A search for hidden white dwarfs in the ROSAT extreme ultraviolet survey

Abstract

The ROSAT WFC survey has provided us with evidence for the existence of a previously unidentified sample of hot white dwarfs (WD) in non-interacting binary systems, through the detection of EUV and soft X-ray emission. These stars are hidden at optical wavelengths due to their close proximity to much more luminous main sequence (MS) companions (spectral type K or earlier). However, for companions of spectral type ∼A5 or later the white dwarfs are easily visible at far-UV wavelengths, and can be identified in spectra taken by IUE. Eleven white dwarf binary systems have previously been found in this way from ROSAT, EUVE and IUE observations (e.g. Barstow et al. 1994). In this paper we report the discovery of three more such systems through our programmes in recent episodes of IUE. The new binaries are HD2133, RE J0357+283 (whose existence was predicted by Jeffries, Burleigh and Robb 1996), and BD+27 • 1888. In addition, we have independently identified a fourth new WD+MS binary, RE J1027+322, which has also been reported in the literature by Genova et al. (1995), bringing the total number of such systems discovered as a result of the EUV surveys to fifteen. We also discuss here six stars which were observed as part of the programme, but where no white dwarf companion was found. Four of these are coronally active. Finally, we present an analysis of the WD+K0IV binary HD18131 (Vennes et al. 1995), which includes the ROSAT PSPC X-ray data.

IP Eridani: A surprising long-period binary system hosting a He white dwarf

“…5 of Vennes et al (1997). parallax of the K star, as discussed below. The corresponding age for the WD is then 7 Myr (Burleigh et al 1997). The WD parameters inferred by Burleigh et al (1997) locate it among He WDs in the log g − log T eff diagram of Driebe et al (1998).…”

“…The corresponding age for the WD is then 7 Myr (Burleigh et al 1997). The WD parameters inferred by Burleigh et al (1997) locate it among He WDs in the log g − log T eff diagram of Driebe et al (1998). Its mass of 0.43 M is incompatible with a CO WD since the minimum CO core mass at the base of the AGB (just at the end of core He-burning) is 0.51 M (for a star of initial mass 0.9 M ; e.g., Eq.…”

“…Their model-atmosphere analysis of the EUV photometry reveals a hot, hydrogen-rich (DA) WD (with an effective temperature of about 30 000 K) that is the most likely source of the EUV emission. In the grid of models fitted to the WD spectrum by Burleigh et al (1997), the model with a temperature of 29 290 K, a gravity of log g = 7.5 and a mass of 0.43 M locates the WD at a distance of 93 pc, consistent with the Hipparcos . The emission present in the cores is somewhat more intense than the one presented in Fig.…”

To Ba or not to Ba: Enrichment ins-process elements in binary systems with WD companions of various masses

“…References. (1) Fekel et al (1993); (2) Landsman et al (1993); (3) Vennes et al (1998) (4) Burleigh et al (1997); (5) Merle et al (2014); (6) Jorissen et al (1996); (7) ; (8) Stefanik et al (2011); (9) Dominy & Lambert (1983); (10) Griffin & Keenan (1992); (11) Schindler et al (1982); (12) Griffin (2006); (13) Frankowski & Jorissen (2006); (14) Böhm-Vitense (1980); (15) Jorissen et al (1998); (16) Jorissen et al (1995); (17) Fekel & Simon (1985).…”

Structure and Evolution of White Dwarfs and their Interaction with the Local Interstellar Medium

“…For example, a major result of the EUV sky surveys was the discovery of many unresolved binary systems containing white dwarfs and companion spectral types ranging from A to K (e.g. Barstow et al 1994;Burleigh, Barstow & Fleming 1997;Vennes, Christian & Thorstensen 1998). In visible light the presence of a companion of spectral type earlier than mid-K will swamp the signature of the white dwarf making it undetectable.…”