Early gray dust formation in the type IIn SN 2005ip

TL;DR

This study investigates dust formation in supernova SN 2005ip, revealing early gray dust with high R_V values, indicating different dust properties than those in the Milky Way, based on modeling observed light curves.

Contribution

It provides the first detailed analysis of dust extinction properties in SN 2005ip, demonstrating early formation of gray dust with high R_V values through light curve modeling.

Findings

Dust formed about two months after explosion.

Extinction A_V increases up to 1 mag over 150 days.

R_V remains high (4.5–8), indicating gray dust.

Abstract

The physical characteristics of dust formed in supernovae is poorly known. In this paper, we investigate the extinction properties of dust formed in the type IIn SN 2005ip. The observed light curves of SN 2005ip all exhibit a sudden drop around 50 days after discovery. This has been attributed to dust formation in the dense circumstellar medium. We modeled the intrinsic light curves in six optical bands, adopting a theoretical model for the luminosity evolution of supernovae interacting with their circumstellar material. From the difference between the observed and intrinsic light curves, we calculated extinction curves as a function of time. The total-to-selective extinction ratio, $R_V$, was determined from the extinction in the B and V bands. The resulting extinction, $A_V$, increases monotonically up to about 1 mag, 150 days after discovery. The inferred $R_V$ value also increases slightly with time, but appears constant in the range 4.5--8, beyond 100 days after discovery. The analysis confirms that dust is likely formed in SN 2005ip, starting about two months after explosion. The high value of $R_V$, that is, gray dust, suggests dust properties different from of the Milky Way. While this result hinges on the assumed theoretical intrinsic light curve evolution, it is encouraging that the fitted light curves are as expected for standard ejecta and circumstellar medium density structures.