2006/11/02 by M. Fiocchi, Mariateresa Fiocchi, Angela Bazzano +5 · 1 citation
Earth and Planetary Sciences · Engineering · Physics and Astronomy · #Accretion (finance) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Binary number #Black-body radiation #Compton scattering #Galaxy #High-pressure geophysics and materials #Luminosity #Mechanics and Biomechanics Studies #Neutron star #Nuclear physics #Optics #Photon #Physics #Radiation #Reflection (computer programming) #Spectral line #X-ray binary #astro-ph
paper · pdf · doi:10.1086/510573
published as Astrophys.J.657:448-452,2007 · accepted ApJ
arxiv created 2006/11/02 · openalex publication_date 2007/03/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
We present data from INTEGRAL and BeppoSAX satellites showing spectral state transitions of the neutron star, atoll-type, low-mass X-ray binary 4U 1705-44. Its energy spectrum can be described as the sum of one or two blackbody components, a 6.4 keV Fe line, and a component due to thermal Comptonization. In addition, and for the first time in this source, we find a strong signature of Compton reflection, presumably due to illumination of the optically thick accretion disk by the Comptonization spectrum. The two blackbody components, which the soft-state data require, presumably arise from both the disk and the neutron star surface. The Comptonization probably takes place in a hot inner flow irradiated by some of the blackbody photons. The spectral transitions are shown to be associated with variations in the bolometric luminosity, most likely proportional to the accretion rate. Independently of the spectral state, we also see changes in the temperature of the Comptonizing electrons and the strength of Compton reflection.