Recurrent nova M31N 2008-12a: Swift/XRT detection of the SSS following the 2024 eruption
ATel #16957; K. L. Page (U. Leicester) and M. J. Darnley (LJMU)
on 19 Dec 2024; 07:52 UT
Credential Certification: Kim Page (kpa@star.le.ac.uk)
The 2024 eruption of the yearly recurrent nova M31N 2008-12a was
reported in ATel #16942, with the earliest optical detection of 2024
December 12.9875 being provided in ATel #16946; we
take this date as T0 in this analysis. As noted in ATel #16947, Target
of Opportunity observations by the Neil Gehrels Swift Observatory
began at T0+0.87 days, and these have been continuing daily.
Data collected on December 18 show the emergence of the supersoft
X-ray source (SSS) phase of the nova. In a short snapshot taken at
T0+5.13 day, no X-ray source was visible, to a 3σ upper limit of
0.02 count s-1. The following observation, at T0+5.52 day,
revealed a faint X-ray source, at a count rate of 0.010 ± 0.002
count s-1, which rose to 0.020 ± 0.004 by T0+5.58 day. The
X-ray spectrum is consistent with SSS emission, with all the counts
below 0.8 keV.
Taking the midpoint of the last X-ray non-detection and first
detection as the start of the SSS phase, the appearance of the X-ray
counterpart on day 5.3 +/- 0.2 day is in line with the findings for
previous eruptions (e.g. ATels #5627, #6558, #7984, #9872, #12207, #13290,
#14152, #15050, #15798).
We thank the Swift PIs, duty scientists and science planners for their approval and scheduling of these observations.
