2004IAUC.8347....2M

D. Magee, B. Holden, R. Bouwens, and G. Illingworth, University of California, Santa Cruz; J. Blakeslee and H. Ford, Johns Hopkins University, and the Advanced Camera for Surveys (ACS) Science Team report the discovery of an apparent supernova in the galaxy cluster CL 1358+62, observed in exposures obtained with the Hubble Space Telescope's ACS Wide Field Camera with the F850LP filter (at m_AB = 26.3 ± 0.2; 'AB' magnitudes are defined by Oke 1974, Ap.J. Suppl. 27, 21) on Apr. 6.82 UT, with the F775W filter (at m_AB = 25.67 ± 0.06) on Apr. 7.81, with the F850LP filter (at m_AB = 26.5 ± 0.3) on May 6.62, and with the F625W filter (at m_AB = 25.60 ± 0.05) on May 7.19. The new object is located at R.A. = 13h59m51s.06, Decl. = +62o30'27".9 (equinox 2000.0), which is 0".6 east and 0".5 north of the center of the brightest nearby galaxy [having redshift 0.3174; cf. Fabricant et al. (1991, Ap.J. 831, 33)]. It is not clear if the nearby galaxy is the host galaxy or if the new object may reside in a background galaxy. SN 2004bx is not present in ACS observations from 2002 May 14 with the F775W filter (5-sigma limiting m_AB 27.9) and with the F850LP filter (5-sigma limiting m_AB 27.1).