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What We Learn from the X-Ray Grating Spectra of Nova SMC 2016

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journal contribution
posted on 03.07.2019, 16:16 by M Orio, J-U Ness, A Dobrotka, E Gatuzz, N Ospina, E Aydi, E Behar, DAH Buckley, S Ciroi, M Della Valle, M Hernanz, M Henze, JP Osborne, KL Page, T Rauch, G Sala, S Starrfield, RE Williams, CE Woodward, P Zemko
Nova SMC 2016 has been the most luminous nova known in the direction of the Magellanic Clouds. It turned into a very luminous supersoft X-ray source between days 16 and 28 after the optical maximum. We observed it with Chandra, the HRC-S camera, and the Low Energy Transmission Grating on 2016 November and 2017 January (days 39 and 88 after optical maximum), and with XMM-Newton on 2016 December (day 75). We detected the compact white dwarf (WD) spectrum as a luminous supersoft X-ray continuum with deep absorption features of carbon, nitrogen, magnesium, calcium, probably argon, and sulfur on day 39, and oxygen, nitrogen, and carbon on days 75 and 88. The spectral features attributed to the WD atmosphere are all blueshifted, by about 1800 km s−1 on day 39 and up to 2100 km s−1 in the following observations. Spectral lines attributed to low-ionization potential transitions in the interstellar medium are also observed. Assuming the distance to the Small Magellanic Cloud, the bolometric luminosity exceeded the Eddington level for at least three months. A preliminary analysis with atmospheric models indicates an effective temperature of around 700,000 K on day 39, peaking at the later dates in the 850,000–900,000 K range, as expected for a ;1.25 Me WD. We suggest a possible classification as an oxygen–neon WD, but more precise modeling is needed to accurately determine the abundances. The X-ray light curves show a large, aperiodic flux variability, which is not associated with spectral variability. We detected red noise, but did not find periodic or quasiperiodic modulations.

Funding

Facilities: Chandra - , XMM-Newton - . Software: XSPEC (v12.6.0 Arnaud 1996), CIAO (v4.9; Fruscione et al. 2006), XMM-SAS v16.1.0

History

Citation

Astrophysical Journal, 2018, 862 (2)

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

VoR (Version of Record)

Published in

Astrophysical Journal

Publisher

American Astronomical Society, IOP Publishing

issn

0004-637X

eissn

1538-4357

Acceptance date

22/06/2018

Copyright date

2018

Available date

03/07/2019

Publisher version

https://iopscience.iop.org/article/10.3847/1538-4357/aacf06

Language

en