A Search for Quiet Massive X-Ray Binaries M. Virginia McSwain Yale University Tabetha S. Boyajian Erika Grundstrom Douglas R. Gies Georgia State University

A Quiet Massive X-ray Binary? 2 typical mechanisms produce X-rays in MXRBs: Mass accretion through a Roche lobe overflow stream Accretion of the stellar wind of the luminous primary (Bondi & Hoyle 1944; Davidson & Ostriker 1973; Kaper 1998) In the wind accretion model of MXRBs, the observed X-ray luminosity depends on: the system separation, the relative wind and companion velocities, the stellar mass-loss rate, and the mass of the accretor (Lamers et al. 1976)

Target Selection Runaway or field OB stars Suspected single-line spectroscopic binaries (SB1) or known radial velocity variables Known SB1s with poorly determined orbits Most targets not known X-ray emitters Selected 12 targets for radial velocity study Goal: to find SB1s with eccentric orbits, suggestive of past supernova in binary system

HD 1976 P = 26.0 d e = 0.0 (Not an MXRB candidate)

HD 14633 P = 15.41 d e = 0.70 See also Boyajian et al. (2005)

HD 15137 P = 28.99 d e = 0.41 See also Boyajian et al. (2005)

HD 30614 P = 3.19 d e = 0.35 Gas stream between stars

HD 37737 P = 7.85 d e = 0.40

Spectral Models – O Stars Hot O stars require non-LTE spectral modeling Used TLUSTY model atmospheres to compute grid of model spectra He I 4121 and Si IV 4116 lines highly sensitive to Teff,log g, V sin i (Walborn 1971) These lines were used to determine best fit parameters

HD 14633 – Model Fit Teff = 33000 K log g = 3.95 V sin i = 140 km/s

Spectral Models – B Stars TLUSTY cannot calculate models below T of 28000 K But, B stars can be modeled well using LTE Kurucz model atmospheres Fit H Balmer and He I line profiles with grid of model spectra Mean value from many lines provides Teff, log g, V sin i

HD 1976 – Model Fit Teff = 15400 K log g = 3.7 V sin i = 160 km/s

HD 14633 – Spectral Energy Distribution

Conclusions & Further Work Of 12 stars studied, we find 6 MXRB candidates 3 are weak or moderate X-ray sources: HD 30614, HD 52533, HD 188001 3 not known X-ray emitters: HD 14633, HD 15137, HD 37737 Currently finishing work on spectral models and SED fits to investigate stellar parameters New X-ray, IR observations will be useful to conclusively identify post-supernova systems with compact companions