Name: Pinaki Roy
Affiliation: Indian Institute of Science Education and Research, Mohali
Conference ID : ASI2022_630
Title : Thermonuclear X-ray Bursts from Low-mass X-ray Binary 4U 1636-536 observed with AstroSat and NuSTAR
Authors : Pinaki Roy (IISER-M), Aru Beri (IISER-M), Sudip Bhattacharyya (TIFR)
Abstract Type: Oral
Abstract Category : Stars, ISM and Galaxy
Abstract : Thermonuclear (Type I) X-ray bursts are sudden surges in X-ray emission from an accreting neutron star in a Low-Mass X-ray Binary (LMXB). They result from the unstable burning of hydrogen and helium on the surface of the neutron star. X-ray bursts have been found to recur on timescales of hours or days. Burst occurring within 45 minutes of the preceding burst is conventionally labelled as short waiting time (SWT) burst. In this talk, I will present results from the spectro-timing analysis of 43 X-ray bursts in AstroSat and NuSTAR observations of a neutron star X-ray binary and well-known X-ray burster, 4U 1636−536. We identify five doublets and a triplet. Recurrence time as short as 3.8 minutes is seen in one of the doublets. To the best of our knowledge, this is the shortest recurrence time known for this source. In some of these bursts, thermonuclear burst oscillations (TBOs) are detected at ~581 Hz with five sigma confidence. TBOs are timing features around the stellar spin frequency observed during X-ray bursts because of the asymmetric brightness patches in the burning surface layers of accreting neutron stars. This is the first time a detailed timing study of burst oscillations with AstroSat has been performed. We will discuss the plausible origin of TBOs and SWT X-ray bursts and compare our observational results with proposed models.