TY - JOUR
T1 - What We Learn from the X-Ray Grating Spectra of Nova SMC 2016
AU - Orio, M.
AU - Ness, J. U.
AU - Dobrotka, A.
AU - Gatuzz, E.
AU - Ospina, N.
AU - Aydi, E.
AU - Behar, E.
AU - Buckley, D. A.H.
AU - Ciroi, S.
AU - Della Valle, M.
AU - Hernanz, M.
AU - Henze, M.
AU - Osborne, J. P.
AU - Page, K. L.
AU - Rauch, T.
AU - Sala, G.
AU - Starrfield, S.
AU - Williams, R. E.
AU - Woodward, C. E.
AU - Zemko, P.
N1 - Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved..
PY - 2018/8/1
Y1 - 2018/8/1
N2 - 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 M o 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.
AB - 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 M o 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.
KW - X-rays: stars
KW - novae, cataclysmic variables
KW - stars: abundances
KW - stars: dwarf novae
KW - stars: individual (N SMC 2016a)
UR - http://www.scopus.com/inward/record.url?scp=85051492343&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85051492343&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/aacf06
DO - 10.3847/1538-4357/aacf06
M3 - Article
AN - SCOPUS:85051492343
SN - 0004-637X
VL - 862
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 164
ER -