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PS1-12fo (=CSS120121): luminous Ic supernova at z=0.175 in the PS1 3Pi survey

ATel #3918; S. J. Smartt, D. Wright, S. Valenti, R. Kotak, M. McCrum, L. Magill, K. Smith, T.-W. Chen, M. Fraser (Queen's University Belfast), F. Bresolin, R. Kudritzki, J. Tonry, E. Magnier, M. Huber, K. Chambers, N. Kaiser, J. Morgan, W. Burgett, J. Heasley, W. Sweeney, C. Waters, H. Flewelling (University of Hawaii), C. Stubbs (Harvard), P. A. Price (Princeton).
on 10 Feb 2012; 11:06 UT
Credential Certification: Stephen Smartt (s.smartt@qub.ac.uk)

Subjects: Optical, Supernovae

Referred to by ATel #: 3925, 3931, 4329, 4498

Further to Valenti et al. (ATels #2668, #3351) we report the independent discovery of a spectroscopically confirmed, very luminous supernova PS1-12fo in the Pan-STARRS1 3Pi Faint Galaxy Supernova Survey. PS1-12fo (Coord: 09:46:12.91 +19:50:28.7; J2000.0) was discovered at g=18.33 +/- 0.01 (in PS1 system ; see Tonry et al. 2012, ApJ, 745, 42) on Jan 19 .9 UT. This is the CRTS source CSS120121:094613+195028 (ATel #3873), first detected at mag = 19 +/- 0.1 on 2011-12-31. It is within 0.12" of the position of the faint host galaxy SDSS J094612.91+195028.6 (g~22.1). A low-resolution spectrum of PS1-12fo was obtained on Jan 29.0 UT with the Nordic Optical Telescope (+ ALFOSC; range 320-910 nm). Host galaxy nebular emission lines of H-alpha, H-beta, and [OIII] give an unambiguous redshift of z=0.175, suggesting the transient is very luminous, with M_g = -21.1. The spectrum shows a blue continuum with broad and shallow absorption features. It is almost identical to SN2010gx at +4D after peak (Pastorello et al. 2010, ApJ, 724, L16). The OII absorption characteristic of early spectra of objects of this type (Quimby et al. 2011, Nat. 474. 487) has disappeared and the broad absorption is likely to be the beginning of FeII absorption and the transformation into a Ic type spectrum (Pastorello et al. 2010). The host galaxy appears to be a compact dwarf at M_g = - 17.3. The combined data from CRTS, PS1 and the spectrum suggests a rise time of more than 2 weeks, much longer than SN2010gx but similar to other Quimby et al. (2011) objects and the higher redshift SNe PS1-10ky and PS1-10awh (Chomiuk et al 2011, ApJ, 743, 114). The discovery was enabled using the PS1 System operated by the PS1 Science Consortium (PS1SC) and its member institutions, http://www.ps1sc.org/PS1_System_ATel.htm . We thank the PS1 telescope operators for their support of PS1 observations.