Infrared spectroscopy of the 2022 eruption of the recurrent nova U Sco

Evans, A; Banerjee, D P K; Woodward, C E; Geballe, T R; Gehrz, R D; Page, K L; Starrfield, S

Abstract

We present near-infrared spectroscopy of the 2022 eruption of the recurrent nova U Sco, over the period from 5.2 to 45.4 days after outburst. This is the most intensive infrared study of this nova. Our observations started early after the outburst and extended almost to the end of the ‘Super Soft’ X-ray phase. A major find is the presence of coronal lines from day 9.41, one of the earliest appearances of these in any nova, classical or recurrent. The temperature of the coronal gas is 7 × 105 K. There is also evidence for the presence of much cooler (? 2.5 × 104 K) gas. Remarkable changes are seen in the Hei 1.083µm line, the strength of which declines, then recovers, in anti-correlation with the X-ray behaviour. We conclude that shock ionisation is the dominant excitation mechanism for the coronal line emission. There is evidence in the infrared spectra for the presence of black body emission at ~20000 K, which we tentatively identify with the irradiated secondary, and for free-free/free-bound emission. For the previously determined binary inclination of 82.?7, the implied ejection velocities are as high as 22000kms-1. These velocities appear unprecedented in nova outflows, and are comparable to those seen in supernovae, thereby marking U Sco as a truly remarkable object.

Citation

Evans, A., Banerjee, D. P. K., Woodward, C. E., Geballe, T. R., Gehrz, R. D., Page, K. L., & Starrfield, S. (2023). Infrared spectroscopy of the 2022 eruption of the recurrent nova U Sco. Monthly Notices of the Royal Astronomical Society, 522(4), 4841-4851. https://doi.org/10.1093/mnras/stad1209

• Journal Article Type: Article
• Acceptance Date: Apr 14, 2023
• Online Publication Date: Apr 25, 2023
• Publication Date: 2023-07
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 522
• Issue: 4
• Pages: 4841-4851
• DOI: https://doi.org/10.1093/mnras/stad1209
• Keywords: stars: individual: U Sco, novae, cataclysmic variables, infrared: stars
• Publisher URL: https://academic.oup.com/mnras/advance-article-abstract/doi/10.1093/mnras/stad1209/7143117?redirectedFrom=fulltext
• Additional Information: Accepted manuscripts are PDF versions of the author’s final manuscript, as accepted for publication by the journal but prior to copyediting or typesetting. They can be cited using the author(s), article title, journal title, year of online publication, and DOI. They will be replaced by the final typeset articles, which may therefore contain changes. The DOI will remain the same throughout.; ; © 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society; This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)