Other
Scientific paper
Dec 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992aas...181.7302o&link_type=abstract
American Astronomical Society, 181st AAS Meeting, #73.02; Bulletin of the American Astronomical Society, Vol. 24, p.1236
Other
Scientific paper
Optical spectroscopy of X-ray Nova Muscae 1991 was carried out 3 April 1992 with the CTIO 4m (see also accompanying poster from Remillard et al.) The spectra show absorption lines characteristic of K stars and broad, double-peaked emission lines characteristic of an accretion disk. There were 21 spectra taken, which nearly cover the 10.4 hour orbital period. The double-peaked Hα emission profile made by averaging all 21 observations was fit to a symmetric profile produced by an optically thin, Keplerian disk. The projected velocity of the outer edge of the disk is K_d=v_dsin i=450 +/- 10 km*s(-1) , and the ratio of the radius of the inner edge of the disk to the radius of the outer edge is r_1=0.05. The semiamplitude of the secondary K star is K_s=409 +/- 18 km*s(-1) , which gives K_d/K_s = 1.10+/- 0.08. This ratio of velocities depends only the mass ratio of the binary system, so it can be used to further constrain the mass of the primary. The 21 individual spectra were placed into 6 bins based on the orbital phase of the observation. The two peaks of the emission profiles are of unequal height and the difference in height changes over the orbit. This behavior can be fit by the addition of a simple ``hot spot'' to the accretion disk. We find that a profile produced by an optically thin disk fits the data at some phases while a profile produced by an optically thick disk is needed to fit the data at other phases. The Hα profile is broader in the blue wing than in the red wing, and this asymmetry appears in all individual phase bins. This asymmetry is perhaps caused by an outflow of mass from the disk or from the system as a whole. The secondary star is a type between K2 and K4. There are strong molecular bands (TiO and MgH) which normally appear in K giants. The short orbital period rules out the possibility of a giant secondary, but the Roche potential itself may give rise to reduced surface gravity for a star nearly filling its Roche lobe, or the secondary K star may be severely undermassive and hence have reduced surface gravity.
Bailyn Charles D.
McClintock Jeffrey E.
Orosz Jerome A.
Remillard Ronald A.
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