- ID:
- ivo://CDS.VizieR/J/MNRAS/403/1213
- Title:
- Tracers of stellar mass-loss. I.
- Short Name:
- J/MNRAS/403/1213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical and IR integrated colours and SBF magnitudes, computed from stellar population synthesis models that include emission from the dusty envelopes surrounding TP-AGB stars undergoing mass-loss. We explore the effects of varying the mass-loss rate by one order of magnitude around the fiducial value, modifying accordingly both the stellar parameters and the output spectra of the TP-AGB stars plus their dusty envelopes. The models are single burst, and range in age from a few Myr to 14Gyr, and in metallicity between Z=0.0001 and Z=0.07; they combine new calculations for the evolution of stars in the TP-AGB phase, with star plus envelope SEDs produced with the radiative transfer code DUSTY. We compare these models to optical and near-IR data of single AGB stars and Magellanic star clusters. This comparison validates the current understanding of the role of mass-loss in determining stellar parameters and spectra in the TP-AGB. However, neither broad-band colours nor SBF measurements in the optical or the near-IR can discern global changes in the mass-loss rate of a stellar population. We predict that mid-IR SBF measurements can pick out such changes, and actually resolve whether a relation between metallicity and mass-loss exists.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/856/170
- Title:
- Tracers of stellar mass-loss. II.
- Short Name:
- J/ApJ/856/170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I present integrated colors and surface brightness fluctuation magnitudes in the mid-infrared (IR), derived from stellar population synthesis models that include the effects of the dusty envelopes around thermally pulsing asymptotic giant branch (TP-AGB) stars. The models are based on the Bruzual & Charlot CB* isochrones; they are single-burst, range in age from a few Myr to 14Gyr, and comprise metallicities between Z=0.0001 and Z=0.04. I compare these models to mid-IR data of AGB stars and star clusters in the Magellanic Clouds, and study the effects of varying self-consistently the mass-loss rate, the stellar parameters, and the output spectra of the stars plus their dusty envelopes. I find that models with a higher than fiducial mass-loss rate are needed to fit the mid-IR colors of "extreme" single AGB stars in the Large Magellanic Cloud. Surface brightness fluctuation magnitudes are quite sensitive to metallicity for 4.5{mu}m and longer wavelengths at all stellar population ages, and powerful diagnostics of mass-loss rate in the TP-AGB for intermediate-age populations, between 100Myr and 2-3Gyr.
- ID:
- ivo://CDS.VizieR/J/ApJ/809/77
- Title:
- Transiting Exoplanet Survey Satellite (TESS)
- Short Name:
- J/ApJ/809/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Transiting Exoplanet Survey Satellite (TESS) is a NASA-sponsored Explorer mission that will perform a wide-field survey for planets that transit bright host stars. Here, we predict the properties of the transiting planets that TESS will detect along with the EB stars that produce false-positive photometric signals. The predictions are based on Monte Carlo simulations of the nearby population of stars, occurrence rates of planets derived from Kepler, and models for the photometric performance and sky coverage of the TESS cameras. We expect that TESS will find approximately 1700 transiting planets from 2x10^5^ pre-selected target stars. This includes 556 planets smaller than twice the size of Earth, of which 419 are hosted by M dwarf stars and 137 are hosted by FGK dwarfs. Approximately 130 of the R<2R_{Earth}_ planets will have host stars brighter than Ks=9. Approximately 48 of the planets with R<2R_{Earth}_ lie within or near the habitable zone (0.2<S/S_{Earth}_<2); between 2 and 7 such planets have host stars brighter than Ks=9. We also expect approximately 1100 detections of planets with radii 2-4R_{Earth}_, and 67 planets larger than 4R_{Earth}_. Additional planets larger than 2R_{Earth}_ can be detected around stars that are not among the pre-selected target stars, because TESS will also deliver full-frame images at a 30-minute cadence. The planet detections are accompanied by over 1000 astrophysical false positives. We discuss how TESS data and ground-based observations can be used to distinguish the false positives from genuine planets. We also discuss the prospects for follow-up observations to measure the masses and atmospheres of the TESS planets.
- ID:
- ivo://CDS.VizieR/J/AJ/161/24
- Title:
- TRICERATOPS predictions for 384 TOIs
- Short Name:
- J/AJ/161/24
- Date:
- 10 Dec 2021
- Publisher:
- CDS
- Description:
- We present TRICERATOPS, a new Bayesian tool that can be used to vet and validate TESS Objects of Interest (TOIs). We test the tool on 68 TOIs that have been previously confirmed as planets or rejected as astrophysical false positives. By looking in the false-positive probability (FPP)-nearby false-positive probability (NFPP) plane, we define criteria that TOIs must meet to be classified as validated planets (FPP<0.015 and NFPP<10^-3^), likely planets (FPP<0.5 and NFPP<10^-3^), and likely nearby false positives (NFPP>10^-1^). We apply this procedure on 384 unclassified TOIs and statistically validate 12, classify 125 as likely planets, and classify 52 as likely nearby false positives. Of the 12 statistically validated planets, 9 are newly validated. TRICERATOPS is currently the only TESS vetting and validation tool that models transits from nearby contaminant stars in addition to the target star. We therefore encourage use of this tool to prioritize follow-up observations that confirm bona fide planets and identify false positives originating from nearby stars.
- ID:
- ivo://CDS.VizieR/J/A+A/654/A108
- Title:
- Triple-frequency meteor radar reflection coeff.
- Short Name:
- J/A+A/654/A108
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Radar scattering from meteor trails depends on several poorly constrained quantities, such as electron line density, q, initial trail radius, r0, and ambipolar diffusion coefficient, D. The goal is to apply a numerical model of full wave backscatter to triple frequency echo measurements to validate theory and constrain estimates of electron radial distribution, initial trail radius, and the ambipolar diffusion coefficient. A selection of 50 transversely polarized and 50 parallel polarized echoes with complete trajectory information were identified from simultaneous tri-frequency echoes recorded by the Canadian Meteor Orbit Radar (CMOR). The amplitude-time profile of each echo was fit to our model using three different choices for the radial electron distribution assuming a Gaussian, parabolic exponential, and 1-by-r^2^ electron line density model. The observations were manually fit by varying, q, r0, and D per model until all three synthetic echo-amplitude profiles at each frequency matched observation. The Gaussian radial electron distribution was the most successful at fitting echo power profiles, followed by the 1/r^2^. We were unable to fit any echoes using a profile where electron density varied from the trail axis as an exponential-parabolic distribution. While fewer than 5% of all examined echoes had self-consistent fits, the estimates of r0 and D as a function of height obtained were broadly similar to earlier studies, though with considerable scatter. Most meteor echoes are found to not be described well by the idealized full wave scattering model.
686. TROY project. I.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A96
- Title:
- TROY project. I.
- Short Name:
- J/A+A/609/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The detection of Earth-like planets, exocomets or Kuiper belts show that the different components found in the solar system should also be present in other planetary systems. Trojans are one of these components and can be considered fossils of the first stages in the life of planetary systems. Their detection in extrasolar systems would open a new scientific window to investigate formation and migration processes. In this context, the main goal of the TROY project is to detect exotrojans for the first time and to measure their occurrence rate (eta-Trojan). In this first paper, we describe the goals and methodology of the project. Additionally, we used archival radial velocity data of 46 planetary systems to place upper limits on the mass of possible trojans and investigate the presence of co-orbital planets down to several tens of Earth masses. We used archival radial velocity data of 46 close-in (P<5-days) transiting planets (without detected companions) with information from high-precision radial velocity instruments. We took advantage of the time of mid-transit and secondary eclipses (when available) to constrain the possible presence of additional objects co-orbiting the star along with the planet. This, together with a good phase coverage, breaks the degeneracy between a trojan planet signature and signals coming from additional planets or underestimated eccentricity. We identify nine systems for which the archival data provide >1-sigma evidence for a mass imbalance between L4 and L5. Two of these systems provide >2{sigma} detection, but no significant detection is found among our sample. We also report upper limits to the masses at L4/L5 in all studied systems and discuss the results in the context of previous findings.
- ID:
- ivo://CDS.VizieR/J/A+A/634/A37
- Title:
- TURTLS Light curves of ^56^Ni distributions
- Short Name:
- J/A+A/634/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent studies have shown how the distribution of ^56^Ni within the ejected material of type Ia supernovae can have profound consequences on the observed light curves. Observations at early times can therefore provide important details on the explosion physics in thermonuclear supernovae, which are poorly constrained. To this end, we present a series of radiative transfer calculations that explore variations in the ^56^Ni distribution. Our models also show the importance of the density profile in shaping the light curve, which is often neglected in the literature. Using our model set, we investigate the observations that are necessary to determine the 56Ni distribution as robustly as possible within the current model set. Additionally, we find that this includes observations beginning at least 14 days before B-band maximum, extending to approximately maximum light with a relatively high (<~3 day) cadence, and in at least one blue and one red band are required (such as B and R, or g and r). We compare a number of well-observed type Ia supernovae that meet these criteria to our models and find that the light curves of 70-80% of objects in our sample are consistent with being produced solely by variations in the ^56^Ni distributions. The remaining supernovae show an excess of flux at early times, indicating missing physics that is not accounted for within our model set, such as an interaction or the presence of short-lived radioactive isotopes. Comparing our model light curves and spectra to observations and delayed detonation models demonstrates that while a somewhat extended ^56^Ni distribution is necessary to reproduce the observed light curve shape, this does not negatively affect the spectra at maximum light. Investigating current explosion models shows that observations typically require a shallower decrease in the ^56^Ni mass towards the outer ejecta than is produced for models of a given ^56^Ni mass. Future models that test differences in the explosion physics and detonation criteria should be explored to determine the conditions necessary to reproduce the 56Ni distributions found here.
- ID:
- ivo://CDS.VizieR/J/A+A/457/637
- Title:
- UBVJHK synthetic photometry of Galactic O stars
- Short Name:
- J/A+A/457/637
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The development of powerful infrared observational techniques enables the study of very extincted objects and young embedded star-forming regions. This is especially interesting in the context of massive stars that form and spend a non negligible fraction of their life still enshrouded in their parental molecular cloud. Spectrophotometric calibrations are thus necessary to constrain the physical properties of heavily extincted objects.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A87
- Title:
- Ultra-massive white dwarfs evolution models
- Short Name:
- J/A+A/625/A87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ultra-massive white dwarfs are powerful tools to study various physical processes in the Asymptotic Giant Branch (AGB), type Ia supernova explosions and the theory of crystallization through white dwarf asteroseismology. Despite the interest in these white dwarfs, there are few evolutionary studies in the literature devoted to them. Here, we present new ultra-massive white dwarf evolutionary sequences that constitute an improvement over previous ones. In these new sequences, we take into account for the first time the process of phase separation expected during the crystallization stage of these white dwarfs, by relying on the most up-to-date phase diagram of dense oxygen/neon mixtures. Realistic chemical profiles resulting from the full computation of progenitor evolution during the semidegenerate carbon burning along the super-AGB phase are also considered in our sequences. Outer boundary conditions for our evolving models are provided by detailed non-gray white dwarf model atmospheres for hydrogen and helium composition. We assessed the impact of all these improvements on the evolutionary properties of ultra-massive white dwarfs, providing up-dated evolutionary sequences for these stars. We conclude that crystallization is expected to affect the majority of the massive white dwarfs observed with effective temperatures below 40000K. Moreover, the calculation of the phase separation process induced by crystallization is necessary to accurately determine the cooling age and the mass-radius relation of massive white dwarfs. We also provide colors in the GAIA photometric bands for our H-rich white dwarf evolutionary sequences on the basis of new models atmospheres. Finally, these new white dwarf sequences provide a new theoretical frame to perform asteroseismological studies on the recently detected ultra-massive pulsating white dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/847/142
- Title:
- Ultra-metal-poor stars LTE and NLTE abundances
- Short Name:
- J/ApJ/847/142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new ultra-metal-poor stars parameters with [Fe/H] < -4.0 based on line-by-line non-local thermodynamic equilibrium (NLTE) abundances using an up-to-date iron model atom with a new recipe for non-elastic hydrogen collision rates. We study the departures from LTE in their atmospheric parameters and show that they can grow up to ~1.00dex in [Fe/H], ~150K in Teff and ~0.5dex in logg toward the lowest metallicities. Accurate NLTE atmospheric stellar parameters, in particular [Fe/H] being significantly higher, are the first step to eventually providing full NLTE abundance patterns that can be compared with Population III supernova nucleosynthesis yields to derive properties of the first stars. Overall, this maximizes the potential of these likely second-generation stars to investigate the early universe and how the chemical elements were formed.
