HD 314884: a slowly pulsating B star in a close binary

Abstract

We present the results of a spectroscopic and photometric analysis of HD314884, a slowly pulsating B star (SPB) in a binary system with detected soft X-ray emission. We spectrally classify the B star as a B5V-B6V star with T ef f = 15,490 ± 310 K, log g = 3.75 ± 0.25 dex, and a photometric period of P 0 = 0.889521(12) days. A spectroscopic period search reveals an orbital period for the system of P orb = 1.3654(11) days. The discrepancy in the two periods and the identification of a second and third distinct frequency in the photometric fourier transform at P 1 = 3.1347(56) and P 2 = 1.517(28) days provides evidence that HD314884 is a slowly pulsating B star (SPB) with at least three oscillation frequencies. These frequencies appear to originate from higher-order, non-linear tidal pulsations. Using the dynamical parameters obtained from the radial velocity curve, we find the most probable companion mass to be M 1 = ∼0.8 M ⊙ assuming a typical mass for the B star and most probable inclination. We conclude that the X-ray source companion to HD314884 is most likely a coronally active G-type star or a white dwarf (WD), with no apparent emission lines in the optical spectrum. The mass probability distribution of the companion star mass spans 0.6-2.3 M ⊙ at 99% confidence which allows the possibility of a neutron star companion. The X-ray source is unlikely to be a black hole unless it is of a very low mass or low binary inclination.

The relationship between X-ray luminosity and duty cycle for dwarf novae and their specific frequency in the inner Galaxy

“…Towards the goal of classifying each X-ray source in the GBS, multiwavelength photometric and spectroscopic followup campaigns have been undertaken. Some of these focus on classifying new interesting sources with detailed followup, such as new CVs (Britt et al 2013;Ratti et al 2013), a possible new black hole binary (Britt et al 2013), a Slowly Pulsating B star with a white dwarf or coronally active G-type companion (Johnson et al 2014), and a likely Carbon star Symbiotic Binary (Hynes et al 2014). In terms of more comprehensive followup, Britt et al (2014) focuses on variable optical counterparts to GBS sources including the identification of DNe in outburst; Greiss et al (2014) identifies the infrared counterparts; Hynes et al (2012) cross matches GBS sources with bright star catalogs such as Tycho and ASAS; Maccarone et al (2012) cross matches GBS sources with existing catalogs of radio sources; Torres et al (2014) and Wu et al (2015) provide optical spectroscopy of stars with an Hα excess near GBS sources.…”