SN1997dn – discovery

Tom Boles

On 29 October 1997, Tom Boles became the third UK amateur to discover a supernova (following discoveries by Mark Armstrong and Stephen Laurie): SN1997dn in NGC 3451. Guy Hurst, Basingstoke, reported the discovery of an apparent supernova (magnitude about 16.0) by Tom Boles, Wellingborough, on CCD frames taken during October 29.177–29.217 UT as part of the UK Nova/Supernova Patrol. The star was also present at a similar brightness on an image taken by Tom on October 30.177. Nick James, Chelmsford, provided the following astrometry for SN1997dn from Tom’s discovery image: RA 10h 54m 18s.95, Dec +27º 14' 07".3 (equinox 2000.0), which is about 35" west and 20" south of the centre of NGC 3451. No star is present at this location on a master CCD image of NGC 3451 taken by Tom on May 31. IAU Circular 6763 : S. Jha, P. Garnavich, P. Challis and R. Kirshner, Harvard–Smithsonian Center for Astrophysics, report that a spectrum of SN 1997dn taken by P. Berlind at the Whipple Observatory 1.5-m telescope on Oct. 30.5 UT indicates that it is a type II supernova after maximum. A prominent P Cyg profile of H-alpha is visible with a photometric expansion velocity (measured from peak to trough) of 6,500 km/s. Also present in the spectrum are H-beta, H-gamma, He I (587.5 nm) and Fe II. The redshift of the host galaxy is 1,300 km/s measured from narrow-band H-alpha emission.