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dc.contributor.authorCorbet, Robin H. D.
dc.contributor.authorColey, Joel B.
dc.contributor.authorKrimm, Hans A.
dc.contributor.authorPottschmidt, Katja
dc.contributor.authorRoche, Paul
dc.date.accessioned2020-11-20T19:52:08Z
dc.date.available2020-11-20T19:52:08Z
dc.description.abstractHard X-ray observations with the Neil Gehrels Swift Observatory Burst Alert Telescope (BAT) reveal superorbital modulation in the wind-accreting supergiant high-mass X-ray binary (HMXB) 4U 1538-52 at a period of 14.9130 +/- 0.0026 days that is consistent with four times the 3.73 day orbital period. These periods agree with a previously suggested correlation between superorbital and orbital periods in similar HMXBs. During the ~14 years of observations the superorbital modulation changes amplitude, and since ~MJD 57,650 it was no longer detected in the power spectrum, although a peak near the second harmonic of this was present for some time. Measurements of the spin period of the neutron star in the system with the Fermi Gamma-ray Burst Monitor show a long-term spin-down trend which halted towards the end of the light curve, suggesting a connection between dP(spin)/dt and superorbital modulation, as proposed for 2S 0114+650. However, an earlier torque reversal from INTEGRAL observations was not associated with superorbital modulation changes. B and V band photometry from the Las Cumbres Observatory reveals orbital ellipsoidal photometric variability, but no superorbital optical modulation. However the photometry was obtained when the 14.9130 day period was no longer detected in the BAT power spectrum. We revisit possible superorbital modulation in BAT observations of IGR J16393-4643 but cannot conclusively determine whether this is present, although is not persistent. We consider superorbital modulation mechanisms, and suggest that the Corotating Interaction Region model, with small deviations from orbital synchronization, appears promising.en_US
dc.description.sponsorshipThis work makes use of optical observations from the LCOGT network, and we thank the XB-NEWS team and especially Dan Bramich and Dave Russell for providing the photometric analysis of these and advice. This paper made use of Swift/BAT transient monitor results provided by the Swift/BAT team and Fermi GBM results provided by the Fermi GBM team. We thank Malcolm Coe for productive discussion on optical monitoring and Nazma Islam for useful discussion on superorbital models. We also thank the referee for valuable comments.en_US
dc.description.urihttps://arxiv.org/abs/2010.12556en_US
dc.format.extent15 pagesen_US
dc.genrejournal articles preprintsen_US
dc.identifierdoi:10.13016/m2ablw-p9dm
dc.identifier.citationRobin H. D. Corbet, Joel B. Coley, Hans A. Krimm, Katja Pottschmidt and Paul Roche, Superorbital Modulation in the High-Mass X-ray Binary 4U 1538-52, and Possible Modulation in IGR J16393-4643, https://arxiv.org/abs/2010.12556en_US
dc.identifier.urihttp://hdl.handle.net/11603/20127
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 item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.
dc.rightsPublic Domain Mark 1.0*
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.
dc.rights.urihttp://creativecommons.org/publicdomain/mark/1.0/*
dc.titleSuperorbital Modulation in the High-Mass X-ray Binary 4U 1538-52, and Possible Modulation in IGR J16393-4643en_US
dc.typeTexten_US


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This item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.
Except where otherwise noted, this item's license is described as This item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.