Jet-triggered Type Ia Supernovae in Radio Galaxies?

Abstract

We report the serendipitous discovery of a supernova (SN) in the nearby radio galaxy 3C 78. Observations obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope show, at a distance of 0.54" (300 pc) from the galaxy nucleus, a second bright source, not present in previous images. As this source was fortuitously covered by the spectrograph slit, its spectrum was obtained, and it is characteristic of a Type Ia SN. This SN is closely aligned with the radio jet of 3C 78. Analysis of historical records shows that such a close association between jet and SN occurred in six of the 14 reported SNe in radio galaxies. The probability that this results from a random distribution of SNe in the host galaxy is less than ~0.05%. We then argue that jets might trigger SN explosions. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555 and STScI grant GO-3594.01-91A.