1998A&A...339L..69F

We report on two X-ray observations of the transient source XTE J0421+560 performed by BeppoSAX, and on a series of observations performed by the 0.7 m Teramo-Normale Telescope. Outburst peak occurrence time and duration depend on photon energy: the outburst peak is achieved first in the X-ray band, then in the optical and finally in the radio. An exponential decay law fits well the X-ray data except in the TOO2 0.5-1.0keV band, where erratic time variability is detected. During TOO1 the e-folding time scale decreases with energy up to ∼20keV, when it achieves a saturation; during TOO2 it decreases up to ∼2keV and then increases. This change is correlated with a spectral change, characterized by the onset of a soft (≲2keV) component in TOO2 (Orr et al., 1998, A&A, submitted). This component might originate from the relativistic jets, while the hard component is more likely associated to processes occurring in the circumstellar matter and/or near the compact object. Optical observations show that the object appears intrinsically red even during the outburst. The nature of the compact object is discussed.