2001/10/30 by Zhongxiang Wang, Deepto Chakrabarty, P. Roche +10 · 4 citations
Earth and Planetary Sciences · Physics and Astronomy · #Accretion (finance) #Accretion disc #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Binary number #Flux (metallurgy) #High-pressure geophysics and materials #Millisecond #Millisecond pulsar #Neutron star #Photometry (optics) #Physics #Pulsar #Pulsars and Gravitational Waves Research #Stars #astro-ph
paper · pdf · doi:10.1086/338357
4 pages including 1 figure. Accepted for publication in ApJ Letters
arxiv created 2001/10/30 · openalex publication_date 2001/12/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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 A V = 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, M c = 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.