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Astron. Astrophys. 323, L29-L32 (1997)


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Letter to the Editor

Low-energy line emission from Cygnus X-2 observed with the BeppoSAX LECS

E. Kuulkers 1, 2, A.N. Parmar 1, A. Owens 1, T. Oosterbroek 1 and U. Lammers 1

1 Astrophysics Division, Space Science Department of ESA, ESTEC, P.O. Box 299, 2200 AG Noordwijk, The Netherlands
2 Astrophysics, University of Oxford, Nuclear and Astrophysics Laboratory, Keble Road, Oxford, OX1 3RH, UK

Received 17 April 1997 / Accepted 1 May 1997

Abstract

We present a 0.2-10 keV spectrum of the low-mass X-ray binary Cygnus X-2 obtained using the Low Energy Concentrator Spectrometer on-board BeppoSAX. The spectrum can be described by a cut-off power-law model with absorption of (2.28 [FORMULA] 0.07) [FORMULA] 1021 atoms cm-2, a power-law index of 0.78 [FORMULA] 0.02 and a cut-off energy of 4.30 [FORMULA] 0.08 keV (68% confidence errors), except at energies near [FORMULA] 1 keV where excess emission is present. This can be modeled by a broad Gaussian line feature with an energy of 1.02 [FORMULA] 0.04 keV, a full width half-maximum of 0.47 [FORMULA] 0.07 keV and an equivalent width of 74 [FORMULA] eV. This result confirms earlier reports of line emission near 1 keV and shows the intensity and structure of the feature to be variable.

Key words: accretion - binaries:close - stars:individual (Cyg X-2) - stars:neutron - X-rays: general

Send offprint requests to: E. Kuulkers: erik@astro.ox.ac.uk

© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998

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