The SDSS spectroscopic catalogue of white dwarf-main-sequence binaries: new identifications from DR 9–12

Abstract

We present an updated version of the spectroscopic catalogue of white dwarf-main-sequence (WDMS) binaries from the Sloan Digital Sky Survey (SDSS). We identify 938 WDMS binaries within the data releases (DR) 9-12 of SDSS plus 40 objects from DR 1-8 that we missed in our previous works, 646 of which are new. The total number of spectroscopic SDSS WDMS binaries increases to 3294. This is by far the largest and most homogeneous sample of compact binaries currently available. We use a decomposition/fitting routine to derive the stellar parameters of all systems identified here (white dwarf effective temperatures, surface gravities and masses, and secondary star spectral types). The analysis of the corresponding stellar parameter distributions shows that the SDSS WDMS binary population is seriously affected by selection effects. We also measure the Na I λλ 8183.27, 8194.81 absorption doublet and H α emission radial velocities (RV) from all SDSS WDMS binary spectra identified in this work. 98 objects are found to display RV variations, 62 of which are new. The RV data are sufficient enough to estimate the orbital periods of three close binaries.Key words: binaries: close -binaries: spectroscopic -stars: low-mass -white dwarfs. I N T RO D U C T I O NA large fraction of main-sequence stars are found in binary systems (Duquennoy & Mayor 1991;Raghavan et al. 2010;Yuan et al. 2015b). It is expected that ∼25 per cent of all main-sequence binaries are close enough to begin mass transfer interactions when the more massive star becomes a red giant or an asymptotic giant star (Willems & Kolb 2004). This has been observationally verified e.g. by Farihi, Hoard & Wachter (2010) and by Nebot . Because the mass transfer rate generally exceeds the Eddington limit, the secondary star is not able to accrete the transferred material and the system evolves through a common envelope phase. That is, the core of the giant and the main-sequence companion orbit within a common envelope formed by the outer layers of the giant star. Drag forces between the two stars and the envelope lead to the shrinkage of the orbit and therefore to the release E-mail: alberto.rebassa@upc.edu of orbital energy. The orbital energy is deposited into the envelope and is eventually used to eject it (Webbink 2008). The outcome of common envelope evolution is hence a close binary formed by the core of the giant star (which later becomes a white dwarf) and a main-sequence companion, i.e. a close white dwarf-main-sequence (WDMS) binary. These are commonly referred to as post-common envelope binaries (PCEBs). The remaining ∼75 per cent of mainsequence binaries are wide enough to avoid mass transfer interactions. In these cases the more massive stars evolve like single stars until they eventually become white dwarfs. The orbital separations of such WDMS binaries are similar to those of the main-sequence binaries from which they descend.During the last years we have mined the Sloan Digital Sky Survey (SDSS; York et al. 2000) spectroscopic data base to build up th...

The critical binary star separation for a planetary system origin of white dwarf pollution

“…We consider three sets, from Debes (2006), Holberg et al (2013) and Rebassa-Mansergas et al (2016a), and plot values from all in Fig. 3.…”

“…The final sample is the spectroscopic catalogue of white dwarf-M dwarf binaries from the SDSS (Rebassa-Mansergas et al 2016a). With more than 3200 objects, this catalogue is the largest and most homogeneous sample of white dwarf binaries to date.…”

White Dwarf Stars

“…More than 10% of the spectroscopically identified white dwarfs in SDSS have red companions. 49,59 Refs. 60,61 show that nearly 25% of all main sequence binaries are close enough that mass transfer interactions occur when the more massive star becomes a red giant or an asymptotic giant star.…”

Pulsating white dwarfs

“…[47] demonstrates that while around 70% of stars more massive than the Sun are in binaries, two-thirds of the most common stars, M type dwarf stars, are single. More than 10% of the spectroscopically identified white dwarfs in SDSS have red companions ( [38,48]). [49,50] show that nearly 25% of all main sequence binaries are close enough that mass transfer interactions occur when the more massive star becomes a red giant or an asymptotic giant star.…”