Hubble's Recurrent Nova M31N 1923-12c Erupts Again!

A. W. Shafter (SDSU), M. J. Darnley and M. F. Bode (LJMU, UK), R. Ciardullo (PSU), F. Schweizer (Carnegie Observatories) Astronomer's Telegram #3914

On January 22, 2012 we obtained the following spectrum of the M31 Nova, M31N 2012-01b, using the Low Resolution Spectrograph on the 9.2 m Hobby-Eberly Telescope:

The spectrum revealed that the nova was a member of the relatively rare "He/N" class of novae, which often are associated with recurrent novae. To test the possibility that the nova was in fact recurrent, we compared M31N 2012-01b's position with those of more than 800 nova candidates that have been seen to erupt in M31 over the past century. We discovered that the nova, M31N 1923-12c, originally discovered by Edwin Hubble on December 11, 1923 had a reported position only 6" away from that of M31N 2012-01b. Given that the reported positions of the early novae are uncertain at this level, we (in collaboration with Francois Schweizer at Carnegie Observatories) tracked down Hubble's original plate in the Carnegie archives in order to determine its position more accurately. Revised astrometry revealed the position of Hubble's nova was coincident with M31N 2012-01b to within measurement errors of ~1" (see comparison below). We conclude that M31N 2012-01b is a subsequent outburst of Hubble's nova, and that M31N 1923-12c is in fact a recurrent nova system. The discovery that Hubble's nova was recurrent generated attention in the popular press: Hubble's 1923 Nova in Andromeda Erupts again! and SDSU Confirms Huge Explosion in Andromeda Galaxy.

A comparison of the positions of M31N 2012-01b and M31N 1923-12c

Left: A finding chart of PNV J00423804+4108417 (M31N 2012-01b) courtesy of Koichi Nishiyama and Fujio Kabashima (Miyaki-Argenteus Observatory, Japan), with the nova marked near the center of the image.

Right: A reproduction of Hubble's plate taken on December 11, 1923 showing the position of a nova, later designated as M31N 1923-12c (the smudges near the center are Hubble's original ink marks identifying the nova).

The images are approximately 5' x 5' with N up and E left.