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Independent iPTF detection and spectroscopic follow-up observations of the Type II SN 2013am = iPTF13aaz in M65

ATel #4910; O. Yaron, A. Gal-Yam (Weizmann), O. D. Fox, P. Kelly, W. Zheng, S. B. Cenko, A. V. Filippenko (UC Berkeley), J. M. Silverman (U Texas), E. S. Walker (Yale), P. A. Mazzali (Liverpool, MPA, INAF-Padova), E. Pian (SNS, INAF-Trieste), P. E. Nugent (LBNL), Y. Cao, A. Horesh (Caltech), and M. M. Kasliwal (Carnegie/Princeton) report on behalf of the iPTF collaboration
on 23 Mar 2013; 22:34 UT
Credential Certification: Assaf Horesh (assafh@astro.caltech.edu)

Subjects: Optical, Ultra-Violet, X-ray, Supernovae, Transient

The iPTF (ATel #4807) announces its independent detection, spectroscopic classification, and follow-up observations of the Type II SN in the nearby galaxy M65 (d = 12.6 Mpc; NED), at RA = 11:18:56.9, Dec = +13:03:50.0 (J2000). The object was discovered on 2013-03-21.637 by M. Sugano, Kakogawa, Hyogo-ken, Japan and posted on the CBAT TOCP page, http://www.cbat.eps.harvard.edu/unconf/followups/J11185695+1303494.html , where it was designated PSN J11185695+1303494 and later renamed SN 2013am (CBET #3440). The SN was detected by iPTF with the 48-inch Oschin Schmidt telescope at Palomar Observatory on 2013-03-22.17 (UT) at magnitude 16.3 in PTF r-band (absolute mag -14.0). The object was identified by the iPTF automatic software and vetted by the Weizmann duty astronomer, and it is designated internally as iPTF13aaz. Nothing was detected at this location on 2013-03-19.34 to a limiting r-band magnitude of 21.36. A spectrum of the SN was obtained on 2013-03-22.497 (just 7.8 hours from first detection during the same night) using the Kast spectrograph on the 3 m Shane telescope at Lick Observatory. The spectrum shows a reddened continuum, an asymmetric H-alpha P-Cygni profile with prominent broad emission and shallow absorption, as well as H-beta having a P-Cygni profile, thus confirming the object as a young Type II SN. Absorption minima indicate expansion velocities of the ejecta of order 8000-9000 km/s. A Swift ToO was triggered under ongoing PTF-Swift program (PI Kasliwal) to obtain the following UV/Optical Telescope (UVOT) measurements: U = 16.7 at 2013-03-22, 16:14:00; UVW1 = 17.5 at 2013-03-22, 16:05:14; UVW2 = 18.3 at 2013-03-22, 16:18:28; UVM2 = 18.3 at 2013-03-22, 15:52:05. Nothing was detected by the XRT. These weak Swift UV detections confirm a significant extinction, in agreement with the reddened optical spectrum (as also reported by ATel #4909). A higher quality spectrum was obtained with DOLORES on the Telescopio Nazionale di Galileo (TNG) situated at La Palma on 2013-03-23.12. The spectrum shows prominent Balmer lines (H-alpha through H-delta), with P-Cygni profiles indicating expansion velocities around 7000 km/s. Strong Na D absorption confirms the high extinction. Prominent He 5876 having a P-Cygni profile is identified. We thank the Swift team for scheduling the observations promptly.