HD 314884: a slowly pulsating B star in a close binary. Issue 2 (29th August 2014)

• Record Type: Journal Article
• Authors: Johnson, Christopher B.; Hynes, R. I.; Maccarone, T.; Britt, C. T.; Davis, H.; Jonker, P. G.; Torres, M. A. P.; Steeghs, D.; Greiss, S.; Nelemans, G.
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 444:Issue 2(2014)
• Page Start: 1584
• Page End: 1590
• Publication Date: 2014-08-29
• Subjects: stars: pulsations -- X-rays: binaries; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stu1539
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract : We present the results of a spectroscopic and photometric analysis of HD 314884, 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 eff = 15 490 ± 310 K, log g = 3.75 ± 0.25 dex, and a photometric period of P 0 = 0.889 521(12) d. A spectroscopic period search reveals an orbital period for the system of P orb = 1.3654(11) d. 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) d provides evidence that HD 314884 is an 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 HD 314884 is most likely a coronally active G-type star or a white dwarf, 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 per cent 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.