- ID:
- ivo://CDS.VizieR/J/A+A/645/A30
- Title:
- SB updated census in SACY sample
- Short Name:
- J/A+A/645/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Nearby young associations offer one of the best opportunities for a detailed study of the properties of young stellar and substellar objects thanks to their proximity (<200pc) and age (~5-150Myr). Previous works have identified spectroscopic (<5au) binaries, close (5-1000au) visual binaries, and wide or extremely wide (1000-100000au) binaries in the young associations. Inmost of the previous analyses, single-lined spectroscopic binaries (SB1) were identified based on radial velocities variations. However, this apparent variation may also be caused by mechanisms unrelated to multiplicity. We seek to update the spectroscopy binary fraction of the Search for Associations Containing Young stars (SACY) sample, taking into consideration all possible biases in our identification of binary candidates, such as activity and rotation. Using high-resolution spectroscopic observations, we produced ~1300 cross-correlation functions (CCFs) to disentangle the previously mentioned sources of contamination. The radial velocity values we obtained were cross-matched with the literature and then used to revise and update the spectroscopic binary (SB) fraction in each object of the SACY association. In order to better describe the CCF profile, we calculated a set of high-order cross-correlation features to determine the origin of the variations in radial velocities. We identified 68 SB candidates from our sample of 410 objects. Our results hint that at the possibility that the youngest associations have a higher SB fraction. Specifically, we found sensitivity-corrected SB fractions of 22^+15^_-11_% for {epsilon} Cha, 31^+16^_-14_% for TW Hya and 32^+9^_-8_% for {beta} Pictoris, in contrast to the five oldest associations we have sampled (~35-125Myr) which are ~10% or lower. This result seems independent of the methodology used to asses membership to the associations. The new CCF analysis, radial velocity estimates, and SB candidates are particularly relevant for membership revision of targets in young stellar associations. These targets would be ideal candidates for follow-up campaigns using high-resolution techniques to confirm binarity, resolve orbits, and, ideally, calculate dynamical masses. Additionally, if the results on the SB fraction in the youngest associations were confirmed, it could hint at a non-universal multiplicity among SACY associations.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/650/A102
- Title:
- SDSS J160429.12+100002.2 spectra
- Short Name:
- J/A+A/650/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the past, SDSS J160429.12+100002.2 was spectroscopically classified as a blue horizontal branch (BHB) star. Assuming a luminosity that is characteristic of BHB stars, the object's radial velocity and proper motions from Gaia Early Data Release 3 would imply that its Galactic rest-frame velocity exceeds its local escape velocity. Consequently, the object would be considered a hypervelocity star, which would prove particularly interesting because its Galactic trajectory points in our direction. However, based on the spectroscopic analysis of follow-up observations, we show that the object is actually a short-period (P~3.4h) single-lined spectroscopic binary system with a visible B-type star (effective temperature Teff=15840+/-160K and surface gravity log(g)=4.86+/-0.04) that is less luminous than typical BHB stars. Accordingly, the distance of the system is lower than originally thought, which renders its Galactic orbit bound to the Galaxy. Nevertheless, it is still an extreme halo object on a highly retrograde orbit. The abundances of He, C, N, O, Ne, Mg, Al, Si, S, and Ca are subsolar by factors from 3 to more than 100, while Fe is enriched by a factor of about 6. This peculiar chemical composition pattern is most likely caused by atomic diffusion processes. Combining constraints from astrometry, orbital motion, photometry, and spectroscopy, we conclude that the visible component is an unevolved proto-helium white dwarf with a thin hydrogen envelope that was stripped by a substellar companion through common-envelope ejection. Its unique configuration renders the binary system an interesting test bed for stellar binary evolution in general and common-envelope evolution in particular.
- ID:
- ivo://CDS.VizieR/J/MNRAS/424/1841
- Title:
- SDSS-UKIDSS white dwarf-main sequence binaries
- Short Name:
- J/MNRAS/424/1841
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We develop optical and near-infrared colour-selection criteria based on the model colours of binaries consisting of a white dwarf and a main-sequence star. Using our colour-selection algorithm, we present a catalogue of 523 white dwarf-main sequence (WDMS) binaries from the spectroscopic Sloan Digital Sky Survey Data Release 7 (SDSS DR7), most of them previously identified. Among them, we identify 86 objects as new WDMS binaries. 95 WDMS candidates are also found from the photometric SDSS DR7, cross-matched with the United Kingdom Infrared Telescope (UKIRT) Infrared Sky Survey Data Release 5 (UKIDSS DR5). Based on a {chi}^2^ minimization technique, we derive independent stellar parameters such as the effective temperatures, surface gravities, masses and distances of the white dwarfs and secondary stars and the metallicities of the secondaries.
- ID:
- ivo://CDS.VizieR/J/AJ/125/2621
- Title:
- SDSS WD-M binary parameters
- Short Name:
- J/AJ/125/2621
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified 109 white dwarf (WD)-M dwarf pairs in the Sloan Digital Sky Survey (SDSS) with g<20th magnitude. For each system we determined the temperature of the WD primary and the spectral type of the M dwarf secondary. Using H{alpha} emission as a proxy for the chromospheric activity level of the M dwarf, we investigated correlations between the activity level and properties of the system. Compared with field M dwarfs previously observed in the Palomar/MSU Survey, we see a slightly higher active fraction of early-type stars, with activity levels similar to the field. We have conducted follow-up observations at the ARC 3.5m telescope to obtain radial velocity information and to search for short-period binaries that may be on the verge of interacting. We report on one system with a 4.1hr period and several additional systems with significant velocity variations.
- 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/542/A95
- Title:
- 9 Sgr spectra 1999-2011
- Short Name:
- J/A+A/542/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The O-type object 9 Sgr is a well-known synchrotron radio emitter. This feature is usually attributed to colliding-wind binary systems, but 9 Sgr was long considered a single star. We have conducted a long-term spectroscopic monitoring of this star to investigate its multiplicity and search for evidence for wind-wind interactions.
- ID:
- ivo://CDS.VizieR/J/ApJS/249/31
- Title:
- Short period spec. & EBs (LPSEB) from LAMOST & PTF
- Short Name:
- J/ApJS/249/31
- Date:
- 10 Dec 2021 16:35:10
- Publisher:
- CDS
- Description:
- Binaries play key roles in determining stellar parameters and exploring stellar evolution models. We build a catalog of 88 eclipsing binaries with spectroscopic information, taking advantage of observations from both the Large Sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) and the Palomar Transient Factory (PTF) surveys. A software pipeline is constructed to identify binary candidates by examining their light curves. The orbital periods of binaries are derived from the Lomb-Scargle method. The key distinguishing features of eclipsing binaries are recognized by a new filter, Flat Test. We classify the eclipsing binaries by applying a Fourier analysis on the light curves. Among all the binary stars, 13 binaries are identified as eclipsing binaries for the first time. The catalog contains the following information: the position, primary eclipsing magnitude and time, eclipsing depth, the number of photometry and radial velocity observations, largest radial velocity difference, binary type, the effective temperature of the observable star Teff, and surface gravity of the observable star logg. The false-positive probability is calculated by using both a Monte Carlo simulation and real data from the Sloan Digital Sky Survey Stripe 82 Standard Catalog. The binaries in the catalog are mostly with a period of less than one day. The period distribution shows a 0.22 day cutoff, which is consistent with the low probability of an eclipsing binary rotating with such a period.
- ID:
- ivo://CDS.VizieR/J/A+A/399/315
- Title:
- sigma^2^ CrB radial velocities
- Short Name:
- J/A+A/399/315
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first Doppler image for both stellar components of the F9+G0 ZAMS binary {sigma}^2^ CrB and found evidence for the coexistence of cool and warm spots on both stars. Cool spots appear mainly at polar or high latitudes while a confined equatorial warm belt appears on the trailing hemisphere of each of the two stars with respect to the orbital motion. We also present an update of the TempMap imaging code that allows us to solve the stellar surface temperature distribution on both binary components simultaneously, including photometric input. Several test reconstructions are performed to demonstrate its reliability and robustness. Our new orbital solution results in very precise masses for both components - good to 0.4% - and confirms the spectral classifications of F9 and G0 for the primary and secondary, respectively. The visual component, {sigma}^1^, seems to be G4 rather than G0. All three components are on or very close to the ZAMS which is also confirmed by the relatively high lithium abundance of about twenty times the solar abundance.
- ID:
- ivo://CDS.VizieR/J/A+A/542/A57
- Title:
- Six year spectroscopy of V2028 Cyg
- Short Name:
- J/A+A/542/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of nearly six years long spectroscopic observations of the B[e] star V2028 Cyg. The presence of the cold type absorption lines combined with the hot type spectrum indicate a binarity of this object. Since the B[e] stars are embedded in an extended envelope, the usage of common stellar atmosphere models for the analysis is not very appropriate. Therefore we focus on the analysis of the long term spectral line variations in order to determine the nature of this object. We present time dependencies of the equivalent width and radial velocities of the H{alpha} line, [OI] 6300{AA}, FeII 6427, 6433, and 6456{AA} lines. The bisector variations and line intensities are shown for the H{alpha} line. The radial velocities are also measured for the absorption lines of the K component. No periodic variation was found. The observed data show correlations between the measured quantities, which can be used for the future modelling.
- ID:
- ivo://CDS.VizieR/J/A+A/496/191
- Title:
- Spectral analysis of 636 SDSS WD-M binaries
- Short Name:
- J/A+A/496/191
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 857 WD-M star binaries from the Sloan Digital Sky Survey (SDSS), most of which were previously identified by other authors, and the results of our spectral analysis for a subsample of 636 WD-M composite spectra. Our automatic fitting procedure bases on a chi^2^ minimization technique, yielding a decomposition of each combined spectrum and a derivation of independent parameter estimates for both components. On the respective photometric data from the SDSS, we also find 41 optically resolved binaries. We also investigated the spectra for hydrogen and helium emission.
