Early gray dust formation in the type IIn SN 2005ip

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 totalto-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.

A decade of ejecta dust formation in the Type IIn SN 2005ip

“…Only very small masses of dust are required to produce the asymmetries observed at these very early times since the radius of the ejecta is still small. We determine that a dust mass of ∼10 −5 M has condensed in the ejecta by 169 d. Recent analysis by Nielsen et al (2018) identified an acceleration in the decline of the optical light curve commencing at around 50 days. Dust formation in the ejecta would explain this sudden drop.…”

“…Smith et al (2017) suggested that the SN blast wave was still interacting with a dense, clumpy CSM as late as early 2016, contrary to analysis of the X-ray flux by Katsuda et al (2014) who claim that the forward shock has escaped the CSM shell. Most recently, Nielsen et al (2018) used the light curve evolution of SN 2005ip to determine dust optical depths, concluding that dust formation had occurred in SN 2005ip starting as early as two months after discovery.…”

The slow demise of the long-lived SN 2005ip

“…Fox et al (2010) obtained a Spitzer Space Telescope Infrared Spectrograph (Houck et al 2004) spectrum of SN 2005ip [the only mid-IR (MIR) spectrum of a SN IIn to date], which revealed the presence of a cooler dust component associated with a pre-existing dust shell radiatively heated by this ongoing CSM interaction. Bevan et al (2018) modelled the spectral line evolution and confirmed that a significant amount of dust can be explained by dust formation in the ejecta, and Nielsen, Hjorth & Gall (2018) found the dust properties to be unlike those of Milky Way dust. Stritzinger et al (2012) continued to monitor SN 2005ip throughout ∼5 yr post-explosion and showed that the optical and NIR light curves underwent little decline over that time.…”

Dust Models for the Extinction of Type IIn Supernova SN 2010jl

“…Note that the radius of the blackbody is just a lower limit of the size of dust shell (Fox et al 2013;Sarangi et al 2018), thus the dust mass calculated with this radius should be regarded as the lower limit and smaller than that derived from the infrared emission. Besides, an inhomogeneous and clumpy structure of dust distribution around SN 2010jl could bring deviation to the estimation of dust mass (Nielsen et al 2018).…”

“…A few previous studies show that some Type IIn supernovae have larger value of 𝑅 𝑉 . For example, Nielsen et al (2018) found that 𝑅 𝑉 of the type IIn supernova SN 2005ip increased and became stable in the range of 4.5 to 8.0 after 100 days. However, it is still controversial whether such large value of 𝑅 𝑉 is universal for the type IIn supernovae.…”