The First NuSTAR Observation of 4U 1538–522: Updated Orbital Ephemeris and a Strengthened Case for an Evolving Cyclotron Line Energy

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dc.contributor.authorHemphill, Paul B.
dc.contributor.authorRothschild, Richard E.
dc.contributor.authorCheatham, Diana M.
dc.contributor.authorFürst, Felix
dc.contributor.authorKretschmar, Peter
dc.contributor.authorKühnel, Matthias
dc.contributor.authorPottschmidt, Katja
dc.contributor.authorStaubert, Rüdiger
dc.contributor.authorWilms, Jörn
dc.contributor.authorWolff, Michael T.
dc.date.accessioned2023-08-29T19:02:44Z
dc.date.available2023-08-29T19:02:44Z
dc.date.issued2019-03-05
dc.description.abstractWe have performed a comprehensive spectral and timing analysis of the first NuSTAR observation of the high-mass X-ray binary 4U 1538−522. The observation covers the X-ray eclipse of the source, plus the eclipse ingress and egress. We use the new measurement of the mid-eclipse time to update the orbital parameters of the system and find marginally significant evolution in the orbital period, with Pₒᵣb / Pₒᵣb= (-0.95 ± 0.37)* 10⁻⁶ yr⁻¹. The cyclotron line energy is found to be approximately 1.2 keV higher than RXTE measurements from 1997 to 2003, in line with the increased energy observed by Suzaku in 2012 and strengthening the case for secular evolution of 4U 1538−522's CRSF. We additionally characterize the behavior of the iron fluorescence and emission lines and line-of-sight absorption as the source moves into and out of eclipse.en_US
dc.description.sponsorshipThis work was supported by NASA grant NNX17AC33G. We have made extensive use of the ISISscripts, a collection of ISIS routines provided by ECAP/Remeis observatory and MIT (http://www.sternwarte.uni-erlangen.de/isis/). The colors used in plots are selected based on Paul Tol's recommendations found in SRON Technical Note SRON/EPS/TN/09-002 (https://personal.sron.nl/~pault/data/colourschemes.pdf). Some computations in Section 3 were carried out using Mathematica, version 11.3. We thank Alan Levine and Nevin Weinberg for useful discussions, and the anonymous referee for their useful suggestions.en_US
dc.description.urihttps://iopscience.iop.org/article/10.3847/1538-4357/ab03d3en_US
dc.format.extent13 pagesen_US
dc.genrejournal articlesen_US
dc.identifierdoi:10.13016/m2bpxe-4ajs
dc.identifier.citationHemphill, Paul B., Richard E. Rothschild, Diana M. Cheatham, Felix Fürst, Peter Kretschmar, Matthias Kühnel, Katja Pottschmidt, Rüdiger Staubert, Jörn Wilms, and Michael T. Wolff. “The First NuSTAR Observation of 4U 1538–522: Updated Orbital Ephemeris and a Strengthened Case for an Evolving Cyclotron Line Energy.” The Astrophysical Journal 873, no. 1 (March 2019): 62. https://doi.org/10.3847/1538-4357/ab03d3.en_US
dc.identifier.urihttps://doi.org/10.3847/1538-4357/ab03d3
dc.identifier.urihttp://hdl.handle.net/11603/29418
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 Student Collection
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 First NuSTAR Observation of 4U 1538–522: Updated Orbital Ephemeris and a Strengthened Case for an Evolving Cyclotron Line Energyen_US
dc.typeTexten_US
dcterms.creatorhttps://orcid.org/0000-0002-4656-6881en_US

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