Discovery of two new supernovae and a possible AGN/luminous SN IIn in the Pan-STARRS1 3Pi faint galaxy supernova survey

ATel #2838; S. Valenti, E. Kankare, S. Mattila, A. Pastorello, S. Smartt, K. Smith, R. Kotak (Queen's University Belfast); M. Ward (Durham University); S. Gezari (JHU); R. Chornock (Harvard/CfA); A., F. Bresolin, R. Kudritzki, J. Tonry, E. Magnier, K. Chambers, N. Kaiser, J. Morgan, W. Burgett, J. Heasley, W. Sweeney, C. Waters, H. Flewelling (Institute for Astronomy, University of Hawaii); P. A. Price (Princeton)
on 9 Sep 2010; 11:31 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Stefano Valenti (s.valenti@qub.ac.uk)

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report the discovery of two new supernovae and a possible AGN/luminous SN IIn in the Pan-STARRS 1 "3Pi Faint galaxy supernova survey". During the course of the PS1 3Pi sky survey, PS1-1000791 was detected on Aug 14.40 (UT) (Coord: 20:45:13.089 -06:56:11.090, J2000) at g=19.4 and detected again on Aug 19.33 at r=18.64 within 0.9 arcsec of the faint SDSS galaxy (J204513.14-065611.2). A spectrum of PS1-1000791 was obtained at the Nordic Optical Telescope (+ALFOSC+Gr4 ; range 350-950nm) on Aug 30.0 (UT). Cross-correlation of the observed spectrum with a library of supernova spectra with the "GELATO" code (Harutyunyan et al. 2008, A.Ap. 488, 383, available at https://gelato.tng.iac.es/login.cgi) shows it to be a SN Ia soon after maximum. Using the redshift of z= 0.086, measured from the Balmer narrow lines of the host galaxy, a distance modulus of 37.91 and the Sloan r magnitude of the host (20.90), the host galaxy has an absolute magnitude of -17.01. PS1-1000790 was detected on Aug 1.44 (UT) (Coords: 21:33:28.573 +10:20:39.54, J2000) at i=18.18 and on Aug 8.47 at g=18.04 within 2 arcsec of the faint SDSS galaxy (J213328.65+102038.1). The spectrum of PS1-1000790, obtained at the Nordic Optical Telescope (+ALFOSC+Gr4 ; range 350-950nm) on Aug 24.87 (UT), show that PS1-1000790 is a SN Ia similar to 1994D around 1 month post maximum. The redshift of the host galaxy is close to 0.05 and using a distance modulus of 36.67 and the g magnitude (18.04, the closest detection to the peak maximum), the SN has a peak magnitude of -18.63 . At redshift 0.5 the host galaxy has a magnitude of r=-15.93. PS1-1000789 was detected on Aug 15.35 (UT) (Coords: 20:42:44.749 +15:30:32.240, J2000) at r=17.34 within 0.1 arcsec of the SDSS galaxy (J204244.74+153032.1). A spectrum was obtained on Aug 29.95 (UT) at the Nordic Optical Telescope (+ALFOSC+Gr4; range 350-950nm) and a second one on Sept 2.9 (UT) Using ALFOSC+Gr8; range 580-830nm). The spectrum show a blue continuum with narrow (FWHM ~ 1200 km/s) Balmer lines at a redshift of 0.20. Using a distance modulus of 39.9 the r absolute magnitudes of PS1-1000789 and of the host galaxy are -22.6 and -20.2 respectively. The Spectrum is similar to some narrow-line Seyfert Galaxies (Osterbrock & Pogge 1985, Apj, 297, 166) with a weak [O III] 500.7nm line and possibly also [N II] 658.3nm detected but it also shows similarity to the spectra of SNe IIn (e.g., SN 1994W and 1995G). Thus the possibility that PS1-1000789 is an AGN can not be completely ruled out but PS1-1000789 could also be one of the most luminous SN IIn ever observed. This 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 would like to thank the PS1 telescope operators for their support of PS1 observations.