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Late Emission from the Type Ib/c SN 2001em: Overtaking the Hydrogen Envelope

Nikolai N. Chugai·Roger A. Chevalier
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Abstract

The Type Ib/c supernova SN 2001em was observed to have strong radio, X-ray, and Halpha emission at an age of about 2.5 yr. Although the radio and X-ray emission have been attributed to an off-axis gamma-ray burst, we model the emission as the interaction of normal SN Ib/c ejecta with a dense, massive (3 Msun) circumstellar shell at a distance about 7 x 10^{16} cm. We investigate two models, in which the circumstellar shell has or has not been overtaken by the forward shock at the time of the X-ray observation. The circumstellar shell was presumably formed by vigorous mass loss with a rate (2-10) x 10^{-3} Msun/yr at 1000-2000 yr prior to the supernova explosion. The hydrogen envelope was completely lost, and subsequently was swept up and accelerated by the fast wind of the presupernova star up to a velocity of 30-50 km/s. Although interaction with the shell can explain most of the late emission properties of SN 2001em, we need to invoke clumping of the gas to explain the low absorption at X-ray and radio wavelengths.

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Nikolai N. Chugai, Roger A. Chevalier. 2005-10-12. Late Emission from the Type Ib/c SN 2001em: Overtaking the Hydrogen Envelope. https://doi.org/10.1086/500539

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