Upper limit for circumstellar gas around the Type Ia SN 2000cx

TL;DR

This study uses high-resolution spectroscopy to search for circumstellar material around the peculiar Type Ia SN 2000cx, finding no detectable NaID absorption and thus constraining the progenitor system's environment.

Contribution

It applies a novel spectroscopic method to a peculiar Type Ia supernova to set upper limits on circumstellar material, expanding understanding of progenitor diversity.

Findings

No NaID absorption detected, setting strict upper limits.

SN 2000cx differs from SN 2006X in circumstellar environment.

Results suggest possible differences in progenitor systems or viewing angles.

Abstract

The nature of the companion stars in Type Ia Supernova (SNe) progenitor systems remains unclear. One possible way to discriminate between different scenarios is the presence (or absence) of circumstellar material, the left overs from the progenitor evolution that may be revealed by their interaction with the SN. A new method to probe the circumstellar environment has been exploited for the normal Type Ia SN 2006X, leading for the first time to the direct detection of material which escaped the progenitor system. In this paper we apply the same analysis to the peculiar Type Ia SN 2000cx, with the aim of constraining the properties of its progenitor system. Using multi-epoch, high-resolution spectroscopy we have studied the spectral region where narrow, time-variable NaID absorption features are expected in case circumstellar material is present along the line of sight. No NaID absorption is detected in the rest-frame of the host galaxy to a level of a few mA, setting a stringent upper limit to the column density of the absorbing material (N(NaI)<=2 x 10^10 cm-2). In this respect the peculiar Type Ia SN 2000cx is different from the normal Ia SN 2006X. Whether this is to be attributed to a different progenitor system, to viewing-angle effects or to a low metallicity remains to be clarified.