- 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.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/429/2934
- Title:
- SDSS magnetic white dwarf stars
- Short Name:
- J/MNRAS/429/2934
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To obtain better statistics on the occurrence of magnetism among white dwarfs, we searched the spectra of the hydrogen atmosphere white dwarf stars (DAs) in the Data Release 7 of the Sloan Digital Sky Survey (SDSS) for Zeeman splittings and estimated the magnetic fields. We found 521 DAs with detectable Zeeman splittings, with fields in the range from around 1 to 733MG, which amounts to 4% of all DAs observed. As the SDSS spectra have low signal-to-noise ratios, we carefully investigated by simulations with theoretical spectra how reliable our detection of magnetic field was.
- ID:
- ivo://CDS.VizieR/J/MNRAS/413/1121
- Title:
- SDSS post-common envelope binaries. X
- Short Name:
- J/MNRAS/413/1121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first white dwarf mass distributions of a large and homogeneous sample of post-common envelope binaries (PCEBs) and wide white dwarf main-sequence (WDMS) binaries directly obtained from observations. Both distributions are statistically independent, with PCEBs showing a clear concentration of systems towards the low-mass end of the distribution and the white dwarf mass distribution of wide WDMS binaries being similar to that of single white dwarfs. Our results provide evidence that the majority of low-mass (Mwd<~0.5M_{sun}_) white dwarfs are formed in close binaries.
- 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/MNRAS/382/515
- Title:
- SDSS ultracool and halo WD candidates
- Short Name:
- J/MNRAS/382/515
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A 2.5x100{deg}^2^ region along the celestial equator (Stripe 82) has been imaged repeatedly from 1998 to 2005 by the Sloan Digital Sky Survey (SDSS). A new catalogue of ~4 million light-motion curves, together with over 200 derived statistical quantities, for objects in Stripe 82 brighter than r~21.5 has been constructed by combining these data by Bramich et al. (2008MNRAS.386..887B). This catalogue is at present the deepest catalogue of its kind. Extracting ~130000 objects with highest signal-to-noise ratio proper motions, we build a reduced proper motion diagram to illustrate the scientific promise of the catalogue. In this diagram, disc and halo subdwarfs are well-separated from the cool white dwarf sequence. Our sample of 1049 cool white dwarf candidates includes at least eight and possibly 21 new ultracool H-rich white dwarfs (Teff<4000K) and one new ultracool He-rich white dwarf candidate identified from their SDSS optical and UKIDSS infrared photometry. At least 10 new halo white dwarfs are also identified from their kinematics.
- ID:
- ivo://CDS.VizieR/J/MNRAS/382/1377
- Title:
- SDSS WD main-sequence binaries
- Short Name:
- J/MNRAS/382/1377
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed analysis of 101 white dwarf main-sequence binaries (WDMS) from the Sloan Digital Sky Survey (SDSS) for which multiple SDSS spectra are available.
- 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/ApJ/815/63
- Title:
- SDSS wide double white dwarfs spectroscopy
- Short Name:
- J/ApJ/815/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observational constraints on the initial-final mass relation (IFMR) using wide double white dwarfs (DWDs). We identify 65 new candidate wide DWDs within the Sloan Digital Sky Survey, bringing the number of candidate wide DWDs to 142. We then engage in a spectroscopic follow-up campaign and collect existing spectra for these objects; using these spectra, we derive masses and cooling ages for 54 hydrogen (DA) WDs in DWDs. We also identify one new DA/DB pair, four candidate DA/DC pairs, four candidate DA/DAH pairs, and one new candidate triple degenerate system. Because wide DWDs are co-eval and evolve independently, the difference in the pre-WD lifetimes should equal the difference in the WD cooling ages. We use this to develop a Bayesian hierarchical framework and construct a likelihood function to determine the probability that any particular IFMR fits a sample of wide DWDs. We then define a parametric model for the IFMR and find the best parameters indicated by our sample of DWDs. We place robust constraints on the IFMR for initial masses of 2-4M_{sun}_. The WD masses produced by our model for stars within this mass range differ from those predicted by semi-empirical fits to open cluster WDs. Within this mass range, where there are few constraining open cluster WDs and disagreements in the cluster ages, wide DWDs may provide more reliable constraints on the IFMR. Expanding this method to the many wide DWDs expected to be discovered by Gaia may transform our understanding of the IFMR.
- ID:
- ivo://CDS.VizieR/J/ApJ/894/19
- Title:
- SOAR spectra of the WD EPIC 228939929
- Short Name:
- J/ApJ/894/19
- Date:
- 03 Dec 2021 00:38:57
- Publisher:
- CDS
- Description:
- We report the discovery of short-period photometric variability and modulated Zeeman-split hydrogen emission in SDSSJ125230.93-023417.72 (EPIC 228939929), a variable white dwarf star observed at long cadence in K2 Campaign 10. The behavior is associated with a magnetic (B=5.0MG) spot on the stellar surface, making the 317.278s period a direct measurement of the stellar rotation rate. This object is therefore the fastest-rotating, apparently isolated (without a stellar companion) white dwarf yet discovered and the second found to exhibit chromospheric Balmer emission after GD 356, in which the emission has been attributed to a unipolar inductor mechanism driven by a possible rocky planet. We explore the properties and behavior of this object, and consider whether its evolution may hold implications for white dwarf mergers and their remnants.
