The nature of supernovae 2010O and 2010P in arp 299-II. Radio emission

We report radio observations of two stripped-envelope supernovae (SNe), 2010O and 2010P, which exploded within a few days of each other in the luminous infrared galaxy Arp 299. Whilst SN 2010O remains undetected at radio frequencies, SN 2010P was detected (with an astrometric accuracy better than 1milli arcsec in position) in its optically thin phase in epochs ranging from ̃1 to ̃3 yr after its explosion date, indicating a very slow radio evolution and a strong interaction of the SN ejecta with the circumstellar medium. Our latetime radio observations towards SN 2010P probe the dense circumstellar envelope of this SN, and imply M [M⊙ yr-1]/υwind[10 kms-1] = (3.0-5.1) × 10-5, with a 5 GHz peak luminosity of ̃1.2 × 1027 erg s-1 Hz-1 on day ̃464 after explosion. This is consistent with a Type IIb classification for SN 2010P, making it the most distant and most slowly evolving Type IIb radio SN detected to date. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.