We report the discovery of a new transient in James Webb Space Telescope (JWST) NIRCam exposures of the massive galaxy cluster PLCK G165.7+67 (G165; Canameras et al. 2015; Harrington et al. 2016) taken as part of the PEARLS program (GTO-1176; PI: R. Windhorst) on UT 2023 March 30. The source was not detected in Cycle 23 Hubble Space Telescope (HST) WFC3/IR F110W and F160W images acquired on UT 2016 May 30 (GO-24223; PI: B. Frye) reaching m_AB = 28.94 and 27.97 mag (3-sigma; Pascale et al. 2022), respectively.
The transient appears to be associated with a galaxy host at z = 1.8 estimated by its NIRCam-based photometric redshift and by a lens model prediction (Frye et al. 2019; Pascale et al. 2022). This one transient is detected in three different locations (a, b, and c) as a result of strong lensing by the foreground galaxy cluster G165. Although all three images are detected, our lens model predicts that light of the transient arrived first in image “a,” followed by “c,” and then “b”. This transient, which we designate as "SN H0pe," is a probable supernova of which the type is not yet established via spectroscopy, and is likely to be a SN Ia based on the redshift and intrinsic brightness (de-magnified using our lens model) and the inferred age of the host galaxy. Follow-up observations, including spectroscopy, have been scheduled with JWST (DD-4446; PI: B. Frye).
The J2000 positions of the SN images are (11:27:15.31, +42:28:41.0) for "a", (11:27:15.60, +42:28:33.8) for "b", and (11:27:15.94, +42:28:28.9) for "c". Our NIRCam photometry gives
m_{F150W,AB} = 23.91 +- 0.2 mag for the brightest image ("b").
Comments