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.; 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.

Citation

Wang, Z., Chakrabarty, D., Roche, P., Charles, P. A., Kuulkers, E., Shahbaz, T., …Helsdon, S. 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(1), L61-L64. https://doi.org/10.1086/338357

• Journal Article Type: Article
• Publication Date: 2001-12
• Deposit Date: May 20, 2008
• Journal: Astrophysical Journal Letters
• Print ISSN: 2041-8205
• Electronic ISSN: 2041-8213
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 563
• Issue: 1
• Pages: L61-L64
• DOI: https://doi.org/10.1086/338357
• Keywords: Accretion disks, Stars, Binaries, Pulsars, SAX J1808.4-3658, V4580 Sagittarii, Neutron.
• Public URL: https://durham-repository.worktribe.com/output/1582237
• Publisher URL: http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001ApJ...563L..61W&db_key=AST