AstroNote 2024-121

Supernova rates in galaxies are usually small. However, a small number of galaxies have a large supernova rate. The record holder is the luminous infrared galaxy Arp 299, a system of interacting galaxies at a redshift z = 0.010300, that has been extensively studied.

On November 4th 2023 SN 2023wrk was discovered by Godson et al. (2023, TNS Astronomical Transient Report No. 192729) in Arp 299 at a large distance from the two main interacting galaxies and classified spectroscopically as a type Ia SN by Li et al. (2023, TNS Classification Report No. 15965), see also Arrizabalaga-Díaz-Caneja et al. (2023, AstroNote 2023-296). Five months later, a new supernova, SN 2024gzk, has been discovered in Arp 299 and classified as a SN IIb by Kankare et al.
(2024, TNS Astronomical Transient Report No. 208195 and TNS Classification Report No. 16929) who noticed that the new supernova is at a small ~1 arcsec projected separation from SN 2019lqo. Both supernovae are associated with the same ZTF object (ZTF19abgbbzy) but the Nordic Optical Telescope observations of Kankare et al. and our analysis of the positions of the individual ZTF alerts show that the 2019 and 2024 detections correspond to two different supernovae.

Using the ATLAS forced photometry server (Shingles et al. 2021, AstroNote 2021-7) we find a good  significance first detection of SN 2024gzk on MJD = 60409.39001 at orange-ATLAS = 19.103 +/- 0.095, about three days before the first ZTF detection on MJD = 60412.34936 at g-ZTF = 19.004 ± 0.137. The attached figure of the ATLAS forced-photometry light curve shows that SN 2024gzk is already past maximum light.

We observed Arp 299 with one of the Las Cumbres Observatory 1-m telescopes at the Teide Observatory node on MJD = 60423.04612.  The attached figure shows clearly SN 2024gzk and also the fading type Ia SN 2023wrk.

We have studied the environment of SN 2024gzk using archival HST imaging and the stellar cluster catalog of the Hubble imaging Probe of Extreme Environments and Clusters ("HiPEEC") project (Adamo et al. 2020, MNRAS, 499, 3267) and found that SN 2024gzk is at only ~0.1" from the Arp 299 HiPEEC stellar cluster nr. 1044 with RA = 172.135029 deg, Dec = 58.562228 deg.

We noticed also in the notes of David Bishop on Bright Supernovae that an unclassified supernova in Arp 299, PSN J11283070+5833456 (XM122HT), was reported to CBAT and TNS by Tan et al. (XOSS), with discovery magnitud 17.7 (clear) on 2023-03-29 19:38:37 UT. This transient is 2.38" away from the position of SN 2020fkb and the XOSS discovery was assigned by TNS to SN 2020fkb without receiving a new TNS name. Assuming this transient was also a SN, the SN rate in Arp 299 has been ~3/year in the last year.

Apart from the optically-selected SNe, a large number of SNe have been detected in the radio in the obscured regions of these interacting galaxies (e.g. Neff, Ulvestad, and Teng 2004, ApJ, 611, 186;
Pérez-Torres et al. 2009, A&A, 507, L17; and other studies).

To facilitate further analysis of this interesting supernova factory, we provide attached a figure with the locations of 14 of the 15 known optical supernovae / possible supernovae in the central part of the galaxy (SN 2023wrk is outside the 70" x 35" field displayed in the figure) and links to TNS in the related objects section below.

This work makes use of observations from the Las Cumbres Observatory global telescope network (program IAC2024A-008).

We thank David Bishop for his great database on supernovae and for the notes on galaxies with two or more supernovae.

The HST image used in one of the attached figures is from the High Level Science Products of the Hubble imaging Probe of Extreme Environments and Clusters ("HiPEEC") project (Adamo et al. 2020, MNRAS, 499, 3267) available in the Mikulski Archive for Space Telescopes (MAST).