- ID:
- ivo://CDS.VizieR/J/AJ/150/200
- Title:
- Photometry and spectroscopy of stars in Cz 30
- Short Name:
- J/AJ/150/200
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new photometric and spectroscopic data of the old open cluster Czernik 30. Wide field BVI photometry allows us to correct for the high field contamination by statistical subtraction to produce a color-magnitude diagram (CMD) that clearly reveals the cluster sequence. From spectra of stars in the cluster field obtained with the Hydra spectrograph on the Wisconsin-Indiana-Yale-NOAO 3.5m telescope we determine a mean cluster velocity of +79.9+/-1.5km/s and provide membership information that helps further define the cluster giant branch and red clump. Stellar abundances for the brighter giants in the cluster indicate a mean metallicity of [Fe/H]=-0.2+/-0.15. Fitting theoretical isochrones to the CMD we determine the following properties of Czernik 30: age=2.8+/-0.3Gyr, (m-M)_v_=14.8+/-0.1, E(B-V)=0.24+/-0.06, and E(V-I)=0.36+/-0.04. Czernik 30 is an old, sub-solar metallicity cluster located at a Galactocentric radius of R_gc_~13.3kpc. Given its age and position just beyond the transition to a flat abundance gradient seen in the open cluster population, Czernik 30 provides an interesting target for future observations.
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- ID:
- ivo://CDS.VizieR/J/A+A/615/A6
- Title:
- Photospheric parameters of CARMENES stars
- Short Name:
- J/A+A/615/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The new CARMENES instrument comprises two high-resolution and high-stability spectrographs that are used to search for habitable planets around M dwarfs in the visible and near-infrared regime via the Doppler technique. Characterising our target sample is important for constraining the physical properties of any planetary systems that are detected. The aim of this paper is to determine the fundamental stellar parameters of the CARMENES M-dwarf target sample from high-resolution spectra observed with CARMENES. We also include several M-dwarf spectra observed with other high-resolution spectrographs, that is CAFE, FEROS, and HRS, for completeness. We used a {chi}^2^ method to derive the stellar parameters effective temperature T_eff, surface gravity log g, and metallicity [Fe/H] of the target stars by fitting the most recent version of the PHOENIX-ACES models to high-resolution spectroscopic data. These stellar atmosphere models incorporate a new equation of state to describe spectral features of low-temperature stellar atmospheres. Since Teff, logg, and [Fe/H] show degeneracies, the surface gravity is determined independently using stellar evolutionary models. We derive the stellar parameters for a total of 300 stars. The fits achieve very good agreement between the PHOENIX models and observed spectra. We estimate that our method provides parameters with uncertainties of {sigma}_Teff_=51K, {sigma}_logg_=0.07, and {sigma}_[Fe/H]_=0.16, and show that atmosphere models for low-mass stars have significantly improved in the last years. Our work also provides an independent test of the new PHOENIX-ACES models, and a comparison for other methods using low-resolution spectra. In particular, our effective temperatures agree well with literature values, while metallicities determined with our method exhibit a larger spread when compared to literature results.
- ID:
- ivo://CDS.VizieR/J/MNRAS/482/5379
- Title:
- Physical & orbital properties of detached EBs
- Short Name:
- J/MNRAS/482/5379
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified and photometrically characterized a sample of 230 detached close-orbiting eclipsing binaries with low-mass main-sequence components (LMMS) from the Catalina Sky Survey. These low-mass stars have both components below 1.0M_{sun}_, orbital periods shorter than 2-days and effective temperatures below to 5720K. The adopted method provided a robust estimate of stellar parameters (as mass and fractional radius) by using only light curves and photometric colors, since no spectroscopic information was available for these objects. Each light curve was modeled with the JKTEBOP code together with an asexual genetic algorithm to obtain the most coherent values for the fitted parameters. This new sample of short-period detached eclipsing binaries, with low-mass main-sequence stars (LMMS) considerably increases the number of previously known systems. Which allows us to derive masses and radii in statistically significant samples for the investigation of the correlation between radius inflation and other basic stellar parameters.
- 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/742/L19
- Title:
- Physics of Kepler hot rocky planetary candidates
- Short Name:
- J/ApJ/742/L19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper outlines a simple approach to evaluate the atmospheric composition of hot rocky planets by assuming different types of planetary composition and using corresponding model calculations. To explore hot atmospheres above 1000K, we model the vaporization of silicate magma and estimate the range of atmospheric compositions according to the planet's radius and semi-major axis for the Kepler 2011 February data release. Our results show five atmospheric types for hot, rocky super-Earth atmospheres, strongly dependent on the initial composition and the planet's distance to the star. We provide a simple set of parameters that can be used to evaluate atmospheric compositions for current and future candidates provided by the Kepler mission and other searches.
- ID:
- ivo://CDS.VizieR/J/AJ/156/22
- Title:
- Planetary candidates from K2 Campaign 16
- Short Name:
- J/AJ/156/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Given that Campaign 16 of the K2 mission is one of just two K2 campaigns observed so far in "forward-facing" mode, which enables immediate follow-up observations from the ground, we present a catalog of interesting targets identified through photometry alone. Our catalog includes 30 high-quality planet candidates (showing no signs of being non-planetary in nature), 48 more ambiguous events that may be either planets or false positives, 164 eclipsing binaries, and 231 other regularly periodic variable sources. We have released light curves for all targets in C16 and have also released system parameters and transit vetting plots for all interesting candidates identified in this paper. Of particular interest is a candidate planet orbiting the bright F dwarf HD 73344 (V=6.9, K=5.6) with an orbital period of 15 days. If confirmed, this object would correspond to a 2.56+/-0.18 R_{Earth}_ planet and would likely be a favorable target for radial velocity characterization. This paper is intended as a rapid release of planet candidates, eclipsing binaries, and other interesting periodic variables to maximize the scientific yield of this campaign, and as a test run for the upcoming TESS mission, whose frequent data releases call for similarly rapid candidate identification and efficient follow up.
- ID:
- ivo://CDS.VizieR/J/AJ/155/21
- Title:
- Planet candidates from K2 campaigns 5-8
- Short Name:
- J/AJ/155/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 151 planet candidates orbiting 141 stars from K2 campaigns 5-8 (C5-C8), identified through a systematic search of K2 photometry. In addition, we identify 16 targets as likely eclipsing binaries, based on their light curve morphology. We obtained follow-up optical spectra of 105/141 candidate host stars and 8/16 eclipsing binaries to improve stellar properties and to identify spectroscopic binaries. Importantly, spectroscopy enables measurements of host star radii with ~10% precision, compared to ~40% precision when only broadband photometry is available. The improved stellar radii enable improved planet radii. Our curated catalog of planet candidates provides a starting point for future efforts to confirm and characterize K2 discoveries.
- ID:
- ivo://CDS.VizieR/J/AJ/153/136
- Title:
- Planets and their host stars with Gaia parallaxes
- Short Name:
- J/AJ/153/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present empirical measurements of the radii of 116 stars that host transiting planets. These radii are determined using only direct observables - the bolometric flux at Earth, the effective temperature, and the parallax provided by the Gaia first data release - and thus are virtually model independent, with extinction being the only free parameter. We also determine each star's mass using our newly determined radius and the stellar density, a virtually model independent quantity itself from previously published transit analyses. These stellar radii and masses are in turn used to redetermine the transiting-planet radii and masses, again using only direct observables. The median uncertainties on the stellar radii and masses are 8% and 30%, respectively, and the resulting uncertainties on the planet radii and masses are 9% and 22%, respectively. These accuracies are generally larger than previously published model-dependent precisions of 5% and 6% on the planet radii and masses, respectively, but the newly determined values are purely empirical. We additionally report radii for 242 stars hosting radial-velocity (non-transiting) planets, with a median achieved accuracy of ~2%. Using our empirical stellar masses we verify that the majority of putative "retired A stars" in the sample are indeed more massive than ~1.2 M_{sun}_. Most importantly, the bolometric fluxes and angular radii reported here for a total of 498 planet host stars-with median accuracies of 1.7% and 1.8%, respectively-serve as a fundamental data set to permit the re-determination of transiting-planet radii and masses with the Gaia second data release to ~3% and ~5% accuracy, better than currently published precisions, and determined in an entirely empirical fashion.
- ID:
- ivo://CDS.VizieR/J/AJ/159/194
- Title:
- Planets around main sequence stars in GALEX UV
- Short Name:
- J/AJ/159/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most (~82%) of the over 4000 confirmed exoplanets known today orbit very close to their host stars, within 0.5au. Planets at such small orbital distances can result in significant interactions with their host stars, which can induce increased activity levels in them. In this work, we have searched for statistical evidence for star-planet interactions in the ultraviolet (UV) using the largest sample of 1355 Galaxy Evolution Explorer (GALEX) detected host stars with confirmed exoplanets and making use of the improved host-star parameters from Gaia DR2. From our analysis, we do not find any significant correlation between the UV activity of the host stars and their planetary properties. We further compared the UV properties of planet host stars to that of chromospherically active stars from the RAdial Velocity Experiment (RAVE) survey. Our results indicate that the enhancement in chromospheric activity of host stars due to star-planet interactions may not be significant enough to reflect in their near and far V broadband flux.