- ID:
- ivo://CDS.VizieR/J/MNRAS/419/2844
- Title:
- Radial metallicity gradient from RAVE DR3
- Short Name:
- J/MNRAS/419/2844
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate radial metallicity gradients for a sample of dwarf stars from the RAdial Velocity Experiment (RAVE) Data Release 3 (DR3, Cat. III/265). We select a total of approximately 17000 F-type and G-type dwarfs, using a selection of colour, log g and uncertainty in the derived space motion, and calculate for each star a probabilistic (kinematic) population assignment to a thick or thin disc using space motion and additionally another (dynamical) assignment using stellar vertical orbital eccentricity. We additionally subsample by colour, to provide samples biased toward young thin-disc and older thin-disc stars. We derive a metallicity gradient as a function of Galactocentric radial distance, i.e. d[M/H]/dRm=-0.051+/-0.005dex/kpc, for the youngest sample, F-type stars with vertical orbital eccentricities e_v_<=0.04. Samples biased toward older thin-disc stars show systematically shallower abundance gradients.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/813/89
- Title:
- Radial velocities of Milky Way inner halo stars
- Short Name:
- J/ApJ/813/89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure the three components of velocity dispersion, {sigma}_R_, {sigma}_{theta}_, {sigma}_{phi}_, for stars within 6<R<30kpc of the Milky Way using a new radial velocity sample from the MMT telescope. We combine our measurements with previously published data so that we can more finely sample the stellar halo. We use a maximum likelihood statistical method for estimating mean velocities, dispersions, and covariances assuming only that velocities are normally distributed. The alignment of the velocity ellipsoid is consistent with a spherically symmetric gravitational potential. From the spherical Jeans equation, the mass of the Milky Way is M(R<=12kpc)=1.3x10^11^M_{sun}_ with an uncertainty of 40%. We also find a region of discontinuity, 15<~R<~25kpc, where the estimated velocity dispersions and anisotropies diverge from their anticipated values, confirming the break observed by others. We argue that this break in anisotropy is physically explained by coherent stellar velocity structure in the halo, such as the Sgr stream. To significantly improve our understanding of halo kinematics will require combining radial velocities with future Gaia proper motions.
- ID:
- ivo://CDS.VizieR/J/ApJS/147/103
- Title:
- Radial velocities of overluminous F stars
- Short Name:
- J/ApJS/147/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a radial-velocity survey of bright (V<9), overluminous, F stars within 80pc. Of the total of 118 stars selected, the radial velocities of 77 have been measured with the Cambridge CORAVEL in the present survey.
- ID:
- ivo://CDS.VizieR/J/ApJ/595/1206
- Title:
- ROSAT view of Hipparcos F stars
- Short Name:
- J/ApJ/595/1206
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For a set of 11900 F stars that have uvby photometry and are in the Hipparcos (Cat. <I/239>) catalog, we have found 1980 X-ray counterparts (~17%) in the ROSAT All-Sky Surveys (RASS, Cat. <IX/10> and <IX/29>). In this paper we analyze X-ray properties of these ROSAT F stars and compare that sample with the entire set of our F stars.
- ID:
- ivo://CDS.VizieR/J/A+A/398/647
- Title:
- Rotational velocities of F and G stars
- Short Name:
- J/A+A/398/647
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed study of rotation and differential rotation analyzing high resolution high S/N spectra of 142 F-, G- and early K-type field stars. Using Least Squares Deconvolution we obtain broadening profiles for our sample stars and use the Fourier transform method to determine projected rotational velocities vsini. Distributions of rotational velocities and periods are studied in the HR-diagram. For a subsample of 32 stars of spectral type F0-G0 we derive the amount of differential rotation. We find evidence for differential rotation in ten of the 32 stars. The observations were done with the ESO 3.6m telescope at La Silla, Chile, in October 2000, October 2001 and April 2002. The CES instrument (resolution 235000) was used, in the wavelength regions 577-581nm and 322.5-627nm.
- ID:
- ivo://CDS.VizieR/J/A+A/412/813
- Title:
- Rotation in F-stars
- Short Name:
- J/A+A/412/813
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtained high quality spectra of 135 stars of spectral types F and later and derived "overall" broadening functions in selected wavelength regions utilizing a Least Squares Deconvolution (LSD) procedure. Precision values of the projected rotational velocity vsini were derived from the first zero of the Fourier transformed profiles and the shapes of the profiles were analyzed for effects of differential rotation. The broadening profiles of 70 stars rotating faster than vsini=45km/s show no indications of multiplicity nor of spottedness. In those profiles we used the ratio of the first two zeros of the Fourier transform q2/q1 to search for deviations from rigid rotation. In the vast majority the profiles were found to be consistent with rigid rotation. Five stars were found to have flat profiles probably due to cool polar caps, in three stars cuspy profiles were found. Two out of those three cases may be due to extremely rapid rotation seen pole on, only in one case (vsini=52km/s) solar-like differential rotation is the most plausible explanation for the observed profile. These results indicate that the strength of differential rotation diminishes in stars rotating as rapidly as vsini>50km/s.
- ID:
- ivo://CDS.VizieR/J/ApJ/738/122
- Title:
- ScoCen debris disks Around F- and G-type stars
- Short Name:
- J/ApJ/738/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtained Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS) 24 micron and 70 micron observations of 182 nearby, Hipparcos F- and G-type common proper motion single and binary systems in the nearest OB association, Scorpius-Centaurus. We also obtained Magellan/MIKE R~50,000 visual spectra at 3500-10500{AA} for 181 candidate ScoCen stars in single and binary systems. Combining our MIPS observations with those of other ScoCen stars in the literature, we estimate 24 micron F+G-type disk fractions of 9/27 (33%+/-11%), 21/67 (31%+/-7%), and 25/71 (35%+/-7%) for Upper Scorpius (~10Myr), Upper Centaurus Lupus (~15Myr), and Lower Centaurus Crux (~17Myr), respectively. We confirm previous IRAS and MIPS excess detections and present new discoveries of 41 protoplanetary and debris disk systems, with fractional infrared luminosities ranging from L_IR/L_*=10^-5^ to 1.0^-2^ and grain temperatures ranging from T_gr_=40-300K. We searched for an increase in 24 micron excess at an age of 15-20Myr, consistent with the onset of debris production predicted by coagulation N-body simulations of outer planetary systems. We found such an increase around 1.5M_{sun}_ stars but discovered a decrease in the 24 micron excess around 1.0M_{sun}_ stars. We additionally discovered that the 24 micron excess around 1.0M_{sun}_ stars is larger than predicted by self-stirred models. Finally, we found a weak anti-correlation between fractional infrared luminosity (L_IR/L_*) and chromospheric activity (R'_HK), that may be the result of differences in stellar HK properties, such as mass, luminosity, and/or winds. We obtained Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS) 24 micron and 70 micron observations of 182 nearby, Hipparcos F- and G-type common proper motion single and binary systems in the nearest OB association, Scorpius-Centaurus. We also obtained Magellan/MIKE R~50,000 visual spectra at 3500-10500{AA} for 181 candidate ScoCen stars in single and binary systems. Combining our MIPS observations with those of other ScoCen stars in the literature, we estimate 24 micron F+G-type disk fractions of 9/27 (33%+/-11%), 21/67 (31%+/-7%), and 25/71 (35%+/-7%) for Upper Scorpius (~10Myr), Upper Centaurus Lupus (~15Myr), and Lower Centaurus Crux (~17Myr), respectively. We confirm previous IRAS and MIPS excess detections and present new discoveries of 41 protoplanetary and debris disk systems, with fractional infrared luminosities ranging from L_IR/L_* = 10^-5^ to 10^-2^ and grain temperatures ranging from T_gr_=40-300K. We searched for an increase in 24 micron excess at an age of 15-20Myr, consistent with the onset of debris production predicted by coagulation N-body simulations of outer planetary systems. We found such an increase around 1.5M_{sun}_ stars but discovered a decrease in the 24 micron excess around 1.0M_{sun}_ stars. We additionally discovered that the 24 micron excess around 1.0M_{sun}_ stars is larger than predicted by self-stirred models.
- ID:
- ivo://CDS.VizieR/J/A+A/651/A11
- Title:
- SOPHIE radial velocities of 27 F/G stars
- Short Name:
- J/A+A/651/A11
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Distinguishing classes within substellar objects and understanding their formation and evolution need larger samples of substellar companions such as exoplanets, brown dwarfs, and low-mass stars. In this paper, we look for substellar companions using radial velocity surveys of FGK stars with the SOPHIE spectrograph at the Observatoire de Haute-Provence. We assign here the radial velocity variations of 27 stars to their orbital motion induced by low-mass companions. We also constrained their plane-of-the-sky motion using HIPPARCOS and Gaia Data Release 1 measurements, which constrain the true masses of some of these companions. We report the detection and characterization of six cool Jupiters, three brown dwarf candidates, and 16 low-mass stellar companions. We additionally update the orbital parameters of the low-mass star HD 8291 B, and we conclude that the radial velocity variations of HD 204277 are likely due to stellar activity despite resembling the signal of a giant planet. One of the new giant planets, BD+631405 b, adds to the population of highly eccentric cool Jupiters, and it is presently the most massive member. Two of the cool Jupiter systems also exhibit signatures of an additional outer companion. The orbital periods of the new companions span 30 days to 11.5 years, their masses 0.72M_Jup_ to 0.61M_{sun}_, and their eccentricities 0.04 to 0.88. These discoveries probe the diversity of substellar objects and low-mass stars, which will help constrain the models of their formation and evolution.
- ID:
- ivo://CDS.VizieR/J/PAZh/30/173
- Title:
- Space velocities of solar neighborhood stars
- Short Name:
- J/PAZh/30/173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For 77 main-sequence F-G stars in the solar neighborhood with published iron, magnesium, and europium abundances and with the ages we calculated the spatial velocities using Hipparcos data and the galactic orbital elements. A comparison with the orbital elements of the globular clusters that are known to have been accreted by our Galaxy in the past reveals stars of the extragalactic origin. We show that the abundance ratios of r- and {alpha}-elements in all the accreted stars differ sharply from those in the stars that are genetically associated with the Galaxy.
- ID:
- ivo://CDS.VizieR/J/AJ/160/52
- Title:
- Spectral classification for 631 {rho}Puppis stars
- Short Name:
- J/AJ/160/52
- Date:
- 09 Mar 2022
- Publisher:
- CDS
- Description:
- The {rho}Puppis stars are mid-F-type stars that show peculiar chemical-abundance patterns similar to those of the Am stars. Typically they exhibit overabundances of iron-peak elements such as Fe and Ni and s- and r-process elements such as Sr and Eu, and underabundances of certain other elements including He, Ca, and Sc. It has been proposed that these stars are evolving Am stars passing through the short-lived phase that occurs between the re-establishment of convection and the consequent erasure of their chemical peculiarities. In this paper we suggest a second hypothesis: these stars may have acquired their peculiar abundance patterns in a fashion similar to the Barium stars, i.e., they may have gained the s-process element enhancements via mass transfer from a once asymptotic giant-branch companion star, now turned white dwarf. This study will detail our efforts to investigate the {rho}Puppis stars with regard to these two hypotheses, with a view to understanding these stars and their significance in terms of stellar evolution. We have performed a spectral classification survey, and a detailed chemical-abundance analysis of selected {rho}Puppis stars. This paper gives an overview of the {rho}Puppis stars and describes the spectral classification survey which has increased the number of {rho}Puppis stars currently known from 6 to 49. A future paper will describe the chemical-abundance analysis which should provide insight into the nature of these stars.
