- ID:
- ivo://CDS.VizieR/J/AJ/159/173
- Title:
- Photometry & RVs of 4 dwarfs hosting giant planets
- Short Name:
- J/AJ/159/173
- Date:
- 09 Dec 2021
- Publisher:
- CDS
- Description:
- We report the discovery of four transiting giant planets around K-dwarfs. The planets HATS-47b, HATS-48Ab, HATS-49b, and HATS-72b have masses of 0.369_-0.021_^+0.031^M_J_, 0.243_-0.030_^+0.022^M_J_, 0.353_-0.027_^+0.038^M_J_, and 0.1254{+/-}0.0039M_J_, respectively, and radii of 1.117{+/-}0.014R_J_, 0.800{+/-}0.015R_J_, 0.765{+/-}0.013R_J_, and 0.7224{+/-}0.0032R_J_, respectively. The planets orbit close to their host stars with orbital periods of 3.9228days, 3.1317days, 4.1480days, and 7.3279days, respectively. The hosts are main-sequence K-dwarfs with masses of 0.674_-0.012_^+0.016^M_{odot}_, 0.7279{+/-}0.0066M_{odot}_, 0.7133{+/-}0.0075M_{odot}_, and 0.7311{+/-}0.0028, and with V-band magnitudes of V=14.829{+/-}0.010, 14.35{+/-}0.11, 14.998{+/-}0.040 and 12.469{+/-}0.010. The super-Neptune HATS-72b (a.k.a. WASP-191b and TOI294.01) was independently identified as a transiting planet candidate by the HATSouth, WASP, and TESS surveys, and we present a combined analysis of all of the data gathered by each of these projects (and their follow-up programs). An exceptionally precise mass is measured for HATS-72b thanks to high-precision radial velocity (RV) measurements obtained with VLT/ESPRESSO, FEROS, HARPS, and Magellan/PFS. We also incorporate TESS observations of the warm Saturn-hosting systems HATS-47 (a.k.a. TOI1073.01), HATS-48A, and HATS-49. HATS-47 was independently identified as a candidate by the TESS team, while the other two systems were not previously identified from the TESS data. The RV orbital variations are measured for these systems using Magellan/PFS. HATS-48A has a resolved 5.4" neighbor in Gaia DR2, which is a common-proper-motion binary star companion to HATS-48A with a mass of 0.22M_{odot}_ and a current projected physical separation of ~1400au.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/700/L73
- Title:
- Photospheric fluxes at 24 and 70{mu}m
- Short Name:
- J/ApJ/700/L73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dust in debris disks is generated by collisions among planetesimals. The existence of these planetesimals is a consequence of the planet-formation process, but the relationship between debris disks and planets has not been clearly established. Here we analyze Spitzer/MIPS 24 and 70um data for 150 planet-bearing stars, and compare the incidence of debris disks around these stars with a sample of 118 stars around which planets have been searched for, but not found. Together they comprise the largest sample ever assembled to deal with this question. The use of survival analysis techniques allows us to account for the large number of non-detections at 70um. We discovered 10 new debris disks around stars with planets and one around a star without known planets. We found that the incidence of debris disks is marginally higher among stars with planets, than among those without, and that the brightness of the average debris disk is not significantly different in the two samples. We conclude that the presence of a planet that has been detected via current radial velocity techniques is not a good predictor for the presence of a debris disk detected at infrared wavelengths.
- ID:
- ivo://CDS.VizieR/J/ApJ/786/97
- Title:
- Photospheric properties of T Tauri stars
- Short Name:
- J/ApJ/786/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Estimates of the mass and age of young stars from their location in the H-R diagram are limited by not only the typical observational uncertainties that apply to field stars, but also by large systematic uncertainties related to circumstellar phenomena. In this paper, we analyze flux-calibrated optical spectra to measure accurate spectral types and extinctions of 281 nearby T Tauri stars (TTSs). The primary advances in this paper are (1) the incorporation of a simplistic accretion continuum in optical spectral type and extinction measurements calculated over the full optical wavelength range and (2) the uniform analysis of a large sample of stars, many of which are well known and can serve as benchmarks. Comparisons between the non-accreting TTS photospheric templates and stellar photosphere models are used to derive conversions from spectral type to temperature. Differences between spectral types can be subtle and difficult to discern, especially when accounting for accretion and extinction. The spectral types measured here are mostly consistent with spectral types measured over the past decade. However, our new spectral types are one to two subclasses later than literature spectral types for the original members of the TW Hya Association (TWA) and are discrepant with literature values for some well-known members of the Taurus Molecular Cloud. Our extinction measurements are consistent with other optical extinction measurements but are typically 1 mag lower than near-IR measurements, likely the result of methodological differences and the presence of near-IR excesses in most CTTSs. As an illustration of the impact of accretion, spectral type, and extinction uncertainties on the H-R diagrams of young clusters, we find that the resulting luminosity spread of stars in the TWA is 15%-30%. The luminosity spread in the TWA and previously measured for binary stars in Taurus suggests that for a majority of stars, protostellar accretion rates are not large enough to significantly alter the subsequent evolution.
- ID:
- ivo://CDS.VizieR/J/A+A/555/A150
- Title:
- Physical parameters of cool solar-type stars
- Short Name:
- J/A+A/555/A150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Temperature, surface gravity, and metallicity are basic stellar atmospheric parameters necessary to characterize a star. There are several methods to derive these parameters and a comparison of their results often shows considerable discrepancies, even in the restricted group of solar-type FGK dwarfs. We want to check the differences in temperature between the standard spectroscopic technique based on iron lines and the infrared flux method (IRFM). We aim to improve the description of the spectroscopic temperatures especially for the cooler stars where the differences between the two methods are higher, as presented in a previous work. Our spectroscopic analysis was based on the iron excitation and ionization balance, assuming Kurucz model atmospheres in LTE. The abundance analysis was determined using the code MOOG. We optimized the line list using a cool star (HD 21749) with high resolution and high signal-to-noise spectrum, as a reference in order to check for weak, isolated lines. We test the quality of the new line list by re-deriving stellar parameters for 451 stars with high resolution and signal-to-noise HARPS spectra, that were analyzed in a previous work with a larger line list. The comparison in temperatures between this work and the latest IRFM for the stars in common shows that the differences for the cooler stars are significantly smaller and more homogeneously distributed than in previous studies for stars with temperatures below 5000K.
- ID:
- ivo://CDS.VizieR/J/A+A/531/A141
- Title:
- Physical parameters of PMS in open clusters
- Short Name:
- J/A+A/531/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our aims are twofold: To determine the physical parameters of PMS members in young open clusters (YOCs), and to check and compare the performances of different model isochrones. We compare UBVRI photometric observations of eleven YOCs to theoretical isochrones in the photometric diagrams. The comparison simultaneously provides membership assignments for MS and PMS stars and estimates for the masses, ages, and spatial distribution of the candidate members. The relations found between the different cluster parameters show that the procedure applied to assign cluster membership, and to measure physical parameters for the selected members, is well founded.
- ID:
- ivo://CDS.VizieR/J/ApJ/705/1226
- Title:
- Planet-bearing stars in Spitzer
- Short Name:
- J/ApJ/705/1226
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the MIPS camera on the Spitzer Space Telescope, we have searched for debris disks around 104 stars known from radial velocity studies to have one or more planets. Combining this new data with 42 already published observations of planet-bearing stars, we find that 14 of the 146 systems have IR excess at 24 and/or 70um. Only one star, HD 69830, has IR excess exclusively at 24um, indicative of warm dust in the inner system analogous to that produced by collisions in the solar system's asteroid belt. For the other 13 stars with IR excess the emission is stronger at 70um, consistent with cool dust (<100K) located beyond 10AU, well outside of the orbital location of the known planets.
- ID:
- ivo://CDS.VizieR/J/ApJS/185/451
- Title:
- PMS stars in the Cepheus flare region
- Short Name:
- J/ApJS/185/451
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of optical spectroscopic and BVR_C_I_C_ photometric observations of 77 pre-main-sequence (PMS) stars in the Cepheus flare region. A total of 64 of these are newly confirmed PMS stars, originally selected from various published candidate lists. We estimate effective temperatures and luminosities for the PMS stars, and comparing the results with PMS evolutionary models, we estimate stellar masses of 0.2-2.4M_{sun}_ and stellar ages of 0.1-15Myr. Among the PMS stars, we identify 15 visual binaries with separations of 2-10". From archival IRAS, Two Micron All Sky Survey, and Spitzer data, we construct their spectral energy distributions (SEDs) and classify 5% of the stars as Class I, 10% as Flat SED, 60% as Class II, and 3% as Class III young stellar objects. We identify 12 classical T Tauri stars and two weak-line T Tauri stars as members of NGC 7023, with a mean age of 1.6Myr. The 13 PMS stars associated with L1228 belong to three small aggregates: RNO 129, L1228A, and L1228S. The age distribution of the 17 PMS stars associated with L1251 suggests that star formation has propagated with the expansion of the Cepheus flare shell. We detect sparse aggregates of ~6-7Myr old PMS stars around the dark clouds L1177 and L1219, at a distance of ~400pc. Three T Tauri stars appear to be associated with the Herbig Ae star SV Cep at a distance of 600pc. Our results confirm that the molecular complex in the Cepheus flare region contains clouds of various distances and star-forming histories.
- ID:
- ivo://CDS.VizieR/J/ApJ/862/2
- Title:
- Post-starburst galaxy ages from SDSS
- Short Name:
- J/ApJ/862/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detailed modeling of the recent star formation histories (SFHs) of post-starburst (or "E+A") galaxies is impeded by the degeneracy between the time elapsed since the starburst ended (post-burst age), the fraction of stellar mass produced in the burst (burst strength), and the burst duration. To resolve this issue, we combine GALEX ultraviolet photometry, SDSS photometry and spectra, and new stellar population synthesis models to fit the SFHs of 532 post-starburst galaxies. In addition to an old stellar population and a recent starburst, 48% of the galaxies are best fit with a second recent burst. Lower stellar mass galaxies (logM*/M_{sun}_<10.5) are more likely to experience two recent bursts, and the fraction of their young stellar mass is more strongly anticorrelated with their total stellar mass. Applying our methodology to other, younger post-starburst samples, we identify likely progenitors to our sample and examine the evolutionary trends of molecular gas and dust content with post-burst age. We discover a significant (4{sigma}) decline, with a 117-230Myr characteristic depletion time, in the molecular gas to stellar mass fraction with the post-burst age. The implied rapid gas depletion rate of 2-150M_{sun}_/yr cannot be due to current star formation, given the upper limits on the current star formation rates in these post- starbursts. Nor are stellar winds or supernova feedback likely to explain this decline. Instead, the decline points to the expulsion or destruction of molecular gas in outflows, a possible smoking gun for active galactic nucleus feedback.
- ID:
- ivo://CDS.VizieR/J/A+A/556/A144
- Title:
- Proper motions of young stars in Chamaeleon
- Short Name:
- J/A+A/556/A144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for new candidate members of the Chamaeleon I and II star forming regions based on proper motions and multiwavelength photometry. Kinematic candidate members are initially selected in an area of 3 degrees around each cloud on the basis of proper motions and colours using the UCAC4 catalogue. The SEDs of the objects are constructed using photometry retrieved from the Virtual Observatory and other resources, and fitted to models of stellar photospheres in order to derive effective temperatures, gravity values and luminosities. Masses and ages are estimated by comparison with theoretical evolutionary tracks in a Hertzprung-Russell diagram. Objects with ages <=20Myr are selected as probable members of the moving groups. The properties of our candidates are compared with those of the previously known members of the clouds.
- ID:
- ivo://CDS.VizieR/J/AJ/155/149
- Title:
- Properties of co-moving stars observed by Gaia
- Short Name:
- J/AJ/155/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have estimated fundamental parameters for a sample of co-moving stars observed by Gaia and identified by Oh et al (2017, J/AJ/153/257). We matched the Gaia observations to the 2MASS and Wide-Field Infrared Survey Explorer catalogs and fit MIST isochrones to the data, deriving estimates of the mass, radius, [Fe/H], age, distance, and extinction to 9754 stars in the original sample of 10606 stars. We verify these estimates by comparing our new results to previous analyses of nearby stars, examining fiducial cluster properties, and estimating the power-law slope of the local present-day mass function. A comparison to previous studies suggests that our mass estimates are robust, while metallicity and age estimates are increasingly uncertain. We use our calculated masses to examine the properties of binaries in the sample and show that separation of the pairs dominates the observed binding energies and expected lifetimes.
