Page, KL, Beardmore, AP, Osborne, JP, Munari, U, Ness, J-U, Evans, PA, Bode, MF, Darnley, MJ, Drake, JJ, Kuin, NPM, O'Brien, TJ, Orio, M, Shore, SN, Starrfield, S and Woodward, CE (2022) The 2021 outburst of the recurrent nova RS Ophiuchi observed in X-rays by the Neil Gehrels Swift Observatory: a comparative study. Monthly Notices of the Royal Astronomical Society, 514 (2). pp. 1557-1574. ISSN 0035-8711

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Abstract

On 2021 August 8, the recurrent nova RS Ophiuchi (RS Oph) erupted again, after an interval of 15.5 yr. Regular monitoring by the Neil Gehrels Swift Observatory began promptly, on August 9.9 (0.37 d after the optical peak), and continued until the source passed behind the Sun at the start of November, 86 d later. Observations then restarted on day 197, once RS Oph emerged from the Sun constraint. This makes RS Oph the first Galactic recurrent nova to have been monitored by Swift throughout two eruptions. Here we investigate the extensive X-ray data sets between 2006 and 2021, as well as the more limited data collected by the European X-ray Observatory Satellite (EXOSAT) in 1985. The hard X-rays arising from shock interactions between the nova ejecta and red giant wind are similar following the last two eruptions. In contrast, the early supersoft source (SSS) in 2021 was both less variable and significantly fainter than in 2006. However, 0.3–1 keV light curves from 2021 reveal a 35 s quasi-periodic oscillation consistent in frequency with the 2006 data. The Swift X-ray spectra from 2021 are featureless, with the soft emission typically being well parametrized by a simple blackbody, while the 2006 spectra showed much stronger evidence for superimposed ionized absorption edges. Considering the data after day 60 following each eruption, during the supersoft phase the 2021 spectra are hotter, with smaller effective radii and lower wind absorption, leading to an apparently reduced bolometric luminosity. We explore possible explanations for the gross differences in observed SSS behaviour between the 2006 and 2021 outbursts.

Item Type:	Article
Uncontrolled Keywords:	astro-ph.HE; astro-ph.HE
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	Oxford University Press
Related URLs:	http://arxiv.org/abs/2205.03232v1
SWORD Depositor:	A Symplectic
Date Deposited:	05 Aug 2022 09:37
Last Modified:	05 Aug 2022 09:45
DOI or ID number:	10.1093/mnras/stac1295
URI:	https://researchonline.ljmu.ac.uk/id/eprint/17347

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