We obtained a deep optical spectrum of the Type Ia supernova (SN) 2021aefx at approximately 1200 days post maximum light using the Very Large Telescope (VLT) FORS2 long-slit spectrograph (ESO DDT Programme 114.28LC.001, PI: L. A. Kwok). The spectrum combines multiple exposures over the course of several days between 2025 March 25 and 2025 April 1 for a total exposure time of 4.2 hr, with the supernova at an approximate magnitude of r ~ 23.3 mag. After host galaxy subtraction using HostSub_GP (C. Liu et al., in prep), the spectrum shows that the optical flux of SN 2021aefx is now being dominated by a light echo. An empirical light echo model based on the early-time, photometrically-calibrated spectral sequence of SN 2021aefx (Hosseinzadeh et al. 2022, ApJ, 933, L45), combined with a 1/wavelength^2 scattering efficiency, closely matches the observed spectrum.
Additional follow-up and monitoring of the light echo of SN 2021aefx is encouraged.
| Catalog | Name | Reported RA | Reported DEC | Reported Obj-Type | Reported Redshift | Host Name | Host Redshift | Remarks | TNS RA | TNS DEC | TNS Obj-Type | TNS Redshift |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| TNS | 2021aefx [DLT21ae] | 04:19:53.400 | -54:56:53.09 | SN Ia | 0.005 | NGC1566 | 04:19:53.400 | -54:56:53.09 | SN Ia | 0.005 |
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