Abstract Details
| Name: Aru Beri Affiliation: IISER, Mohali Conference ID: ASI2019_310 Title : NICER and AstroSat Observations of Swift J1658.2-4242 during its 2017 Outburst Authors and Co-Authors : Aru Beri, Diego Altamirano (University of Southampton), James F. Steiner,(MIT, U.S.A), Zaven Arzoumanian (NASA, U.S.A) + NICER Team Abstract Type : Oral Abstract Category : Stars, ISM and Galaxy Abstract : Swift J1658.2-4242 (J1658) is a newly discovered X-ray transient which was preliminarily classified as a black hole candidate based on the radio/X-ray properties and an assumed distance larger than 3kpc. During its outburst, J1658 was regularly monitored with the Neutron star Interior Composition Explorer (NICER). During this talk, we will present a comprehensive spectral study in 0.4-12 keV band using all the observations made with NICER. Contrary to previous claims, preliminary results based on spectral decomposition suggest that J1658 is a neutron star X-ray binary. As a part of several X-ray and radio monitoring campaigns of J1658, the Indian space facility AstroSat observed J1658 between February 20, 2018, and February 21, 2018. The observations made with LAXPC onboard AstroSat revealed the presence of a strong QPO at around 2.46 Hz with a quality factor of 8.2\pm0.5. We found that the energy-dependent time-lag spectra show a soft lag (soft photons trail behind hard photons) at the QPO frequency and the fractional rms of the QPO increases with the photon energy. During this talk, we will also discuss these results in the context of detailed broadband spectral study based on AstroSat data from the SXT and LAXPC instruments. |