ATLAS23nax (AT2023mdv): discovery of a candidate SN in NGC 3087 (38 Mpc)

Here we report the ATLAS discovery of the transient ATLAS23nax (AT2023mdv) in galaxy NGC 3087 at magnitude m_o = 18.32 +/- 0.19. At a distance of 38 Mpc (redshift independent, from NED), the transient was discovered on MJD = 60124.01 (2023-06-29.01) with an absolute magnitude of M = -14.8 +/- 0.2. The last non-detection through forced photometry was on MJD = 60119.76. Forced photometry indicates that the transient is rising. Spectroscopic classification is encouraged.