JWST Spectroscopy of SN H0pe: Classification and Time Delays of a Triply Imaged Type Ia Supernova at z = 1.78
Grogin, Norman A.; Koekemoer, Anton M.; Frye, Brenda L.; Conselice, Christopher J.; Kelly, Patrick L.; Yan, Haojing; Zitrin, Adi; Windhorst, Rogier A.; Cohen, Seth H.; Willner, S. P.; Furtak, Lukas J.; Pascale, Massimo; Jha, Saurabh W.; Siebert, Matthew R.; Pierel, Justin; Meena, Ashish K.; Chen, Wenlei; Johansson, Joel; Gilman, Daniel; Engesser, Michael; Huber, Simon; Larison, Conor
United States, United Kingdom, Germany, Sweden, Israel
Abstract
SN H0pe is a triply imaged supernova (SN) at redshift z = 1.78 discovered using the James Webb Space Telescope. In order to classify the SN spectroscopically and measure the relative time delays of its three images (designated A, B, and C), we acquired NIRSpec follow-up spectroscopy spanning 0.6–5 μm. From the high signal-to-noise spectra of the two bright images B and C, we first classify the SN, whose spectra most closely match those of SN 1994D and SN 2013dy, as a Type Ia SN. We identify prominent blueshifted absorption features corresponding to Si II λ6355 and Ca II H λ3970 and K λ3935. We next measure the absolute phases of the three images from our spectra, which allow us to constrain their relative time delays. The absolute phases of the three images, determined by fitting the three spectra to Hsiao07 SN templates, are