Strongly lensed SN Refsdal: refining time delays based on the supernova explosion models

TL;DR

This study models supernova Refsdal's explosion to refine gravitational lensing time delays and magnifications, enabling improved measurements of the Hubble constant using a unique lensed supernova at z=1.5.

Contribution

It provides detailed radiation hydrodynamics models of SN Refsdal, refining time delay and magnification estimates for the first gravitationally lensed supernova with multiple images.

Findings

Progenitor likely a blue supergiant similar to SN 1987A.

Refined time delays between images with higher accuracy.

Estimated Hubble constant of approximately 68.6 km/s/Mpc.

Abstract

We explore the properties of supernova (SN) "Refsdal" - the first discovered gravitationally lensed SN with multiple images. A large magnification provided by the galactic-scale lens, augmented by the cluster lens, gave us a unique opportunity to perform a detailed modelling of a distant SN at z=1.5. We present results of radiation hydrodynamics modelling of SN Refsdal. According to our calculations, the SN Refsdal progenitor is likely to be a more massive and energetic version of SN 1987A, i.e. a blue supergiant star with the following parameters: the progenitor radius $R_0 = (50 \pm 1) R_{\odot}$, the total mass $M_{tot}= (25\pm 2) M_{\odot}$, the radioactive $^{56}$Ni mass $M_{^{56}\mathrm{Ni}} = (0.26 \pm 0.05) \,M_{\odot}$, and the total energy release $E_{burst}=(4.7 \pm 0.8)\times10^{51}$ erg. Reconstruction of SN light curves allowed us to obtain time delays and magnifications for the images S2-S4 relative to S1 with higher accuracy than previous template-based estimates of Rodney \& et al. (2016). The measured time delays are $\Delta t_{S2-S1} = 9.5^{+2.6}_{-2.7} $ days, $\Delta t_{S3-S1} = 4.2^{+2.3}_{-2.3} $ days, and $\Delta t_{S4-S1} = 30^{+7.8}_{-8.2} $ days. The obtained magnification ratios are $\mu_{S2/S1}= 1.14 \pm 0.02$, $\mu_{S3/S1} = 1.01 \pm 0.02 $, and $\mu_{S4/S1} = 0.35\pm 0.02$. We estimate the Hubble constant $H_0 = 68.6^{+13.6}_{-9.7}$ km s$^{-1}$ Mpc$^{-1}$ via re-scaling the time delays predicted by different lens models to match the values obtained in this work. With more photometric data on the fifth image SX, we will be able to further refine the time delay and magnification estimates for SX and obtain competitive constraints on $H_0$.