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Astron. Astrophys. 334, 857-862 (1998)

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The X-ray emission of the polar BL Hydri

G. Matt 1, R. Barcaroli 1, T. Belloni 2, K. Beuermann 3, J.M. Bonnet-Bidaud 4, D. De Martino 5, C. Done 6, B.T. Gänsicke 3, M. Guainazzi 7, M. Mouchet 8, 9 and K. Mukai 10

1 Dipartimento di Fisica, Università degli studi "Roma Tre", Via della Vasca Navale 84, I-00146 Roma, Italy
2 Astronomical Institute "Anton Pannekoek", University of Amsterdam and Center for High-Energy Astrophysics, Kruislaan 403,
1098 SJ Amsterdam, The Netherlands
3 Universitätssternwarte Göttingen, Geismarlandstrasse 11, D-37083 Göttingen, Germany
4 CEA, DSN/DAPNIA/Service d'Astrophysique, CEN Saclay, F-91191 Gif-sur-Yvette Cedex, France
5 Osservatorio Astronomico di Capodimonte, Via Moiariello 16, I-80131 Napoli, Italy
6 Department of Physics, University of Durham, South Road, Durham DH1 3LE, UK
7 SAX/SDC Nuova Telespazio, Via Corcolle 19, I-00131 Roma, Italy
8 DAEC, Observatoire de Paris, Section de Meudon, F-92195 Meudon Cedex, France
9 Université Denis Diderot, 2 Place Jussieu, F-75005 Paris, France
10 NASA/GSFC, Code 668, Greenbelt MD 20771, USA

Received 28 November 1997 / Accepted 2 March 1998


We report on the analysis of the ASCA and BeppoSAX X-ray observations of the polar system BL Hyi, performed in October 94 and September 96, respectively.

Emission from both poles is apparent from the folded light curves of both observations; the emission from the second pole varies from cycle to cycle, indicating non-stationary accretion there.

The temperature of the post-shock region is estimated to be about 10 keV. Inclusion of both complex absorption and Compton reflection significantly improves the quality of the fit. No soft X-ray component is observed; the BeppoSAX/LECS upper limit to the soft component is in agreement with theoretical expectations for this low magnetic field system.

Key words: stars: novae, cataclysmic variables – X-rays: stars – stars: individual: BL Hydri

© European Southern Observatory (ESO) 1998

Online publication: June 2, 1998