Evaluating Spectral Models and the X-ray States of Neutron-Star X-ray Transients

Abstract

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 T^4 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.

15 pages, 15 figures, accepted for publication in the ApJ

References in corpus (3)

• X-ray Properties of Black-Hole Binaries
• A Long, Hard Look at the Low-Hard State in Accreting Black Holes
• A Prominent Accretion Disk in the Low-Hard State of the Black Hole Candidate SWIFT J1753.5-0127

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