December 20, 2007: Further to CBETs #1172 (Drake et al.; Daniel W.E. Green, editor), #1173 (Naito et al.), and #1174 (Umbriaco et al.), the optical transient in NGC 4038 discussed in AAVSO Special Notice #84 has been identified as a supernova of Type Ia, and given the name SN 2007sr. Umbriaco et al. have determined the supernova is a few days past maximum light based upon spectroscopic template fitting.
The supernova was at magnitude 12.9 on 2007 December 18.53 UT (JD 2454453.03; Drake et al., CBET #1172). Subsequent multiband photometry confirms this detection: B=13.20, V=12.85, R=12.80 (all accurate to +/- 0.05 magnitudes) on Dec 19.42 (JD 2454453.92; Guido & Sostero, CBET #1172); mag=12.9 on Dec 19.52 (JD 2454454.02; Li, CBET #1172); B=13.42, V=12.86 on Dec 19.8 (JD 2454454.3; Naito et al., CBET #1173); B=12.83, V=13.03, R=12.99 on Dec 20.47 (JD 2454454.97; Nicholson, BAAVSS-Alert).
Supernova 2007sr is located at the following coordinates:
RA: 12:01:52.80 , Dec: -18:58:21.7 (J2000)
A comparison star sequence for this supernova has now been added to VSP, and charts of the field may be plotted online:
It is advisable to check the "Use DSS Image" option so that NGC 4038-4039 is included on the chart.
Please SUBMIT OBSERVATIONS TO THE AAVSO with the name "SN 2007SR" (AAVSO 1156-18C).
Staff Astronomer, AAVSO
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