Discovery of a bright radio supernova in the circumnuclear starburst of the luminous infrared Seyfert 1 galaxy NGC 7469

This Letter reports the first detection ever of a radio supernova (RSN) in the circumnuclear region of a highly luminous infrared, QSO-like, galaxy. The RSN, named RSN J230315+0852.4, is located in the circumnuclear starburst of the Seyfert 1 galaxy NGC 7469, at a distance of 600 pc from its QSO-like nucleus. The 8.4 GHz emission of RSN J230315+0852.4 represents about 7% of the total flux density emitted from within 1 kpc of the nucleus and 13% of the flux density emitted by the Seyfert nucleus itself. RSN J230315+0852.4, with an 8.4 GHz luminosity of 1.1 × 1021 W Hz-1, is one of the most luminous and most distant RSNe ever detected and is also the closest of all known RSNe to a galactic nucleus. From the available radio information, no firm conclusion on the type of supernova, nor on the mass of the progenitor that has produced this RSN, can be made. An ongoing radio-monitoring program will be able to answer these questions.