AstroNote 2024-197

AT 2024nqr / ZTF24aauekqv and AT 2024pgd / ZTF24aauywft were discovered in the ZTF public alert stream. AT 2024nqr (https://alerce.online/object/ZTF24aauekqv) was discovered on Jun 27, 2024 at RA = 15:12:27.278, Dec = +32:32:44.54 (J2000); it was reported to TNS by ZTF (Sollerman et al. 2024). Meanwhile, AT 2024pgd (https://alerce.online/object/ZTF24aauywft) was discovered on Jul 10, 2024 at RA = 15:12:26.332, Dec = +32:32:44.29 (J2000); it was reported to TNS by SGLF (Perez-Fournon et al. 2024).

We attach a figure that displays light curves for both transients, based on PSF forced photometry on ZTF difference images (Masci et al. 2023) at their mean locations, including the last 100 observed days (MJD = 60407 to 60507).  AT 2024nqr and AT 2024pgd reached measured peak g-band magnitudes of 19.1+-0.1 on Jun 10 and 19.2+-0.1 on Jun 12, respectively (quoted magnitudes are difference AB magnitudes). A gap in ZTF observations between Jun 3 and 10 prevents us from characterizing the shape of the AT 2024nqr light curve just before its brightest measured magnitude.

AT 2024nqr and AT 2024pgd are separated by ~12 arcsec. Both transients lie towards 2MASX J15122674+3232460 (Skrutskie et al. 2006), a Seyfert 2 galaxy (Toba et al. 2014) at z = 0.08915 (SDSS DR9; Ahn et al. 2012). According to the Tempel et al. (2017) catalog of SDSS groups and clusters, this galaxy belongs to a group centered ~1.9 arcmin to the NE (GroupID = 18657, M200 = 3.9e12 Msun) and has the highest luminosity rank among its four members. There is another group nearby (GroupID=83196, ~2.2 arcmin to the SW) that has three members, z = 0.04662 and M200 = 1.3e13 Msun.

We encourage additional follow-up observations of these transients. They may help to confirm whether these correspond to e.g. supernova siblings with 2MASX J15122674+3232460 as host, or to multiple images of a transient that was gravitationally lensed by this galaxy and/or its galaxy group.

This report is based on observations obtained with the Samuel Oschin 48-inch Telescope and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. The ZTF forced-photometry service was funded under the Heising-Simons Foundation grant #12540303 (PI: M. J. Graham). We acknowledge the use of the ALeRCE broker, in particular its Web Interface and the ZTF Forced Photometry Notebook.