Radio Supernovae as Distance Indicators

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Session 33 -- Supernovae
Oral presentation, Monday, 9, 1995, 2:00pm - 3:30pm

[33.06] Radio Supernovae as Distance Indicators

K.~W.~Weiler (NRL), S.~D.~Van Dyk (UCB), R.~A.~Sramek (NRAO/VLA), N.~Panagia (STScI)

\noindent Analysis of the evolution of radio emission from supernovae indicates that systematics exist which can be used to define the supernova type and a relative radio luminosity, using only the spectral and temporal radio behavior. The availability of a radio luminosity estimate then allows relative distance estimates to be made for the radio supernovae, independent of measurements or assumptions made at other wavelengths. When combined with independent distance information, absolute luminosities and distances for all radio supernovae and their parent galaxies can be estimated. In particular, we have found that, based on four objects, Type Ib/c supernovae may be approximate radio ``standard candles,'' with a 6 cm peak luminosity of $\sim 10^{27}$ erg s$^{-1}$ Hz$^{-1}$. Type II supernovae have a large range of properties, but appear to obey a relation $L_{\rm 6\ cm\ max} \simeq 4 \times 10^{22} (t_{\rm 6\ cm\ max} - t_0)^{1.8}$, where $L_{\rm 6\ cm\ max}$ is the peak 6 cm luminosity in erg s$^{-1}$ Hz$^{-1}$ of the supernova at time $t_{\rm 6\ cm\ max}$ and $t_0$ is the date of explosion.

If these relations are supported by further observations, they provide the first possibility for distance determinations solely from radio continuum observations. With currently available sensitivity of the Very Large Array (VLA), it should be possible, with diligent effort, to extend such radio supernova distance determinations beyond the Virgo Cluster to $\sim 100$ Mpc.

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