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Possible supernova in IC 883

ATel #3245; E. Kankare (Turku), S. Ryder (AAO), S. Mattila (Stockholm)
on 29 Mar 2011; 12:04 UT
Credential Certification: Seppo Mattila (seppo.mattila@utu.fi)

Subjects: Infra-Red, Supernovae

Referred to by ATel #: 3291

We report the discovery of a possible supernova (PSN J13203538+3408222) on near-infrared images of the luminous infrared galaxy IC 883 in the course of the follow-up of supernova 2010cu (cf. CBETs 2213, 2286) discovered earlier in the same host galaxy. The possible supernova was detected in J, H, and K-band images obtained using NIRI and the ALTAIR laser-guide-star adaptive-optics system on the Gemini-North Telescope on 2011 Feb. 11.6 UT, via comparison with images obtained with the same instrument on 2010 May 4.5 UT. It is located 0".65 east and 0".45 south of the galaxy's K-band nucleus, at R.A = 13h20m35s.38, Decl. = +34o08'22".23 (equinox 2000.0). Adopting a distance of 100 Mpc for IC 883 (z = 0.023299; Rothberg and Joseph 2006, A.J. 131, 185; and H_o = 70 km/s/Mpc), this corresponds to a projected distance of about 380 pc. Approximate discovery magnitudes are J=17.5, H=16.9, and K=16.5. The colours and absolute magnitudes are consistent with a 'slowly declining' core-collapse supernova (Mattila and Meikle 2001, MNRAS 324, 325) about 3 months after the maximum. The new source is measured to remain stationary in the J, H, and K-band images with a precision of 0".01 (spatial resolution FWHM about 0".1), with the K and the J-band images separated by about 47 minutes. A variable foreground star also provides a very improbable alternative explanation, given the small field-of-view (22".5 x 22".5) of the Gemini frames and the fact no transient source except SN 2010cu has been detected in this galaxy in the previous eight epochs of Gemini imaging over a period of 28 months. Based on these arguments and the fact that large numbers of core-collapse supernovae are expected in the central few-hundred-parsec regions of luminous infrared galaxies as a result of the large star-formation rates therein, explanations other than a supernova for this object are extremely unlikely. High spatial resolution follow-up observations at infrared and radio wavelengths are encouraged.