Discovery of a probable nova in Messier 31 – 01 Oct. 2023.
We report the discovery of a probable nova in Messier 31, found during our survey work on this galaxy.
Probable nova in Messier 31 discovered by G. Masi on 1 Oct. 2023.
Updates
- 3 Oct.: 3.7776 Oct. 2023, R= 17.4
- 2 Oct.: 2.7636 Oct. 2023, R= 17.8
On 1 Oct. 2023, we compared just captured images of Messier 31 to archive ones, taken a few weeks earlier. Both series were collected with our 250mm-f/4.5 astrograph, under the excellent, dark skies of Manciano, in the Tuscan Maremma, where our robotic facility is: Manciano offers the darkest starry skies of Italy and this is vital to the success of similar scientific works. This effort is part of our transient survey work on Messier 31 and Messier 33 galaxies, which already led us to the discovery of two variable stars in the field of M33 and the discovery of long term variability and a likely large flare of a blazar in the field of M31.
While blinking these unfiltered images, we spotted a transient in the SW part of the Andromeda galaxy, at the following J2000.0 coordinates:
RA: 00 40 29.67
Decl.: +40 51 41.4
R=17.9
The R magnitude was estimated using R-mags from the Gaia DR2 catalogue. A slightly fainter star is about 3” SW from this transient.
We immediately checked for known sources at that position, retrieving no known objects to the date of 1 Oct. 2023. We also checked the Panstarss DR1 and SDSS9 catalogues, finding no sources down to R=23.0 or so. We labelled this source as VTP J004029.67+405141.4 within our survey program.
Panstarss archival data, with no source, compared to the our data.
So, this transient qualifies as a probable nova in M31 and we reported it to CBAT.
On the next night, we managed to confirm the existence of the source, found marginally brighter than at the discovery. Also, we used the C14 robotic unit to get an higher resolution image, showing the transient well separated from the close star we mentioned earlier (the image is on the top of this post). Below it is an animation done comparing the excellent 2 Oct. image with the 11 Sept. 2023 ones.
The transient as seen on 2 Oct. 2023, compared to an old image, where it is not visible. A few known variable stars are visible, too.
Spectroscopy would be very welcome to definitely address the nova nature of this transient.
On 3 Oct., the nova was significantly brighter, at R=17.4, as clear from the comparison panel below.
Brightness increase of the nova in 24 hours.
We plan to follow-up this source, as long as it will be visible.
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