AstroNote 2022-56

We report the discovery of ZTF22aacyiqk / AT 2022ebw, a transient candidate reported by the ALeRCE broker (TNS #138925) using the ZTF public alert stream. The object was detected on a ZTF r-band difference image obtained on Mar 3rd, 2022 at 7:50 UT with 19.40+-0.14 mag, 2 days after the last reported non-detection in ZTF r-band (19.89 mag). From these, we derive a light curve rise of 0.24+-0.07 mag/day. The ZTF light curve for this object can be explored in https://alerce.online/object/ZTF22aacyiqk.

From further exploration of ZTF PSF-fit forced photometry data using difference images at the object coordinates, we note a previous r-band measurement 2 days before the first ZTF alert that has 19.86+-0.22 mag (S/N=5.47). This is consistent with both the reported non-detection in ZTF alerts and derived light curve rise.

ZTF22aacyiqk is located in the galaxy NGC 4605, which has a redshift of 0.000454 (Epinat et al. 2008) and a distance of ~5.25 Mpc (Bottinelli et al. 1985). Assuming zero reddening, this redshift implies an absolute (difference) magnitude of -7.03+-0.14 mag for its first ZTF alert. Swift observations have been requested, and we encourage additional follow-up observations of this transient candidate, likely a nova or supernova.