Cyclotron line energy in Hercules X-1: stable after the decay
| dc.contributor.author | Staubert, R. | |
| dc.contributor.author | Ducci, L. | |
| dc.contributor.author | Ji, L. | |
| dc.contributor.author | Fürst, F. | |
| dc.contributor.author | Wilms, J. | |
| dc.contributor.author | Rothschild, R.E. | |
| dc.contributor.author | Pottschmidt, Katja | |
| dc.contributor.author | Brumback, M. | |
| dc.contributor.author | Harrison, F. | |
| dc.date.accessioned | 2020-10-08T16:30:54Z | |
| dc.date.available | 2020-10-08T16:30:54Z | |
| dc.date.issued | 2020-10-20 | |
| dc.description.abstract | We summarize the results of a dedicated effort made between 2012 and 2019 to follow the evolution of the cyclotron line in Her X-1 through repeated NuSTAR observations. The previously observed nearly 20-year-long decay of the cyclotron line energy has ended in 2012: from then on, the pulse-phase-averaged flux-corrected cyclotron line energy has remained stable and constant at an average value of Ecyc = (37.44 ± 0.07) keV (normalized to a flux level of 6.8 RXTE/ASM-cts/s). The flux dependence on Ecyc discovered in 2007 is now measured with high precision, giving a slope of (0.675 ± 0.075) keV/(ASM-cts/s), corresponding to an increase of 6.5% of Ecyc for an increase in flux by a factor of two. We also find that all line parameters as well as the continuum parameters show a correlation with X-ray flux. While a correlation between Ecyc and X-ray flux (both positive and negative) is now known for several accreting binaries with various suggestions for the underlying physics, the phenomenon of a long-term decay has so far only been seen in Her X-1 and Vela X-1, with far less convincing explanations. | en_US |
| dc.description.sponsorship | We would like to acknowledge the dedication of all the people who have contributed to the great success of all relevant missions, in particular NuSTAR. We especially thank the “schedulers”, foremost Karl Forster, for his efforts with respect to the non-standard scheduling of the observations of Her X-1. We acknowledge the historical contributions to the subject at hand by Dmitry Klochkov. We thank the anonymous referee for valuable comments. | en_US |
| dc.description.uri | https://www.aanda.org/articles/aa/full_html/2020/10/aa38855-20/aa38855-20.html | en_US |
| dc.format.extent | 12 pages | en_US |
| dc.genre | journal articles | en_US |
| dc.identifier | doi:10.13016/m2auwv-39n3 | |
| dc.identifier.citation | Staubert, R., “Cyclotron line energy in Hercules X-1: stable after the decay”, Astronomy and Astrophysics, vol. 642, 2020. doi:10.1051/0004-6361/202038855. | en_US |
| dc.identifier.uri | https://doi.org/10.1051/0004-6361/202038855 | |
| dc.identifier.uri | http://hdl.handle.net/11603/19767 | |
| dc.language.iso | en_US | en_US |
| dc.publisher | EDP sciences | en_US |
| dc.relation.isAvailableAt | The University of Maryland, Baltimore County (UMBC) | |
| dc.relation.ispartof | UMBC Physics Department Collection | |
| dc.relation.ispartof | UMBC Faculty Collection | |
| dc.relation.ispartof | UMBC Center for Space Sciences and Technology (CSST)/Center for Research and Exploration in Space Sciences and Technology II (CREST II) | |
| dc.rights | 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. | |
| dc.title | Cyclotron line energy in Hercules X-1: stable after the decay | en_US |
| dc.type | Text | en_US |
| dcterms.creator | https://orcid.org/0000-0002-4656-6881 |