A decade of dust formation in the Type IIn SN 2005ip
A. Bevan, R. Wesson, M.J. Barlow, I. De Looze, J.E. Andrews, G.C. Clayton, K. Krafton, M. Matsuura & D. Milisavljevic, 2019, MNRAS, 485, 5192
In order to understand the contribution of core-collapse supernovae to the dust budget of the early universe, it is important to understand not only the mass of dust that can form in core-collapse supernovae but also the location and rate of dust formation. SN 2005ip is of particular interest since dust has been inferred to have formed in both the ejecta and the post-shock region behind the radiative reverse shock. We have collated eight optical archival spectra that span the lifetime of SN 2005ip and we additionally present a new X-shooter optical-NIR spectrum of SN 2005ip at 4075 d post-discovery. Using the Monte Carlo line transfer code DAMOCLES, we have modelled the blueshifted broad and intermediate width Hα, Hβ and He I lines from 48d to 4075 d post-discovery. We find that ejecta dust can account for the asymmetries observed in the broad and intermediate width Hα, Hβ and He I line profiles at all epochs and that it is not necessary to invoke post-shock dust formation to explain the blueshifting observed in the intermediate width post-shock lines. Using a Bayesian approach, we have determined the evolution of the ejecta dust mass in SN 2005ip and infer a gradual increase over >5 yr. We deduce a current ejecta dust mass of ~0.1 M⊙.
Measuring dust in core-collapse supernovae with a Bayesian approach to line profile modelling
Antonia Bevan, 2018, MNRAS, 480, 4659
I present the application of an affine invariant Markov Chain Monte Carlo (MCMC) ensemble sampler (emcee) to the DAMOCLES code in order to investigate the multi-dimensional parameter space rigorously and characterise the posterior probability distribution. This Bayesian approach is applied to four simulated line profiles in order to test the method and investigate its efficacy. The majority of parameters can be tightly constrained using this method, and a strong (predictable) dependence between the grain size and the dust mass is quantified. The new approach is also applied to the Hα line and [O I]6300,6363A doublet of SN1987A at 714d post-outburst investigating a new, more complex, 10-dimensional model that treats both features simultaneously. The dust mass, dust grain size and a range of other parameters can be well constrained using this technique, representing a significant improvement over the previous manual approach.
Dust masses for SN 1980K, SN1993J and Cassiopeia A from red-blue emission line asymmetries
Antonia Bevan, M. J. Barlow and D. Milisavljevic, 2017, MNRAS, 465, 4044
We present Monte Carlo line transfer models that investigate the effects of dust on the very late time emission line spectra of the core collapse supernovae SN 1980K and SN 1993J and the young core collapse supernova remnant Cassiopeia A. Their blue-shifted emission peaks, resulting from the removal by dust of redshifted photons emitted from the far sides of the remnants, and the presence of extended red emission wings are used to constrain dust compositions and radii and to determine the masses of dust in the remnants. We estimate dust masses of between 0.08 - 0.15 M⊙ for SN 1993J at year 16, 0.12 - 0.30 M⊙ for SN 1980K at year 30 and ∼1.1 M⊙ for Cas A at year ∼330. Our models for the strong oxygen forbidden lines of Cas A require the overall modelled profiles to be shifted to the red by between 700 - 1000 km s−1, consistent with previous estimates for the shift of the dynamical centroid of this remnant.
Modelling supernova line profile asymmetries to determine ejecta dust masses: SN 1987A from days 714 to 3604
Antonia Bevan and M. J. Barlow, 2016, MNRAS, 456, 1269
The late time optical and near-IR line profiles of many core-collapse supernovae exhibit a red-blue asymmetry as a result of greater extinction by internal dust of radiation emitted from the receding parts of the supernova ejecta. We present here a new code, DAMOCLES, that models the effects of dust on the line profiles of core-collapse supernovae in order to determine the masses of newly formed dust. As noted by Lucy et al. (1989), the presence of an extended red scattering wing in late-time line profiles can also indicate dust formation. We find that dust-affected line profiles need not necessarily be flux-biased towards to the blue, although the profile peak will always be blue-shifted. We have collated optical spectra of SN 1987A from a variety of archival sources and have modelled the evolution of the Hα line from days 714 to 3604, as well as that of the [OI] 6300,6363A doublet between days 714 and 1478. A variety of evidence points to the presence of clumping and we find that our clumped dust models require significantly higher dust masses than smoothly distributed dust models. Our line profile fits imply day 714 dust masses of <3 × 10−3 M⊙ for all grain types apart from very high albedo pure magnesium silicates, for which up to 0.07M⊙ can be accommodated. Large grain radii (>0.6μm) are generally required to fit the line profiles even at the earlier epochs. We find that a large dust mass (>0.1M⊙) had formed by day 3604 and infer that the majority of the present dust mass must have formed after this epoch. Our findings agree with recent estimates from SED fits for the dust mass evolution of SN 1987A and support the inference that the majority of SN 1987A's dust formed many years after the initial explosion.