Multiwavelength Analysis of Six Luminous Fast Blue Optical Transients

We present early (≲1 yr) multiwavelength observations and analysis of six luminous fast blue optical transients (LFBOTs). We identified these LFBOTs in Zwicky Transient Facility survey data from their fast light-curve evolution ( t 1/2 ≤ 12 days), blue colors at peak brightness ( g − r ≤ −0.2 mag), a visible host galaxy, high optical luminosity ( M g < −20 mag), and an X-ray and/or radio detection. With the exception of AT2024aehp (ZTF24abygbss), these transients exhibit peaks in their 10 GHz radio light curves at t rest ≈ 50–100 days, with peak radio luminosities ranging from 10 38 to 10 40 erg s −1 . Modeling the radio emission as synchrotron radiation indicates a fast ( v = 0.1–0.3 c ) shock in a dense ( n e ≈ 10 3 –10 4 cm −3 ) medium. The X-ray emission varies by ≈2 orders of magnitude in luminosity (10 42 –10 44 erg s −1 ) at t rest ∼ 20 days. Analysis of the host-galaxy photometry and spectroscopy for each transient shows that LFBOTs are predominantly nonnuclear (a few kiloparsecs offset) with star-forming host galaxies of stellar masses = 10 9 –10 11 M ⊙ . Unlike all other LFBOTs to date, AT2024aehp exhibited a luminous ( M < −19 mag) plateau in the optical light curve and its 6–15 GHz radio emission brightened by over an order of magnitude from t rest ≈ 70 to 130 days. The mostly consistent radio behavior between these LFBOTs implies a similar circumburst medium, leading us to prefer a progenitor scenario in which mass is lost in a consistent way shortly prior to the terminal event.