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 Teff = 15 490 ± 310 K, log g = 3.75 ± 0.25 dex, and a photometric period of P0 = 0.889 521(12) d. A spectroscopic period search reveals an orbital period for the system of Porb = 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 P1 = 3.1347(56) and P2 = 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 radialvelocity curve, we find the most probable companion mass to be M1 =~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 0.6-2.3M⊙ 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.
Publication Source (Journal or Book title)
Monthly Notices of the Royal Astronomical Society
Johnson, C., Hynes, R., Maccarone, T., Britt, C., Davis, H., Jonker, P., Torres, M., Steeghs, D., Greiss, S., & Nelemans, G. (2014). HD 314884: A slowly pulsating B star in a close binary. Monthly Notices of the Royal Astronomical Society, 444 (2), 1584-1590. https://doi.org/10.1093/mnras/stu1539