2009CBET.2012....1R

Further to CBET 1988, on behalf of the PS1 Science Consortium, A. Rest, G. Narayan, E. Berger, and R. J. Foley, Harvard-Smithsonian Center for Astrophysics (CfA); M. Huber, Johns Hopkins University (JHU); C. Stubbs, CfA; J. Tonry and P. A. Price, Institute for Astronomy, University of Hawaii; A. Riess, JHU; W. M. Wood-Vasey, University of Pittsburgh; R. P. Kirshner, P. Challis, and A. Soderberg, CfA; S. Smartt, S. Valenti, A. Pastorello, and C. Trundle, Queen's University, Belfast; and S. Mattila and E. Kankare, University of Turku, report the discovery of eight confirmed type-Ia supernovae and four additional possible supernovae via the Pan-STARRS Telescope 1 (PS1) sky survey. Images from PS1 Medium-Deep-Fields 1, 2, and 9 were processed by the PS1 "Image Processing Pipeline", and detections were filtered with a prototype module of the Transient Science Server at Harvard. Each object was detected on three or more nights in multiple (two to ten), dithered, 240-s g-, r-, i-, and z-band exposures on any one night, spanning 10-20 days. Images taken in the first half of Sept. 2009 were used as templates in the subtractions. Since the time between template and images is in some cases less than three weeks, some of the templates might contain some supernova light.

---------------------------------------------------------------------------— SN 2009 UT R.A. (2000.0) Decl. Mag. z Offset ---------------------------------------------------------------------------— 2009ks Sep. 22.46 22 15 48.06 + 1 11 05.4 21.1 0.28 0".29 E, 1".11 N 2009kt Sep. 30.75 2 28 28.37 - 4 04 44.1 21.5 0.27 0".33 W, 0".08 S 2009ku Oct. 4.83 3 29 53.23 -28 05 12.2 19.9 0.08 0".12 W, 0".09 S 2009kv Oct. 18.75 2 21 06.60 - 5 01 23.8 21.2 0.32 – 2009kw Oct. 18.76 3 38 23.39 -28 15 11.8 21.3 0.24 – 2009kx Oct. 18.78 2 21 13.75 - 3 54 35.8 21.0 0.23 0".47 E, 0".14 N 2009ky Oct. 18.78 3 34 28.80 -27 54 30.3 20.8 0.26 0".15 E, 0".23 N 2009kz Oct. 18.79 2 22 40.07 - 4 01 38.3 21.0 0.27 0".09 W, 1".14 S ---------------------------------------------------------------------------—

No clear host galaxies are visible for 2009kv and 2009kw. Spectra of 2009ks were taken with the GMOS spectrograph on the 8-m Gemini-North telescope (Principal Investigator Berger) on Sept. 24, indicating that it is a type-Ia supernova at z = 0.28, about 1-2 months after maximum light, using the "SuperNova IDentification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) for cross-correlation against a library of template spectra. The spectra of 2009kt, also taken with Gemini-North, reveals a type-Ia supernova at z = 0.27, about 3-8 days after maximum light (via SNID). Spectra of 2009ku were taken with the 8-m Gemini-South telescope (+ GMOS) on Oct. 12, the 2.5-m Nordic Optical Telescope (+ ALFOSC) on Oct. 13, and the 6.5-m Magellan Clay telescope (+ MagE) on Oct. 17, showing it to be a peculiar type-Ia supernova similar to SN 2002cx (Li et al. 2003, PASP 115, 453). Spectra of 2009kw and 2009ky were obtained with the 8-m Gemini-North telescope (+ GMOS) on Oct. 20 and 21, respectively; spectra of 2009kx, 2009kv, and 2009kz were obtained with the 8-m Gemini-South telescope (+ GMOS) on Oct. 21. The spectra of the other five objects tabulated above indicate that all are of type-Ia supernovae; using SNID, these spectra are found to have the following phases in days past maximum brightness: 2009kv, 9; 2009kw, 7; 2009kx, 8; 2009ky, 17; 2009kz, 8. The four transients that have not been confirmed as supernovae are listed below:

---------------------------------------------------------------------------— PSN 2009 UT R.A. (2000.0) Decl. Mag. Offset ---------------------------------------------------------------------------— K0909-1 Sep. 22.47 22 19 45.87 + 0 50 12.6 21.4 0".17 E, 0".24 N K0910-1 Oct. 18.78 22 13 13.92 + 0 02 57.5 21.2 0".15 W, 0".32 N K0910-2 Oct. 18.79 2 22 19.17 - 3 46 45.8 21.6 0".81 E, 0".33 S K0910-3 Oct. 19.20 3 30 49.84 -28 47 37.6 20.5 0".26 W, 0".01 N ---------------------------------------------------------------------------—

A spectrum of PSN K0909-1 taken with Gemini-North (+ GMOS) on Oct. 13 revealed only host-galaxy light with a redshift of z = 0.32 from the O III 495.9- and 500.7-nm and the H-alpha emission lines. Spectroscopy was not attempted for the other three possible supernovae tabulated above. During the following dates, images were taken that did not show the four confirmed supernovae, to limiting mag about 22.5: PSN K0909-1, 2009 June 3 to July 17; PSN K0910-1, 2009 June 3 to Sept. 9; PSN K0910-2, 2009 Aug. 29 to Sept. 1; PSN K0910-3, 2009 Aug. 29. All these discoveries were made with the PS1 System (http://ps1sc.org/PS1_System_IAU.htm).