- ID:
- ivo://CDS.VizieR/J/AJ/157/149
- Title:
- Transit parameters for planets around subgiants
- Short Name:
- J/AJ/157/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of seven new planets and eight planet candidates around subgiant stars, as additions to the known sample of planets around "retired A stars". Among these are the possible first three-planet systems around subgiant stars, HD 163607 and HD 4917. Additionally, we present calculations of possible transit times, durations, depths, and probabilities for all known planets around subgiant (3<logg<4) stars, focused on possible transits during the TESS mission. While most have transit probabilities of 1%-2%, we find that there are three planets with transit probabilities >9%.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/162/55
- Title:
- 65 Transit-timing variation planets properties
- Short Name:
- J/AJ/162/55
- Date:
- 16 Mar 2022 00:18:00
- Publisher:
- CDS
- Description:
- Transit surveys have revealed a significant population of compact multiplanet systems, containing several sub-Neptune-mass planets on close-in, tightly-packed orbits. These systems are thought to have formed through a final phase of giant impacts, which would tend to leave systems close to the edge of stability. Here, we assess this hypothesis, comparing observed eccentricities in systems exhibiting transit-timing variations versus the maximum eccentricities compatible with long-term stability. We use the machine-learning classifier SPOCK (Tamayo et al.) to rapidly classify the stability of numerous initial configurations and hence determine these stability limits. While previous studies have argued that multiplanet systems are often maximally packed, in the sense that they could not host any additional planets, we find that the existing planets in these systems have measured eccentricities below the limits allowed by stability by a factor of 2-10. We compare these results against predictions from the giant-impact theory of planet formation, derived from both N-body integrations and theoretical expectations that, in the absence of dissipation, the orbits of such planets should be distributed uniformly throughout the phase space volume allowed by stability. We find that the observed systems have systematically lower eccentricities than this scenario predicts, with a median eccentricity about four times lower than predicted. This suggests that, if these systems formed through giant impacts, then some dissipation must occur to damp their eccentricities. This may occur through interactions with the natal gas disk or a leftover population of planetesimals, or over longer timescales through the coupling of tidal and secular processes.
- ID:
- ivo://CDS.VizieR/J/AJ/154/5
- Title:
- Transit timing variations of 145 Kepler planets
- Short Name:
- J/AJ/154/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conduct a uniform analysis of the transit timing variations (TTVs) of 145 planets from 55 Kepler multiplanet systems to infer planet masses and eccentricities. Eighty of these planets do not have previously reported mass and eccentricity measurements. We employ two complementary methods to fit TTVs: Markov chain Monte Carlo simulations based on N-body integration, and an analytic fitting approach. Mass measurements of 49 planets, including 12 without previously reported masses, meet our criterion for classification as robust. Using mass and radius measurements, we infer the masses of planets' gaseous envelopes for both our TTV sample and transiting planets with radial velocity observations. Insight from analytic TTV formulae allows us to partially circumvent degeneracies inherent to inferring eccentricities from TTV observations. We find that planet eccentricities are generally small, typically a few percent, but in many instances are nonzero.
- ID:
- ivo://CDS.VizieR/J/ApJ/893/27
- Title:
- TRENDS high-contrast imaging survey. VIII.
- Short Name:
- J/ApJ/893/27
- Date:
- 19 Jan 2022 00:39:50
- Publisher:
- CDS
- Description:
- The physical properties of faint stellar and substellar objects often rely on indirect, model-dependent estimates. For example, the masses of brown dwarfs are usually inferred using evolutionary models, which are age dependent and have yet to be properly calibrated. With the goal of identifying new benchmark objects to test low-mass stellar and substellar models, we have carried out a comprehensive adaptive optics survey as part of the TaRgetting bENchmark-objects with the Doppler Spectroscopy (TRENDS) high-contrast imaging program. Using legacy radial velocity measurements from the High Resolution Echelle Spectrometer at Keck, we have identified several dozen stars that show long-term Doppler accelerations. We present follow-up high-contrast observations from the campaign and report the discovery of 31 comoving companions, as well as 11 strong candidate companions, to solar-type stars with well-determined parallax and metallicity values. Benchmark objects of this nature lend themselves to orbit determinations, dynamical mass estimates, and independent compositional assessment. This compendium of benchmark objects will serve as a convenient test group to substantiate theoretical evolutionary and atmospheric models near the hydrogen fusing limit.
- ID:
- ivo://CDS.VizieR/J/MNRAS/389/925
- Title:
- Triple and quadruple stars
- Short Name:
- J/MNRAS/389/925
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The statistics of catalogued quadruple stars consisting of two binaries (hierarchy 2+2), is studied in comparison with triple stars, with respective sample sizes of 81 and 725. Seven representative quadruple systems are discussed in greater detail.
- ID:
- ivo://CDS.VizieR/J/ApJ/893/56
- Title:
- T Tauri star IR excesses & Ha eq. widths
- Short Name:
- J/ApJ/893/56
- Date:
- 19 Jan 2022 11:42:19
- Publisher:
- CDS
- Description:
- We present a study of the evolution of the inner few astronomical units of protoplanetary disks around low-mass stars. We consider nearby stellar groups with ages spanning from 1 to 11Myr, distributed into four age bins. Combining PANSTARSS photometry with spectral types, we derive the reddening consistently for each star, which we use (1) to measure the excess emission above the photosphere with a new indicator of IR excess and (2) to estimate the mass accretion rate (dM/dt) from the equivalent width of the H{alpha} line. Using the observed decay of dM/dt as a constraint to fix the initial conditions and the viscosity parameter of viscous evolutionary models, we use approximate Bayesian modeling to infer the dust properties that produce the observed decrease of the IR excess with age, in the range between 4.5 and 24{mu}m. We calculate an extensive grid of irradiated disk models with a two-layered wall to emulate a curved dust inner edge and obtain the vertical structure consistent with the surface density predicted by viscous evolution. We find that the median dust depletion in the disk upper layers is {epsilon}~3x10^-3^ at 1.5Myr, consistent with previous studies, and it decreases to {epsilon}~3x10^-4^ by 7.5Myr. We include photoevaporation in a simple model of the disk evolution and find that a photoevaporative wind mass-loss rate of ~1-3x10^-9^M_{sun}_/yr agrees with the decrease of the disk fraction with age reasonably well. The models show the inward evolution of the H_2_O and CO snowlines.
- ID:
- ivo://CDS.VizieR/J/A+A/580/A26
- Title:
- T Tauri star population in Lupus
- Short Name:
- J/A+A/580/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a recent study, we derived individual distances for 109 pre-main sequence stars that define the Lupus kinematic association of young stars. Here, we use these new distances to derive the masses and ages of Lupus T Tauri stars with the aim of better constraining the lifetime of their circumstellar disks. Using the photometric and spectroscopic information available in the literature, we computed the photospheric luminosity of 92 T Tauri stars in the Lupus association. Then, we estimated their masses and ages from theoretical evolutionary models. Based on Monte Carlo simulations and statistical tests, we compare the mass and age distribution of the classical T Tauri stars (CTTS) and weak-line T Tauri (WTTS) in our sample. We show that the CTTSs are on average younger than the WTTSs and that the probability that both T Tauri subclasses are drawn from the same mass and age parental distribution is very low. Our results favor the scenario proposed earlier for the Taurus-Auriga association, where the CTTSs evolve into WTTSs when their disks are fully accreted by the star. Based on an empirical disk model, we find that the average disk lifetime for the T Tauri stars in the Lupus association is {tau}_d_=3x10^6^(M_*_/M_{sun}_)^0.55^yr. We find evidence that the average lifetime of the circumstellar disks in the Lupus association is shorter than in the Taurus-Auriga association and discuss the implications of this result.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A81
- Title:
- T Tauri stars X-ray/accretion anti correlation
- Short Name:
- J/A+A/587/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Depending on whether a T Tauri star accretes material from its circumstellar disk or not, different X-ray emission properties can be found. The accretion shocks produce cool heating of the plasma, contributing to the soft X-ray emission from the star. Using X-ray data from the Chandra Orion Ultra-deep Project and accretion rates that were obtained with the Hubble Space Telescope/WFPC2 photometric measurements in the Orion Nebula Cluster, we studied the relation between the accretion processes and the X-ray emissions of a coherent sample of T Tauri sources in the region. We performed regression and correlation analyses of our sample of T Tauri stars between the X-ray parameters, stellar properties, and the accretion measurements. We find that a clear anti-correlation is present between the residual X-ray luminosity and the accretion rates in our samples in Orion that is consistent with that found on the XMM-Newton Extended Survey of the Taurus molecular cloud (XEST) study. A considerable number of classified non-accreting sources show accretion rates comparable to those of classical T Tauri Stars (CTTS). Our data do not allow us to confirm the classification between classical and weak-line T Tauri stars (WTTS), and the number of WTTS in this work is small compared to the complete samples. Thus, we have used the entire samples as accretors in our analysis. We provide a catalog with X-ray luminosities (corrected from distance) and accretion measurements of an Orion Nebula Cluster (ONC) T Tauri stars sample.
- ID:
- ivo://CDS.VizieR/J/ApJ/841/102
- Title:
- Type 2 AGN host galaxies in Chandra-COSMOS
- Short Name:
- J/ApJ/841/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the star formation properties of a large sample of ~2300 X-ray-selected Type 2 Active Galactic Nuclei (AGNs) host galaxies out to z~3 in the Chandra COSMOS Legacy Survey in order to understand the connection between the star formation and nuclear activity. Making use of the existing multi-wavelength photometric data available in the COSMOS field, we perform a multi-component modeling from far-infrared to near-ultraviolet using a nuclear dust torus model, a stellar population model and a starburst model of the spectral energy distributions (SEDs). Through detailed analyses of SEDs, we derive the stellar masses and the star formation rates (SFRs) of Type 2 AGN host galaxies. The stellar mass of our sample is in the range of 9<logM_stellar_/M_{sun}_<12 with uncertainties of ~0.19dex. We find that Type 2 AGN host galaxies have, on average, similar SFRs compared to the normal star-forming galaxies with similar M_stellar_ and redshift ranges, suggesting no significant evidence for enhancement or quenching of star formation. This could be interpreted in a scenario, where the relative massive galaxies have already experienced substantial growth at higher redshift (z>3), and grow slowly through secular fueling processes hosting moderate-luminosity AGNs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/406/782
- Title:
- Type Ia supernovae luminosities
- Short Name:
- J/MNRAS/406/782
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Precision cosmology with Type Ia supernovae (SNe Ia) makes use of the fact that SN Ia luminosities depend on their light-curve shapes and colours. Using Supernova Legacy Survey (SNLS) and other data, we show that there is an additional dependence on the global characteristics of their host galaxies: events of the same light-curve shape and colour are, on average, 0.08mag (~4.0{sigma}) brighter in massive host galaxies (presumably metal-rich) and galaxies with low specific star formation rates (sSFR).
