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Astron. Astrophys. 322, 183-192 (1997)

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The Be/X-ray binary LS I + [FORMULA] 235/RX J0146.9+6121: physical parameters and V/R variability

P. Reig 1, J. Fabregat 2, M.J. Coe 1, P. Roche 3, D. Chakrabarty 4, 5, I. Negueruela 1 and I. Steele 6

1 Physics and Astronomy Department, Southampton University, Southampton. SO17 1BJ, UK
2 Departament d'Astronomia i Astrofísica, Universitat de Valencia, E-46100 Burjassot-Valencia, Spain
3 Astronomy Centre, CPES, University of Sussex, Falmer, Brighton, BN1 9QH, UK
4 Palomar Observatory and Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125, USA
5 Center for Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
6 John Moores University, Liverpool, UK

Received 3 September 1996 / Accepted 2 December 1996


We present the results of spectroscopic and photometric observations of LS I + [FORMULA] 235. Blue 4100-4900 Å spectra of the system are used to assign a spectral type of B1V to the optical companion while detailed [FORMULA] photometric data permit us to derive its astrophysical parameters. The monitoring of this high mass X-ray binary since its discovery in 1991 has resulted in the detection of considerable variability in the H [FORMULA] line profile. The observations cover a complete V/R cycle with a period of approximately three years. We discuss models which may explain the origin of the variation and conclude that these variations are due to intrinsic changes of the circumstellar envelope rather than being caused by the neutron star. The model which best fits the observational data is the global one-armed oscillation model.

Key words: stars: individual: LS I +61O 235 – binaries: close – X-rays: stars – stars: fundamental parameters

Send offprint requests to: pablo@astro.soton.ac.uk

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© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998