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Astron. Astrophys. 344, 607-613 (1999)

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The eclipse of the symbiotic star SY Muscae *

C.B. Pereira, V.G. Ortega and I. Monte-Lima

Observatório Nacional, Departamento de Astronomia Galáctica e Extra-Galáctica, Rua Gen. José Cristino, 77, São Cristóvão, CEP 20921-400, Rio de Janeiro, Brazil

Received 21 August 1998 / Accepted 11 January 1999


We present ultra-violet observations of the symbiotic star SY Mus obtained with IUE in 1996. The observations were timed to cover ingress and egress. We observe phase dependent intensity variations of the continuum and of the emission lines. These variations are caused by a wavelength dependent opacity with the characteristics of Rayleigh scattering plus a wavelength independent attenuation. From the Rayleigh scattering opacity we derive the column densities of neutral hydrogen as a function of orbital phase. We then apply inversion methods to investigate the giant's cool wind velocity profile. A new convenient analytical expression for this profile is presented and compared to other laws. The modeling of the giant's cool wind and the assumption of a terminal velocity of 30 km s-1, leads to a mass loss rate of [FORMULA] [FORMULA] yr-1 for SY Mus.

Key words: stars: binaries: eclipsing – stars: binaries: symbiotic – stars: individual: SY Mus – stars: mass-loss

* Based on observations by the International Ultraviolet Explorer taken at VILSPA.

Send offprint requests to: C.B. Pereira

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© European Southern Observatory (ESO) 1999

Online publication: March 18, 1999