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Astron. Astrophys. 325, 212-216

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

Michael Maisack1, J. Eric Grove2, Eckhard Kendziorra1, Peter Kretschmar1, Rüdiger Staubert1, and Mark S. Strickman2

1Institut für Astronomie und Astrophysik, Abteilung Astronomie, Universität Tübingen, D-72076 Tübingen, Germany
2E.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,

© European Southern Observatory (ESO) 1997