do Sol, e combinadas, elas têm cerca de 6000 vezes a luminosidade do Sol.
Os astrônomos sabem de muito tempo que a Epsilon Lupi é um sistema binário, mas não tinham ideia de que as duas estrelas pudessem possuir campos magnéticos.
“A origem do magnetismo entre estrelas massivas é um mistério e essa descoberta pode ajudar a trazer uma luz numa questão de por que essas estrelas possuem campos magnéticos”, disse Matt Shultz da Universidade de Queen no Canadá, e o principal autor do artigo aceito para publicação no Monthly Notices of the Royal Astronomical Society e que descreve a descoberta.
Evidence for an intermediate-mass black hole in the globular cluster NGC 6624Sérgio Sacani
This document summarizes evidence for an intermediate-mass black hole located at the center of the globular cluster NGC 6624. The authors present over 25 years of timing observations of the millisecond pulsar PSR B1820-30A, which is located very close to the cluster center. Modeling of the higher order rotational frequency derivatives reveals that the pulsar is likely in a high-eccentricity orbit around a massive companion with a mass greater than 7500 solar masses located at the cluster center, which would be an intermediate-mass black hole. Additional evidence from modeling the cluster gravitational potential and dynamics supports the presence of a central black hole with a minimum mass of around 60,000 solar masses. The observations of this
The behaviour of_dark_matter_associated_with_4_bright_cluster_galaxies_in_the...Sérgio Sacani
The document presents new Hubble Space Telescope imaging and Very Large Telescope integral-field spectroscopy of galaxy cluster Abell 3827. It finds that each of the four central galaxies in the cluster's 10 kpc core retains an associated massive dark matter halo. At least one galaxy is offset from its dark matter halo, with an offset of 1.62+0.50−0.47 kpc, within the uncertainties of mass modeling and statistical errors. If interpreted as evidence for self-interacting dark matter, this offset implies a dark matter self-interaction cross-section of (1.7 ± 0.7)×10−4 cm2/g.
Hoag's Object is a peculiar ring galaxy with a central elliptical core. New observations from Hubble Space Telescope and Russian 6-m telescope provide additional data on its structure and kinematics. The data show Hoag's Object has an old stellar core surrounded by a luminous quasi-spiral pattern and massive HI disk. Previous formation scenarios are reviewed in light of the new data. A new scenario is proposed where the elliptical core formed early in the Universe and the HI disk later formed by cold accretion of primordial gas.
This document discusses optomechanics and the use of quantum optics techniques to control mechanical systems. It provides a brief history of mechanical effects of light, including early predictions of radiation pressure and recent experiments cooling mechanical modes into the quantum ground state using laser radiation pressure. Current optomechanical systems are described, along with proposals to generate optomechanical entanglement and use optomechanics to teleport quantum states. Requirements for achieving quantum optomechanics experiments are discussed, and progress on developing systems meeting these requirements is summarized.
The physical conditions_in_a_pre_super_star_cluster_molecular_cloud_in_the_an...Sérgio Sacani
The document summarizes a study of an extreme molecular cloud in the Antennae galaxies that has properties consistent with forming a globular cluster. ALMA observations reveal a cloud with a radius of 24 pc and mass greater than 5 million solar masses. While capable of forming a globular cluster, a lack of associated thermal radio emission indicates star formation has not yet begun to alter the environment, suggesting the cloud is in an early stage of evolution. For the cloud to be confined as observed, an external pressure over 10,000 times greater than typical interstellar pressure is required, supporting the theory that high pressures are needed to form globular clusters in extreme environments like mergers.
This document appears to be a citation to a 1987 astronomical journal article with the volume number 93 and page number 1514 by an author with the last name Z. The citation is repeated multiple times but there is no other contextual information provided about the article itself.
Kinematics and the_origin_of_the_internal_structures_in_hl_tau_jet_hh151Sérgio Sacani
1) The document analyzes the kinematics and origin of internal structures in the HL Tau jet (HH 151).
2) It finds that structures with low and high radial velocities show the same proper motion, indicating they represent bow shocks and Mach disks from episodic outflows.
3) The bend in the jet and increase in brightness coincides with a stationary deflecting shock, and interactions with the ambient medium could explain changes in structure.
Stars and gas_in_the_very_large_interacting_galaxy_ngc6872Sérgio Sacani
This document summarizes observations of stars and gas in the interacting galaxy NGC 6872 using radio telescope data and numerical simulations. It finds:
1) NGC 6872 contains 1.4x1010 solar masses of atomic hydrogen gas distributed in an extended rotating disk.
2) Massive gas concentrations of about 109 solar masses are detected at the tips of both tidal tails and in the northern optical arm near a companion galaxy.
3) Simulations reproducing the galaxy's morphology, inner bar, tidal tail extent and thinness support a gravitational interaction scenario with a small nearby companion galaxy.
A possible carbonrich_interior_in_superearth_55_cancrieSérgio Sacani
1) The document analyzes the possibility that the interior of the super-Earth exoplanet 55 Cancri e could be carbon-rich rather than oxygen-rich.
2) Models that assume an oxygen-rich interior with iron, silicates, and a water envelope cannot fully explain 55 Cancri e's mass and radius measurements. However, a carbon-rich interior containing iron, silicon carbide, and/or carbon could explain the observations without needing a volatile envelope.
3) A carbon-rich interior for 55 Cancri e is plausible given the reported carbon-rich composition of its host star, though more data is needed on the star's elemental abundances and the planet's atmosphere.
A supermassive black_hole_in_a_ultra_compact_dwarf_galaxySérgio Sacani
Hubble e Gemini observam a galáxia ultra compacta M60-UCD1 e por meio de imagens e medidas de espectrometria descobrem buraco negro que representa 15% da massa da galáxia. Um buraco negro gigante em uma galáxia anã.
This study uses asteroseismology to reveal fast core rotation in red giant stars, finding that the cores rotate at least 10 times faster than the surface by analyzing rotational splitting of mixed modes. Mixed modes that probe the core show larger rotational splitting than modes dominated by the outer layers, indicating non-rigid rotation that increases towards the stellar interior. Models are able to reproduce the observations, confirming theoretical predictions of a steep rotational gradient within red giant cores.
The new approach provides practical considerations for selection of the elements and their isotopes suitable for cold fusion energy and minimization of the radioactive waste.
Dust production and_particle_acceleration_in_supernova_1987_a_revealed_with_almaSérgio Sacani
This document presents spatially resolved submillimeter observations of supernova remnant SN 1987A using the Atacama Large Millimeter/Submillimeter Array (ALMA). The observations reveal that at longer wavelengths (2.8 mm - 1.4 mm), the emission is from a torus associated with the supernova shock wave, while at shorter wavelengths (870 μm - 450 μm) the emission is dominated by the inner supernova ejecta. For the first time, the dust emission is unambiguously shown to originate from the inner ejecta rather than from the surrounding material, supporting theoretical models of significant dust production in supernovae. The observations also allow separation of synchrotron emission from shock-accelerated particles in
The identification of_93_day_periodic_photometric_variability_for_yso_ylw_16aSérgio Sacani
This study identifies a 93 day periodic photometric variability in the Class I young stellar object (YSO) YLW 16A in the Rho Ophiuchus star forming region. Light curve analysis reveals variations of ~0.5 magnitudes in the Ks band over this period. The authors propose a triple system model consisting of an inner binary with a 93 day period eclipsed by a warped circumbinary disk, with a tertiary companion at ~40 AU responsible for warping the disk. This model is similar to one previously proposed for another YSO, WL 4, and may indicate such triple systems with eclipsing disks are common around young stars. Understanding these systems can provide insights into stellar and planetary formation and evolution.
A mildly relativistic wide-angle outflow in the neutron-star merger event GW1...Sérgio Sacani
GW170817 was the first gravitational wave detection of a binary
neutron-star merger1
. It was accompanied by radiation across the
electromagnetic spectrum and localized2
to the galaxy NGC 4993
at a distance of 40 megaparsecs. It has been proposed that the
observed γ-ray, X-ray and radio emission is due to an ultrarelativistic
jet launched during the merger, directed away from
our line of sight3–6. The presence of such a jet is predicted from
models that posit neutron-star mergers as the central engines
that drive short hard γ-ray bursts7,8
. Here we report that the radio
light curve of GW170817 has no direct signature of an off-axis
jet afterglow. Although we cannot rule out the existence of a jet
pointing elsewhere, the observed γ-rays could not have originated
from such a jet. Instead, the radio data require a mildly relativistic
wide-angle outflow moving towards us. This outflow could be the
high-velocity tail of the neutron-rich material dynamically ejected
during the merger or a cocoon of material that breaks out when a
jet transfers its energy to the dynamical ejecta. The cocoon model
explains the radio light curve of GW170817 as well as the γ-rays
and X-rays (possibly also ultraviolet and optical emission)9–15, and
is therefore the model most consistent with the observational data.
Cocoons may be a ubiquitous phenomenon produced in neutronstar
mergers, giving rise to a heretofore unidentified population of
radio, ultraviolet, X-ray and γ-ray transients in the local Universe
Graphical 3D Modeling of Molecules and Nanostructures in Sub-nanometer Scale ...Stoyan Sarg Sargoytchev
The Basic Structures of Matter – Supergravitation Unified Theory (BSM-SG) reveals non-spherical shapes of the stable elementary particles, composed of two types of helical structures with opposite twisting. Proton and neutron have one and the same toroidal sub-structure, but the shape of proton is a twisted torus like the figure 8, while the neutron is a double folded. The shape of proton permits modulation of the space fabrics creating a positive E-field. At neutron such modulation is locked in the near field, so it is not detectable, but when in motion it creates a magnetic field. Due to it’s near E-field the neutron is stable over the proton, forming a deuteron. The electron is a different three body system with two intrinsic frequencies. Its structure and dynamic properties provide classical explanations of: Compton frequency, anomalous magnetic moment, spin and relativistic effect of mass increase. The near Coulomb field of the proton defines the trace of orbiting electron. The atomic nuclei are 3D compositions of protons and neutrons, kept by the attractive supergravitational forces, while balancing the repulsive forces between protons. The increase of number of protons reveals the build-up trend of the atomic nuclei showing a perfect match with the pattern of the Periodic Table. The features defining the valences and the angular restrictions of the chemical bonds are apparent. The rotational freedom of neutrons over protons is behind the nuclear magnetic moment. The BSM-SG atomic models are convenient for 3D graphical modeling of complex molecules and nanostructures with sub-nanometer resolution.
Theoretical Feasibility of Cold Fusion According to the BSM-SG Unified TheoryStoyan Sarg Sargoytchev
Report at 31 Annual Meeting of SSE, 2012
Advances in the field of cold fusion or LENR need a deeper understanding of the nuclear reactions and, more particularly, the possibility for modification of the Coulomb barrier. The treatise “Basic Structures of Matter – Supergravitation Unified Theory”, based on an alternative concept of the physical vacuum, suggests non spherical shapes of the protons and neutrons. Held by strong nuclear forces the non-spherical protons and neutrons form atomic nuclei as fractal three-dimensional structures. Such nuclear structures exhibit an excellent match to the pattern of Periodic Table, showing signatures of valences, and angular restrictions of the chemical bonds. The Coulomb barrier in these nuclear structures does not converge to a small size according to the Bohr nuclear model and it could be modified by some technical methods. The analysis of some cold fusion experiments, using BSM-SG model, resulted for practical and suggestions for other nuclear reactions.
Video-record: http://www.youtube.com/watch?v=S3gJp8rLHWg
A giant galaxy in the young Universe with a massive ringSérgio Sacani
In the local (redshift z ≈ 0) Universe, collisional ring galaxies make up only ~0.01% of galaxies1 and are formed by head-on galactic collisions that trigger radially propagating density waves2–4. These striking systems provide key snapshots for dissecting galactic disks and are studied extensively in the local Universe5–9. However, not much is known about distant (z > 0.1) collisional rings10–14. Here we present a detailed study of a ring galaxy at a look-back time of 10.8 Gyr (z = 2.19). Compared with our Milky Way, this galaxy has a similar stellar mass, but has a stellar half-light radius that is 1.5–2.2 times larger and is forming stars 50 times faster. The extended, dif- fuse stellar light outside the star-forming ring, combined with a radial velocity on the ring and an intruder galaxy nearby, provides evidence for this galaxy hosting a collisional ring. If the ring is secularly evolved15,16, the implied large bar in a giant disk would be inconsistent with the current understand- ing of the earliest formation of barred spirals17–21. Contrary to previous predictions10–12, this work suggests that massive col- lisional rings were as rare 11 Gyr ago as they are today. Our discovery offers a unique pathway for studying density waves in young galaxies, as well as constraining the cosmic evolution of spiral disks and galaxy groups.
Confirmation of the_planetary_microlensing_signal_and_star_and_planet_mass_de...Sérgio Sacani
This document summarizes follow-up Hubble Space Telescope observations of the planetary microlensing event OGLE-2005-BLG-169. The HST observations confirm the relative proper motion between the source and lens stars predicted by the planetary signal in the original light curve. This provides the first confirmation of a planetary microlensing signal. The HST observations also measure the brightness of the planetary host star, allowing a precise determination of the planet and host star masses as well as their projected separation. Combined with measurements from Keck adaptive optics, the HST observations confirm the identification of the lens star and characterization of the planetary system.
1) The document reports on optical spectroscopic monitoring of the ultraluminous X-ray source M 101 ULX-1.
2) Analysis revealed the companion is a Wolf-Rayet star in an 8.2 day orbit around a black hole with a minimum mass of 5 solar masses.
3) M 101 ULX-1 has an exceptionally soft X-ray spectrum that violates expectations for accretion onto stellar-mass black holes, challenging current models of ultraluminous X-ray sources.
Detection of magnetic_fields_in_both_b_type_components_of_epsilon_lupi_system...Sérgio Sacani
Uma equipe de astrônomos detectou um chamado campo magnético fóssil em ambos os componentes de um sistema estelar binário, chamado de Epsilon Lupi.
Epsilon Lupi, também conhecida como HD 136504, é uma estrela binária brilhante, localizada na constelação do hemisfério sul de Lupus.
O par de estrelas está localizado a aproximadamente 500 anos-luz de distância da Terra, e cada estrela tem entre 7 e 8 vezes a massa do Sol, e combinadas, elas têm cerca de 6000 vezes a luminosidade do Sol.
Os astrônomos sabem de muito tempo que a Epsilon Lupi é um sistema binário, mas não tinham ideia de que as duas estrelas pudessem possuir campos magnéticos.
“A origem do magnetismo entre estrelas massivas é um mistério e essa descoberta pode ajudar a trazer uma luz numa questão de por que essas estrelas possuem campos magnéticos”, disse Matt Shultz da Universidade de Queen no Canadá, e o principal autor do artigo aceito para publicação no Monthly Notices of the Royal Astronomical Society e que descreve a descoberta.
Evidence for an intermediate-mass black hole in the globular cluster NGC 6624Sérgio Sacani
This document summarizes evidence for an intermediate-mass black hole located at the center of the globular cluster NGC 6624. The authors present over 25 years of timing observations of the millisecond pulsar PSR B1820-30A, which is located very close to the cluster center. Modeling of the higher order rotational frequency derivatives reveals that the pulsar is likely in a high-eccentricity orbit around a massive companion with a mass greater than 7500 solar masses located at the cluster center, which would be an intermediate-mass black hole. Additional evidence from modeling the cluster gravitational potential and dynamics supports the presence of a central black hole with a minimum mass of around 60,000 solar masses. The observations of this
The behaviour of_dark_matter_associated_with_4_bright_cluster_galaxies_in_the...Sérgio Sacani
The document presents new Hubble Space Telescope imaging and Very Large Telescope integral-field spectroscopy of galaxy cluster Abell 3827. It finds that each of the four central galaxies in the cluster's 10 kpc core retains an associated massive dark matter halo. At least one galaxy is offset from its dark matter halo, with an offset of 1.62+0.50−0.47 kpc, within the uncertainties of mass modeling and statistical errors. If interpreted as evidence for self-interacting dark matter, this offset implies a dark matter self-interaction cross-section of (1.7 ± 0.7)×10−4 cm2/g.
Hoag's Object is a peculiar ring galaxy with a central elliptical core. New observations from Hubble Space Telescope and Russian 6-m telescope provide additional data on its structure and kinematics. The data show Hoag's Object has an old stellar core surrounded by a luminous quasi-spiral pattern and massive HI disk. Previous formation scenarios are reviewed in light of the new data. A new scenario is proposed where the elliptical core formed early in the Universe and the HI disk later formed by cold accretion of primordial gas.
This document discusses optomechanics and the use of quantum optics techniques to control mechanical systems. It provides a brief history of mechanical effects of light, including early predictions of radiation pressure and recent experiments cooling mechanical modes into the quantum ground state using laser radiation pressure. Current optomechanical systems are described, along with proposals to generate optomechanical entanglement and use optomechanics to teleport quantum states. Requirements for achieving quantum optomechanics experiments are discussed, and progress on developing systems meeting these requirements is summarized.
The physical conditions_in_a_pre_super_star_cluster_molecular_cloud_in_the_an...Sérgio Sacani
The document summarizes a study of an extreme molecular cloud in the Antennae galaxies that has properties consistent with forming a globular cluster. ALMA observations reveal a cloud with a radius of 24 pc and mass greater than 5 million solar masses. While capable of forming a globular cluster, a lack of associated thermal radio emission indicates star formation has not yet begun to alter the environment, suggesting the cloud is in an early stage of evolution. For the cloud to be confined as observed, an external pressure over 10,000 times greater than typical interstellar pressure is required, supporting the theory that high pressures are needed to form globular clusters in extreme environments like mergers.
This document appears to be a citation to a 1987 astronomical journal article with the volume number 93 and page number 1514 by an author with the last name Z. The citation is repeated multiple times but there is no other contextual information provided about the article itself.
Kinematics and the_origin_of_the_internal_structures_in_hl_tau_jet_hh151Sérgio Sacani
1) The document analyzes the kinematics and origin of internal structures in the HL Tau jet (HH 151).
2) It finds that structures with low and high radial velocities show the same proper motion, indicating they represent bow shocks and Mach disks from episodic outflows.
3) The bend in the jet and increase in brightness coincides with a stationary deflecting shock, and interactions with the ambient medium could explain changes in structure.
Decoding the ancient_greek_astronomical_calculator_known_as_the_antikythera_m...Sérgio Sacani
The document summarizes research into decoding the ancient Greek astronomical calculator known as the Antikythera Mechanism. Key findings include:
1) Researchers used high-resolution X-ray tomography and digital imaging to further decode inscriptions and reconstruct the device's functions.
2) The mechanism included geared dials to track the Metonic and Callippic lunar cycles and the Saros eclipse cycle, displaying astronomical periods with unexpected sophistication for the time.
3) Glyphs on the Saros dial were correlated with historical eclipse data, identifying the mechanism's method of predicting lunar and solar eclipses based on Babylonian arithmetic cycles.
This document summarizes a study of the Ara OB1a stellar association based on new optical photometry. The photometry was used to estimate the fundamental parameters of two prominent clusters in the association, NGC 6167 and NGC 6193, as well as the IRAS 16375-4854 source. NGC 6167 was found to be an intermediate-age cluster of 20-30 Myr, while NGC 6193 is very young at 1-5 Myr with evidence of ongoing star formation. The IRAS source is the youngest, containing several young stellar objects. The differences in ages support a picture of sequential star formation triggered over several tens of million years in the Ara OB1a region.
An interacting binary_system_powers_precessing_outflows_of_an_evolved_starSérgio Sacani
1) The authors discovered that the central star system in the planetary nebula Fleming 1 is a binary system with an orbital period of 1.1953 days.
2) They determine that the binary likely consists of a white dwarf primary star with a mass of 0.56-0.7 solar masses and a hotter white dwarf secondary star with a temperature over 120,000 K that provides the ionizing photons to power the nebula.
3) The discovery confirms that binary interactions can explain the precessing outflows and point-symmetric structures seen in Fleming 1 and other planetary nebulae with similar features.
This document summarizes research on the Monoceros R2 molecular cloud and star forming region. It discusses the reflection nebulae that were first recognized in the area. The nebulae are associated with a giant molecular cloud that is one of the closest massive star forming regions to Earth. The document reviews properties of the molecular cloud and global star formation activity, as well as prominent star forming regions within the cloud.
This document presents aluminum abundances for about 100 red giant stars in each of the Galactic globular clusters 47 Tuc and M 4. The abundances were derived from intermediate-resolution FLAMES/GIRAFFE spectra, focusing on the Al I doublet at 8772-8773 Å. Previous homogeneous abundances of O, Na, Mg, and Si were also analyzed to study multiple stellar populations in these clusters. The data confirm two stellar populations are visible in M 4, while 47 Tuc shows evidence of at least three distinct stellar groups based on the abundances of O, Na, Mg, Al, and N.
The document discusses the benefits of exercise for both physical and mental health. It notes that regular exercise can reduce the risk of diseases like heart disease and diabetes, improve mood, and reduce feelings of stress and anxiety. The document recommends that adults get at least 150 minutes of moderate exercise or 75 minutes of vigorous exercise per week to gain these benefits.
Models of the_intergalactic_gas_in_stephan_quintetSérgio Sacani
This document summarizes a numerical simulation study of the intergalactic gas in Stephan's Quintet galaxy group. The simulation uses smoothed particle hydrodynamics to model the formation of hot X-ray gas, large-scale shocks, and emission line gas seen in observations, as NGC 7318b collides with the group. The simulation reproduces the general morphology of the group, but requires adjustments to better match velocities and temperatures seen in radio, X-ray, and infrared observations. Future work will fine-tune the model parameters and cooling processes to improve agreement with multi-wavelength data.
Detection of the_central_star_of_the_planetary_nebula_ngc_6302Sérgio Sacani
The document summarizes the detection of the central star of the planetary nebula NGC 6302 using new observations from the Hubble Space Telescope's Wide Field Camera 3. Key points:
1) The central star is directly detected for the first time at the center of the nebula, confirming its location but not at the center of the inner dust torus.
2) Photometry of the central star yields a reddening value of c=3.1, corresponding to AV=6.6 magnitudes of extinction, mostly from circumstellar dust.
3) Estimates of the stellar temperature, luminosity, and distance suggest a fairly massive central star of around 0.64 solar masses that is evolving rapidly and fading over time
An energetic stellar_outburst_accompanied_by_circumstellar_light_echoesSérgio Sacani
1) V838 Monocerotis (V838 Mon) underwent an energetic stellar outburst in early 2002, temporarily becoming the brightest star in the Milky Way. 2) Hubble Space Telescope images revealed expanding light echoes in the circumstellar dust surrounding V838 Mon, allowing astronomers to set a minimum distance of over 6 kiloparsecs. 3) The light echoes, combined with the object's high luminosity and evidence that it resides in a binary system, indicate that V838 Mon represents a new class of stellar outburst not fully explained by current models.
This document summarizes observations of IGR J12580+0134, a newly discovered hard X-ray source associated with the Seyfert 2 galaxy NGC 4845, which underwent an unusual X-ray flare. Follow-up observations with XMM-Newton, Swift, MAXI, and INTEGRAL are presented and analyzed. The spectrum is well described by an absorbed power law plus soft excess. The hard X-ray flux increased over weeks and decreased over a year as expected for a tidal disruption event. Fast variations near peak allowed estimating the black hole mass as ∼3×105 M⊙, indicating disruption of ∼10% of a 14-30 Jupiter mass object. Hard X-ray emission is from a corona forming
The exceptional soft_x_ray_halo_of_the_galaxy_merger_ngc6240Sérgio Sacani
The document summarizes a recent 150-ks Chandra observation of the galaxy merger NGC 6240. Extended soft X-ray emission is detected over a 110x80 kpc region around NGC 6240. Spectral analysis finds the emission comes from hot gas with a temperature of around 7.5 million K and a total mass of about 10^10 solar masses. The gas properties suggest widespread star formation over the past 200 Myr rather than a recent nuclear starburst. The fate of the diffuse hot gas after the galaxy merger is uncertain but it may be retained and evolve into the halo of an elliptical galaxy.
Extended x ray emission in the h i cavity of ngc 4151- galaxy-scale active ga...Sérgio Sacani
The document summarizes the discovery of diffuse soft X-ray emission extending about 2 kpc from the active nucleus of NGC 4151, filling the cavity of H i material. The X-ray emission has a luminosity of about 1039 erg s-1 and can be fit with either a thermal plasma model with a temperature of around 0.25 keV, or a photoionized model. This interaction between the AGN and interstellar medium implies the last episode of high nuclear activity occurred relatively recently, around 104 years ago.
Hard xray emission_in_the_star_formation_region_on2Sérgio Sacani
This document reports on XMM-Newton observations of the star-forming region ON 2 and the massive star cluster Berkeley 87. Diffuse hard X-ray emission was detected from two regions within ON 2 - the northern region ON 2N, encompassing the H II regions GAL 75.84+0.40 and GAL 75.84+0.36, and the southern region ON 2S adjacent to the ultra-compact H II region Cygnus 2N. The emission from ON 2N has a luminosity of 10^32 erg/s and can be fit by either a thermal plasma model above 30 MK or a power-law model with gamma=-2.6. The emission from ON 2S has a
This document summarizes the results of a deep near-infrared survey of the Carina Nebula complex using the HAWK-I instrument on the VLT. The survey imaged an area of 0.36 square degrees down to magnitudes of J=23, H=22, and Ks=21, detecting over 600,000 infrared sources. Color-magnitude diagrams of the sources were analyzed to determine properties of the low-mass stellar population such as ages and masses. The survey found that about 3200 sources have masses above 1 solar mass, consistent with expectations from the initial mass function. It also found that about half of the young stars in Carina are in a widely distributed, non-clustered configuration. Six
This study uses deep Chandra observations to examine the X-ray morphology of the circum-nuclear region of NGC 4151 on spatial scales down to 30 pc. Extended soft X-ray emission is detected out to 1.3 kpc from the nucleus, farther than seen in previous studies. The X-ray emission is more absorbed towards the boundaries of the ionization cone and perpendicular to the bicone, suggesting absorption by a torus. The innermost X-ray emission, coincident with H2 emission and dusty spirals, supports X-ray excitation of molecular gas. The extended X-ray emission may be due to hot gas heated by the AGN outflow or photoionized by past AGN activity.
The document summarizes information about the Lagoon Nebula and its surrounding regions. It is located in the Sagittarius-Carina Arm of the Milky Way, about 1.3 kpc away. The Lagoon Nebula contains the young open cluster NGC 6530 (1-3 Myr old), which has several O and B type stars. Younger star formation is ongoing in regions like the Hourglass Nebula and M8 E. The complex structure of the region has been shaped by interactions between massive stars and molecular gas over multiple episodes of star formation.
1. VFTS 682 is a very massive star located 29 pc in projection from the young massive cluster R136 in the Tarantula Nebula of the LMC.
2. Spectral modeling finds it has an unusually high luminosity of log(L/L) = 6.5, corresponding to a present-day mass of ~150 solar masses.
3. Its isolation and mass pose the question of whether it formed in situ, which would profoundly impact theories of massive star formation, or if it was ejected from R136, making it the most massive runaway star known.
The open cluster_ngc6520_and_the_nearby_dark_molecular_cloud_barnard_86Sérgio Sacani
This document presents optical photometry and CO observations of the open cluster NGC 6520 and nearby dark molecular cloud Barnard 86. Analysis of the optical data finds the cluster radius is 1.0±0.5 arcmin, smaller than previous estimates. The cluster age is estimated to be 150±50 Myr with reddening of EB−V =0.42±0.10. The distance from the Sun is estimated to be 1900±100 pc, larger than previous estimates. CO observations are used to derive basic properties of Barnard 86 under the assumption it lies at the same distance as the cluster.
The document presents observations of the starburst galaxy NGC 253 using near-infrared imaging and spectroscopy as well as mid-infrared spectroscopy. The observations are used to derive physical properties of the starburst such as the star formation rate, stellar population, and evolutionary stage. Evolutionary synthesis modeling is applied to interpret the observations and show that the starburst in NGC 253 is in a late phase, has been ongoing for 20-30 million years, and is consistent with a modified Salpeter initial mass function.
Detection of brown dwarf like objects in the core of ngc3603Sérgio Sacani
This document describes observations of the massive galactic cluster NGC 3603 using the Wide Field Camera 3 on the Hubble Space Telescope. Near-infrared data was obtained using narrow and medium band filters spanning the J and H bands, which are sensitive to the 1.3-1.5μm H2O molecular absorption band unique to brown dwarfs. Nine objects were identified having effective temperatures between 1700-2200K, typical of brown dwarfs, located strongly clustered towards the luminous core of NGC 3603. However, if located at the distance of the cluster, these objects would be too luminous to be normal brown dwarfs. The authors explore the possibility that these objects could represent a new class of stars having
Identification of the central compact object in the young supernova remnant 1...Sérgio Sacani
Oxygen-rich young supernova remnants1
are valuable objects
for probing the outcome of nucleosynthetic processes in massive
stars, as well as the physics of supernova explosions.
Observed within a few thousand years after the supernova
explosion2
, these systems contain fast-moving oxygen-rich and
hydrogen-poor filaments visible at optical wavelengths: fragments
of the progenitor’s interior expelled at a few thousand
kilometres per second during the supernova explosion. Here
we report the identification of the compact object in the supernova
remnant 1E 0102.2–7219 in reprocessed Chandra X-ray
Observatory data, enabled by the discovery of a ring-shaped
structure visible primarily in optical recombination lines of
Ne i and O i. The optical ring has a radius of (2.10 ± 0.35)″≡
(0.63 ± 0.11) pc, and is expanding at a velocity of 90 . 5 30
+40 − km s−1
.
It surrounds an X-ray point source with an intrinsic X-ray luminosity
Li
(1.2–2.0 keV) = (1.4 ± 0.2) × 1033 erg s−1
. The energy
distribution of the source indicates that this object is an isolated
neutron star: a central compact object akin to those
present in the Cas A3–5
and Pup A6 supernova remnants, and
the first of its kind to be identified outside of our Galaxy.
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.
A surge of light at the birth of a supernovaSérgio Sacani
It is difficult to establish the properties of massive stars that explode
as supernovae1,2
. The electromagnetic emission during the first
minutes to hours after the emergence of the shock from the stellar
surface conveys important information about the final evolution
and structure of the exploding star3–6. However, the unpredictable
nature of supernova events hinders the detection of this brief initial
phase7–9. Here we report the serendipitous discovery of a newly
born, normal type IIb supernova (SN 2016gkg)10, which reveals a
rapid brightening at optical wavelengths of about 40 magnitudes
per day. The very frequent sampling of the observations allowed
us to study in detail the outermost structure of the progenitor of
the supernova and the physics of the emergence of the shock. We
develop hydrodynamical models of the explosion that naturally
account for the complete evolution of the supernova over distinct
phases regulated by different physical processes. This result
suggests that it is appropriate to decouple the treatment of the
shock propagation from the unknown mechanism that triggers
the explosion.
1) The VVV survey discovered a new globular cluster candidate, named VVV CL001, near the known globular cluster UKS 1 in the direction of the Galactic bulge.
2) Photometry of UKS 1 from the VVV survey was used to measure its reddening as E(B-V)=2.2 mag, distance modulus as (m-M)0=16.01 mag, and distance as 15.9 kpc.
3) Near-infrared color-magnitude diagrams of VVV CL001 suggest it has similar reddening as UKS 1 and is at least as metal-poor, though its distance remains uncertain. Further observations are needed to confirm if they are
Solving the Multimessenger Puzzle of the AGN-starburst Composite Galaxy NGC 1068Sérgio Sacani
Multiwavelength observations indicate that some starburst galaxies show a dominant nonthermal contribution from
their central region. These active galactic nuclei (AGN)-starburst composites are of special interest, as both
phenomena on their own are potential sources of highly energetic cosmic rays and associated γ-ray and neutrino
emission. In this work, a homogeneous, steady-state two-zone multimessenger model of the nonthermal emission
from the AGN corona as well as the circumnuclear starburst region is developed and subsequently applied to the
case of NGC 1068, which has recently shown some first indications of high-energy neutrino emission. Here, we
show that the entire spectrum of multimessenger data—from radio to γ-rays including the neutrino constraint—can
be described very well if both, starburst and AGN corona, are taken into account. Using only a single emission
region is not sufficient.
Spectral and morphological_analysis_of_the_remnant_of_supernova_1987_a_with_a...Sérgio Sacani
The document provides a spectral and morphological analysis of the remnant of Supernova 1987A using data from the Australia Telescope Compact Array (ATCA) and the Atacama Large Millimeter/submillimeter Array (ALMA). ALMA images from 94 GHz to 672 GHz reveal non-thermal synchrotron and thermal dust emission components. The analysis shows a decreasing east-west asymmetry with frequency, attributed to shorter synchrotron lifetimes at high frequencies. Across the radio to far-infrared transition, excess emission is seen that could be due to a second synchrotron component, implying a pulsar wind nebula in the remnant interior.
Off nuclear star_formation_and_obscured_activity_in_the_luminous_infrared_gal...Sérgio Sacani
The document summarizes observations of the luminous infrared galaxy NGC 2623 from multiple telescopes. Hubble Space Telescope images reveal over 100 bright star clusters in a 3.2 kpc extension south of the galaxy's nucleus, making it one of the richest concentrations of clusters observed. The clusters have ages between 1-100 Myr based on their optical colors. Archival GALEX data show the extension is very bright in far-ultraviolet but less significant at longer wavelengths. Spitzer data detect [Ne V] emission, confirming the presence of an active galactic nucleus. The off-nuclear star formation corresponds to a rate of 0.1-0.2 solar masses per year, while the bulk of the infrared
Similar to Detection of the_central_star_of_the_planetary_nebula_ngc6302 (20)
Compositions of iron-meteorite parent bodies constrainthe structure of the pr...Sérgio Sacani
Magmatic iron-meteorite parent bodies are the earliest planetesimals in the Solar System,and they preserve information about conditions and planet-forming processes in thesolar nebula. In this study, we include comprehensive elemental compositions andfractional-crystallization modeling for iron meteorites from the cores of five differenti-ated asteroids from the inner Solar System. Together with previous results of metalliccores from the outer Solar System, we conclude that asteroidal cores from the outerSolar System have smaller sizes, elevated siderophile-element abundances, and simplercrystallization processes than those from the inner Solar System. These differences arerelated to the formation locations of the parent asteroids because the solar protoplane-tary disk varied in redox conditions, elemental distributions, and dynamics at differentheliocentric distances. Using highly siderophile-element data from iron meteorites, wereconstruct the distribution of calcium-aluminum-rich inclusions (CAIs) across theprotoplanetary disk within the first million years of Solar-System history. CAIs, the firstsolids to condense in the Solar System, formed close to the Sun. They were, however,concentrated within the outer disk and depleted within the inner disk. Future modelsof the structure and evolution of the protoplanetary disk should account for this dis-tribution pattern of CAIs.
Signatures of wave erosion in Titan’s coastsSérgio Sacani
The shorelines of Titan’s hydrocarbon seas trace flooded erosional landforms such as river valleys; however, it isunclear whether coastal erosion has subsequently altered these shorelines. Spacecraft observations and theo-retical models suggest that wind may cause waves to form on Titan’s seas, potentially driving coastal erosion,but the observational evidence of waves is indirect, and the processes affecting shoreline evolution on Titanremain unknown. No widely accepted framework exists for using shoreline morphology to quantitatively dis-cern coastal erosion mechanisms, even on Earth, where the dominant mechanisms are known. We combinelandscape evolution models with measurements of shoreline shape on Earth to characterize how differentcoastal erosion mechanisms affect shoreline morphology. Applying this framework to Titan, we find that theshorelines of Titan’s seas are most consistent with flooded landscapes that subsequently have been eroded bywaves, rather than a uniform erosional process or no coastal erosion, particularly if wave growth saturates atfetch lengths of tens of kilometers.
SDSS1335+0728: The awakening of a ∼ 106M⊙ black hole⋆Sérgio Sacani
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼ 106M⊙ black hole (BH) that is currently in the process of ‘turning on’. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼ 106M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGNobserved in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour. Key words. galaxies: active– accretion, accretion discs– galaxies: individual: SDSS J133519.91+072807.4
Discovery of An Apparent Red, High-Velocity Type Ia Supernova at 𝐳 = 2.9 wi...Sérgio Sacani
We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
�
(
�
−
�
)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
�
Ca-rich population. Although such an object is too red for any low-
�
cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
�
) with
Λ
CDM. Therefore unlike low-
�
Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
�
truly diverge from their low-
�
counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary S...Sérgio Sacani
Wereport the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ±0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ287 as well as the dense monitoring sample of Krakow.
Candidate young stellar objects in the S-cluster: Kinematic analysis of a sub...Sérgio Sacani
Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole SgrA* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H−K and K−L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and midinfrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of SgrA* are much shorter ( 2yr) than the epochs covered by the observations (≈15yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of SgrA*. Alternatively, the gravitational influence of SgrA* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement. Key words. stars: black holes– stars: formation– Galaxy: center– galaxies: star formation
JAMES WEBB STUDY THE MASSIVE BLACK HOLE SEEDSSérgio Sacani
The pathway(s) to seeding the massive black holes (MBHs) that exist at the heart of galaxies in the present and distant Universe remains an unsolved problem. Here we categorise, describe and quantitatively discuss the formation pathways of both light and heavy seeds. We emphasise that the most recent computational models suggest that rather than a bimodal-like mass spectrum between light and heavy seeds with light at one end and heavy at the other that instead a continuum exists. Light seeds being more ubiquitous and the heavier seeds becoming less and less abundant due the rarer environmental conditions required for their formation. We therefore examine the different mechanisms that give rise to different seed mass spectrums. We show how and why the mechanisms that produce the heaviest seeds are also among the rarest events in the Universe and are hence extremely unlikely to be the seeds for the vast majority of the MBH population. We quantify, within the limits of the current large uncertainties in the seeding processes, the expected number densities of the seed mass spectrum. We argue that light seeds must be at least 103 to 105 times more numerous than heavy seeds to explain the MBH population as a whole. Based on our current understanding of the seed population this makes heavy seeds (Mseed > 103 M⊙) a significantly more likely pathway given that heavy seeds have an abundance pattern than is close to and likely in excess of 10−4 compared to light seeds. Finally, we examine the current state-of-the-art in numerical calculations and recent observations and plot a path forward for near-future advances in both domains.
Anti-Universe And Emergent Gravity and the Dark UniverseSérgio Sacani
Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional ‘dark’ gravitational force describing the ‘elastic’ response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton’s constant and the Hubble acceleration scale a0 = cH0, and provide evidence for the fact that this additional ‘dark gravity force’ explains the observed phenomena in galaxies and clusters currently attributed to dark matter.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
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.
Climate extremes likely to drive land mammal extinction during next supercont...
Detection of the_central_star_of_the_planetary_nebula_ngc6302
1. Detection of the Central Star of the Planetary Nebula NGC 6302
C. Szyszka1,2 , J. R. Walsh3 , Albert A. Zijlstra2 , Y. G. Tsamis4,5
cszyszka@eso.org
arXiv:0909.5143v2 [astro-ph.SR] 21 Oct 2009
ABSTRACT
NGC 6302 is one of the highest ionization planetary nebulae known and shows
emission from species with ionization potential >300eV. The temperature of the
central star must be > 200 000K to photoionize the nebula, and has been sug-
gested to be up to ∼ 400 000K. On account of the dense dust and molecular disc,
the central star has not convincingly been directly imaged until now. NGC 6302
was imaged in six narrow band filters by Wide Field Camera 3 on HST as part of
the Servicing Mission 4 Early Release Observations. The central star is directly
detected for the first time, and is situated at the nebula centre on the foreground
side of the tilted equatorial disc. The magnitudes of the central star have been
reliably measured in two filters (F469N and F673N). Assuming a hot black body,
the reddening has been measured from the (4688-6766˚) colour and a value of
A
c=3.1, Av =6.6 mag determined. A G-K main sequence binary companion can be
excluded. The position of the star on the HR diagram suggests a fairly massive
PN central star of about 0.64 M⊙ close to the white dwarf cooling track. A fit
to the evolutionary tracks for (T, L, t) = (200 000K, 2000L⊙ , 2200yr), where t is
the nebular age, is obtained; however the luminosity and temperature remain
uncertain. The model tracks predict that the star is rapidly evolving, and fading
at a rate of almost 1% per year. Future observations could test this prediction.
Subject headings: planetary nebulae: individual (NGC 6302) — stars: AGB and
post-AGB — stars: imaging
1
European Southern Observatory, Karl-Schwarzschild Strasse 2, D-85748 Garching, Germany
2
Jodrell Bank Centre for Astrophysics, School of Physics & Astronomy, University of Manchester, Oxford
Road, Manchester M13 9PL, UK
3
Space Telescope European Coordinating Facility, European Southern Observatory, Karl-Schwarzschild
Strasse 2, D-85748 Garching, Germany
4
Instituto de Astrofis´ de Andaluc´ (CSIC), Apartado 3004, 18080 Granada, Spain
ıca ıoa
5
Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes MK7 6AA,
UK
2. –2–
1. Introduction
Planetary nebulae (PN) trace one of the fastest phases of stellar evolution. They form
when an Asymptotic Giant Branch (AGB) star ejects its envelope in a massive wind, leaving
only the remnant degenerate C/O core. After the ejection, the star heats up rapidly, reaching
temperatures over 100 000K, within typically a few thousand years. The hydrogen burning
ceases at this point, and the star quickly fades by a large factor, before entering the white
dwarf cooling track. The hot star ionizes the previously ejected nebula: the bright ionized
nebula combined with the very hot, optically faint star, can make the stellar emission difficult
to detect. This is made worse if circumstellar extinction hides the star from direct view in
the optical and ultra-violet domain.
The central star of NGC 6302 has proven to be one of the most elusive of all PN cen-
tral stars. In spite of many attempts, it has not been detected so far. NGC 6302 shows a
strongly bipolar morphology, with filamentary emission extending over 7′ . Bipolar morpholo-
gies are thought to be associated with circumstellar discs and torii (Balick et al. 1987; Icke
2003), which are commonly seen in post-AGB nebulae (Si´dmiak et al. 2008). NGC 6302
o
provides an extreme case for such a massive, optically opaque torus (Matsuura et al. 2005;
Peretto et al. 2007; Dinh-V-Trung et al. 2008).
The central star of NGC 6302 is believed to be extremely hot, as indicated by the opti-
cal spectrum (e.g. Tsamis et al. 2003) and observation of infrared coronal lines of highly
ionized elements, of which the highest observed is Si+8 with an ionization potential of
303eV (Casassus et al. 2000). To produce such high ionization species various authors have
suggested very hot stars: Ashley & Hyland (1988) proposed a black body of 430 000 K;
Pottasch et al. (1996) 380 000K; and Casassus et al. (2000) 250 000K. Groves et al. (2002),
based on the observed scattered continuum, estimated the temperature of the central source
to be 150 000K. Most recently, Wright et al. (2007), based on 3D photo-ionization modeling,
proposed a hydrogen deficient central star with a surface temperature of 220 000K.
These stellar temperatures are similar to those of NGC 7027, another very bright, com-
pact PN at a similar distance. But whilst the star of NGC 7027 has been unambiguously
identified in images (e.g. Wolff et al. 2000), the star of NGC 6302 has remained hidden even in
previous HST and ground-based images. The only possible detection is from Matsuura et al.
(2005), who located a compact source emitting at 3.94 µm, possibly associated with the
[Si IX] emission line. It is not known whether the star of NGC 6302 is fundamentally dif-
ferent from NGC 7027 (higher temperature or lower luminosity). We here present new HST
observations with the newly-installed WFC3 instrument, which for the first time directly
reveal the central star, and allow us to address these questions.
3. –3–
2. Observations
NGC 6302 was observed as part of the HST Early Release Observations (ERO) to
demonstrate the scientific capabilities of the newly installed Wide Field Camera 3 (WFC3)
on board the Hubble Space Telescope (HST). At optical wavelengths, the UVIS channel
has two 2k×4k CCDs, with a spatial scale of 39 mas/pixel and a field of view of 162 arcsec.
Imaging programme 11504 (PI: K. Noll) was executed on 2009 July 27 using 9 orbits. Table 1
lists the observations in six narrow band filters that isolate emission lines from ionization
potentials of 10eV ([S II] 6716 & 6731 ˚) to >54eV (He II 4686˚).
A A
3. Reduction and Results
The pipeline-reduced long-exposure images for all the filter bands (i.e. FLT files) were
combined using multidrizzle (Fruchter et al. 2009) rebinning the output to 0.040′′/pixel. The
images in different filters were matched using field stars in common. The alignment was
verified by inspecting star positions in the final images. Comparison of the multidrizzled
images with those in the public ERO release showed good agreement.
Figure 1 shows the F673N filter image of the central arcminute of NGC 6302 and the
2.4 ×2.4′′ area around the central star, for all the six HST WFC3 filter images in the ERO
′′
release. This star is well detected on the F469N and F673N filters at the position α =
17h 13m 44.39s , δ = −37◦ 06′ 12.′′ 93 (J2000) and marginally detected on the F502N, F656N
and F658N images. From the filter parameters summarized in Table 1 and the emission line
spectrum of NGC 6302, as taken for example from Groves et al. (2002), the only emission
line contribution to the F469N filter is He II 4686˚. The F673N filter contains weak lines
A
of He I and C IV, in addition to the [S II]6730A ˚ line; the [S II]6716˚ line is just at the half
A
power point. All the other filters contain strong emission lines. The ease of detection of the
star in the F673N filter is accounted for by the lower emission line contribution to the band,
producing a much higher star/background contrast. This also applies to the F469N filter,
where the He II line is < 10% of the strength of the [O III]5007˚ line (in the F502N filter)
∼ A
and of the Hα line in F656N.
Photometry was then performed on the star at the centre of NGC 6302 in the six com-
bined multidrizzled images. Robustness of the results depends on accurate determination
of the high and structured background. We applied three different approaches. First, us-
ing a small aperture (2 pixels radius) and a 3 pixel wide ’sky’ (in reality nebula) annulus.
Second, a surface fit to the local background, excluding a small annulus around the cen-
tral star, was made in the same way for all images: this was subtracted from the image,
4. –4–
and aperture photometry was performed on these images. As a third approach, Sextractor
(Bertin & Arnouts 1996) photometry was performed. For the F469N and F4673N filter im-
ages the results showed good consistency, but for the other images there is a larger scatter of
typically ±0.3mag. In Table 1, the 2.0 pixel radius photometry is listed, where an aperture
correction was applied by performing photometry of uncrowded stars in the periphery of the
nebula with increasing aperture size.
Figure 2 shows the photometric points (in AB magnitudes) plotted as a function of the
wavelength. At the position of each point, a horizontal bar shows the width of the respective
filter. Also plotted on the X-axis (in green) is a compressed log spectrum of NGC 6302 taken
from Groves et al. (2002), applying a logarithmic extinction at Hβ of c = 1.2. A nebular
continuum (computed for Te = 15000K and He/H = 0.18) was added to this emission line
spectrum and the result converted to WFC3 filter photometry using the STSDAS.synphot
package. This allows comparison of the stellar photometry with the colours expected from
the nebula spectrum, the latter shown as red diamonds on Figure 2 (with arbitrary absolute
flux scaling tied to the F656N filter measurement of the stellar magnitude). From this
comparison it is clear that the photometric points for the F469N and F673N filters are
inconsistent with nebular emission. Although there appears to be a feature in the F373N,
F502N, F656N and possibly F658N, filters, at the position of the star in the F469N and
F673N images (see Figure 1), the heavy nebula contribution prevented reliable measurement
of the stellar magnitudes and the results correspond more closely to that of (inadequately
subtracted) nebula emission. The stellar magnitude is marginally measurable on the F502N
image. Even though the stellar flux is higher in the F373N band, the high extinction prevents
reliable detection in this filter.
Taking the two photometric points at 4690 and 6766˚ (Table 1) as reliable detections
A
of a putative central star of NGC 6302, the (4690–6766A ˚) colour was compared with that
of a star of a given black body temperature subjected to line-of-sight extinction. Given the
very high temperature estimates for the central star, a very large value of extinction must be
applied to produce the observed (4690–6766˚) colour of 2.1 mag. Two extinction laws were
A
used to determine the extinction - the standard Galactic law of Seaton (1979) with the ratio
of total to selective extinction of R = 3.2 and, on the basis of the good agreement of the
observed and theoretical nebula continuum determined by Groves et al. (2002), the Whitford
law (as tabulated by Kaler 1976), for the three estimates of the stellar temperature, using a
black body. For such high temperatures, a black body should be a good approximation to
the optical colours. Table 2 lists the values of c determined in these three cases. The values
of c can be directly converted to AV by multiplying by 2.18 and are listed in Table 2.
For such high temperatures there is not sufficient sensitivity to determine the tempera-
5. –5–
ture of the central star, and the extinction only changes by 0.02 for black body temperatures
from 150 000 to 400 000K. From the unreddened flux, taking the F673N magnitude as the
most reliable, assuming a black body, and the distance of 1.17 kpc (Meaburn et al. 2008),
the derived stellar luminosity can be determined and is listed in Table 2.
4. Discussion
The HST point spread function and the excellent optical and CCD quality of WFC3
UVIS have allowed the central star of NGC 6302 to be unambiguously detected for the first
time. The star is situated in the centre of the large-scale nebular outflows, as expected,
and lies on the eastern edge of the thick dust lane. This location is also the expected one
given that the eastern lobe is tilted to the foreground (Meaburn et al. 2008). However the
central star is not at the expected position at the centre of the innermost torus as shown
by the radio data (Matsuura et al. 2005). No optical emission counterpart was found at
the position of the infrared source of Matsuura et al. (2005), which is approximately 2.′′ 6
north from the proposed central star. Nor was a point source detected at the position of the
6cm radio continuum emission peak reported by Matsuura et al. (2005) (about 2.′′ 2 from the
star); only an upper limit of 23.8 (AB mag.) was measured for the F673N magnitude of a
source at this position by aperture photometry. The (4688-6766˚) colour at this radio peak
A
position resembles nebular emission. Thus if a star was present at this position, it would
suffer much higher extinction than indicated by the Matsuura et al. (2005) extinction maps.
The very high extinction towards the central star derives mostly from the circumstellar
torus. From the ratio map of Hα to radio flux, Matsuura et al. (2005) derive AHα = 5–7 for
the central region, corresponding to AV = 6–8. Field stars indicate a foreground extinction
AV = 1.1 (Matsuura et al. 2005), leaving the remainder as circumstellar extinction. The
Brα image of Matsuura et al. (2005) shows that the peak extinction is considerably higher
than derived from Hα, possibly as high as AV = 30: Hα cannot be detected from such
regions. The region of highest extinction is offset from the centre, consistent with the fact
that the torus is seen with a small inclination of 18◦ (Meaburn et al. 2008; Peretto et al.
2007; Dinh-V-Trung et al. 2008).
The distance to NGC 6302 determined by Meaburn et al. (2008) as 1.17 kpc from ex-
pansion proper motions of filaments agrees fairly well with an assumed distance of 0.91 kpc
from Kemper et al. (2002) and 1.0 kpc from Matsuura et al. (2005). Older values include
Rodriguez et al. (1985) who argue for a distance of 1.7 kpc, with a possible association to
the star formation region NGC 6334. Distances much larger than 1 kpc lead to very high
masses for the shell and torus (e.g. Matsuura et al. 2005).
6. –6–
The nebular luminosity, scaled to a distance of 1.17 kpc, was determined as 3.3 × 103 L⊙ ,
based on infrared dust modeling (Matsuura et al. 2005). An almost identical value is derived
from the radio flux of Rodriguez et al. (1985). Both measure the reprocessed stellar radiation,
and, for an optically thick nebula, the nebula luminosity should track the luminosity of the
star. To derive a stellar luminosity from the photometry, a temperature and a spectrum
must be assumed. For a black body, Table 2 shows that the stellar and nebular luminosity
agree well for a stellar temperature of around 200 000K.
Many central stars of PNe are expected to be binaries (de Marco 2009). The central star
of NGC 6302 has also been suggested to be binary: Feibelman (2001) claimed evidence for a
G5V companion based on IUE spectra, although this has been disputed by Meaburn et al.
(2005). A G5V star has MV = +5.1, and for a distance of 1.17kpc and an extinction of
Av = 6.7, the observed V magnitude on the Vega system would be V=22.1. Interpolating
the observed magnitudes in Fig. 2, the AB mag at V (very close to the Vega system) is
21.5, not incompatible with a G5V star. However, for a temperature of 5200K, suggested by
Feibelman, with an extinction of 6.7 mag, the (4688–6766˚) colour would be 1.5 mag. larger
A
than observed. A much lower extinction (c = 1.4) could reproduce the (469–673) colour, but
the absolute V mag would be around 8.1. corresponding to a K5 star. Thus, we can exclude
a G5V star. A K5V star is in principle possible, but requires a much lower extinction than
measured from Hα. In contrast, a hot star precisely fits the measured extinction and is the
preferred interpretation. If we were detecting the companion, the true central star would be
hotter and/or less luminous than derived here (Table 2).
Knowing an accurate luminosity and temperature allows one in principle to obtain the
mass of the star, an important parameter for the stellar modeling. At this phase of evolution,
the stellar mass is close to the mass of the degenerate C/O core, or the later white dwarf.
Typically, this method does not provide accurate masses. The luminosity is typically too
uncertain to allow for an accurate mass determination, because of distance errors. In the
case of NGC 6302, the luminosity is accurate to 25 per cent (based on a distance error of
12% from Meaburn et al. 2008), however the star appears to be on the cooling track where
tracks of different masses are closely clustered.
Instead, the evolutionary time scale can be used to improve on the mass accuracy: the
speed of the evolution along the Bloecker (1995) track is a very strong function of stellar
mass. The surrounding nebula acts as a clock, as its expansion dates from the time the star
departed the AGB. This age, plus the stellar temperature and luminosity, can be used to
derive an accurate stellar mass. This method is described in Gesicki & Zijlstra (2007) and
references therein. The age of the nebula can be derived from the angular extent, distance,
and de-projected expansion velocity. The CO observations of Peretto et al. (2007) show that
7. –7–
the torus ejection ended 2900 yr ago. The bipolar lobes appear to be a little younger, with
an age of 2200 yr (Meaburn et al. 2008). We will assume that 2200 yr represents the full
post-AGB evolution age of the central star.
A luminosity of 4000 L⊙ puts the star at the upper end of the cooling track. We use
interpolations of the Bloecker tracks to obtain a grid of models at a mass resolution of
0.02 M⊙ , as described by (Frankowski 2003). The 0.68M⊙ track passes through the point
at (T = 220 000K, L=4000L⊙ ), however it does so at a post-AGB age of 1000 yr which is
too young to fit NGC 6302. Higher mass tracks are hotter at this luminosity, and much
younger, while lower mass stars are older and a little cooler. Again, the tracks run very
close in the HR diagram, leaving the age as the important discriminant. Figure 3 shows the
possible locations of the star (for both extinction laws in Table 2), the interpolated Bloecker
tracks and the locus of tracks of different masses for an age of 2200 yr. The lines intersect at
(T, L) = (200 000K, 2000L⊙ ), corresponding to a stellar mass of M = 0.646 M⊙ . This fit gives
a temperature a little below that derived by Wright et al. (2007). The different extinction
laws give essentially the same mass: this is because the evolution at this location in the HR
diagram is very fast.
It should be noted that the fit is only as accurate as the models, and there is a consid-
erable systematic uncertainty in the derived mass (Zijlstra et al. 2008). The Bloecker tracks
are calculated for a sparse range of masses only, so that the interpolation is done over a rel-
atively large mass range. The speed of evolution especially of the early post-AGB evolution,
is uncertain, and this uncertainty feeds through to the time scales at later stages. However,
the method is expected to give good constraints on relative masses. Thus, comparison with
the results of Gesicki & Zijlstra (2007) shows that NGC 6302 has a high mass compared to
typical PNe.
The result can also be compared to that of another high-mass PN, NGC 7027. Zijlstra et al.
(2008) derive a mass of 0.655 ± 0.01M⊙ using the same method. The star of NGC 7027 is
still on the horizontal, high luminosity track, and the nebula is much younger. For an age
of 2200 yr, the star of NGC 7027 will have evolved much farther down the cooling track: the
interpolated Bloecker tracks predict L = 250 L⊙ . The comparison therefore suggests that
the star of NGC 6302 is indeed a little less massive than that of NGC 7027.
The fit to the star of NGC 6302 suggests it is currently in a phase of very fast evolution.
The model track shows a decline of the luminosity of ∼ 0.8 per cent per year. Such fast
evolution could leave the ionization of the nebula out of equilibrium.
In summary, this paper presents the first direct detection of the central star of NGC 6302,
among the hottest stars of planetary nebulae. The photometry indicates a hot, significantly
8. –8–
extincted star. The location in the HR diagram and age of the nebula indicates a massive
star, with mass of about 0.64 M⊙ . The models suggest that a star at this location would be
in a phase of rapid fading, and it would be of interest to test this observationally.
This paper uses data obtained with HST (WFC3). YGT acknowledges support from
grants AYA2007-67965-C03-02/CSD2006-00070/CONSOLIDER-2010 of the Spanish Min-
istry of Science. Also CS gratefully acknowledges an ESO studentship and JBCA bursary.
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A
10. – 10 –
Table 1: Exposure details, basic properties of filters used and measured AB and Vega mag-
nitudes of the central star.
Filter λ FWHM Emission Exposures AB Error Vega
[˚]
A [˚]
A Line Long Short [mag] [mag] [mag]
F373N 3730.2 39.2 [O II] 4×1400s ··· 25.0 0.30 24.1
F469N 4688.1 37.2 He II 4×1400s ··· 22.47 0.10 22.63
F502N 5009.6 57.8 [O III] 6×370s 1×35s 21.6 0.30 21.7
F656N 6561.4 13.9 Hα 6×350s 1×35s 19.3 0.20 18.7
F658N 6584.0 23.6 [N II] 6×370s 1×35s 19.0 0.20 18.6
F673N 6765.9 100.5 [S II] 4×1300s 1×100s 20.33 0.07 20.08
Table 2: Derived extinction, dereddened flux and luminosity of the star (assuming a black
body), for three published temperatures. AV is given for the Seaton reddening curve (upper)
and Whitford reddening curve (lower), as tabulated by Kaler (1976). The 4th column lists
the dereddened stellar continuum flux at 6766˚(F673N).
A
TBB c AV F(6765˚)A L
−2 −1
[K] [mag] [erg cm s ] [L⊙ ]
Seaton law
150000 3.05 6.65 1.84E-15 1280
220000 3.06 6.67 1.86E-15 4010
400000 3.07 6.69 1.89E-15 24000
Whitford law
150000 2.88 6.28 1.23E-15 860
220000 2.89 6.30 1.25E-15 2700
400000 2.90 6.32 1.27E-15 16100
11. – 11 –
Fig. 1.— Overview of the central 1′ ×1′ field of NGC 6302 in the F673N filter (upper image).
White square indicates 2.4′′ ×2.4′′ field of six smaller images (below), with the central star
in the middle of each image. Filter names are indicated and orientation.
12. – 12 –
Fig. 2.— The HST narrow band filter magnitudes (AB mag.) for the central star of
NGC 6302 are plotted as a function of the wavelength. At the position of each filter passband
a horizontal bar shows the width of the respective filter. The full blue curve shows the fit of
the photometry by a 220 000K black body extinction corrected by a Seaton (1979) Galactic
reddening of c=3.05, and the dashed blue curve the match with a Whitford reddening law
with c=2.89. (The two features in the Seaton reddening curve occur at the boundaries of the
numerical fit functions to the extinction law.) Also plotted (in green) is a compressed log
spectrum of NGC 6302 taken from Groves et al. (2002). The red diamonds show the WFC3
filter magnitudes computed for the nebula, using the emission line spectrum of Groves et al.
(2002) with the addition of nebular continuum, scaled to the F656N stellar magnitude.
13. – 13 –
Fig. 3.— The central star of NGC 6302 on the HR diagram. Red lines show the possible
locations of the star according to values in Table 2: dashed line corresponding to dereddening
with Seaton law, solid line for Whitford law. The black continuous lines show the interpolated
Bloecker tracks, labeled with their mass (M⊙ ). The blue dashed line shows the locus of all
tracks for a post-AGB age of 2200 yr. The intersection suggests a mass around 0.64 M⊙ .