Peculiar extended X-ray emission around the "radio-loud" black hole candidate 1E 1740.7-2942

We present the discovery of peculiar extended X-ray emission around 1E 1740.7-2942, a black hole candidate that is known to produce prominent, persistent radio jets. The data were obtained with the High-Energy Transmission Grating Spectrometer (HETGS) aboard the Chandra X-Ray Observatory. The zeroth-order image reveals an elongated feature about 3 " in length that is roughly perpendicular to the radio lobes (or jets). The feature is roughly symmetric about the point source. It is spatially resolved in the long direction but not in the short direction. Also, the position of 1E 1740.7-2942 was determined with a statistical accuracy of similar to0." 06 in the right ascension and in the declination, thanks to Chandra's unprecedented spatial resolution. It is about from the radio position, but the difference is well within the uncertainty in the absolute aspect solutions of the observation. The dispersed HETGS spectra of 1E 1740.7-2942 show evidence for the presence of weak, narrow emission lines, although the statistics are quite limited. We discuss possible origins of the extended emission and the implications of the emission lines.