Open AccessPeriodic variability during the X‐ray decline of 4U 1636‐53
Author(s) -
Shih I. C.,
Bird A. J.,
Charles P. A.,
Cornelisse R.,
Tiramani D.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.09224.x
Subject(s) - physics , astrophysics , neutron star , accretion (finance) , x ray binary , flux (metallurgy) , amplitude , accretion disc , x ray , sky , astronomy , nuclear physics , materials science , quantum mechanics , metallurgy
We report the onset of a large amplitude, statistically significant periodicity (∼46 d) in the Rossi X‐ray Timing Explorer/All Sky Monitor ( RXTE /ASM) data of the prototype X‐ray burster 4U 1636‐53, the X‐ray flux of which has been gradually declining over the last 4 yr. This behaviour is remarkably similar to that observed in the neutron star low mass X‐ray binary (LMXB), KS 1731‐260, which is a long‐term transient. We also report on an INTEGRAL/IBIS observation of 4U 1636‐53 during its decline phase, and find that the hard X‐ray flux (20–100 keV) indicates an apparent anticorrelation with soft X‐rays (2–12 keV). We argue that 4U 1636‐53 is transiting from activity to quiescence, as occurred in KS 1731‐260. We also suggest that the variability during the X‐ray decline is the result of an accretion rate variability related to the X‐ray irradiation of the disc.