Radiation Signatures of Electron Acceleration in the Decelerating Jet of MAXI J1348-630

Abstract A discrete jet component (blob) ejection and its subsequent deceleration were observed in the 2019/2020 outburst of the low-mass X-ray binary MAXI J1348-630. A first kinematic analysis of the deceleration due to an abrupt transition from an evacuated cavity to the interstellar medium (ISM) suggested a kinetic energy exceeding 10 46 erg, surpassing estimates of the available total ejection energy. However, incorporating a transition layer with exponential density growth between the cavity and the ISM recently enabled a kinematic analysis with much more realistic energy requirements of approximately 10 44 erg. Here, we study the expected radiative signatures of electrons accelerated within the decelerating blob by introducing a model akin to the relativistic blast wave model for gamma-ray bursts, considering radiative energy losses and radiation drag, to simulate the deceleration of a relativistically moving plasmoid. This model yields snapshot spectral energy distributions and multiwavelength light curves from synchrotron and synchrotron-self-Compton emission. Notably, the synchrotron emission peaks in the X-rays, but the predicted X-ray flux is negligible compared to thermal emission from the accretion disk. The predicted radio light curve closely resembles the observed one during the jet deceleration phase following the outburst in 2019/2020.