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101. LAMOST parameters of Am and non-chemical-peculiar stars
ID:
ivo://CDS.VizieR/J/AJ/162/32
Title:
LAMOST parameters of Am and non-chemical-peculiar stars
Short Name:
J/AJ/162/32
Date:
21 Mar 2022 00:10:05
Publisher:
CDS
Description:
Rotation is a critical physical process operating in the formation of Am stars. There is a strong correlation between low-velocity rotation and chemical peculiarity. However, the existence of many non-chemical-peculiar slow rotators challenges the understanding of Am stars. The purpose of our work is to search for low-velocity rotating non-chemical-peculiar A-type stars and Am stars and to make a comparative analysis. In this paper, we pick out a sample from the LAMOST-Kepler project, including 21 Am stars, 125 non-chemical-peculiar slow rotators, and 53 non-chemical-peculiar fast rotators. We calculate the rotational frequencies through a periodic change of light curves caused by inhomogeneous stellar surfaces and then obtain the rotational velocities. For slow rotators, the age of Am stars is statistically younger than that of non-chemical-peculiar stars in the same temperature bin. In the comparison of the period, the average amplitude, and stellar mass of Am and non-chemical-peculiar stars, we discover that there is no difference in the photometric variability between Am and non-chemical-peculiar stars, which implies similar inhomogeneities on the surfaces. The average amplitude of non-chemical-peculiar stars has a downward trend with the increase of effective temperature and stellar mass, which is consistent with the theoretical prediction caused by weak dynamo-generated magnetic fields in A-type stars. In addition, we confirm four non-chemical-peculiar stars that have flares by checking field-of-view images, pixel images, and pixel-level light curves.
102. LAMOST stars radii, masses, luminosities
ID:
ivo://CDS.VizieR/J/other/AstBu/72.51
Title:
LAMOST stars radii, masses, luminosities
Short Name:
J/other/AstBu/72
Date:
21 Oct 2021
Publisher:
CDS
Description:
Based on the spectral observations of the LAMOST (DR2) survey, the radii, masses, and luminosities of 700480 stars were estimated. These stars belong to spectral types A, F, G, and K, and have metallicities between -0.845 and 0.0. To determine the properties of the stars, we used up-to-date modelsof the stellar interior structure, computed with account for the stellar evolution rate and the initial mass function. The use of evolutionary estimates for two types of stars - with and without rotation - allowed us to account for the uncertainty associated with the lack of data on the rotation velocity of the stars under consideration. The obtained stellar radii, together with the photometric estimates of interstellar extinction and angular diameters can be used to study the dependence of interstellar extinction on distance as well as to estimate the stellar distances.
103. Low-mass stars from the first two TESS sectors
ID:
ivo://CDS.VizieR/J/AJ/158/81
Title:
Low-mass stars from the first two TESS sectors
Short Name:
J/AJ/158/81
Date:
21 Oct 2021
Publisher:
CDS
Description:
Continuous data releases throughout the Transiting Exoplanet Survey Satellite (TESS) primary mission will provide unique opportunities for the exoplanet community at large to contribute to maximizing TESS's scientific return via the discovery and validation of transiting planets. This paper introduces our independent pipeline for the detection of periodic transit events along with the results of its inaugural application to the recently released 2 minute light curves of low-mass stars from the first two TESS sectors. The stellar parameters within our sample are refined using precise parallax measurements from the Gaia DR2 (Cat. I/345), which reduce the number of low-mass stars in our sample relative to those listed in the TESS Input Catalog. In lieu of the follow-up observations required to confirm or refute the planetary nature of transit-like signals, a validation of transit-like events flagged by our pipeline is performed statistically. The resulting vetted catalog contains eight probable blended eclipsing binaries, eight known TOIs, plus seven new planet candidates (PCs) smaller than 4 Earth radii. This work demonstrates the ability of our pipeline to detect sub-Neptune-sized PCs, which to date represent some of the most attractive targets for future atmospheric characterization via transmission or thermal emission spectroscopy and for radial velocity efforts aimed at the completion of the TESS level one requirement to deliver 50 planets smaller than 4 Earth radii with measured masses.
104. M31A eclipsing binaries and Cepheids
ID:
ivo://CDS.VizieR/J/AJ/115/1894
Title:
M31A eclipsing binaries and Cepheids
Short Name:
J/AJ/115/1894
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have undertaken a long-term project, DIRECT, to obtain the direct distances to two important galaxies in the cosmological distance ladder, M31 and M33, using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult to detect, DEBs provide us with the potential to determine these distances with an accuracy better than 5%. The extensive photometry obtained in order to detect DEBs provides us with good light curves for the Cepheid variables. These are essential to the parallel project to derive direct Baade-Wesselink distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries, the distance estimates will be free of any intermediate steps. As a first step in the DIRECT project, between 1996 September and 1997 January we obtained 36 full nights on the Michigan-Dartmouth-MIT Observatory 1.3m telescope and 45 full/partial nights on the F. L. Whipple Observatory 1.2m telescope to search for DEBs and new Cepheids in the M31 and M33 galaxies. In this paper, second in a series, we present the catalog of variable stars, most of them newly detected, found in the field M31A [({alpha},{delta})=(11.34{deg}, 41.73{deg}), J2000.0]. We have found 75 variable stars: 15 eclipsing binaries, 43 Cepheids, and 17 other periodic, possible long-period or nonperiodic variables. The catalog of variables, as well as their photometry and finding charts, is available via anonymous ftp and the World Wide Web. The CCD frames are available upon request.
105. Main sequence magnetic stars properties
ID:
ivo://CDS.VizieR/J/other/AstBu/74.66
Title:
Main sequence magnetic stars properties
Short Name:
J/other/AstBu/74
Date:
21 Oct 2021
Publisher:
CDS
Description:
We reconsidered the previous studies of properties of magnetic stars based on the latest data on average surface magnetic fields of 177 stars. New, corrected results have been obtained that allow a better understanding of the phenomenon of magnetic chemically peculiar stars.
106. Masses and radii of DA white dwarfs in SDSS DR1
ID:
ivo://CDS.VizieR/J/A+A/419/L5
Title:
Masses and radii of DA white dwarfs in SDSS DR1
Short Name:
J/A+A/419/L5
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the sample of 1175 new nonmagnetic DA white dwarfs with the effective temperatures T_eff_>=12000K, which were extracted from the Data Release 1 of the Sloan Digital Sky Survey. We determined masses, radii, and bolometric luminosities of stars in the sample. The above parameters were derived from the effective temperatures T_eff_ and surface gravities logg published in the DR1, and the new theoretical M-R relations for carbon-core and oxygen-core white dwarfs. Mass distribution of white dwarfs in this sample exhibits the peak at M=0.562M_{sun}_ (carbon-core stars), and the tail towards higher masses. Both the shape of the mass distribution function and the empirical mass-radius relation are practically identical for white dwarfs with either pure carbon or pure oxygen cores.
107. Masses and radii of eclipsing binaries
ID:
ivo://CDS.VizieR/J/ApJ/709/535
Title:
Masses and radii of eclipsing binaries
Short Name:
J/ApJ/709/535
Date:
21 Oct 2021
Publisher:
CDS
Description:
The currently favored method for estimating radii and other parameters of transiting-planet host stars is to match theoretical models to observations of the stellar mean density {rho}_*_, the effective temperature T_eff_, and the composition parameter [Z]. This explicitly model-dependent approach is based on readily available observations, and results in small formal errors. Its performance will be central to the reliability of results from ground-based transit surveys such as TrES, HAT, and SuperWASP, as well as to the space-borne missions MOST, CoRoT, and Kepler. Here, I use two calibration samples of stars (eclipsing binaries (EBs) and stars for which asteroseismic analyses are available) having well-determined masses and radii to estimate the accuracy and systematic errors inherent in the {rho}_*_ method. When matching to the Yonsei-Yale stellar evolution models, I find the most important systematic error results from selection bias favoring rapidly rotating (hence probably magnetically active) stars among the EB sample. If unaccounted for, this bias leads to a mass-dependent underestimate of stellar radii by as much as 4% for stars of 0.4M_{sun}_, decreasing to zero for masses above about 1.4M_{sun}_. Relative errors in estimated stellar masses are three times larger than those in radii.
108. Masses & radii of 4 VLM stars in EB systems
ID:
ivo://CDS.VizieR/J/AJ/156/27
Title:
Masses & radii of 4 VLM stars in EB systems
Short Name:
J/AJ/156/27
Date:
21 Oct 2021
Publisher:
CDS
Description:
Eclipsing binaries (EBs) with one of the companions as very low-mass stars (VLMSs; or M dwarfs) are testbeds to substantiate stellar models and evolutionary theories. Here we present four EB candidates with F-type primaries, namely, SAO 106989, HD 24465, EPIC 211682657, and HD 205403, identified from different photometry missions, SuperWASP, Kilodegree Extremely Little Telescope (KELT), Kepler 2 (K2), and Solar Terrestrial Relations Observatory (STEREO). Using the high-resolution spectrograph PRL Advanced Radial velocity Abu-sky Search at the 1.2 m telescope at Mount Abu, Rajasthan, India, we hereby report the detection of four VLMSs as companions to the four EBs. We performed spectroscopic analysis and found the companion masses to be 0.256+/-0.005, 0.233+/-0.002, 0.599+/-0.017, and 0.406+/-0.005 M_{sun}_ for SAO 106989, HD 24465, EPIC 211682657, and SAO 106989B, respectively. We determined orbital periods of 4.39790+/-0.00001, 7.19635+/-0.00002, 3.142023+/-0.000003, and 2.444949+/-0.000001 days and eccentricities of 0.248+/-0.005, 0.208+/-0.002, 0.0097+/- 0.0008, and 0.002+/-0.002 for EBs SAO 106989, HD 24465, EPIC 211682657, and HD 205403, respectively. The radii derived by modeling the photometry data are 0.326+/-0.012 R_{sun}_ for SAO 106989, 0.244+/-0.001 R_{sun}_ for HD 24465B, 0.566+/-0.005 R_{sun}_ for EPIC 211682657B, and 0.444+/-0.014 R_{sun}_ for HD 205403B. The radii of HD 24465B and EPIC 211682657B have been measured by precise Kepler photometry and are consistent with theory within the error bars. However, the radii of SAO 106989B and HD 205403B, measured by KELT and STEREO photometry, are 17%-20% higher than those predicted by theory. A brief comparison of the results of the current work is made with the M dwarfs already studied in the literature.
109. Mass & radius of planets, moons, low mass stars
ID:
ivo://CDS.VizieR/J/ApJ/834/17
Title:
Mass & radius of planets, moons, low mass stars
Short Name:
J/ApJ/834/17
Date:
21 Oct 2021
Publisher:
CDS
Description:
Mass and radius are two of the most fundamental properties of an astronomical object. Increasingly, new planet discoveries are being announced with a measurement of one of these quantities, but not both. This has led to a growing need to forecast the missing quantity using the other, especially when predicting the detectability of certain follow-up observations. We present an unbiased forecasting model built upon a probabilistic mass-radius relation conditioned on a sample of 316 well-constrained objects. Our publicly available code, Forecaster, accounts for observational errors, hyper-parameter uncertainties, and the intrinsic dispersions observed in the calibration sample. By conditioning our model on a sample spanning dwarf planets to late-type stars, Forecaster can predict the mass (or radius) from the radius (or mass) for objects covering nine orders of magnitude in mass. Classification is naturally performed by our model, which uses four classes we label as Terran worlds, Neptunian worlds, Jovian worlds, and stars. Our classification identifies dwarf planets as merely low-mass Terrans (like the Earth) and brown dwarfs as merely high-mass Jovians (like Jupiter). We detect a transition in the mass-radius relation at 2.0_-0.6_^+0.7^M_{Earth}_, which we associate with the divide between solid, Terran worlds and Neptunian worlds. This independent analysis adds further weight to the emerging consensus that rocky super-Earths represent a narrower region of parameter space than originally thought. Effectively, then, the Earth is the super-Earth we have been looking for.
110. Mass-radius relationship for planets with Rp<4
ID:
ivo://CDS.VizieR/J/ApJ/825/19
Title:
Mass-radius relationship for planets with Rp<4
Short Name:
J/ApJ/825/19
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Kepler Mission has discovered thousands of planets with radii <4R_{earth}_, paving the way for the first statistical studies of the dynamics, formation, and evolution of these sub-Neptunes and super-Earths. Planetary masses are an important physical property for these studies, and yet the vast majority of Kepler planet candidates do not have theirs measured. A key concern is therefore how to map the measured radii to mass estimates in this Earth-to-Neptune size range where there are no Solar System analogs. Previous works have derived deterministic, one-to-one relationships between radius and mass. However, if these planets span a range of compositions as expected, then an intrinsic scatter about this relationship must exist in the population. Here we present the first probabilistic mass-radius relationship (M-R relation) evaluated within a Bayesian framework, which both quantifies this intrinsic dispersion and the uncertainties on the M-R relation parameters. We analyze how the results depend on the radius range of the sample, and on how the masses were measured. Assuming that the M-R relation can be described as a power law with a dispersion that is constant and normally distributed, we find that M/M_{earth}_=2.7(R/R_{earth}_)^1.3^, a scatter in mass of 1.9M_{earth}_, and a mass constraint to physically plausible densities, is the "best-fit" probabilistic M-R relation for the sample of RV-measured transiting sub-Neptunes (R_pl_<4R_{earth}_). More broadly, this work provides a framework for further analyses of the M-R relation and its probable dependencies on period and stellar properties.

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