高能暂现源 · 每日文献综述

A multiwavelength study of the flat-spectrum radio quasar PKS 1441 + 25 (z = 0.939), one of the most distant blazars detected in the very-high-energy (VHE; GeV) -ray band, is presented. Using uniformly processed data from the Markarian Multiwavelength Data Center, Fermi-LAT -ray data are combined with Swift XRT/UVOT, NuSTAR, and ground-based optical and infrared measurements (ASAS-SN, ZTF, Pan-STARRS, NEOWISE) to characterize the emission from the source in different states. An adaptively binned light curve shows a prolonged high state in the -ray band starting around MJD 57000, including a bright -ray flare in late January and a hard emission spectrum in April coincident with detection of VHE photons from the source by MAGIC and VERITAS. Using simultaneous data, SEDs are constructed for three characteristic epochs—the bright HE -ray flare in January, the April period with MAGIC and VERITAS VHE detections, and the quiescent states in May and June—and modeled within a one-zone external inverse-Compton framework. The theoretical modeling is implemented using novel convolutional neural-network surrogate models which allow full exploration of parameter space. The modeling shows that the April-June SEDs are reproduced by weak magnetic fields and an emission region of size cm, implying an emitting zone located beyond the broad-line region. In this regime, photons from the dusty torus provide the dominant external field, and internal absorption is negligible, allowing VHE photons to escape from the emitting region. In contrast, the January flare is best described by a more strongly magnetized and compact emission region cm, implying a location much closer to the central black hole, where disk and BLR radiation dominate. Under these conditions, efficient absorption suppresses VHE emission despite the higher GeV flux. The results support a scenario in which the 2015 activity of PKS 1441 + 25 is driven primarily by the relocation and evolution of the dissipation region along the jet rather than by changes in the underlying emission mechanism.