X-rays from RS Ophiuchi's 2021 eruption: shocks in and out of ionization equilibrium
| dc.contributor.author | Islam, Nazma | |
| dc.contributor.author | Mukai, Koji | |
| dc.contributor.author | Sokoloski, Jennifer L. | |
| dc.date.accessioned | 2023-12-12T17:05:05Z | |
| dc.date.available | 2023-12-12T17:05:05Z | |
| dc.date.issued | 2023-11-28 | |
| dc.description.abstract | The recurrent nova RS Ophiuchi (RS Oph) underwent its most recent eruption on 8 August 2021 and became the first nova to produce both detectable GeV and TeV emission. We used extensive X-ray monitoring with the Neutron Star Interior Composition Explorer Mission (NICER) to model the X-ray spectrum and probe the shock conditions throughout the 2021 eruption. The rapidly evolving NICER spectra consisted of both line and continuum emission that could not be accounted for using a single-temperature collisional equilibrium plasma model with an absorber that fully covered the source. We successfully modelled the NICER spectrum as a non-equilibrium ionization collisional plasma with partial-covering absorption. The temperature of the the non-equilibrium plasma show a peak on Day 5 with a kT of approximately 24 keV. The increase in temperature during the first five days could have been due to increasing contribution to the X-ray emission from material behind fast polar shocks or a decrease is the amount of energy being drained from shocks into particle acceleration during that time period. The absorption showed a change from fully covering the source to having a covering fraction of roughly 0.4, suggesting a geometrical evolution of the shock region within the complex global distribution of the circumstellar material. These findings show the evidence of the ejecta interacting with some dense equatorial shell initially and with less dense material in the bipolar regions at later times during the eruption. | |
| dc.description.sponsorship | We thank the anonymous referee for constructive comments which helped improve the manuscript. We thank Marina Orio and Juan Luna for helpful discussions. The scientific results reported here are based on observations made by the NICER X-ray observatory and we thank the NICER team for scheduling and the execution of these Target of Opportunity observations. This research has made use of MAXI data provided by RIKEN, JAXA and the MAXI team. This research has made use of data and/or software provided by the High Energy Astrophysics Science 13 Archive Research Center (HEASARC), which is a service of the Astrophysics Science Division at NASA/GSFC. J.L.S. acknowledges support from NASA grant 80NSSC21K0715 and NSF award AST-1816100. NI acknowledges support from NASA grant 80NSSC21K1994. | |
| dc.description.uri | https://arxiv.org/abs/2311.17156 | |
| dc.format.extent | 16 pages | |
| dc.genre | journal articles | |
| dc.genre | preprints | |
| dc.identifier.uri | https://doi.org/10.48550/arXiv.2311.17156 | |
| dc.identifier.uri | http://hdl.handle.net/11603/31044 | |
| dc.language.iso | en_US | |
| dc.relation.isAvailableAt | The University of Maryland, Baltimore County (UMBC) | |
| dc.relation.ispartof | UMBC Center for Space Sciences and Technology | |
| dc.relation.ispartof | UMBC Faculty Collection | |
| 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.rights | CC BY 4.0 DEED Attribution 4.0 International | en |
| dc.rights.uri | https://creativecommons.org/licenses/by/4.0/ | |
| dc.title | X-rays from RS Ophiuchi's 2021 eruption: shocks in and out of ionization equilibrium | |
| dc.type | Text | |
| dcterms.creator | https://orcid.org/0000-0002-2413-9301 | |
| dcterms.creator | https://orcid.org/0000-0002-8286-8094 |