UIE
 

Hubble Space Telescope observations enabled us to find this supernova. We anticipate that Hubble may be de-orbited and make its final plummet to Earth around the time of the reappearance of TNS AT 2016jka, so we coin the name “SN Requiem” as an ode to the vast new discovery space that Hubble continues to unveil.

Type Ia Supernova discovered in REQUIEM galaxy MRG-M0138 Overview of the MACSJ0138 cluster field and the locations of the SN Requiem images (SN1-3) and its multiply-imaged host galaxy (H1-4). The wide-field view in a) is 40” on a side with ticks indicating 10” intervals. Labels marked 3.1-3.4 indicate the locations of a separate multiply-imaged [OII]-emitter at z=0.77 used to help constrain the lensing potential. Panels b-i show 4” cutouts around the lensed SN images with 1” ticks. The three-color images are generated from the WFC3/IR filters as indicated; panels bcde show the imaging from 2016 July where the SN was visible and fghi show the later imaging from 2019 July where the the SN has faded away. Panels aei indicate the location of the fourth image predicted to appear in ~2037 and panel a shows the final and highly demagnified fifth image (“SN5”). All panels use the late-epoch F125W imaging for the green channel; nevertheless, it is immediately clear that the SN2 image is substantially bluer than the other two, which helps to constrain the relative age of each SN image and the transient classification as a likely Type Ia supernova explosion. From Rodney et al, (2021, Nature Astronomy).

Type Ia Supernova discovered in REQUIEM galaxy MRG-M0138 Overview of the MACSJ0138 cluster field and the locations of the SN Requiem images (SN1-3) and its multiply-imaged host galaxy (H1-4). The wide-field view in a) is 40” on a side with ticks indicating 10” intervals. Labels marked 3.1-3.4 indicate the locations of a separate multiply-imaged [OII]-emitter at z=0.77 used to help constrain the lensing potential. Panels b-i show 4” cutouts around the lensed SN images with 1” ticks. The three-color images are generated from the WFC3/IR filters as indicated; panels bcde show the imaging from 2016 July where the SN was visible and fghi show the later imaging from 2019 July where the the SN has faded away. Panels aei indicate the location of the fourth image predicted to appear in ~2037 and panel a shows the final and highly demagnified fifth image (“SN5”). All panels use the late-epoch F125W imaging for the green channel; nevertheless, it is immediately clear that the SN2 image is substantially bluer than the other two, which helps to constrain the relative age of each SN image and the transient classification as a likely Type Ia supernova explosion. From Rodney et al, (2021, Nature Astronomy).

The beauty of gravitational lensing is that it can cause the light from a distant object that passes very near to a foreground galaxy or cluster to appear as multiple images on the sky. The discovery of multiply-imaged variable sources is a rare treat that allows astronomers to constrain the cosmic expansion rate and dark energy models. By taking careful time delay measurements that track when the variables sources appear, we can place important constraints on cosmological models. Lensed supernovae are particularly exciting owing to their relatively simple photometric behavior and well-behaved light curves and colors. With the REQUIEM data set, we have made the serendipitous discovery of a multiply-imaged supernova, TNS AT 2016jka (also known as “SN Requiem”). It was discovered behind a galaxy cluster in an evolved galaxy MRG-M0138 at z=1.95, making it the third ever (and highest redshift) multiply-imaged supernova discovery to date.

SN Requiem is likely a Type Ia supernova, i.e., the explosion of a low-mass stellar remnant, whose light curve can be used to measure cosmic distances. In archival Hubble Space Telescope imaging, three lensed images of the supernova are detected with relative time delays of <200 days. We predict a fourth image will appear close to the cluster core in the year 2037 (plus or minus 2 years). Observation of the fourth image could provide a time delay precision of ~7 days, <1% of the extraordinary 20 year baseline. The SN classification and the predicted reappearance time could be improved with further lens modeling and a comprehensive analysis of systematic uncertainties.

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