Dynamical masses of a nova-like variable on the edge of the period gap

Abstract

We present the first dynamical determination of the binary parameters of an eclipsing SW Sextantis star in the 3-4 hour orbital period range during a low state. We obtained time-resolved optical spectroscopy and photometry of HS 0220+0603 during its 2004-2005 low brightness state, as revealed in the combined SMARTS, IAC80 and M1 Group long-term optical light curve.The optical spectra taken during primary eclipse reveal a secondary star spectral type of M5.5±0.5 as derived from molecular band-head indices. The spectra also provide the first detection of a DAB white dwarf in a cataclysmic variable. By modelling its optical spectrum we estimate a white dwarf temperature of 30 000 ± 5 000 K.By combining the results of modelling the white dwarf eclipse from ULTRA-CAM light curves with those obtained by simultaneously fitting the emission-and absorption-line radial velocity curves and I-band ellipsoidal light curves, we measure the stellar masses to be M 1 = 0.87 ± 0.09 M and M 2 = 0.47 ± 0.05 M for the white dwarf and the M dwarf, respectively, and an inclination of the orbital plane of i ≈ 79 o . A radius of 0.0103 ± 0.0007 R is obtained for the white dwarf. The secondary star in HS 0220+0603 is likely too cool and undersized for its mass.

Peering into the Dark Side: Magnesium Lines Establish a Massive Neutron Star in PSR J2215+5135

“…To our knowledge, the only similar studies in the literature involve a combination of emission and absorption lines in white dwarf (WD) binaries (e.g., Parsons et al 2010;Rodríguez-Gil et al 2015). Our method relies exclusively on absorption lines from the star's atmosphere, thus eluding the uncertainty sometimes associated with the exact site where Balmer/He/ Bowen emission lines are formed.…”

SW Sex Stars Then and Now: A Review

“…On the right, the M 1 − M 2 plane is plotted with the best-fitting solutions (99 per cent confidence level for red circles) The dashed line corresponds to a mass ratio of q = 0.54. [30] tra show narrow emission lines of Hα, He I and Na-D, as well as TiO absorption troughs which trace the motion of different temperature zones on the irradiated secondary star. While He I and Hα originate at the higher temperature regions of the secondary star close to L1 (which is reflected in their low radial-velocity amplitude), the TiO bands are likely to originate in the non-irradiated, cooler, backside zones of the secondary star (high radial-velocity amplitude).…”

“…A different possibility is that the Hα emitting material moves along prominences originating in a magnetically active secondary star. To explain the observed variation of the satellite lines, only two orientations are possible for these prominences (see Figure 10 for the data and a schematic interpretation) The last example of an analysis of low-state data of a SW Sex system refers to the eclipsing star HS 0220+0603 which was extensively observed during the 2004-2005 low state by Rodríguez-Gil et al (2015) [30]. Their dataset include time-resolved spectroscopy and photometry in various optical bands.…”

“…The last example of an analysis of low-state data of a SW Sex system refers to the eclipsing star HS 0220+0603 which was extensively observed during the 2004-2005 low state by Rodríguez-Gil et al (2015) [30]. Their dataset include time-resolved spectroscopy and photometry in various optical bands.…”

A catalogue of 323 cataclysmic variables from LAMOST DR6

“…Nova-like objects (NLs) are recognized as novae between eruptions and do not have a recorded outburst. Some NLs have been observed to occasionally change from a high state with higher bright-ness to a low state with lower brightness (La Dous 1994; King & Cannizzo 1998;Rodríguez-Gil et al 2015). In the AM Her systems, the magnetic field of the white dwarf is strong enough for both stars to be locked into the same rotation period.…”