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Measuring a Truncated Disk in Aquila X-1We present NuSTAR and Swift observations of the neutron star Aquila X-1 during the peak of its 2014 July outburst. The spectrum is soft with strong evidence for a broad Fe K(alpha) line. Modeled with a relativistically broadened reflection model, we find that the inner disk is truncated with an inner radius of 15 +/- 3RG. The disk is likely truncated by either the boundary layer and/or a magnetic field. Associating the truncated inner disk with pressure from a magnetic field gives an upper limit of B < 5+/- 2x10(exp 8) G. Although the radius is truncated far from the stellar surface, material is still reaching the neutron star surface as evidenced by the X-ray burst present in the NuSTAR observation.
Document ID
20170002456
Document Type
Reprint (Version printed in journal)
Authors
King, Ashley L. (Stanford Univ. Stanford, CA, United States)
Tomsick, John A. (California Univ. Berkeley, CA, United States)
Miller, Jon M. (Michigan Univ. Ann Arbor, MI, United States)
Chenevez, Jerome (Technical Univ. of Denmark Lyngby, Denmark)
Barret, Didier (Toulouse Univ. France)
Boggs, Steven E. (California Univ. Berkeley, CA, United States)
Chakrabarty, Deepto (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Christensen, Finn E. (Technical Univ. of Denmark Lyngby, Denmark)
Craig, William W. (California Univ. Berkeley, CA, United States)
Feurst, Felix (California Inst. of Tech. Pasadena, CA, United States)
V, Charles J. (Columbia Univ. New York, NY, United States)
Harrison, Fiona A. (California Inst. of Tech. Pasadena, CA, United States)
Parker, Michael L. (Institute of Astronomy Cambridge, United Kingdom)
Stern, Daniel (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Romano, Patrizia (Istituto di Astrofisica Spaziale e Fisica Cosmica (INAF-IASF) Palermo, Italy)
Walton, Dominic J. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Zhang, William W. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
March 23, 2017
Publication Date
March 7, 2016
Publication Information
Publication: The Astrophysical Journal Letters
Volume: 819
Issue: 2
ISSN: 0004-637X
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN40139
Funding Number(s)
CONTRACT_GRANT: NAS8-03060
Distribution Limits
Public
Copyright
Other
Keywords
accretion disks aEuro" magnetic fields aEuro" stars: neutron aEuro" X-rays: bin
accretion