1.6 GHz VLBI Observations of SN 1979C: almost-free expansion

TL;DR

This study uses 1.6 GHz VLBI observations to analyze the expansion of supernova SN 1979C, revealing it has been expanding almost freely for over 25 years, contrary to earlier claims of deceleration.

Contribution

The paper provides a reanalysis of VLBI data showing SN 1979C's expansion is nearly free, challenging previous assertions of strong deceleration.

Findings

SN 1979C has been expanding almost freely for over 25 years.

The expansion parameter m is approximately 0.91, indicating minimal deceleration.

Reanalysis of multiple VLBI observations supports the free expansion conclusion.

Abstract

We report on 1.6 GHz Very-Long-Baseline-Interferometry (VLBI) observations of supernova SN 1979C made on 18 November 2002. We derive a model-dependent supernova size. We also present a reanalysis of VLBI observations made by us on June 1999 and by other authors on February 2005. We conclude that, contrary to our earlier claim of strong deceleration in the expansion, SN 1979C has been undergoing almost-free expansion ($m = 0.91\pm0.09$; $R \propto t^m$) for over 25 years.