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Astron. Astrophys. 317, 769-775 (1997)

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GRS 1009-45 (=X-Ray Nova Velorum 1993):
a 'hybrid' soft X-ray transient? *

N. Masetti , A. Bianchini and M. Della Valle

Dipartimento di Astronomia, Università di Padova, vicolo dell'Osservatorio, 5 I-35122 Padua, Italy

Received 16 February 1996 / Accepted 31 May 1996


High-time resolution photometry, performed from November 17 to December 11, 1993, on GRS 1009-45 (=X-Ray Nova Velorum 1993) reveals a V light modulation with a periodicity of 0.1996 days ([FORMULA] [FORMULA].79). If the nature of this modulation is similar to that of the superhumps seen in SU UMa dwarf novae during superoutbursts, then the object would have the shortest orbital period among Soft X-Ray Transients (SXTs). We estimate a lower limit for the mass of the primary of [FORMULA] 1.6 [FORMULA]. An optical secondary maximum or `reflare' around 90 days after the X-ray outburst is also reported. Spectroscopy during light decay confirms the presence of Balmer absorption lines with emission cores.

Key words: accretion, accretion disks – stars: individual (GRS 1009 – 45 = X-Ray Nova Velorum 1993) – X-rays: stars

* Based on observations obtained at the European Southern Observatory, La Silla, Chile.

Send offprint requests to: M. Della Valle, dellavalle@astrpd.pd.astro.it

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© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998