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Continued decay in the cyclotron line energy in Hercules X-1

Staubert, R. and Klochkov, D. and Vybornov, V. and Wilms, J. and Harrison, F. A. (2016) Continued decay in the cyclotron line energy in Hercules X-1. Astronomy and Astrophysics, 590 . Art. No. A91. ISSN 0004-6361. doi:10.1051/0004-6361/201527955.

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The centroid energy E_(cyc) of the cyclotron line in the spectrum of the binary X-ray pulsar Her X-1 has been found to decrease with time on a time scale of a few tens of years – surprisingly short in astrophysical terms. This was found for the pulse phase-averaged line centroid energy using observational data from various X-ray satellites over the time period 1996 to 2012, establishing a reduction of ~4 keV. Here we report on the result of a new observation by NuSTAR performed in August 2015. The earlier results are confirmed and strengthened with respect to both the dependence of E_(cyc) on flux (it is still present after 2006) and the dependence on time: the long-term decay continued with the same rate, corresponding to a reduction of ~5 keV in 20 yr.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Wilms, J.0000-0003-2065-5410
Harrison, F. A.0000-0003-2992-8024
Additional Information:© 2016 ESO. Received 14 December 2015. Accepted 18 March 2016. Published online 19 May 2016. The motivation for this paper are new observational data taken by the NASA satellite NuSTAR. We would like to acknowledge the dedication of all the people who have contributed to the great success of this mission, here especially Karl Forster for his effort with respect to the non-standard scheduling of the observations. Further important data were provided by the equally successful missions RXTE and Swift of NASA and INTEGRAL of ESA. This work was supported by the Deutsche Forschungsgemeinschaft (DFG) through joint grants KL 2734/2-1 and WI 1860/11-1. We thank the anonymous referee for useful comments and suggestions.
Funding AgencyGrant Number
Deutsche Forschungsgemeinschaft (DFG)KL 2734/2-1
Deutsche Forschungsgemeinschaft (DFG)WI 1860/11-1
Subject Keywords:magnetic fields stars: neutron radiation mechanisms: general radiation mechanisms: non-thermal accretion, accretion disks X-rays: binaries
Record Number:CaltechAUTHORS:20160715-103832678
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Official Citation:Continued decay in the cyclotron line energy in Hercules X-1 R. Staubert, D. Klochkov, V. Vybornov, J. Wilms and F. A. Harrison A&A, 590 (2016) A91 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69055
Deposited By: Ruth Sustaita
Deposited On:15 Jul 2016 19:27
Last Modified:11 Nov 2021 04:08

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