Recurrent nova M31N 2008-12a: Swift/XRT detection of the 2020 eruption
ATel #14152; M. J. Darnley (LJMU), K. L. Page (Leicester), M. Henze (SDSU) on behalf of the 12a Collaboration
on 5 Nov 2020; 20:50 UT
Credential Certification: Matt Darnley (M.J.Darnley@ljmu.ac.uk)
Subjects: X-ray, Nova, Transient
In ATel #14130 we announced the discovery of the 2020 eruption of the recurrent nova M31N 2008-12a on 2020-10-30.893 UT (just a week under one year since the 2019 eruption was discovered; ATel #13269). We reported the follow-up UV detection with Neil Gehrels Swift Observatory/UVOT in ATel #14142.
Here we report the emergence of the supersoft X-ray source (SSS) phase of M31N 2008-12a. A faint X-ray counterpart was detected in a 2.69-ks Swift observation between 2020-11-05.376 UT (MJD 59158.376) and 05.589 (MJD 59158.590).
We measured the preliminary XRT count rate to be (21.3 ± 3.2) × 10-3 ct/s. No X-ray source was detected at a significant level in the preceding 3.5-ks Swift observation on 2020-11-04.5 UT with an 3σ upper limit of 2.8 × 10-3 ct/s (nor in any of the previous daily observations since the detection of this eruption).
If we assume an eruption date of 2020-10-30.7 UT (MJD 59152.7), determined by fitting the Liverpool Telescope photometric data of the 2020 eruption to the eruption light-curve template (see Darnley et al. 2016), then the SSS counterpart appeared around day 5.8 after eruption. This preliminary estimate is consistent with the 5.9 ± 0.5 days measured in 2014 (ATel #6558, Henze et al. 2015), the 5.7 ± 0.5 days seen in 2015 (ATel #7984, Darnley et al. 2016), and the 5.8 days observed for the peculiar 2016 eruption (ATel #9872, Henze et al. 2018). The X-ray spectrum at this time is consistent with SSS emission.
We wish to thank the Swift Team for the excellent scheduling of the observations, in particular the duty scientists, and the science planners.
