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Astron. Astrophys. 325, 212-216 (1997)

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Pulse phase spectroscopy of A 0535+26 during its 1994 giant outburst observed with OSSE

Michael Maisack 1, J. Eric Grove 2, Eckhard Kendziorra 1, Peter Kretschmar 1, Rüdiger Staubert 1 and Mark S. Strickman 2

1 Institut für Astronomie und Astrophysik, Abteilung Astronomie, Universität Tübingen, D-72076 Tübingen, Germany
2 E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DC 20375, USA

Received 4 February 1997 / Accepted 10 March 1997


We present pulse phase spectroscopy of A 0535+26 in the energy range 35-200 keV from OSSE observations of its giant outburst in 1994. We discuss the phase dependence of the continuum parameters and the cyclotron resonance feature (CRF) at 110 keV already found in the phase averaged spectrum. We find that a CRF is required at every phase. The behaviour of the line parameters with phase and the pulse shape indicate that the emission occurs in a pencil-beam geometry.

Key words: stars: magnetic fields – stars: neutron – gamma-rays: observations

Send offprint requests to: M. Maisack, maisack@astro.uni-tuebingen.de

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© European Southern Observatory (ESO) 1997

Online publication: May 5, 1998