The smooth cyclotron line in Her X-1 as seen with NuSTAR

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dc.contributor.authorFuerst, Felix
dc.contributor.authorGrefenstette,  Brian W.
dc.contributor.authorStaubert,  Ruediger
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,  Joern
dc.contributor.authorZhang, William
dc.date.accessioned2023-09-07T14:20:19Z
dc.date.available2023-09-07T14:20:19Z
dc.date.issued2013-09-20
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 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 35d super-orbital period. This paper focuses on the shape and evolution of the hard X-ray spectrum. The broad-band spectra can be fitted with a powerlaw 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 is only changing 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. FF would also like to thank the RemeisObservatory Bamberg for their hospitality. JAT acknowledges partial support from NASA Astrophysics Data Analysis Program grant NNX13AE98G. MB was supported by the Centre National d’Etudes Spatiales (CNES).en_US
dc.description.urihttps://arxiv.org/abs/1309.5361en_US
dc.format.extent13 pagesen_US
dc.genrejournal articlesen_US
dc.genrepreprintsen_US
dc.identifierdoi:10.13016/m233r2-zcii
dc.identifier.urihttps://doi.org/10.48550/arXiv.1309.5361
dc.identifier.urihttp://hdl.handle.net/11603/29609
dc.language.isoen_USen_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Center for Space Sciences and Technology
dc.relation.ispartofUMBC Faculty Collection
dc.relation.ispartofUMBC Physics Department
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 NuSTARen_US
dc.typeTexten_US
dcterms.creatorhttps://orcid.org/0000-0002-4656-6881en_US

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