Discovery of a Young Type I Supernova iPTF13dge in the Nearby NGC1762

ATel #5366; Y. Cao (CIT), B. Sesar (CIT), D. Perley (CIT), I. Arcavi (WIS), M. M. Kasliwal (OCIW), S. B. Cenko (GSFC), A. Goobar (OKC), P. E. Nugent (LBL) report on behalf of the intermediate Palomar Transient Factory collaboration
on 5 Sep 2013; 01:37 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Yi Cao (ycao@astro.caltech.edu)

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The intermediate Palomar Transient Factory (ATel #4807) reports a fully robotic discovery of a young supernova, iPTF13dge, at RA=05h03m35.08s, Dec=+01d34m17.4s (J2000), 28.8 arcsec to the west and 6.6 arcsec to the south of NGC 1762 (94.5 Mpc; Springob et al. 2007). iPTF13dge was discovered on 2013 Sept 4.50 UT at r=19.50+/-0.04 mag (calibrated w.r.t. SDSS DR9) i.e. M_r = -15.40 mag Nothing was there at this location on 2013 Sept 2.43 UT to a 5-sigma limiting magnitude of 21.0.

Responding to the robotic trigger, and within 1.4 hours of our second confirmation image being automatically analyzed, we obtained a spectrum with the Low Resolution Imaging Spectrometer (LRIS) mounted on the 10m Keck-I telescope on Sept 4.60. The spectrum covers 3500A to 7000A and shows broad Si II absorption features with a velocity of about 20,000 km/s. It is most similar to PTF11kly (=SN2011fe; Nugent et al. 2011) at a phase of 15 days prior to its maximum. We classify this as a likely Type Ia supernova.

Two hours later, as part of our ongoing iPTF-Swift ToO program, we observed iPTF13dge with Swift and obtained B=19.4+/-0.2, U>20.4 (5-sigma upper limit) and UVW1>21.5 (5-sigma upper limit). All magnitudes are in AB system. There is no detection with XRT to a 3-sigma upper limit of 7.3e-3 counts/sec. We thank the Swift team for their prompt scheduling.