X‐Ray Jet Emission from the Black Hole X‐Ray Binary XTE J1550−564 withChandrain 2000

We have discovered an X-ray jet due to material ejected from the black holeX-ray transient XTE J1550-564. The discovery was first reported by Corbel etal. (Science, 298, 196 and astro-ph/0210224), and here, we present an analysisof the three Chandra observations made between 2000 June and 2000 September.For these observations, a source is present that moves in an eastward directionaway from the point source associated with the compact object. The separationbetween the new source and the compact object changes from 21.3 arcseconds inJune to 23.4 arcseconds in September, implying a proper motion of 21.2 +/- 7.2mas/day, a projected separation of 0.31-0.85 pc and an apparent jet velocitybetween 0.34 +/- 0.12 and 0.93 +/- 0.32 times the speed of light for a sourcedistance range of d = 2.8-7.6 kpc. These observations represent the first timethat an X-ray jet proper motion measurement has been obtained for any accretionpowered Galactic or extra-galactic source. While this work deals with the jetto the east of the compact object, the western jet has also been detected inthe X-ray and radio bands. The most likely scenario is that the eastern jet isthe approaching jet and that the jet material was ejected from the black holein 1998. Along with a 1998 VLBI proper motion measurement, the Chandra propermotion indicates that the eastern jet decelerated between 1998 and 2000. Wepresent results on the morphology and energy spectrum of the jet. We cannotdefinitively determine the X-ray emission mechanism, but a synchrotron originis viable and may provide the simplest explanation for the observations.Comment: 10 pages, accepted by Ap