Optical Photometry of the New Optical Transient SN 2010da in NGC 300

ATel #2640; Howard E. Bond (STScI)
on 26 May 2010; 01:25 UT
Credential Certification: Howard E. Bond (bond@stsci.edu)

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Multicolor images of the new optical transient in NGC 300, discovered by B. Monard (CBET #2289 and private communication), were obtained on 2010 May 25.37 by J. Espinoza with the SMARTS 1.3m telescope at Cerro Tololo and the ANDICAM camera. The transient has received the designation SN 2010da, although spectroscopic observations and the low luminosity suggest that it is most probably an LBV-like outburst on a dust-enshrouded massive star and not a true supernova (e.g., ATEL #2632, #2633, #2636, #2637, #2638).

The 1.3m measurements were calibrated approximately through observations of a Landolt standard field, but the uncertainties are larger than normal, perhaps of order +/-0.1 mag, due to the large difference in airmass between the frames. The results are V = 16.28, B-V = 0.33, V-R = 0.36, and V-I = 0.62. The relatively blue color confirms that the transient does not currently suffer a large amount of extinction (cf. ATEL #2633).

I plan to continue to monitor the light curve of this outburst, for comparison with the optical transient of 2008 in the same galaxy (Bond et al., 2009, ApJ, 695, L154), also discovered by Monard.