Confirmation of PNV J00430400+4117079 as another eruption of the recurrent nova M31N 1990-10a and additional constraints on the eruption date

ATel #9276; M. Henze (CSIC-IEEC), S. C. Williams (Lancaster), M. J. Darnley (LJMU), A. Ederoclite (CEFCA), G. Sala (UPC-IEEC), A. W. Shafter (SDSU), K. Chinetti (Caltech), J. Jose (UPC-IEEC), M. Hernanz (CSIC-IEEC)
on 28 Jul 2016; 21:07 UT
Credential Certification: Martin Henze (henze@ice.cat)

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The discovery of the object PNV J00430400+4117079 in M31 was recently announced by K. Nishiyama and F. Kabashima on the CBAT Transient Objects Confirmation Page (TCOP). The TCOP report noted that the object was close to the position of nova M31N 2007-07a (ATel #1131). The 2007 nova in turn had been identified by Shafter et al. (2015) as a possible recurrence of nova M31N 1990-10a, originally found by Bryan (1990). Based on a detection image of PNV J00430400+4117079 posted by E. Conseil on the TCOP page and the finding chart for M31N 2007-07a provided in the online catalogue of Pietsch et al. (2007) we can confirm that both objects are spatially consistent. PNV J00430400+4117079 is therefore a clear recurrence of M31N 2007-07a, which significantly strengthens the case that M31N 1990-10a was the first recorded eruption of this nova system.

With a time difference of about 9 yr between the M31N 2007-07a and PNV J00430400+4117079 eruptions, and 16.7 yr between M31N 1990-10a and M31N 2007-07a, there is the possibility that this system has an average recurrence period of 8-9 yr. This is slightly shorter than the fastest Galactic recurrent nova, U Sco (average 10 yr; e.g. Schaefer 2010), but much longer than the record M31 recurrent nova M31N 2008-12a (average 0.5 or 1 yr; e.g. Darnley et al. 2016, Henze et al. 2015). In this scenario, there would have been a missed eruption around 1998/99 (but note that Shafter et al. 2015 rejected the possible candidate M31N 1997-10b as a CCD artefact).

Additionally, we report that the nova was not detected on a set of two 400s H-alpha images (central wavelength 660nm; FWHM 14.5nm) obtained on 2016-07-26.051 UT with the JAST/T80 telescope at the Observatorio Astrofisico de Javalambre (OAJ), in Teruel, owned, managed and operated by the Centro de Estudios de Fisica del Cosmos de Aragon. Nothing can be seen down to about 20th magnitude, calibrated with R band data of the Local Group Galaxies Survey (Massey et al. 2006). Together with the discovery date on 2016-07-27.698 UT, reported by Nishiyama and Kabashima, our non-detection constrains the eruption date to 2016-07-26.87 UT with an uncertainty of 0.82 days. This is a significantly improved accuracy with respect to other upper limits reported so far.

Follow-up observations are encouraged. We thank the OAJ Data Processing and Archiving Unit (UPAD) for reducing and calibrating the OAJ data used in this work.