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

2. 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)

3. 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

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

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

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

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

8. HD 37737
P = 7.85 d
e = 0.40

9. 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

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

11. Spectral Models – B Stars
TLUSTY cannot calculate models below T of 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

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

13. HD 14633 – Spectral Energy Distribution

14. 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
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