- ID:
- ivo://CDS.VizieR/J/AJ/135/785
- Title:
- SDSS-DR5 low-mass star spectroscopic sample
- Short Name:
- J/AJ/135/785
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic analysis of over 38000 low-mass stars from the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5). Analysis of this unprecedentedly large sample confirms the previously detected decrease in the fraction of magnetically active stars (as traced by H{alpha} emission) as a function of vertical distance from the Galactic Plane. The magnitude and slope of this effect varies as a function of spectral type. Using simple 1-D dynamical models, we demonstrate that the drop in activity fraction can be explained by thin disk dynamical heating and a rapid decrease in magnetic activity. The timescale for this rapid activity decrease changes according to the spectral type. By comparing our data to the simulations, we calibrate the age-activity relation at each M dwarf spectral type. We also present evidence for a possible decrease in the metallicity as a function of height above the Galactic Plane. In addition to our activity analysis, we provide line measurements, molecular band indices, colors, radial velocities, 3-D space motions and mean properties as a function of spectral type for the SDSS DR5 low-mass star sample.
Number of results to display per page
Search Results
1732. SDSS DR7 M dwarfs
- ID:
- ivo://CDS.VizieR/J/AJ/141/97
- Title:
- SDSS DR7 M dwarfs
- Short Name:
- J/AJ/141/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic catalog of 70,841 visually inspected M dwarfs from the seventh data release of the Sloan Digital Sky Survey. For each spectrum, we provide measurements of the spectral type, a number of molecular band heads, and the H{alpha}, H{beta}, H{gamma}, H{delta}, and CaII-K emission lines. In addition, we calculate the metallicity-sensitive parameter {zeta} and identify a relationship between {zeta} and the g-r and r-z colors of M dwarfs. We assess the precision of our spectral types (which were assigned by individual examination), review the bulk attributes of the sample, and examine the magnetic activity properties of M dwarfs, in particular those traced by the higher order Balmer transitions. Our catalog is cross-matched to 2MASS infrared data, and contains photometric distances for each star. Finally, we identify eight new late-type M dwarfs that are possibly within 25 pc of the Sun. Future studies will use these data to thoroughly examine magnetic activity and kinematics in late-type M dwarfs and examine the chemical and dynamical history of the local Milky Way.
- ID:
- ivo://CDS.VizieR/J/A+A/471/17
- Title:
- SDSS-DR4 nearby clusters global properties
- Short Name:
- J/A+A/471/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Large surveys such as the Sloan Digital Sky Survey have made large amounts of spectroscopic and photometric data of galaxies available, thereby providing important information for studying galaxy evolution in dense environments. We have selected a sample of 88 nearby (z<0.1) galaxy clusters from the SDSS-DR4 with redshift information for the cluster members. In particular, we focus on the galaxy morphological distribution, the velocity dispersion profiles, and the fraction of blue galaxies in clusters. Cluster membership was determined using the available velocity information. We derived global properties for each cluster, such as their mean recessional velocity, velocity dispersion, and virial radii. Cluster galaxies were grouped into two families according to their u-r colours.
- ID:
- ivo://CDS.VizieR/J/ApJ/751/130
- Title:
- SDSS-DR7 red HB stars spectroscopic data
- Short Name:
- J/ApJ/751/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have selected 556 red horizontal branch stars along the streams of the Sagittarius (Sgr) dwarf galaxy from Sloan Digital Sky Survey DR7 spectroscopic data using a theoretical model. The metallicity and {alpha}-element distributions are investigated for stars in the Sgr streams and for Galactic stars at the same locations. We find that the Sgr stars have two peaks in the metallicity distribution while the Galactic stars have a more prominent metal-poor peak. Meanwhile, [{alpha}/Fe] ratios of the Sgr stars are lower than those of the Galactic stars. Among the Sgr stars, we find a difference in the metallicity distribution between the leading and trailing arms of the Sgr tidal tails. The metallicity and [{alpha}/Fe] distribution of the leading arm is similar to that of the Galaxy. The trailing arm is composed mainly of a metal-rich component and [{alpha}/Fe] is obviously lower than that of the Galactic stars. The metallicity gradient is -(1.8+/-0.3)x10^-3^dex/deg in the first wrap of the trailing arm and -(1.5+/-0.4)x10^-3^dex/deg in the first wrap of the leading arm. No significant gradient exists along the second wraps of the leading or trailing arms. It seems that the Sgr dwarf galaxy initially lost the metal-poor component in the second wrap (older) arms due to the tidal force of our Galaxy and then the metal-rich component is disrupted in the first wrap (younger) arms. Finally, we found that the velocity dispersion of the trailing arm from 88{deg}<{Lambda}_{sun}_<112{deg} is {sigma}=9.808+/-1.0km/s, which is consistent with previous work in the literature.
- ID:
- ivo://CDS.VizieR/J/AJ/153/174
- Title:
- SDSS-III/APOGEE. II. The multi-epoch ABE sample
- Short Name:
- J/AJ/153/174
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the H-band spectral variability of classical Be stars observed over the course of the Apache Point Galactic Evolution Experiment (APOGEE), one of four subsurveys comprising SDSS-III. As described in the first paper of this series, the APOGEE B-type emission-line (ABE) star sample was culled from the large number of blue stars observed as telluric standards during APOGEE observations. In this paper, we explore the multi-epoch ABE sample, consisting of 1100 spectra for 213 stars. These "snapshots" of the circumstellar disk activity have revealed a wealth of temporal variability including, but not limited to, gradual disappearance of the line emission and vice versa over both short and long timescales. Other forms of variability include variation in emission strength, emission peak intensity ratios, and emission peak separations. We also analyze radial velocities (RVs) of the emission lines for a subsample of 162 stars with sufficiently strong features, and we discuss on a case-by-case basis whether the RV variability exhibited by some stars is caused by binary motion versus dynamical processes in the circumstellar disks. Ten systems are identified as convincing candidates for binary Be stars with as of yet undetected companions.
- ID:
- ivo://CDS.VizieR/J/MNRAS/402/620
- Title:
- SDSS WD main-sequence binaries
- Short Name:
- J/MNRAS/402/620
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of 1602 white-dwarf-main-sequence (WDMS) binaries from the spectroscopic Sloan Digital Sky Survey Data Release 6 (SDSS DR6). Among these, we identify 440 as new WDMS binaries. We select WDMS binary candidates by template fitting all 1.27 million DR6 spectra, using combined constraints in both chi^2^ and signal-to-noise ratio. In addition, we use Galaxy Evolution Explorer (GALEX) and UKIRT Infrared Sky Survey (UKIDSS) magnitudes to search for objects in which one of the two components dominates the SDSS spectrum. We use a decomposition/fitting technique to measure the effective temperatures, surface gravities, masses and distances to the white dwarfs, as well as the spectral types and distances to the companions in our catalogue
- ID:
- ivo://CDS.VizieR/J/A+A/536/A43
- Title:
- SDSS WD main-sequence binaries. XII.
- Short Name:
- J/A+A/536/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The complexity of the common-envelope phase and of magnetic stellar wind braking currently limits our understanding of close binary evolution. Because of their intrinsically simple structure, observational population studies of white dwarf plus main sequence (WDMS) binaries can potentially test theoretical models and constrain their parameters. The Sloan Digital Sky Survey (SDSS) has provided a large and homogeneously selected sample of WDMS binaries, which we characterise in terms of orbital and stellar parameters. We have obtained radial velocity information for 385 WDMS binaries from follow-up spectroscopy and for an additional 861 systems from the SDSS subspectra. Radial velocity variations identify 191 of these WDMS binaries as post common-envelope binaries (PCEBs). Orbital periods of 58 PCEBs were subsequently measured, predominantly from time-resolved spectroscopy, bringing the total number of SDSS PCEBs with orbital parameters to 79. Observational biases inherent to this PCEB sample were evaluated through extensive Monte Carlo simulations. We find that 21-24% of all SDSS WDMS binaries have undergone common-envelope evolution, which is in good agreement with published binary population models and high-resolution HST imaging of WDMS binaries unresolved from the ground. The bias-corrected orbital period distribution of PCEBs ranges from 1.9h to 4.3d and approximately follows a normal distribution in log(Porb), peaking at ~10.3h. There is no observational evidence for a significant population of PCEBs with periods in the range of days to weeks. The large and homogeneous sample of SDSS WDMS binaries provides the means to test fundamental predictions of binary population models, hence to observationally constrain the evolution of all close compact binaries.
- ID:
- ivo://CDS.VizieR/J/A+A/460/695
- Title:
- Search for Associations Containing Young stars
- Short Name:
- J/A+A/460/695
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report results from a high-resolution optical spectroscopic survey aimed to search for nearby young associations and young stars among optical counterparts of ROSAT All-Sky Survey (<IX/10> and <IX/29>, X-ray sources in the Southern Hemisphere. We selected 1953 late-type (B-V>=0.6), potentially young, optical counterparts out of a total of 9574 1RXS sources for follow-up observations. At least one high-resolution spectrum was obtained for each of 1511 targets. This paper is the first in a series presenting the results of the SACY survey. Here we describe our sample and our observations. We describe a convergence method in the (UVW) velocity space to find associations. As an example, we discuss the validity of this method in the framework of the Beta Pic Association.
- ID:
- ivo://CDS.VizieR/J/A+A/525/A95
- Title:
- Search for brown-dwarf companions of stars
- Short Name:
- J/A+A/525/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The discovery of 9 new brown-dwarf candidates is reported. New CORALIE radial velocities of 6 previously-known hosts of potential brown-dwarf companions are presented. We use Hipparcos data to fully characterise the astrometric orbits of 6 objects, revealing M-dwarf companions with masses between 90M_Jup_ and 0.52M_{sun}_. We obtain an upper limit of 0.6% for the frequency of brown-dwarf companions around Sun-like stars. We find that the companion-mass distribution function is rising at the lower end of the brown-dwarf mass range, suggesting that in fact we detect the high-mass tail of the planetary distribution.
- ID:
- ivo://CDS.VizieR/J/A+A/385/488
- Title:
- Search for duplicity in periodic Be stars
- Short Name:
- J/A+A/385/488
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Four Be stars, HR 1960, HR 2968, HR 3237 and HR 3642, selected according to their periodic variations in Hipparcos and Geneva photometries, have been monitored from 1998 until 2001 with the Coralie spectrograph. HR 1960 and HR 3237 are two new spectroscopic binaries, HR 3642 is a new lambda Eri star, and HR 2968 is stable.
