We report evidence for a rapid re-brightening of the soft X-ray emission from the FBOT AT2024wpp (Ho et al., AstroNote 2024-272) from our Swift-XRT and Chandra campaign (PI Margutti) at ~50 days after optical discovery. The soft X-ray counterpart of AT2024wpp (Ho et al., AstroNote 2024-272; Srinivasaragavan et al., AstroNote 2024-276) showed roughly constant flux until ~7 days, which was followed by a flux decay as Fx~t^-2.3. During the power-law decay the soft X-ray spectrum can be fitted with a power-law model with photon index Gamma~1.1 (+\- 0.2 at 1 sigma confidence level). At around ~50 days the source experienced a rapid brightening over a time scale of a few days. Chandra observations taken on 2024 Nov 13 UT provide evidence for significant spectral hardening (best fitting photon index Gamma= -0.3 (+\- 0.9 at 3 sigma confidence level), which implies a rising Fnu spectrum. We find no evidence for short time scale variability within the 40 ks of Chandra observations. X-ray flaring is not unprecedented in FBOTs at this epoch (see, e.g., the prototypical event AT2018cow; Margutti et al. 2019, ApJ, 872, 18). However, deep Chandra observations are providing first evidence for significant spectral hardening at the time of the brightening, which will help constrain the origin of the X-ray variability. The rapid variability and spectral evolution are suggestive of a central-engine origin.
Further soft and hard X-ray observations of this target are planned.
We are extremely thankful to the Chandra, Swift, and NuSTAR teams for enabling 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 [ZTF24abjjpbo] | 02:42:05.499 | -16:57:22.90 | SN | 02:42:05.499 | -16:57:22.90 | SN |