- ID:
- ivo://CDS.VizieR/J/ApJ/807/23
- Title:
- Companions of RS CVn primaries. I. sig Gem
- Short Name:
- J/ApJ/807/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To measure the properties of both components of the RS Canum Venaticorum binary {sigma} Geminorum ({sigma} Gem), we directly detect the faint companion, measure the orbit, obtain model-independent masses and evolutionary histories, detect ellipsoidal variations of the primary caused by the gravity of the companion, and measure gravity darkening. We detect the companion with interferometric observations obtained with the Michigan InfraRed Combiner at Georgia State University's Center for High Angular Resolution Astronomy Array with a primary-to-secondary H-band flux ratio of 270+/-70. A radial velocity curve of the companion was obtained with spectra from the Tillinghast Reflector Echelle Spectrograph on the 1.5m Tillinghast Reflector at Fred Lawrence Whipple Observatory. We additionally use new observations from the Tennessee State University Automated Spectroscopic and Photometric Telescopes (AST and APT, respectively). From our orbit, we determine model-independent masses of the components (M1=1.28+/-0.07M_{sun}_, M2=0.73+/-0.03M_{sun}_), and estimate a system age of 5+/-1Gyr. An average of the 27 year APT light curve of {sigma} Gem folded over the orbital period (P=19.6027+/-0.0005days) reveals a quasi-sinusoidal signature, which has previously been attributed to active longitudes 180{deg} apart on the surface of {sigma} Gem. With the component masses, diameters, and orbit, we find that the predicted light curve for ellipsoidal variations due to the primary star partially filling its Roche lobe potential matches well with the observed average light curve, offering a compelling alternative explanation to the active longitudes hypothesis. Measuring gravity darkening from the light curve gives {beta}<0.1, a value slightly lower than that expected from recent theory.
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- ID:
- ivo://CDS.VizieR/J/AJ/151/85
- Title:
- Companions to APOGEE stars. I.
- Short Name:
- J/AJ/151/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In its three years of operation, the Sloan Digital Sky Survey Apache Point Observatory Galactic Evolution Experiment (APOGEE-1) observed >14000 stars with enough epochs over a sufficient temporal baseline for the fitting of Keplerian orbits. We present the custom orbit-fitting pipeline used to create this catalog, which includes novel quality metrics that account for the phase and velocity coverage of a fitted Keplerian orbit. With a typical radial velocity precision of ~100-200 m/s, APOGEE can probe systems with small separation companions down to a few Jupiter masses. Here we present initial results from a catalog of 382 of the most compelling stellar and substellar companion candidates detected by APOGEE, which orbit a variety of host stars in diverse Galactic environments. Of these, 376 have no previously known small separation companion. The distribution of companion candidates in this catalog shows evidence for an extremely truncated brown dwarf (BD) desert with a paucity of BD companions only for systems with a<0.1-0.2 AU, with no indication of a desert at larger orbital separation. We propose a few potential explanations of this result, some which invoke this catalog's many small separation companion candidates found orbiting evolved stars. Furthermore, 16 BD and planet candidates have been identified around metal-poor ([Fe/H]<-0.5) stars in this catalog, which may challenge the core accretion model for companions >10 M_Jup_. Finally, we find all types of companions are ubiquitous throughout the Galactic disk with candidate planetary-mass and BD companions to distances of ~6 and ~16 kpc, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/450/681
- Title:
- Companions to close spectroscopic binaries
- Short Name:
- J/A+A/450/681
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have surveyed a sample of 165 solar-type spectroscopic binaries (SB) with periods from 1 to 30 days for higher-order multiplicity. 62 targets have been observed with the NACO adaptive optics system and 13 new physical tertiary companions were detected. Another 12 new wide companions (5 still tentative) were retrieved from the 2MASS (<II/246>) sky survey. Our binaries belong to 161 stellar systems; of these 64 are triple, 11 quadruple and 7 quintuple. After correction for incomplete detection, the fraction of SBs with additional companions is 63+/-5%. We find that this fraction is a strong function of the SB period P, reaching 96% for P<3d and dropping to 36% for P>12d. Period distributions of SBs with and without tertiaries are significantly different, but their mass ratio distributions are identical. New statistical data on the multiplicity of close SBs indicate that their periods and mass ratios were established very early, but periods of SBs within triples were further shortened by angular momentum exchange with companions.
- ID:
- ivo://CDS.VizieR/J/ApJ/607/810
- Title:
- Companions to isolated elliptical galaxies
- Short Name:
- J/ApJ/607/810
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the number of physical companion galaxies for a sample of relatively isolated elliptical galaxies. The NASA/IPAC Extragalactic Database (NED) has been used to reinvestigate the incidence of satellite galaxies for a sample of 34 elliptical galaxies, first investigated by Bothun & Sullivan (1977PASP...89....5B) using a visual inspection of Palomar Sky Survey prints out to a projected search radius of 75 kpc. We have repeated their original investigation using data cataloged in NED. Nine of these elliptical galaxies appear to be members of galaxy clusters; the remaining sample of 25 galaxies reveals an average of +1.0+/-0.5 apparent companions per galaxy within a projected search radius of 75 kpc, in excess of two equal-area comparison regions displaced by 150-300 kpc. This is significantly larger than the +0.12+/-0.42 companions/galaxy found by Bothun & Sullivan (1977PASP...89....5B) for the identical sample. Making use of published radial velocities, mostly available since the completion of the Bothun-Sullivan study, identifies the physical companions and gives a somewhat lower estimate of +0.4 companions per elliptical galaxy. This is still 3 times larger than the original statistical study, but given the incomplete and heterogeneous nature of the survey redshifts in NED, it still yields a firm lower limit on the number (and identity) of physical companions. An expansion of the search radius out to 300 kpc, again restricted to sampling only those objects with known redshifts in NED, gives another lower limit of 4.5 physical companions per galaxy. (Excluding five elliptical galaxies in the Fornax Cluster, this average drops to 3.5 companions per elliptical.) These physical companions are individually identified and listed, and the ensemble-averaged radial density distribution of these associated galaxies is presented. For the ensemble, the radial density distribution is found to have a falloff consistent with {rho}{prop.to}R^-0.5^ out to approximately 150 kpc. For non-Fornax Cluster companions the falloff continues out to the 300 kpc limit of the survey. The velocity dispersion of these companions is found to reach a maximum of 350 km/s at around 120 kpc, after which they fall at a rate consistent with Keplerian falloff. This falloff may then indicate the detection of a cut-off in the mass-density distribution in the elliptical galaxies' dark matter halo at ~100 kpc.
- ID:
- ivo://CDS.VizieR/J/A+A/325/159
- Title:
- Companions to M dwarfs within 5pc
- Short Name:
- J/A+A/325/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper contains four tables which summarise the duplicity status of the 34 M dwarf primaries within 5.0pc. Table 1 gives the basic data for the sample: designation, coordinates, V,J,H,K photometry, parallax Table 2 gives, for the nine southern sources, magnitude limits for possible undetected companions. These limits are given for assumed projected separations of 1AU, 2AU, 5AU, and 10AU. In addition, the circumstances of the observation are given: date, telescope, and observational technique. Table 3 repeats, in updated form, the same information (except for the date) for the 25 northern sources. Table 4 lists the nine M dwarf primaries within 5pc which do have one or more companions.
- ID:
- ivo://CDS.VizieR/J/ApJ/792/119
- Title:
- Companions to nearby stars from Pan-STARRS 1
- Short Name:
- J/ApJ/792/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of 57 wide (>5'') separation, low-mass (stellar and substellar) companions to stars in the solar neighborhood identified from Pan-STARRS 1 (PS1) data and the spectral classification of 31 previously known companions. Our companions represent a selective subsample of promising candidates and span a range in spectral type of K7-L9 with the addition of one DA white dwarf. These were identified primarily from a dedicated common proper motion search around nearby stars, along with a few as serendipitous discoveries from our Pan-STARRS 1 brown dwarf search. Our discoveries include 23 new L dwarf companions and one known L dwarf not previously identified as a companion. The primary stars around which we searched for companions come from a list of bright stars with well-measured parallaxes and large proper motions from the Hipparcos catalog (8583 stars, mostly A-K dwarfs) and fainter stars from other proper motion catalogs (79170 stars, mostly M dwarfs). We examine the likelihood that our companions are chance alignments between unrelated stars and conclude that this is unlikely for the majority of the objects that we have followed-up spectroscopically. We also examine the entire population of ultracool (>M7) dwarf companions and conclude that while some are loosely bound, most are unlikely to be disrupted over the course of ~10 Gyr. Our search increases the number of ultracool M dwarf companions wider than 300 AU by 88% and increases the number of L dwarf companions in the same separation range by 82%. Finally, we resolve our new L dwarf companion to HIP 6407 into a tight (0.13'', 7.4 AU) L1+T3 binary, making the system a hierarchical triple. Our search for these key benchmarks against which brown dwarf and exoplanet atmosphere models are tested has yielded the largest number of discoveries to date.
- ID:
- ivo://CDS.VizieR/J/ApJ/814/91
- Title:
- Comparative habitability of transiting exoplanets
- Short Name:
- J/ApJ/814/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Exoplanet habitability is traditionally assessed by comparing a planet's semimajor axis to the location of its host star's "habitable zone", the shell around a star for which Earth-like planets can possess liquid surface water. The Kepler space telescope has discovered numerous planet candidates near the habitable zone, and many more are expected from missions such as K2, TESS, and PLATO. These candidates often require significant follow-up observations for validation, so prioritizing planets for habitability from transit data has become an important aspect of the search for life in the universe. We propose a method to compare transiting planets for their potential to support life based on transit data, stellar properties and previously reported limits on planetary emitted flux. For a planet in radiative equilibrium, the emitted flux increases with eccentricity, but decreases with albedo. As these parameters are often unconstrained, there is an "eccentricity-albedo degeneracy" for the habitability of transiting exoplanets. Our method mitigates this degeneracy, includes a penalty for large-radius planets, uses terrestrial mass-radius relationships, and, when available, constraints on eccentricity to compute a number we call the "habitability index for transiting exoplanets" that represents the relative probability that an exoplanet could support liquid surface water. We calculate it for Kepler objects of interest and find that planets that receive between 60% and 90% of the Earth's incident radiation, assuming circular orbits, are most likely to be habitable. Finally, we make predictions for the upcoming TESS and James Webb Space Telescope missions.
- ID:
- ivo://CDS.VizieR/J/A+A/547/A108
- Title:
- Comparative modelling of cool giants spectra
- Short Name:
- J/A+A/547/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our ability to extract information from the spectra of stars depends on reliable models of stellar atmospheres and appropriate techniques for spectral synthesis. The corresponding paper aims to compare a wide variety of model codes and strategies for the analysis of stellar spectra that are available today. The online tables list spectral lines used during the analysis together with the basic line parameters.
- ID:
- ivo://CDS.VizieR/J/AJ/161/265
- Title:
- Compared rotation periods for 1189 CKS host stars
- Short Name:
- J/AJ/161/265
- Date:
- 16 Mar 2022 11:58:11
- Publisher:
- CDS
- Description:
- The radius valley, a bifurcation in the size distribution of small, close-in exoplanets, is hypothesized to be a signature of planetary atmospheric loss. Such an evolutionary phenomenon should depend on the age of the star-planet system. In this work, we study the temporal evolution of the radius valley using two independent determinations of host star ages among the California-Kepler Survey (CKS) sample. We find evidence for a wide and nearly empty void of planets in the period-radius diagram at the youngest system ages (<~2-3Gyr) represented in the CKS sample. We show that the orbital period dependence of the radius valley among the younger CKS planets is consistent with that found among those planets with asteroseismically determined host star radii. Relative to previous studies of preferentially older planets, the radius valley determined among the younger planetary sample is shifted to smaller radii. This result is compatible with an atmospheric loss timescale on the order of gigayears for progenitors of the largest observed super-Earths. In support of this interpretation, we show that the planet sizes that appear to be unrepresented at ages <~2-3Gyr are likely to correspond to planets with rocky compositions. Our results suggest that the size distribution of close-in exoplanets and the precise location of the radius valley evolve over gigayears.
- ID:
- ivo://CDS.VizieR/J/A+A/560/A16
- Title:
- Comparison of evolutionary tracks
- Short Name:
- J/A+A/560/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The evolution of massive stars is not fully understood. The relation between different types of evolved massive stars is not clear, and the role of factors such as binarity, rotation or magnetism needs to be quantified. Several groups make available the results of 1D single stellar evolution calculations in the form of evolutionary tracks and isochrones. They use different stellar evolution codes for which the input physics and its implementation varies. In this paper, we aim at comparing the currently available evolutionary tracks for massive stars. We focus on calculations aiming at reproducing the evolution of Galactic stars. Our main goal is to highlight the uncertainties on the predicted evolutionary paths. We compute stellar evolution models with the codes MESA and STAREVOL. We compare our results with those of four published grids of massive stellar evolution models (Geneva, STERN, Padova and FRANEC codes). We first investigate the effects of overshooting, mass loss, metallicity, chemical composition. We subsequently focus on rotation. Finally, we compare the predictions of published evolutionary models with the observed properties of a large sample of Galactic stars.