Other
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21733715w&link_type=abstract
American Astronomical Society, AAS Meeting #217, #337.15; Bulletin of the American Astronomical Society, Vol. 43, 2011
Other
2
Scientific paper
We present extensive radio observations of the nearby Type Ibc supernovae 2004cc, 2004gq, and 2004dk spanning Δ t≈ 8-1800 days after explosion. Using a dynamical model developed for synchrotron emission from a slightly decelerated blastwave, we estimate the velocity and energy of the fastest ejecta and the density profile of the circumstellar medium. The blastwaves for all three supernovae are characterized by non-relativistic velocities of v≈ (0.1-25)c and associated energies of E≈ (2-10)× 1047 erg, in line with the expectations for a typical homologous explosion. Smooth, stellar wind density profiles are indicated by the early radio data and we estimate the progenitor mass loss rates to be ∘ M≈ (8-40)× 10-6 M&sun; yr-1 (wind velocity, vw=103 km s-1). These properties are consistent with those of Wolf-Rayet stars, the favored progenitors of SNe Ibc including those associated with long-duration gamma-ray bursts. However, at late time, each of these SNe show evidence for abrupt radio variability which we attribute to significant circumstellar density modulations (factor of 5-100) at radii of R≈ (1-50)× 1016 cm. For SN 2004gq, the density modulations are marginally consistent with the expectations for a variable and/or clumpy Wolf-Rayet line-driven wind. However, in the case of SNe 2004cc and 2004dk, the density modulations are more intense, ∘ M>/ 10-4M&sun; yr-1, and possibly attributed to continuum-driven winds or hydrodynamic eruptions. We compare the circumstellar environments for these three SNe with those of other Type Ibc supernovae and nearby gamma-ray bursts and find that they are characterized by a more violent progenitor mass loss history in the decades leading up to explosion. This work is supported in part by the NSF REU and DOD ASSURE programs under NSF grant no. 0754568 and by the Smithsonian Institution.
Soderberg Alicia Margarita
Wellons Sarah
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