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Title: Results of the swift monitoring campaign of the X-ray binary 4U 1957+11: constraints on binary parameters

We present new results of uniform spectral analysis of Swift/XRT observations of the X-ray binary system 4U 1957+11. This includes 26 observations of the source made between MJD 54282-55890 (2007 July 01-2011 November 25). All 26 spectra are predominantly thermal and can be modeled well with emission from an accretion disk around a black hole. We analyze all 26 spectra jointly using traditional χ{sup 2} fitting as well as Markov Chain Monte Carlo simulations. The results from both methods agree, and constrain model parameters like inclination, column density, and black hole spin. These results indicate that the X-ray emitting inner accretion disk is inclined to our line of sight by 77.6{sub −2.2}{sup +1.5} deg. Additionally, the other constraints we obtain on parameters such as the column density and black hole spin are consistent with previous X-ray observations. Distances less than 5 kpc are unlikely and not only ruled out based on our analysis but also from other independent observations. Based on model-derived bolometric luminosities, we require the source distance to be >10 kpc if the black hole's mass is >10 M {sub ☉}. If the hole's mass is <10 M {sub ☉}, then the distance could be in the rangemore » of 5-10 kpc.« less
Authors:
 [1] ; ; ;  [2] ;  [3]
  1. Department of Physics and Astronomy, Wheaton College, Norton, MA 02766 (United States)
  2. Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)
  3. Massachusetts Institute of Technology, Kavli Institute for Astrophysics, Cambridge, MA 02139 (United States)
Publication Date:
OSTI Identifier:
22370442
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 794; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; BLACK HOLES; BOLOMETERS; DENSITY; EMISSION; HOLES; INCLINATION; LUMINOSITY; MASS; SPIN; X RADIATION