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]

Quick Facts Event type, Date ...

SN 1998aq

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]
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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]