Title:	LAXPC/AstroSat Study of ~1 and ~2 mHz Quasi-periodic Oscillations in the Be/X-Ray Binary 4U 0115+63 during Its 2015 Outburst
Authors:	Roy, Jayashree Agrawal, P.C. Paul, Biswajit +13 Co-Authors
Keywords:	pulsars individual (4U 0115+63) – stars emission-line Be – X-rays binaries
Issue Date:	10-Feb-2019
Publisher:	IOP Sciences for The American Astronomical Society
Citation:	Astrophysical Journal, 2019, Vol. 872, p33
Abstract:	The Be/X-ray binary 4U 0115+63 was observed by the Large Area X-ray Proportional Counter (LAXPC) instrument on AstroSat on 2015 October 24 during the peak of a giant Type II outburst. Prominent intensity oscillations at ~1 and ~2 MHz frequency were detected during the outburst. Nuclear Spectroscopic Telescope Array (Nu Star) observations made during the same outburst also show millihertz quasi-periodic oscillations (QPOs). Details of the oscillations and their characteristics deduced from LAXPC/AstroSat and Nu Star observations are reported in this paper. Analysis of the archival Rossi X-ray Timing Explorer/Proportional Counter Array data during 2001–2011 also show the presence of millihertz QPOs during some of the outbursts, and details of these QPOs are also reported. Possible models to explain the origin of the millihertz oscillations are examined. Similar QPOs, albeit at higher frequencies, have been reported from other neutron star and black hole sources, and both may have a common origin. Current models to explain the instability in the inner accretion disk causing the intense oscillations are discussed.
Description:	Open Access
URI:	http://hdl.handle.net/2289/7169
ISSN:	0004-637X
Alternative Location:	https://ui.adsabs.harvard.edu//#abs/2019ApJ...872...33R/abstract https://arxiv.org/abs/1901.09382 https://doi.org/10.3847/1538-4357/aafaf1
Copyright:	2019, The American Astronomical Society
Appears in Collections:	Research Papers (A&A)

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