Super-soft X-ray emission on day 6.4 from nova LMC N1968-12a strongly suggests a very high mass white dwarf
Abstract
Swift observations of the 2016 outburst of LMCN 1968-12a (ATel #8578, #8586, #8587) have been continuing daily. The early XRT spectrum, covering 2016 Jan 23 - 25 (days 2.07-4.26 after outburst), can be modelled by a single temperature optically thin emission component of kT & gt; 0.9 keV and NH = (8.3 +21.7/-7.8)x1021 cm-2, with a mean 0.3-10 keV observed flux of (5.1 +8.2/-2.3)x10-13 erg cm-2 s-1. After this time, an increase in soft emission (counts below ~1 keV) was seen, although at first this appeared to be related to a decrease in the absorbing column; no corresponding increase in X-ray count rate was found, remaining around 0.016 count s-1. On 2016 Jan 27 (day 6.4), the X-ray count rate rose to 0.05 count s-1 with the emission being dominated by counts below 1 keV. We identify this as the start of the super-soft source (SSS) phase.
- Publication:
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The Astronomer's Telegram
- Pub Date:
- January 2016
- Bibcode:
- 2016ATel.8615....1P
- Keywords:
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- Nova