Significant brightening of the progenitor of SN2010da at 3.6 micron 6 months prior to the eruption

ATel #2648; Tanmoy Laskar, Edo Berger, Ryan Chornock (Harvard)
on 27 May 2010; 22:59 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Edo Berger (eberger@astro.princeton.edu)

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We report on additional photometry of all available Spitzer/IRAC 3.6 micron observations of the progenitor star of the LBV outburst SN2010da (initially identified in Khan et al. ATEL #2632; Khan et al. 2010, ApJ, 715, 904; see also Berger et al. ATEL #2638). We find that the source remained steady to within a few percent in observations from 2003 Nov 21 and 24 (P01083: PI Helou) and 2007 Dec 29 (P40204: PI Kennicutt). However, the source subsequently brightened by about 0.4 mag in an observation obtained on 2009 Dec 22 (P61002: PI Freedman) and by another 0.5 mag in an observation obtained on 2010 Jan 14 (P61002: PI Freedman). We therefore conclude that the progenitor entered a period of enhanced activity at least 6 months (but less than 2.5 years) prior to the detection of the optical outburst on 2010 May 23 (CBET #2289). This behavior in the mid-IR is similar to the behavior of previous LBV eruptions in the optical (e.g. Smith et al. 2010, AJ, 139. 1451).