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First observations of the reappearance of SN 2009ip with PESSTO

ATel #4953; M. Fraser, R. Kotak (Queen's University Belfast), A. Pastorello, S. Benetti, (INAF - Padova Astronomical Observatory) C. Inserra, S. J. Smartt (Queen's University Belfast), S. Taubenberger (MPA Garching), S. Hachinger (Univ. Wuerzburg), N. Elias-Rosa, A. Morales Garoffolo (ICE-IEEC/CSIC Barcelona), E. S. Walker (Yale University), S. Valenti (LCOGT/UCSB), K. Smith, D. Young (Queen's University Belfast), M. Sullivan (University of Southampton), A. Gal-Yam, O. Yaron (Weizmann Institute for Science)
on 5 Apr 2013; 10:35 UT
Credential Certification: Morgan Fraser (mfraser02@qub.ac.uk)

Subjects: Optical, Star, Supernovae, Transient, Variables

As part of the Public ESO Spectroscopic Survey of Transient Objects (PESSTO; Valenti et al., ATel #4037), and an earlier ESO Large Programme, we conducted an intensive monitoring campaign for SN 2009ip, the results of which were presented in Pastorello et al. (2013, ApJ, 767, 1) and Fraser et al. (2013, astro-ph/1303.3453). The campaign was terminated in late December 2012 by the disappearance of SN 2009ip behind the Sun. Now that SN 2009ip has re-emerged, we have obtained the first optical photometry and spectroscopy of this transient in ~3 months.

V and R-band photometry of SN 2009ip was obtained with EFOSC2 on the 3.6m NTT on 2013 April 2, while an optical spectrum was obtained with the same instrument (+ Gr#13) on April 3. SN 2009ip was recovered at a magnitude of V=+19.3, R=+18.2 (absolute magnitude V=-12.3). This is 0.7 mag fainter in V than the last data point from December 2012, implying that the rapid decline seen in the lightcurve has ended. The average decline rate of SN 2009ip between 2012 December 29 and 2013 April 3 was 0.75 mag per 100d, which is slower than the expected 1 mag per 100d decline if the lightcurve was powered solely by radioactive 56Ni.

The spectrum of SN 2009ip is dominated by line emission from H. Also present are He I, Ca II (both the NIR triplet and the forbidden doublet at 7291,7325 Ang), and Fe II. The high velocity (~10,000 km/s) absorption features seen between August and December 2012 have disappeared, and there is still no evidence for emission attributable to nucleosynthesized material (e.g. [O I] 6300 Ang). The spectrum bears resemblance to that of a Luminous Blue Variable star (and is similar to the spectra of SN 2009ip taken before the 2012 outbursts; see Fig. 5 in Pastorello et al. 2013). This lends credence to the suggestion (Fraser et al. 2013) that the outburst in late 2012 was not a genuine core-collapse SN, and that SN 2009ip is now probably returning to its quiescent state.