We report the NuSTAR detection of hard X-ray emission from the FBOT AT2024wpp (Ho et al., AstroNote 2024-272) obtained ~5 days rest-frame after the first optical detection. NuSTAR observations revealed the presence of a bright hard X-ray source with a 3-30 keV flux of 1.3e-12 erg/s/cm2 (luminosity of ~4e+43 erg/s adopting a distance of ~500 Mpc as implied by the photo-z of 0.11 for the likely host galaxy, Ho et al., AstroNote 2024-272). AT2024wpp is the third FBOT with evidence for hard X-ray emission, after the prototypical event AT2018cow (Margutti et al., 2019, ApJ, 872, 18) and, more recently, AT2024qfm (Margutti et al., AstroNote 2024-214). A preliminary spectral analysis of the NuSTAR data indicates a spectral photon index of Gamma~1.2, which is harder than the power-law component observed in AT2018cow, and potentially suggests the contribution of a fading Compton hump component to the hard X-ray spectrum. A more in-depth broad-band (i.e. soft and hard) X-ray spectral analysis will be able to confirm or rule out this statement.
We thank the entire NuSTAR team for their fast response to our triggers which enabled these observations.
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