Dawn M. Gelino

A Multiwavelength, Multiepoch Study of the Soft X-Ray Transient Prototype, V616 Monocerotis (A0620−00)*

We have obtained optical and infrared photometry of the soft X-ray transient prototype V616 Mon (A0620-00). From this photometry, we find a spectral type of K4 for the secondary star in the system, which is consistent with spectroscopic observations. We present J-, H-, and K-band light curves modeled with WD98, the newest version of the Wilson-Devinney light-curve modeling code, and the ELC code. By combining detailed, independently run models for ellipsoidal variations due to a spotted, nonspherical secondary star and the observed ultraviolet to infrared spectral energy distribution of the system, we show that the most likely value for the orbital inclination is 4075 ± 3°. This inclination angle implies a primary black hole mass of 11.0 ± 1.9 M ⊙.

INFRARED OBSERVATIONS OF NOVA MUSCAE 1991: BLACK HOLE MASS DETERMINATION FROM ELLIPSOIDAL VARIATIONS

We have obtained infrared photometry for the soft X-ray transient GU Mus. We present J- and Ks-band light curves modeled with WD98, the newest version of the Wilson-Devinney light curve–modeling code. Using detailed models for the expected ellipsoidal variations due to the nonspherical secondary star, we show that the most likely value for the orbital inclination is 54° ± 15. This inclination angle is consistent with those previously published, but it has a much smaller error. This inclination implies a primary black hole mass of 6.95 ± 0.6 M⊙. While we do not see any evidence for contamination of our infrared light curves from other sources in the system, a conservative model with a contamination level of 15% increases the uncertainty in the inclination angle to 54 deg.

Infrared Observations of AR Ursae Majoris: Modeling the Ellipsoidal Variations

We have obtained time-series infrared photometry for the highly magnetic cataclysmic variable AR UMa. Our J- and K-band observations occurred during a low state, and they show a distinctive double-humped structure. Using detailed models for the expected ellipsoidal variations in the infrared caused by the nonspherical secondary star, we find that the most likely value for the system inclination is 70°. We also model low-state V-band photometry and find that its observed double-humped structure is caused not by ellipsoidal variations, to which it has been ascribed, but by beamed cyclotron radiation. We use this result to estimate the magnetic field strength of the active southern accretion region (B 190 MG) and its magnetic longitude (ψS ~ 330°).