A Search for Quiet Massive X-Ray Binaries

M. Virginia McSwain Yale University

Tabetha S. BoyajianErika GrundstromDouglas 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 de = 0.0

(Not an MXRB candidate)

HD 14633

P = 15.41 de = 0.70

See also Boyajian et al. (2005)

HD 15137

P = 28.99 de = 0.41

See also Boyajian et al. (2005)

HD 30614

P = 3.19 de = 0.35

Gas stream between stars

HD 37737

P = 7.85 de = 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 Klog 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 Klog 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