We have measured the brightness of the optical counterpart of the black hole X-ray binary Nova Sco 1994 (GRO J1655-40) during 40 nights between 1995 May 3 and July 27. From our observations and data from the literature we refine the orbital period to be 2.620 40 ± 0.000 98 d. We model the R-band light curve as primarily arising from an X-ray heated secondary, using a model that includes a Roche lobe filling secondary star, the effects of X-ray heating on both the concave accretion disc and the X-ray illuminated surface of the secondary, shadowing of the secondary and disc, and mutual eclipses of the disc and the secondary star. From the shape of the light curve we constrain the inclination of the system to lie in the range 65°-76° and constrain the mass ratio q = M1/M2 to lie in the range 3.8-5.5. This implies a mass range for the secondary star and compact object of 0.95-1.8 M⊙ and 4.9-6.8 M⊙, respectively. The (V-R) and (R-i) colour curves do not show evidence of significant variability with orbital phase during 1995 June-July, their average values being 1.06(3) and 0.86(2) mag, respectively. © 1997 RAS.

Item Type:	Refereed Article
Research Division:	Physical Sciences
Research Group:	Astronomical and Space Sciences
Research Field:	Galactic Astronomy
Objective Division:	Expanding Knowledge
Objective Group:	Expanding Knowledge
Objective Field:	Expanding Knowledge in the Physical Sciences
Author:	Greenhill, JG (Dr John Greenhill)
Author:	Hill, KM (Dr Kym Hill)
ID Code:	10555
Year Published:	1997
Web of Science® Times Cited:	15
Deposited By:	Physics
Deposited On:	1997-08-01
Last Modified:	2011-08-11
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