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On the Evolution of the Inner Disk Radius with Flux in the Neutron Star Low-mass X-Ray Binary Serpens X-1We analyze the latest Suzaku observation of the bright neutron star (NS) low-mass X-ray binary Serpens X-1 taken in 2013 October and 2014 April. The observation was taken using the burst mode and only suffered mild pile-up effects. A broad iron line is clearly detected in the X-ray spectrum. We test different models and find that the iron line is asymmetric and best interpreted by relativistic reflection. The relativistically broadened iron line is generally believed to originate from the innermost regions of the accretion disk, where strong gravity causes a series of special and general relativistic effects. The iron line profile indicates an inner radius of approx. 8 R(sub G), which gives an upper limit on the size of the NS. The asymmetric iron line has been observed in a number of previous observations, which gives several inner radius measurements at different flux states. We find that the inner radius of Serpens X-1 does not evolve significantly over the range of L/L(sub Edd) approx. 0.4-0.6, and the lack of flux dependence of the inner radius implies that the accretion disk may be truncated outside of the innermost stable circular orbit by the boundary layer, rather than the stellar magnetic field.
Document ID
20170003481
Document Type
Reprint (Version printed in journal)
Authors
Chiang, Chia - Ying (Wayne State Univ. Detroit, MI, United States)
Morgan, Robert A. (Wayne State Univ. Detroit, MI, United States)
Cackett, Edward M. (Wayne State Univ. Detroit, MI, United States)
Miller, Jon M. (Michigan Univ. Ann Arbor, MI, United States)
Bhattacharyya, Sudip (Tata Inst. of Fundamental Research Mumbai, India)
Strohmayer, Tod E. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
April 14, 2017
Publication Date
October 26, 2016
Publication Information
Publication: The Astrophysical Journal
Volume: 831
Issue: 1
ISSN: 0004-637X
Subject Category
Statistics and Probability
Astrophysics
Astronomy
Report/Patent Number
GSFC-E-DAA-TN41273
Funding Number(s)
CONTRACT_GRANT: GO4-15041X
CONTRACT_GRANT: NAS8-03060
CONTRACT_GRANT: PHY1460853
Distribution Limits
Public
Copyright
Other
Keywords
accretion disks
ccretion