L. Elenin / ISON-NM Observatory

The first supernova discovered at our observatory, was found in survey images from November 18, 2011. In the course of checking archival DSS photographs of the “suspicious” galaxy PGC 2095477 with a star next to it, I was surprised to see that the star was not in them. That meant it was entirely possible that it was an exploding supernova. The object was seen in four images; it was magnitude 18.7m and was clearly not an artifact of the image. After measuring its coordinates, the process began of checking the object against known supernovae, variable stars and Solar System objects. Finally success!, This object turned out to be unknown!

After placing it on the optical transients confirmation page of the Central Bureau for Astronomical Telegrams, CBAT, with the designation PSN J06580768 +3713117, over the next few days, several confirmations of the object were obtained from optical observatories. But for the official recognition of the supernova discovery, spectral evidence was needed, and that took a little over a week. During this time, at our observatory two more estimates of the supernova’s brightness were obtained, and it became clear that at the time of discovery on November 18, it was still getting brighter! By November 22th it had already increased its brightness almost one magnitude and reached 17.9m. By November 28th, it had again returned to a value of 18.5m.

On November 30th the long-awaited CBAT circular officially recognizing the supernova discovery was released, assigning it the designation SN 2011ij. Along with this, the circular included data on the spectral observations of the supernova at the 1.5-m telescope of the FL Whipple Observatory. Interpretation of the data showed that SN 2011ij is a type Ia supernova, and the time the spectrum was taken was about seven days after maximum brightness. This estimate is very well correlated with our observatory’s optical observations. We were lucky, because most supernovae when discovered are already fading. In our case, having an estimate of its brightness near maximum, one can accurately calculate the distance to its host galaxy PGC 2095477.

As mentioned above, while this is our first such discovery, I hope that in the future at the observatory, the search for supernovae will be carried out in semiautomatic mode.

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