The Optical Counterpart of the Accreting Millisecond Pulsar SAX J1808.4-3658 in Outburst: Constraints on the Binary Inclination

Wang, Zhongxiang, Chakrabarty, Deepto, Roche, Paul, Charles, Philip A., Kuulkers, Erik, Shahbaz, Tariq, Simpson, Chris, Forbes, Duncan A. and Helsdon, Stephen F. 2001. The Optical Counterpart of the Accreting Millisecond Pulsar SAX J1808.4-3658 in Outburst: Constraints on the Binary Inclination. Astrophysical Journal Letters 563 , L61-L64. 10.1086/338357

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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-ray-heated accretion disk. Self-consistent modeling of the X-ray and optical emission during the outburst yields a best-fit extinction of AV = 0.68 and an inclination of cos i = 0.65 (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 = 0.05-0.10 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.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Uncontrolled Keywords:	accretion, accretion disks; binaries: close; pulsars: individual (SAX J1808.4-3658); stars: individual (V4580 Sagittarii); stars: neutron
ISSN:	0004-637X
Last Modified:	04 Jun 2017 01:41
URI:	https://orca.cardiff.ac.uk/id/eprint/1643

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