Keck/DEIMOS spectroscopy of SN 2009ip: A Broad P-Cyg He I line re-emerging?

ATel #4491; Saurabh W. Jha, Curtis McCully, Brandon Patel (Rutgers University)
on 16 Oct 2012; 22:35 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Saurabh Jha (saurabh@physics.rutgers.edu)

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We obtained Keck II(+ DEIMOS) spectroscopy of the type IIn SN 2009ip (Smith & Mauerhan, ATel #4412) covering 465-975 nm with the 600 l/mm grating (R ~ 2000) on 2012 October 15.3 UT. The spectrum shows a blue continuum with Balmer, Paschen, and He I emission lines. We see clear intermediate and narrow width components for H-beta, H-alpha, and He I 5876, with the last showing an asymmetric profile. We also report the possible re-emergence of a broad P-Cyg trough for He I 5876, with an expansion velocity of 13,100 km/s at the line minimum. Unlike the broad P-Cyg profiles of SN 2009ip from August-September (Mauerhan et al. 2012, arXiv:1209.6320; Vinko et al., ATel #4435), we do not see as strong absorption in the Balmer lines. Comparing our spectrum to other recent observations (Gall et al., ATel #4454; Bohlsen, ATel #4477; Vinko et al., ATel #4480), it seems clear that SN 2009ip is rapidly evolving. Continuing observations are encouraged. A figure showing our optical spectrum is available at: http://www.physics.rutgers.edu/~saurabh/sn2009ip.png