X-ray outbursts and high-state episodes of HETE J1900.1-2455

0495461 - ASÚ 2019 RIV GB eng J - Článek v odborném periodiku
Šimon, Vojtěch
X-ray outbursts and high-state episodes of HETE J1900.1-2455.
Monthly Notices of the Royal Astronomical Society. Roč. 477, č. 1 (2018), s. 67-73. ISSN 0035-8711. E-ISSN 1365-2966
Grant ostatní: GA ČR(CZ) GA13-33324S
Institucionální podpora: RVO:67985815
Klíčová slova: accretion discs * radiation mechanisms * X-rays
Obor OECD: Astronomy (including astrophysics,space science)
Impakt faktor: 5.231, rok: 2018

HETEJ1900.1-2455 is an ultra-compact low-mass X-ray binary that underwent a long-lasting (about 10 yr) active state. The analysis presented here of its activity uses the observations of RXTE/ASM, Swift/BAT, and ISS/MAXI for investigating this active state and the relation of time evolution of fluxes in the hard and medium X-ray bands. We show that the variations of the flux of HETEJ1900.1-2455 on the time-scales of days and weeks have the form both of the outbursts and occasional high-state episodes. These outbursts are accompanied by the large changes of the hardness of the spectrum in the surroundings of the peaks of their soft X-ray flux. The very strong peaks of these outbursts occur in the soft X-ray band (2-4 keV) and are accompanied by a large depression in the 15-50 keV band flux. We interpret these events as an occasional occurrence of a thermal viscous instability of the accretion disc that gives rise to the outbursts similar to those in the soft X-ray transients. On the other hand, the 2-4 and the 15-50 keV band fluxes are mutually correlated in the high-state episodes, much longer than the outbursts. In the interpretation, the episodes of the X-ray high states of HETEJ1900.1-2455 during the active state bear some analogy with the standstills in the Z Cam type of cataclysmic variables.
Trvalý link: http://hdl.handle.net/11104/0288434