Effects of Winds on the Optical Properties of Type Ib and Ic Supernova Progenitors

TL;DR

This study models how stellar winds influence the optical appearance of Type Ib and Ic supernova progenitors, revealing that wind effects can significantly alter their brightness and color, impacting progenitor detection and characterization.

Contribution

It introduces detailed spectral models incorporating wind effects for SN Ib/Ic progenitors, highlighting their impact on observable properties and progenitor identification.

Findings

Wind increases optical brightness of progenitors by up to 3 mag.

Color dependence on temperature becomes non-monotonic due to winds.

Deeper optical searches are required to detect typical SN Ib/Ic progenitors.

Abstract

We investigate the effects of winds on the observational properties of Type Ib and Ic supernova (SN Ib/Ic) progenitors using spectral models constructed with the non-LTE stellar atmospheric code CMFGEN. We consider SN Ib/Ic progenitor models of the final mass range of 2.16 -- 9.09~$M_\odot$ having different surface temperatures and chemical compositions, and calculate the resulting spectra for various wind mass-loss rates and wind terminal velocities. We find that the progenitors having an optically thick wind would become brighter in the optical for a higher mass-loss rate (or a lower wind terminal velocity), because of the formation of the photosphere in the extended wind matter and the contribution from free-free and line emissions from the wind. As a result, for the standard Wolf-Rayet wind mass-loss rate, helium-deficient compact SN Ic progenitors would be brighter in the optical by $\sim$3 mag compared to the case without the wind effects. We also find that the color dependence on the photospheric temperature is non-monotonic because of the wind effects. Our results imply that inferring the progenitor mass, bolometric luminosity and effective temperature from the optical observation using the standard stellar evolution model prediction can be misleading. By comparing our fiducial model predictions with the detection limits of the previous SN Ib/Ic progenitor searches, we conclude that a deep search with an optical absolute magnitude larger than $\sim -4$ is needed to directly identify most of the ordinary SN Ib/Ic progenitors. We discuss implications of our results for the observed SN Ib/Ic progenitor candidates for iPTF13bvn, SN 2019yvr and SN 2017ein.