SUZAKU OBSERVATIONS OF 4U 1957+11: POTENTIALLY THE MOST RAPIDLY SPINNING BLACK HOLE IN (THE HALO OF) THE GALAXY
Nowak MA, Wilms J, Pottschmidt K, Schulz N, Maitra D, Miller J (2012)
Publication Status: Published
Publication Type: Journal article
Publication year: 2012
Journal
Publisher: IOP PUBLISHING LTD
Book Volume: 744
Article Number: ARTN 107
Journal Issue: 2
DOI: 10.1088/0004-637X/744/2/107
Abstract
We present three Suzaku observations of the black hole candidate 4U 1957+11 (V1408 Aql)-a source that exhibits some of the simplest and cleanest examples of soft, disk-dominated spectra. 4U 1957+11 also presents among the highest peak temperatures found from disk-dominated spectra. Such temperatures may be associated with rapid black hole spin. The 4U 1957+11 spectra also require a very low normalization, which can be explained by a combination of small inner disk radius and a large distance (>10 kpc) which places 4U 1957+11 well into the Galactic halo. We perform joint fits to the Suzaku spectra with both relativistic and Comptonized disk models. Assuming a low-mass black hole and the nearest distance (3 M-circle dot, 10 kpc), the dimensionless spin parameter a* equivalent to Jc/GM(2) greater than or similar to 0.9. Higher masses and farther distances yield a* approximate to 1. Similar conclusions are reached with Comptonization models; they imply a combination of small inner disk radii (or, equivalently, rapid spin) and large distance. Low spin cannot be recovered unless 4U 1957+11 is a low-mass black hole that is at the unusually large distance of greater than or similar to 40 kpc. We speculate whether the suggested maximal spin is related to how the system came to reside in the halo.
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Involved external institutions
University of Michigan
United States (USA) (US)
Massachusetts Institute of Technology (MIT)
United States (USA) (US)
University of Maryland, Baltimore County
United States (USA) (US)
United States (USA) (US)
Massachusetts Institute of Technology (MIT)
United States (USA) (US)
University of Maryland, Baltimore County
United States (USA) (US)
How to cite
APA:
Nowak, M.A., Wilms, J., Pottschmidt, K., Schulz, N., Maitra, D., & Miller, J. (2012). SUZAKU OBSERVATIONS OF 4U 1957+11: POTENTIALLY THE MOST RAPIDLY SPINNING BLACK HOLE IN (THE HALO OF) THE GALAXY. Astrophysical Journal, 744(2). https://dx.doi.org/10.1088/0004-637X/744/2/107
MLA:
Nowak, Michael A., et al. "SUZAKU OBSERVATIONS OF 4U 1957+11: POTENTIALLY THE MOST RAPIDLY SPINNING BLACK HOLE IN (THE HALO OF) THE GALAXY." Astrophysical Journal 744.2 (2012).
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