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Astron. Astrophys. 320, L25-L28 (1997)

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Letter to the Editor

Evidence of X-ray periodicity in LSI +61° 303

J.M. Paredes 1, J. Martí 2, 1, M. Peracaula 1 and M. Ribó 1

1 Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Av. Diagonal 647, E-08028 Barcelona, Spain
2 CEA/DSM/DAPNIA/Service d'Astrophysique, Centre d'Études de Saclay, F-91191 Gif-Sur-Yvette, France

Received 10 January 1997 / Accepted 25 February 1997


We have carried out a period analysis of 2-10 keV observations of the 26.5 d radio periodic X-ray binary LSI [FORMULA] 303 retrieved from the quick-look results database provided by the ASM/RXTE team. After applying different period search methods, we find evidence that X-ray outbursts in LSI [FORMULA] 303 are very likely to recur with the same radio outburst period. Our best estimate of the LSI [FORMULA] 303 X-ray period is [FORMULA] d. The folded X-ray light curve displays a fractional change in flux by a factor of [FORMULA] and its highest emission level overlaps with the active state of the radio emission.

Key words: Stars: LSI+61° 303 – Radio continuum: stars – Stars: variables – X-rays: stars

Send offprint requests to: J.M. Paredes

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© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998