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Title

The optical counterpart of the accreting millisecond pulsar SAX J1808.4-3658 in outburst : constraints on the binary inclination

Author(s)

Wang, Zhongxiang;  Chakrabarty, Deepto;  Roche, Paul;  Charles, Philip A.;  Kuulkers, Erik;  Shahbaz, Tariq;  Simpson, Chris;  Forbes, Duncan A.;  Helsdon, Stephen F.

Abstract

We present multiband optical/IR photometry of V4580 Sgr, the optical counterpart of the accretion-powered millisecond pulsar SAX J1808.4-3658, taken during the 1998 X-ray outburst of the system. The optical flux is consistent with emission from an X-rayheated accretion disk. Self-consistent modeling of the X-ray and optical emission during the outburst yields a best-fit extinction of AV=0.68+0.37-0.15 and an inclination of cosi=0.65+0.23-0.33 (90% confidence), assuming a distance of 2.5 kpc. This inclination range requires that the stellar companion of the pulsar has extremely low mass, Mc=0.050.10 M. Some of the IR observations are inconsistent with disk emission and are too bright to be from either the disk or the companion, even in the presence of X-ray heating.

Publication type

Journal article

Research centre

Swinburne University of Technology. School of Biophysical Science and Electrical Engineering. Centre for Astrophysics and Supercomputing

Source

Astrophysical journal, Vol. 563, no. 1, pt. 2 (Dec. 2001), pp. L61-L64

Publication year

2001

Publisher

University of Chicago Press

Format

pp. L61-L64

ISSN

0004-637X

Publisher URL

Astrophysical journal

Publisher URL

http://dx.doi.org/10.1086/338357

Copyright

© 2001 The American Astronomical Society. Reproduced in accordance with the copyright policy of the publisher.

Full text

Peer reviewed