Radio Observations of SN 2008ha
ATel #1948; Alicia Soderberg (Harvard/CfA)
on 3 Mar 2009; 19:17 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Alicia M. Soderberg (ams@astro.caltech.edu)
Subjects: Radio, Supernovae
I observed the peculiar SN 2008ha (CBET #1567) with the Very Large Array on 2008 Nov 21.99 UT at a frequency of 8.46 GHz. No radio source is detected at the optical SN position to a limit of 93 microJy (3 sigma). At a distance of 21 Mpc, this corresponds to a radio luminosity limit similar to those of nearby Type Ia supernovae (Panagia et al. 2006). It is also consistent with the observed radio luminosities for the nearest Type Ibc supernovae (e.g., SN 2002ap; Berger, Kulkarni & Chevalier 2002), but a factor of 10^3 and 10^5 below the radio luminosities of sub-energetic GRBs (Soderberg et al. 2006) and classical long-duration GRB afterglows (Frail et al. 2003), respectively. Moreover, the
radio upper limit rules out the presence of an off-axis GRB jet, initially directed within 30 degrees of our line-of-sight (Soderberg et al. 2006).
While the non-detection of radio emission from SN 2008ha does not distinguish it to be either a thermonuclear or core-collapse supernova, the observations clearly rule out an on-axis GRB jet or sub-energetic GRB. Additional radio observations are underway to constrain the late-time radio evolution from this explosion, including any emission from a misdirected GRB jet.
