Visual Discovery of SN1995V in NGC 1087.

(Robert Evans)

My basic supernova search still continues with my backyard 41cm telescope. This year a strand has developed with the occasioanl use of the Australian National University 1 meter telescope at Siding Spring Observatory. The discovery of supernova 1995V in NGC 1087 is the second discovery to be made this year with the larger telescope.

The Time Allocation Committee at Mount Stromlo Observatory granted me some observing time on this telescope between late December 1994 and early March 1995. It was in this period that the visual discovery of SN1995G in NGC 1643 occurred.

No more observiong time was allocated to me until early June. Of 15 days in June and July, nine were close to full moon (and were badly affected by clouds), while six days were in the dark of the moon. But no supernovae of any kind were observed.

Another fifteen days have been allocated in the quarter from August to October, commencing with August 1-3. My helpers on this occasion were Tom Cragg, the well-known variable star observer from Coonabarabran and John Jarman who leads the Western Sidney Amateur Astronomer Group in Penrith. Eighteen year old Queensland amateur Samantha Beaman could not come on this occasion and John Shobbrock was unavailable, having recently undergone heart surgery.

Of these three nights in early August, the first was the only fully fine night. The telescope is very slow to move from one object to another, but we managed to observe over 240 objects until 5am, when we turned to NGC 1087, and saw the supernova.

The reference pictures available to us which showed the inner details of the galaxy were in John Vicker's 'CCD Deep Space Atlas' and in the 'Revised Shapley-Ames Galaxy Catalogue'. Both showed faint knots near the position of the new star, but nothing like what we could now see.

At that late time of the night, the only way we could get quick confirmation for our discovery was to contact the observers using the alt-az 2.3m telescope a short distance away. Dr. Michael Dopita and Dr. C. Trung Huia were due to finish ttheir observing programme in a few minutes, as twilight approched. After this, they took two CCD pictures of NGC 1087 from which the magnitude of the supernova could be calculated in relation to a nearby measured star, and the offsets of the supernova could also be measured. (Mag 15.0, 21" east, 3" south).

With this information we ran the gaunlet of hitting kangaroos in the growing light, and went first to my place, and then to Tom's. I consulted my observing records and found thet I had observed this galaxy as recently as July 25 with my 41cm telescope enjoying very good transparency, but without seeing any new star. A star of mag 15.0 should have been visible, although probably less than one magnitude above the visible limit.

>From Tom's place we rang Dr. Brian Marsden at the Central Bureau for Astronomical Telegrams, explaining the whole situation to him. He immediately alerted a list of contacts who were specifically interested in supernovae, hoping to gain spectral confirmation quickly. This was provided by Dr. Stefano Benetti of ESO in Chile, showing that the supernova was of Type II around maximum light, and with expansion velocities up to 15,500 kms/sec.

Subsequent professional observations showed that the supernova had indeed been found very early in its history, was heavily reddened by material in the parent galaxy, but would nevertheless be very useful in current research seeking to use supernova studies to measure the age of the universe and distances within it.