- ID:
- ivo://CDS.VizieR/J/AJ/147/86
- Title:
- From binaries to multiples. I. The FG-67 sample
- Short Name:
- J/AJ/147/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Data on the multiplicity of F- and G-type dwarf stars within 67pc of the Sun are presented. This distance-limited sample based on the Hipparcos catalog contains 4847 primary stars (targets) with 0.5<V-I_C_<0.8 and is >90% complete. There are 2196 known stellar pairs; some of them belong to 361 hierarchical systems from triples to quintuples. Models of companion detection by radial velocity, astrometric acceleration, direct resolution, and common proper motion are developed. They serve to compute completeness for each target, using the information on its coverage collected here. About 80% of companions to the primary stars are detected, but the census of subsystems in the secondary components is only about 30%. Masses of binary components are estimated from their absolute magnitudes or by other methods; the periods of wide pairs are evaluated from their projected separations. A third of binaries with periods shorter than ~100yr are spectroscopic and/or astrometric pairs with yet unknown periods and mass ratios. These data are used in the accompanying Paper II to derive unbiased statistics of hierarchical multiple systems.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/2127
- Title:
- Fundamental parameters of Kepler stars
- Short Name:
- J/MNRAS/452/2127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of 33 Kepler planet-candidate host stars for which asteroseismic observations have sufficiently high signal-to-noise ratio to allow extraction of individual pulsation frequencies. We implement a new Bayesian scheme that is flexible in its input to process individual oscillation frequencies, combinations of them, and average asteroseismic parameters, and derive robust fundamental properties for these targets. Applying this scheme to grids of evolutionary models yields stellar properties with median statistical uncertainties of 1.2 per cent (radius), 1.7 per cent (density), 3.3 per cent (mass), 4.4 per cent (distance), and 14 per cent (age), making this the exoplanet host-star sample with the most precise and uniformly determined fundamental parameters to date. We assess the systematics from changes in the solar abundances and mixing-length parameter, showing that they are smaller than the statistical errors. We also determine the stellar properties with three other fitting algorithms and explore the systematics arising from using different evolution and pulsation codes, resulting in 1 per cent in density and radius, and 2 per cent and 7 per cent in mass and age, respectively. We confirm previous findings of the initial helium abundance being a source of systematics comparable to our statistical uncertainties, and discuss future prospects for constraining this parameter by combining asteroseismology and data from space missions. Finally, we compare our derived properties with those obtained using the global average asteroseismic observables along with effective temperature and metallicity, finding excellent level of agreement. Owing to selection effects, our results show that the majority of the high signal-to-noise ratio asteroseismic Kepler host stars are older than the Sun.
- ID:
- ivo://CDS.VizieR/J/MNRAS/445/4395
- Title:
- Fundamental properties of giant gas planets
- Short Name:
- J/MNRAS/445/4395
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is already stated in the previous studies that the radius of the giant planets is affected by stellar irradiation. The confirmed relation between radius and incident flux depends on planetary mass intervals. In this study, we show that there is a single relation between radius and irradiated energy per gram per second (l-), for all mass intervals. There is an extra increase in radius of planets if l- is higher than 1100 times energy received by the Earth (l_{earth}_). This is likely due to dissociation of molecules. The tidal interaction as a heating mechanism is also considered and found that its maximum effect on the inflation of planets is about 15 percent. We also compute age and heavy element abundances from the properties of host stars, given in the TEPCat catalogue (Southworth). The metallicity given in the literature is as [Fe/H]. However, the most abundant element is oxygen, and there is a reverse relation between the observed abundances [Fe/H] and [O/Fe]. Therefore, we first compute [O/H] from [Fe/H] by using observed abundances, and then find heavy element abundance from [O/H]. We also develop a new method for age determination. Using the ages we find, we analyse variation of both radius and mass of the planets with respect to time, and estimate the initial mass of the planets from the relation we derive for the first time. According to our results, the highly irradiated gas giants lose 5 percent of their mass in every 1Gyr.
- ID:
- ivo://CDS.VizieR/J/other/RMxAA/53.439
- Title:
- Gaia stars with GALEX NUV excess
- Short Name:
- J/other/RMxAA/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate parallaxes from Gaia DR1 (TGAS) are combined with GALEX visual Nuv magnitudes to produce absolute MNUV magnitudes and an ultraviolet HR diagram for a large sample of astrometric stars. A functional fit is derived of the lower envelope main sequence of the nearest 1403 stars (distance <40pc), which should be reddening-free. Using this empirical fit, 50 nearby stars are selected with significant Nuv excess. These are predominantly late K and early M dwarfs, often associated with X-ray sources, and showing other manifestations of magnetic activity. The sample may include systems with hidden white dwarfs, stars younger than the Pleiades, or, most likely, tight interacting binaries of the BY Dra-type. A separate collection of 40 stars with precise trigonometric parallaxes and Nuv-G colors bluer than 2mag is presented. It includes several known novae, white dwarfs, and binaries with hot subdwarf (sdOB) components, but most remain unexplored.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A116
- Title:
- Galactic Cepheids and RR Lyrae multiplicity. I.
- Short Name:
- J/A+A/623/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Classical Cepheids (CCs) and RR Lyrae stars (RRLs) are important classes of variable stars used as standard candles to estimate galactic and extragalactic distances. Their multiplicity is imperfectly known, particularly for RRLs. Astoundingly, only one RRL is convincingly demonstrated to be a binary as of today, TU UMa, out of tens of thousands of known RRLs. We aim at detecting the binary and multiple stars present in a sample of Milky Way CCs and RRLs. In the present article, we combine the Hipparcos and Gaia DR2 positions to determine the mean proper motion of the targets, and we search for proper motion anomalies (PMa) caused by close-in orbiting companions. We identify 57 CC binaries from PMa out of 254 tested stars, and 75 additional candidates, confirming the high binary fraction of these massive stars. For 28 binary CCs, we determine the companion mass by combining their spectroscopic orbital parameters and astrometric PMa. We detect 13 RRLs showing a significant PMa out of 198 tested stars, and 61 additional candidates. We determine that the binarity fraction of CCs is likely above 80%, while that of RRLs is at least 7%. The newly detected systems will be useful to improve our understanding of their evolutionary states. The discovery of a significant number of RRLs in binary systems also resolves the long-standing mystery of their extremely low apparent binarity fraction.
- ID:
- ivo://CDS.VizieR/J/A+A/518/A1
- Title:
- Galactic massive stars with AstraLux
- Short Name:
- J/A+A/518/A1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive stars have high-multiplicity fractions, and many of them have still undetected components, thus hampering the study of their properties. I study a sample of massive stars with high angular resolution to better characterize their multiplicity. I observed 138 fields that include at least one massive star with AstraLux, a lucky imaging camera at the 2.2m Calar Alto telescope. I also used observations of 3 of those fields with ACS/HRC on HST to obtain complementary information and to calibrate the AstraLux data. The results were compared with existing information from the Washington Double Star Catalog, Tycho-2, 2MASS, and other literature results.
- ID:
- ivo://CDS.VizieR/J/MNRAS/487/2474
- Title:
- GALAH unresolved triple Sun-like star
- Short Name:
- J/MNRAS/487/2474
- Date:
- 02 Mar 2022 00:37:36
- Publisher:
- CDS
- Description:
- The latest Gaia data release enables us to accurately identify stars that are more luminous than would be expected on the basis of their spectral type and distance. During an investigation of the 329 best solar twin candidates uncovered among the spectra acquired by the GALAH survey, we identified 64 such overluminous stars. In order to investigate their exact composition, we developed a data-driven methodology that can generate a synthetic photometric signature and spectrum of a single star. By combining multiple such synthetic stars into an unresolved binary or triple system and comparing the results to the actual photometric and spectroscopic observations, we uncovered 6 definitive triple stellar system candidate and an additional 14 potential candidates whose combined spectrum mimics the solar spectrum. Considering the volume correction factor for a magnitude-limited survey, the fraction of probable unresolved triple stars with long orbital periods is 2 per cent. Possible orbital configurations of the candidates were investigated using the selection and observational limits. To validate the discovered multiplicity fraction, the same procedure was used to evaluate the multiplicity fraction of other stellar types.
- ID:
- ivo://CDS.VizieR/J/ApJ/766/9
- Title:
- GALEX observations of exoplanet host stars
- Short Name:
- J/ApJ/766/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the far-UV (FUV) and near-UV (NUV) photometry from the NASA Galaxy Evolution Explorer (GALEX), we searched for evidence of increased stellar activity due to tidal and/or magnetic star-planet interactions (SPI) in the 272 known FGK planetary hosts observed by GALEX. With the increased sensitivity of GALEX, we are able probe systems with lower activity levels and at larger distances than what has been done to date with X-ray satellites. We compared samples of stars with close-in planets (a<0.1AU) to those with far-out planets (a>0.5AU) and looked for correlations of excess activity with other system parameters. This statistical investigation found no clear correlations with a, M_p_, or M_p_/a, in contrast to some X-ray and CaII studies. However, there is tentative evidence (at a level of 1.8{sigma}) that stars with radial-velocity-(RV)-detected close-in planets are more FUV-active than stars with far-out planets, in agreement with several published X-ray and Ca II results. The case is strengthened to a level of significance to 2.3{sigma} when transit-detected close-in planets are included. This is most likely because the RV-selected sample of stars is significantly less active than the field population of comparable stars, while the transit-selected sample is similarly active. Given the factor of 2-3 scatter in fractional FUV luminosity for a given stellar effective temperature, it is necessary to conduct a time-resolved study of the planet hosts in order to better characterize their UV variability and generate a firmer statistical result.
- ID:
- ivo://CDS.VizieR/J/ApJ/670/1367
- Title:
- Gemini Deep Planet Survey
- Short Name:
- J/ApJ/670/1367
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the Gemini Deep Planet Survey, a near-infrared adaptive optics search for giant planets and brown dwarfs around 85 nearby young stars. The observations were obtained with the Altair adaptive optics system at the Gemini North telescope, and angular differential imaging was used to suppress the speckle noise of the central star. Typically, the observations are sensitive to angular separations beyond 0.5" with 5{sigma} contrast sensitivities in magnitude difference at 1.6um of 9.5 at 0.5", 12.9 at 1", 15.0 at 2", and 16.5 at 5". These sensitivities are sufficient to detect planets more massive than 2M_{Jup}_ with a projected separation in the range 40-200AU around a typical target. Second-epoch observations of 48 stars with candidates (out of 54) have confirmed that all candidates are unrelated background stars. A detailed statistical analysis of the survey results is presented.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A12
- Title:
- GG Tau A ALMA ^13^CO and C^18^O(3-2) maps
- Short Name:
- J/A+A/635/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- GG Tau A is the prototype of a young triple T Tauri star that is surrounded by a massive and extended Keplerian outer disk. The central cavity is not devoid of gas and dust and at least GG Tau Aa exhibits its own disk of gas and dust emitting at millimeter wavelengths. Its observed properties make this source an ideal laboratory for investigating planet formation in young multiple solartype stars. We used new ALMA ^13^CO and C^18^O(3-2) observations obtained at high angular resolution (~0.2") together with previous CO(3-2) and (6-5) ALMA data and continuum maps at 1.3 and 0.8mm in order to determine the gas properties (temperature, density, and kinematics) in the cavity and to a lesser extent in the outer disk. By deprojecting, we studied the radial and azimuthal gas distribution and its kinematics. We also applied a new method to improve the deconvolution of the CO data and in particular better quantify the emission from gas inside the cavity. We perform local nonlocal thermodynamic equilibrium studies in order to determine the excitation conditions and relevant physical parameters inside the ring and in the central cavity. Residual emission after removing a smooth-disk model indicates unresolved structures at our angular resolution, probably in the form of irregular rings or spirals. The outer disk is cold, with a temperature <20K beyond 250au that drops quickly ({prop.to}r^-1^). The kinematics of the gas inside the cavity reveals infall motions at about 10% of the Keplerian speed. We derive the amount of gas in the cavity, and find that the brightest clumps, which contain about 10% of this mass, have kinetic temperatures 40-80K, CO column densities of a few 10^17^cm^-2^, and H_2_ densities around 10^7^cm^-3^. Although the gas in the cavity is only a small fraction of the disk mass, the mass accretion rate throughout the cavity is comparable to or higher than the stellar accretion rate. It is accordingly sufficient to sustain the circumstellar disks on a long timescale.