SN 1998aq
Supernova in the constellation Ursa Major
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SN 1998aq is a nearby supernova located in the intermediate spiral galaxy NGC 3982, offset 18″ west and 7″ of the galactic nucleus. It was discovered April 13, 1998 by amateur astronomer Mark Armstrong[2] and was confirmed by fellow British amateur Ron Arbour; both members of the U.K. Supernova/Nova Patrol.[4] The event was not visible on a prior check by Armstrong made April 7.[5] It reached peak brightness on April 27, and 15 days later had declined by 1.14 magnitudes in the B (blue) band.[4]
| Event type | Supernova |
|---|---|
| Type Ia[1] | |
| Date | April 13, 1998[2] |
| Constellation | Ursa Major |
| Right ascension | 11h 56m 25.87s[1] |
| Declination | +55° 07′ 43.2″[1] |
| Distance | 70.38 ± 0.23 Mly (21.58 ± 0.07 Mpc)[3] |
| Redshift | 0.0004, 0.0003, 0.002  |
| Host | NGC 3982[1] |
| Colour (B-V) | −0.18[4] (peak) |
| Peak apparent magnitude | 12.36[1] |
Spectroscopic observations determined this was a Type Ia supernova event, and it became one of the best-studied supernova of its type, at least in the visual band.[4] An absorption feature of singly-ionized carbon was (probably) detected nine days before maximum, an indication of unburned ash left over from the original carbon-oxygen core of the progenitor white dwarf.[7] Brightness calibration using Cepheid variables in NGC 3982 gives a peak absolute magnitude estimate of at least −19.47±0.15 (assuming no extinction in the host galaxy).[8]