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NIR monitoring of SN 2009ip: Accelerated fading of SN?

ATel #4532; Myungshin Im (Seoul National University)
on 31 Oct 2012; 02:10 UT
Credential Certification: Myungshin Im (myungshin.im@gmail.com)

Subjects: Infra-Red, Supernovae, Transient

Using WFCAM/UKIRT at Mauna Kea, Hawaii, we are monitoring the ZYJHK light curve of SN 2009ip, the LBV/SN impostor that has transitioned to a Type-IIn SN (e.g., Smith & Mauerhan, Atel #4412). The monitoring observation started at 2012-09-23.35 UT, and the observation has been carried out on almost daily basis. The NIR light curve exhibited a plateau between 20121004.41 UT through 20121014.24 UT at K=13.24 +- 0.02 mag, then SN 2009ip started dimming at 20121024.32, with the dimming rate of 0.045 +- 0.003 mag/day in ZYJ, 0.041 +- 0.003 mag/day in H, and 0.039 +- 0.003 mag/day in K. We note that the starting epoch of the decline in the NIR light curve coincides with a possible re-emergence of P-Cygni profile noted earlier (Jha et al. ATel #4491) and a possible fading in X-ray (Campana & Margutti ATel #4499). The fading started accelerating at around 20121026, with the measured dimming between 20121027.24 UT and 20121029.31 UT at 0.11 +- 0.02 mag/day in all filters. The NIR magnitudes at 20121029.31 UT are (Vega system, magnitude errors in parenthesis), Z=14.54(0.03), Y=14.63(0.02), J=14.42(0.02), H=14.29(0.03), K=14.06(0.03)