The Astrophysical Journal (Jan 2023)

The Magnificent Five Images of Supernova Refsdal: Time Delay and Magnification Measurements

  • Patrick L. Kelly,
  • Steven Rodney,
  • Tommaso Treu,
  • Simon Birrer,
  • Vivien Bonvin,
  • Luc Dessart,
  • Ryan J. Foley,
  • Alexei V. Filippenko,
  • Daniel Gilman,
  • Saurabh Jha,
  • Jens Hjorth,
  • Kaisey Mandel,
  • Martin Millon,
  • Justin Pierel,
  • Stephen Thorp,
  • Adi Zitrin,
  • Tom Broadhurst,
  • Wenlei Chen,
  • Jose M. Diego,
  • Alan Dressler,
  • Or Graur,
  • Mathilde Jauzac,
  • Matthew A. Malkan,
  • Curtis McCully,
  • Masamune Oguri,
  • Marc Postman,
  • Kasper Borello Schmidt,
  • Keren Sharon,
  • Brad E. Tucker,
  • Anja von der Linden,
  • Joachim Wambsganss

DOI
https://doi.org/10.3847/1538-4357/ac4ccb
Journal volume & issue
Vol. 948, no. 2
p. 93

Abstract

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In late 2014, four images of supernova (SN) “Refsdal,” the first known example of a strongly lensed SN with multiple resolved images, were detected in the MACS J1149 galaxy-cluster field. Following the images’ discovery, the SN was predicted to reappear within hundreds of days at a new position ∼8″ away in the field. The observed reappearance in late 2015 makes it possible to carry out Refsdal’s original proposal to use a multiply imaged SN to measure the Hubble constant H _0 , since the time delay between appearances should vary inversely with H _0 . Moreover, the position, brightness, and timing of the reappearance enable a novel test of the blind predictions of galaxy-cluster models, which are typically constrained only by the positions of multiply imaged galaxies. We have developed a new photometry pipeline that uses DOLPHOT to measure the fluxes of the five images of SN Refsdal from difference images. We apply four separate techniques to perform a blind measurement of the relative time delays and magnification ratios between the last image SX and the earlier images S1–S4. We measure the relative time delay of SX–S1 to be $\displaystyle {376.0}_{-5.5}^{+5.6}$ days and the relative magnification to be $\displaystyle {0.30}_{-0.3}^{+0.5}$ . This corresponds to a 1.5% precision on the time delay and 17% precision for the magnification ratios and includes uncertainties due to millilensing and microlensing. In an accompanying paper, we place initial and blind constraints on the value of the Hubble constant.

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