J. Brit. Astron. Assoc., 110, 1, 2000, p.54-55

The discovery of supernovae 1999eg and 1999eh

In the summer of 1998 an idea formed in my mind to set up an automated supernova telescope. Over a year later on 1999 August 28 first light was realised. The system consists of a Meade 12-inch LX200 with a British CCD camera, the Hale EAC512-11. The WIDE software to automate the system was written by Steve Foulkes, a BAA supernova patroller from Worcestershire.

The software slews the LX200 to the target galaxy and triggers the CCD to image the galaxy, saving it to disk. The CCD camera is so sensitive that 30-second integrations reach at least magnitude +19 and the system can obtain typically 85-90 galaxy fields per hour. Unlike my manual patrol, at present images are not able to be checked in real time, although Nick James is currently investigating professional software capable of automatically checking these images for supernovae.

On October 3/4 the system was working through galaxies in Aries, imaging IC 1861 in the process. I checked these images the next day and noticed a mag +17.5 suspect just to the east of IC 1861. However, despite making a note to investigate I forgot about it until October 10! As this was a single image I had no way of ruling out the possibility that this was an asteroid, although a search of the Minor Planet Center database was negative. Also I had no previous image of this galaxy and neither did the UK Nova/Supernova patrol archive. On the positive side the online Digitised Sky Survey (DSS) image showed nothing at the position of the suspect. I reported the suspect to Guy Hurst who issued an alert, requesting further images. On October 11/12 Tom Boles, Steve Foulkes and myself recorded the suspect still in the same position and Guy reported to the Central Bureau for Astronomical Telegrams (CBAT).

The International Astronomical Union circular (IAUC) 7275 was issued on October 12, designating the suspect supernova 1999eg. As you can imagine I was delighted at my fifth discovery after an 18-month drought and the first for the automated system. IAUC 7280 on October 14 revealed the supernova to be a Type II around maximum light. Type IIs are thought to be massive stars of approx. 10 solar masses minimum, which explode having reached the end of their evolution. IC 1861 is a type S0 or lenticular galaxy, one step away from an elliptical galaxy, where star formation is thought to have ceased. So perhaps a Type II in this type of galaxy was unusual? Peter Garnavich from the Harvard-Smithsonian Center for Astrophysics, one of the team who secured the spectrum with the F. L. Whipple Observatory 1.5m telescope (+ FAST spectrograph) advised: 'Type IIs will go off anywhere there is some star formation. This galaxy has lots of hydrogen in the radio so it probably has some forming stars.'

Whilst I was waiting for spectral confirmation of 1999eg I had another suspect in NGC 2770, a nice spiral in Lynx. This galaxy was imaged on October 11/12 by the automated system and I noticed a mag +17.5 suspect just west of the nucleus upon checking the image on October 13. All the same checks were carried out as for 1999eg and once again this looked like a good supernova candidate.

An IAUC was issued on October 15 designating the suspect supernova 1999eh and the spectrum showed it to be a Type Ib two months past maximum. This type is thought to involve the same core collapse processes that cause Type IIs but the massive star has previously lost its outer layer of hydrogen through a strong stellar wind or, more commonly, through mass transfer onto a binary companion star. There is another sub group, Type Ic, where even helium is thought to have been lost.

To get successive designations is extremely pleasing although I really don't mind how they come. This brings my discoveries to six and 14 in total for UK observers since I discovered 1996bo, the first from the UK on 1996 October 23. It must be stressed that because Ron Arbour, Tom Boles and myself have made recent discoveries, it has not suddenly become easy or less important. All of us have made an enormous number of observations over many nights for these successes. My records show I have made over 44,000 patrols in 2200 hours over 518 nights since June 1995, with an additional 3500 automated patrols. I also made approx. 25,000 patrols without success between my fourth and recent fifth discoveries.

We still need more discoveries, especially before maximum light, as we still need more data to understand the nature of the beasts, not only for supernova research itself but the wider cosmological scenario. The kick I get out of contributing to our science is great and it remains, in my opinion among the most important, if not the most important activity amateurs can undertake.