VLBI Observations of the Nearby Type IIb Supernova 2011dh

Abstract

We report on phase-referenced VLBI radio observations of the Type IIb supernova 2011dh, at times t = 83 days and 179 days after the explosion and at frequencies, respectively, of 22.2 and 8.4 GHz. We detected SN 2011dh at both epochs. At the first epoch only an upper limit on SN 2011dh's angular size was obtained, but at the second epoch, we determine the angular radius SN 2011dh's radio emission to be 0.25 +- 0.08 mas by fitting a spherical shell model directly to the visibility measurements. At a distance of 8.4 Mpc this angular radius corresponds to a time-averaged (since t=0) expansion velocity of the forward shock of 21000 +- 7000 km/s. Our measured values of the radius of the emission region are in excellent agreement with those derived from fitting synchrotron self-absorbed models to the radio spectral energy distribution, providing strong confirmation for the latter method of estimating the radius. We find that SN 2011dh's radius evolves in a power-law fashion, with R proportional to t^(0.92 +- 0.10).

8 pages; accepted to Astrophysical Journal

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• The Progenitor of Supernova 2011dh Has Vanished
• Light curve and spectral evolution of the Type IIb SN 2011fu
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• Oblique Shock Breakout in Supernovae and Gamma-Ray Bursts: I. Dynamics and Observational Implications
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• Injection and Acceleration of Electrons at A Strong Shock: Radio and X-ray Study of Young Supernova 2011dh
• Long-Lasting X-Ray Emission from Type IIb Supernova 2011dh and Mass-Loss History of The Yellow Supergiant Progenitor
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• AT 2018cow VLBI: No Long-Lived Relativistic Outflow
• Inhomogeneities and the modeling of radio supernovae
• The origin of the late-time luminosity of supernova 2011dh
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• Probing Shock Breakout and Progenitors of Stripped-Envelope Supernovae through Their Early Radio Emissions
• Evolution of the progenitors of SNe 1993J and 2011dh revealed through late time radio and X-ray studies
• Imaging the Expanding Shell of SN 2011dh
• Multi-wavelength Observations of the Type IIb Supernova 2009mg
• The Exceptional X-ray Evolution of SN1996cr in High Resolution
• VLBI Constraints on Type I b/c Supernovae
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• VLBI Observations of SN 2012au Reveal a Compact Radio Source a Decade Post Explosion
• Analysis of 14 Years of X-Ray Emission From SN 2011DH