THE SMOOTH CYCLOTRON LINE IN HER X-1 AS SEEN WITH NUCLEAR SPECTROSCOPIC TELESCOPE ARRAY

dc.contributor.authorFürst, Felix
dc.contributor.authorGrefenstette, Brian W.
dc.contributor.authorStaubert, Rüdiger
dc.contributor.authorTomsick, John A.
dc.contributor.authorBachetti, Matteo
dc.contributor.authorBarret, Didier
dc.contributor.authorBellm, Eric C.
dc.contributor.authorBoggs, Steven E.
dc.contributor.authorChenevez, Jerome
dc.contributor.authorChristensen, Finn E.
dc.contributor.authorCraig, William W.
dc.contributor.authorHailey, Charles J.
dc.contributor.authorHarrison, Fiona
dc.contributor.authorKlochkov, Dmitry
dc.contributor.authorMadsen, Kristin K.
dc.contributor.authorPottschmidt, Katja
dc.contributor.authorStern, Daniel
dc.contributor.authorWalton, Dominic J.
dc.contributor.authorWilms, Jörn
dc.contributor.authorZhang, William
dc.date.accessioned2023-09-07T14:15:56Z
dc.date.available2023-09-07T14:15:56Z
dc.date.issued2013-11-26
dc.description.abstractHer X-1, one of the brightest and best studied X-ray binaries, shows a cyclotron resonant scattering feature (CRSF) near 37 keV. This makes it an ideal target for a detailed study with the Nuclear Spectroscopic Telescope Array (NuSTAR), taking advantage of its excellent hard X-ray spectral resolution. We observed Her X-1 three times, coordinated with Suzaku, during one of the high flux intervals of its 35 day superorbital period. This paper focuses on the shape and evolution of the hard X-ray spectrum. The broadband spectra can be fitted with a power law with a high-energy cutoff, an iron line, and a CRSF. We find that the CRSF has a very smooth and symmetric shape in all observations and at all pulse phases. We compare the residuals of a line with a Gaussian optical-depth profile to a Lorentzian optical-depth profile and find no significant differences, strongly constraining the very smooth shape of the line. Even though the line energy changes dramatically with pulse phase, we find that its smooth shape does not. Additionally, our data show that the continuum only changes marginally between the three observations. These changes can be explained with varying amounts of Thomson scattering in the hot corona of the accretion disk. The average, luminosity-corrected CRSF energy is lower than in past observations and follows a secular decline. The excellent data quality of NuSTAR provides the best constraint on the CRSF energy to date.en_US
dc.description.sponsorshipThis work was supported under NASA contract No. NNG08FD60C and made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software, and Calibration teams for support with the execution and analysis of these observations. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). We would like to thank John E. Davis for the slxfig module, which was used to produce all figures in this work. F.F. would also like to thank the Remeis-Observatory Bamberg for their hospitality. J.A.T. acknowledges partial support from NASA Astrophysics Data Analysis Program grant NNX13AE98G. M.B. was supported by the Centre National d'Études Spatiales (CNES).en_US
dc.description.urihttps://iopscience.iop.org/article/10.1088/0004-637X/779/1/69en_US
dc.format.extent13 pagesen_US
dc.genrejournal articlesen_US
dc.identifierdoi:10.13016/m2np1n-9vnc
dc.identifier.citationFürst, Felix, Brian W. Grefenstette, Rüdiger Staubert, John A. Tomsick, Matteo Bachetti, Didier Barret, Eric C. Bellm, et al. “The Smooth Cyclotron Line in HER X-1 as Seen with Nuclear Spectroscopic Telescope Array.” The Astrophysical Journal 779, no. 1 (November 2013): 69. https://doi.org/10.1088/0004-637X/779/1/69.en_US
dc.identifier.urihttps://doi.org/10.1088/0004-637X/779/1/69
dc.identifier.urihttp://hdl.handle.net/11603/29605
dc.language.isoen_USen_US
dc.publisherIOP Publishingen_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Center for Space Sciences and Technology
dc.relation.ispartofUMBC Physics Department
dc.relation.ispartofUMBC Faculty Collection
dc.rightsThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.en_US
dc.rightsPublic Domain Mark 1.0*
dc.rights.urihttp://creativecommons.org/publicdomain/mark/1.0/*
dc.titleTHE SMOOTH CYCLOTRON LINE IN HER X-1 AS SEEN WITH NUCLEAR SPECTROSCOPIC TELESCOPE ARRAYen_US
dc.typeTexten_US
dcterms.creatorhttps://orcid.org/0000-0002-4656-6881en_US

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