We report the first case of spectral inversion in radio observations of the Fast Blue Optical Transient AT2024wpp (Ho et al., AstroNote 2024-272) at t ~ 133-161 days rest frame after the first optical detection. We monitored AT2024wpp in the radio bands starting from ~2 weeks post-discovery. The radio spectral peak moved to frequencies lower than 5 GHz by ~128 days, resulting in an optically thin spectral index of alpha ~ -1.5 (F_nu \propto nu^\alpha) at 5-9 GHz. However, in later observations, we find evidence for a spectral inversion, with \alpha \sim +0.6 and +0.2 at 133 and 161 days (rest frame), respectively. This kind of spectral inversion is unprecedented in FBOTs and may signal the emergence of a new emission component.
We thank the ATCA team for their support in scheduling and executing these observations.
| 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 | 2024wpp | 02:42:05.499 | -16:57:22.90 | FBOT | 0.0868 | 02:42:05.499 | -16:57:22.90 | SN |
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