2007/02/28 by Dacheng Lin, Ronald A. Remillard, Jeroen Homan · 1 citation
Physics and Astronomy · #astro-ph
paper · pdf · doi:10.1086/521181
15 pages, 15 figures, accepted for publication in the ApJ
arxiv created 2007/06/22 · arxiv updated 2009/12/01
We propose a hybrid model to fit the X-ray spectra of atoll-type X-ray transients in the soft and hard states. This model uniquely produces luminosity tracks that are proportional to T4 for both the accretion disk and boundary layer. The model also indicates low Comptonization levels for the soft state, gaining a similarity to black holes in the relationship between Comptonization level and the strength of integrated rms variability in the power density spectrum. The boundary layer appears small, with a surface area that is roughly constant across soft and hard states. This result may suggestion that the NS radius is smaller than its inner-most stable circular orbit.