2010CBET.2224....3P

J. Prieto, Carnegie Observatories, reports on a low-resolution spectrum (range 350-950 nm; resolution 0.3 nm) and images of 2010ay obtained with the du Pont 2.5-m telescope (+ WFCCD) at Las Campanas Observatory on Mar. 22.2 UT. The spectrum shows very broad spectral features characteristic of broad-line type-Ic supernovae around maximum light, confirming the classification by Filippenko et al., above. The Si II 635.5-nm absorption feature is detected in the supernova spectrum with a blueshifted velocity of 22600 km/s after correcting for the host-galaxy redshift. The spectrum is contaminated by strong, nebular emission lines ([O II], [O III], [N II] and the Balmer series) from the blue, star-forming dwarf host galaxy at z = 0.067, catalogued in the Sloan Digital Sky Survey as SDSS J123527.19+270402.7. Prieto obtained almost- simultaneous BVR photometry of the field with WFCCD. The magnitudes of the source, which include both supernova and host-galaxy flux and were calibrated using an SDSS star in the field, are B = 18.39, V = 17.61, R = 17.44 (uncertainty ± 0.05 mag). After correcting for the distance modulus (mu = 37.4 mag for standard cosmology) and the estimated contamination from the host flux estimated from SDSS photometry (V = 19.0), an absolute magnitude of the supernova of Mv = -19.4 was obtained for 2010ay. This potentially makes it one of the most luminous broad-line type-Ic supernovae (see, e.g., Young et al. 2010, http://arxiv.org/abs/0910.2248; A.Ap., in press). The luminous nature of the event and star-forming dwarf host makes 2010ay an interesting target to search for radio emission, as was seen at late times in the broad- lined type-Ic supernova 2007bg (Prieto et al. 2009, posted at website URL http://www.astronomerstelegram.org/?read=2065).