- ID:
- ivo://CDS.VizieR/J/MNRAS/443/2815
- Title:
- Cerro Armazones spectroscopy of F dwarfs
- Short Name:
- J/MNRAS/443/2815
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic survey of a sample of F stars that have not yet been searched for planets. The observations of 187 stars obtained with the Bochum Echelle Spectrographic Observer of the Cerro Armazones Observatory were aimed at nearby (closer than 70pc) main-sequence stars without sufficient archive ([fiber-fed extended range optical spectrograph (FEROS)/high accuracy radial velocity planet search (HARPS)]) spectroscopy. The primary goal of the survey was to select the best candidates for radial-velocity searches of extrasolar planets. The spectra were analysed using the broadening-function technique, the method of choice for rapid rotators later than about A5. The analysis was focused not only at the determination of projected rotational velocity (defining precision of radial-velocity determination), but also at the detection of previously unknown spectroscopic binaries/multiples or stars showing strong line asymmetries. 12 previously unknown spectroscopic binaries/triples were detected. For all observed targets the spectral type was determined. About 140 stars are rotating faster than the resolution limit of 10km/s sampling the onset of convection and slow rotation at mid-F spectral types in great detail. Radial-velocity precision of the data (about 100m/s) is insufficient to detect planets but could indicate most SB1 systems with stellar companions. As there are already 2-3 observations per object for these newly detected binary stars, only a few additional follow-up observations will be needed to obtain constraints on orbital parameters. We identified a sample of 68 bright F-type dwarf stars which are perfect targets for future planet searches. They rotate moderately or slowly and do not show any sign of binarity, pulsations, or surface activity.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/636/1098
- Title:
- Debris disks around solar-type stars
- Short Name:
- J/ApJ/636/1098
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have searched for infrared excesses around a well-defined sample of 69 FGK main-sequence field stars. These stars were selected without regard to their age, metallicity, or any previous detection of IR excess; they have a median age of 4Gyr.
- ID:
- ivo://CDS.VizieR/J/MNRAS/367/1329
- Title:
- Elemental abundances for 176 stars
- Short Name:
- J/MNRAS/367/1329
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed an abundance analysis for F- and G- dwarfs of the Galactic thick-disc component. A sample of 176 nearby (d<=150pc) thick-disc candidate stars was chosen from the Hipparcos catalogue and subjected to a high-resolution spectroscopic analysis. Using accurate radial velocities combined with the Hipparcos astrometry, kinematics (U, V and W) and Galactic orbital parameters were computed. We estimate the probability for a star to belong to the thin disc, the thick disc or the halo. With a probability P>=70 per cent taken as certain membership, we assigned 95 stars to the thick disc, 13 to the thin disc, and 20 to the halo. The remaining 48 stars in the sample cannot be assigned with reasonable certainty to one of the three components. Abundances of C, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Ba, Ce, Nd and Eu have been obtained.
- ID:
- ivo://CDS.VizieR/J/A+A/381/500
- Title:
- Eu abundances in F and G disk stars
- Short Name:
- J/A+A/381/500
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Europium abundances for 74 F and G dwarf stars of the galactic disk have been determined. The stars were selected from the sample of Edvardsson et al. (1993, Cat. <J/A+A/275/101>) and [Eu/Fe] shows a smaller scatter and a slightly weaker trend with [Fe/H] than found by Woolf et al. (1995ApJ...453..660W). The data of the two analyses are homogeneized and merged.
- ID:
- ivo://CDS.VizieR/J/MNRAS/360/1345
- Title:
- F- and G-type stars in solar neighbourhood
- Short Name:
- J/MNRAS/360/1345
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new metallicity distribution and an age-metallicity relation are presented for 437 nearby F and G turn-off and sub-giant stars selected from radial velocity data of Nidever et al. (2002, Cat. J/ApJS/141/503). Photometric metallicities are derived from uvby-H{beta} photometry, and the stellar ages from the isochrones of Bergbusch & VandenBerg (2001ApJ...556..322B) as transformed to uvby photometry using the methods of Clem et al. (2004, Cat. J/AJ/127/1227).
- ID:
- ivo://CDS.VizieR/J/A+A/415/993
- Title:
- FeII, ZNI and SI abundances on halo stars
- Short Name:
- J/A+A/415/993
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The table gives equivalent widths (in m{AA}) for 19 FeII lines, two ZnI lines, and four SI lines, as measured in high resolution VLT/UVES spectra of 34 metal-poor, main sequence and subgiant, halo stars.
- ID:
- ivo://CDS.VizieR/J/AJ/160/217
- Title:
- 342 FGK-dwarfs ages using GALEX FUV magnitudes
- Short Name:
- J/AJ/160/217
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar age cannot be directly measured, yet age determinations are fundamental to understanding the evolution of stars, planets, and galaxies. The work presented here builds upon the idea of a stellar-activity age. We utilized far-ultraviolet (FUV) photometry acquired by the Galaxy Evolution Explorer (GALEX) space telescope as an indicator of chromospheric activity to infer ages of late-F, G, and K type dwarf stars. We derived a purely empirical correlation between FUV magnitudes and stellar age in conjunction with (B-V) color. Our attention is restricted to Sun-like stars with color range 0.55<=(B-V)<=0.71 and absolute magnitude range 4.3<=MV<=5.3. The correlation is defined in terms of a FUV-excess parameter Q(FUV-B,B-V). We related stellar age, {tau}, to Q through the relation log_e_({tau})=log_e_(a)+bQ, where a and b are fit parameters and functions of (B-V). This correlation is functional up to 6Gyr for FGK dwarfs. With such a correlation, one only needs Johnson (B-V) and FUV measurements to estimate the stellar age for Population i dwarf stars of solar-like temperature and metallicity. Such a calibration has utility in population studies of FGK dwarfs for further understanding of the chemical evolution of the Milky Way. As an illustration of one such application, we have constructed activity and FUV-age distributions for a sample of thin and thick disk stars, as distinguished by their chemical abundances. Considerable overlap is found between the activity distribution and age range of the two populations. We discuss the possibility that some high-[{alpha}/Fe] thick disk stars were formed as a result of the accretion of dwarf galaxies as recently as 4Gyr ago.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A57
- Title:
- F-G-K stars activity indicators
- Short Name:
- J/A+A/658/A57
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Different relationships between the H{alpha} and CaII chromospheric emissions have been reported in solar-type stars. In particular, the time-series of emissions in these two lines are clearly anti-correlated for a few percent of the stars, contrary to what is observed on the Sun. Our objective is to characterise these relationships in more detail using complementary criteria, and to constrain the properties of filaments and plages that are necessary to explain the observations. We analysed the average level and variability of the H{alpha} and CaII emission for 441 F-G-K stars, paying particular attention to their (anti-)correlations on both short and long timescales. We also computed synthetic H{alpha} and CaII time-series for different assumptions of plage and filament properties and compared them with the observations. We were not able to find plage properties that, alone, are sufficient to reproduce the observations at all timescales simultaneously, even when allowing different H{alpha} and CaII emission relationships for different stars. We also specified the complex and surprising relationship between the average activity levels of both indexes, in particular for low-activity stars. We conclude that plages alone are unlikely to explain the observed variety of relationships between CaII and H{alpha} emission, and that the presence of other phenomena like filaments may help to reconcile the models with observations.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/9
- Title:
- FGK stars magnetic activity in LAMOST-Kepler field
- Short Name:
- J/ApJS/247/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Monitoring chromospheric and photospheric indexes of magnetic activity can provide valuable information, especially the interaction between different parts of the atmosphere and their response to magnetic fields. We extract chromospheric indexes, S and R_HK_^+^, for 59816 stars from LAMOST spectra in the LAMOST-Kepler program, and photospheric index, Reff, for 5575 stars from Kepler light curves. The log Reff shows positive correlation with logR_HK_^+^. We estimate the power-law indexes between Reff and R_HK_^+^ for F-, G-, and K-type stars, respectively. We also confirm the dependence of both chromospheric and photospheric activity on stellar rotation. Ca ii H and K emissions and photospheric variations generally decrease with increasing rotation periods for stars with rotation periods exceeding a few days. The power-law indexes in exponential decay regimes show different characteristics in the two activity-rotation relations. The updated largest sample including the activity proxies and reported rotation periods provides more information to understand the magnetic activity for cool stars.
- ID:
- ivo://CDS.VizieR/J/A+A/636/A85
- Title:
- 3748 FGK stars spectroscopic parameters
- Short Name:
- J/A+A/636/A85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Apache Point Observatory Galactic Evolution Experiment (APOGEE) has observed the H-band spectra of over 200000 stars with R~22 000. The main motivation for this work is to test an alternative method to the standard APOGEE pipeline (APOGEE Stellar Parameter and Chemical Abundances Pipeline, ASPCAP) to derive parameters in the near-infrared (NIR) for FGK dwarfs. iSpec and Turbospectrum are used to generate synthetic spectra matching APOGEE observations and to determine the parameters through chi^2^ minimization. We present spectroscopic parameters (Teff, [M/H], logg, v_mic_) for a sample of 3748 main-sequence and subgiant FGK stars, obtained from their APOGEE H-band spectra. We compare our output parameters with the ones obtained with ASPCAP for the same stellar spectrum, and find that the values agree within the expected uncertainties. A comparison with the optical samples, California Planet Survey, HARPS-GTO, and PASTEL is also available, and median differences below 10K for Teff and 0.2dex for [M/H] are found. Reasons for these differences are explored. The full H-band line list, the line selection for the synthesis, and the synthesized spectra are available for download, as are the calculated parameters and their estimated uncertainties.
