The Story Behind Supernova 2005ba in NGC 3746

by Mikkel Steine

A group of amateurs and good friends of mine had planned to spend the weekend at the cabin of Ståle Kildahl on Vegglifjell in Norway. The group consisted of Arne Danielsen, Ole-Bjørn Fogth, Stig Foss, Geir Hagabråten, Ståle Kildahl, Gitte Rydberg Steine, Mikkel Steine and Øyvind Tangen.

Ståle has built and owns a nice cozy cabin with an observatory almost just as big right next to it. Inside there is a brand new Celestron 14 on a monstrous Paramount ME mount, a "tiny" 10-inch Meade LX-200 and spacious control room with a PC and extra bed. A lot of effort and money has gone into this observatory and it looks really great!

The Discovery

On Friday April 1st the weather looked promising and we prepared for a night of photographing and testing of this new equipment. On our plan were several galaxies with known supernovae in them. A lot of focusing and testing was done and then we started the real photographing. There was something slightly wrong with the tracking, but the system delivered nice results nonetheless. The last series of images were taken by Ståle Kildahl and Arne Danielsen around midnight local summer time (22:05 UT) of Copeland's Septet in Leo. Clouds moved in and we went to bed.

Saturday the Sun was shining and a lot of H-alpha observing and photographing was done. Around mid-day we decided it was time we went ahead with the astrophotography workshop we had planned and a projector and large screen was erected and the images from Friday night was shown. The last image show was that of Copeland's Septet, and immediately a tiny speck of light in one of the arms of NGC 3746 intrigued me. I brought up the false colour DSS image I had made a few days earlier of this same group and found that it was not on DSS. Could it be...?

First we had to check for asteroids. Stig Foss had the latest asteroid definitions and found several candidates within a degree of this field, the closest being around 10 arc minutes north. However the image we had was a combined 20 minute exposure and we believed that an asteroid would have moved noticeably in this period. So the anticipation grew yet a notch.

Arne Danielsen went online with his cell phone and PDA and did not find anything on Rochester's Astronomy Club supernova page about any supernova in this galaxy, except a three year old supernova at a different location in this galaxy (SN2002ar). Is it really...?

A supernova has been discovered only one time earlier by a Norwegian, namely Odd Trondal in Oslo in 1999. We called him up and he helped us prepare a report and told us how to proceed. He would take an exposure as soon as it turned dark to confirm the find. We did the same. As soon as Leo was visible in the sky we took our confirmation exposure of the septet and the star was still there! This could really be something!

We sent our report to Dan Green at Harvard University and waited eagerly for his response. Odd Trondal also confirmed the discovery with his image of the galaxy. Later in the evening we got a mail from Dan Green confirming that a request for spectral confirmation had been sent to professional astronomers. Nothing mentioned a previous discovery of this (to us now almost certain) supernova. Fantastic!

By chance we had a local reporter visiting us to take images of Ståle's observatory and to write a story about Ståle and his observatory in the local newspaper. He had found out about this observatory by himself. Now he had (as he saw it) a scoop and wrote an article about us. We helped him with the details, but urged him not to post it before we had confirmed a true discovery. He didn't pay attention to that part, so we found ourselves pictured on the web page of the local newspaper on Sunday. Monday the full article was featured spread over two pages in the same paper in the news stands.

We took several more images of the septet to be able to provide as good an image of this supernova as possible to be able to make magnitude measurements.

Monday morning I woke up and checked my e-mail. There I found a mail from variable star expert Bjørn-Håkon Granslo congratulating us on the official confirmation of the discovery. Wow! It really started to dawn on me now.

It was really a team effort, this discovery. Ståle Kildahl and Arne Danielsen were credited because they took the actual image, and I because I first noticed the tiny speck. The rest of the group were (alphabetically) Ole-Bjørn Fogth, Stig Foss, Geir Hagabråten, Gitte Rydberg Steine and Øyvind Tangen. Without the help of Odd Trondal it would not have been possible to do this, so we owe him a debt of gratitude.