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NuSTAR Discovery of a Cyclotron Line in the Accreting X-Ray Pulsar IGR J16393-4643The high-mass X-ray binary and accreting X-ray pulsar IGR J16393-4643 was observed by the Nuclear Spectroscope Telescope Array in the 3-79 keV energy band for a net exposure time of 50 ks. We present the results of this observation which enabled the discovery of a cyclotron resonant scattering feature with a centroid energy of -29.3(sup +1.1)(sub -1.3) keV. This allowed us to measure the magnetic field strength of the neutron star for the first time: B = (2.5 +/- 0.1) x 10(exp 12) G. The known pulsation period is now observed at 904.0+/- 0.1 s. Since 2006, the neutron star has undergone a long-term spin-up trend at a rate of P= -2 x 10(exp -8) s s(exp -1) (-0.6 s per year, or a frequency derivative of v = 3 x 10(exp -14) Hz s(exp -1)). In the power density spectrum, a break appears at the pulse frequency which separates the zero slope at low frequency from the steeper slope at high frequency. This addition of angular momentum to the neutron star could be due to the accretion of a quasi-spherical wind, or it could be caused by the transient appearance of a prograde accretion disk that is nearly in corotation with the neutron star whose magnetospheric radius is around 2 x 10(exp 8) cm.
Document ID
Document Type
Reprint (Version printed in journal)
Bodaghee, Arash
(Georgia Coll. and State Univ. Milledgeville, GA, United States)
Tomsick, John A.
(California Univ. Berkeley, CA, United States)
Fornasini, Francesca M.
(California Univ. Berkeley, CA, United States)
Krivonos, Roman
(Academy of Sciences (USSR) Moscow, Russian Federation)
Stern, Daniel
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Mori, Kaya
(Columbia Univ. New York, NY, United States)
Rahoui, Farid
(European Southern Observatory Munich, Germany)
Boggs, Steven E.
(California Univ. Berkeley, CA, United States)
Christensen, Finn E.
(Technical Univ. of Denmark Lyngby, Denmark)
Craig, William W.
(California Univ. Berkeley, CA, United States)
Zhang, William W.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
April 6, 2017
Publication Date
June 1, 2016
Publication Information
Publication: The Astrophysical Journal
Volume: 823
Issue: 2
ISSN: 0004-637X
Subject Category
Report/Patent Number
Funding Number(s)
Distribution Limits
accretion disks – gamma-ray burst: general – stars: neutron – X-rays: bin

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