2015/01/01 by Akifumi Yoshikawa, A. Yoshikawa, Shin'ya Yamada +8
Engineering · Physics and Astronomy · #Accretion (finance) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Black hole (networking) #Black-body radiation #Low Mass #Mechanics and Biomechanics Studies #Optics #Physics #Pulsars and Gravitational Waves Research #RADIUS #Radiation #Softening #Spectral line #Stars #Tin #astro-ph.HE
paper · pdf · doi:10.1093/pasj/psu140
11 pages, 10 figures, PASJ, accepted
openalex publication_date 2015/01/01 · arxiv created 2015/03/04 · arxiv updated 2015/03/05 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Abstract We report MAXI and Swift observations of short-term spectral softenings of the Galactic black hole X-ray binary Swift J1753.5−0127 in the low/hard state. These softening events are characterized by a simultaneous increase of soft X-rays (2–4 keV) and a decrease of hard X-rays (15–50 keV) lasting for a few tens of days. The X-ray energy spectra during the softening periods can be reproduced with a model consisting of a multi-color disk blackbody and its Comptonized component. The fraction of the Comptonized component decreased from 0.30 to 0.15 when the spectrum became softer; meanwhile the inner disk temperature (Tin) increased from 0.2 to 0.45 keV. These results imply that the softening events are triggered by a short-term increase of the mass accretion rate. During the observed spectral softening events, the disk flux (Fdisk) and Tin did not obey the Fdisk ∝ (Tin )4 relation, suggesting that the inner disk radius does not reach the innermost stable circular orbit.