2010CBET.2413....1P

A. Pastorello, S. J. Smartt, M. T. Botticella, L. Magill, D. Young, S. Valenti, and R. Kotak, Queen's University, Belfast, on behalf of the PS1 Collaboration (see, e.g., CBETs 1617, 1988, 2214), report that a luminous optical transient detected by three wide-field surveys has evolved into a type-Ic supernova. The Catalina Real Time Transient Survey first announced the discovery of an optical transient (designated as CSS 100313:112547-084941) at R.A. = 11:25:46.71, Decl. = -8:49:41.4 (equinox 2000.0; cf. Mahabal and Drake 2010, website URL http://www.astronomerstelegram.org/?read=2490 and/?read=2508), on Mar. 13 (at SDSS r magnitude 18.6), and subsequently the "Palomar Transient Factory" (PTF) collaboration reported an independent discovery on images obtained during Mar. 5-16 (and designated PTF10cwr; Quimby et al. 2010, URL http://www.astronomerstelegram.org/?read=2492). Pastorello et al. (2010, http://www.astronomerstelegram.org/?read=2504) noted that the transient was also detected by PS1 in the course of the 3Pi survey during Mar. 12-23 (which they designated PS1-1000037). Early spectra by the CRTS, PTF, and PS1 teams all indicated a blue continuum with broad O II features and a host-galaxy (SDSS J112546.72-084942.0) redshift of z = 0.23. The host redshift implies a very luminous transient (absolute mag < -21), and the spectra were similar to the "ultra-bright" supernova 2005ap (see http://www.astronomerstelegram.org/?read=2490,/?read=2508,/?read=2492,/?read=2504; also, Quimby et al. 2007, Ap.J. 668, L99). Further detailed spectroscopic monitoring with the Gemini South telescope and the William Herschel Telescope by the PS1 team shows that – 25 days after discovery – the transient (here designated supernova 2010gx) evolved unambiguously into a type-Ic event with the characteristic broad Fe II, Si II, Mg II, and Ca II features. The spectra at +25 days are most similar to those of SN 1994I (at six days before peak; Baron et al. 1996, MNRAS 279, 799) and SN 2003jd (at peak; Valenti et al. 2008, MNRAS 383, 1485). This indicates a link between the "ultra-bright" optical transients and type-Ic supernovae; further details are reported by Pastorello et al. (2010, Ap.J., submitted).