H.E.S.S observations of the microquasars Cir X-1, Cyg X-1 and 4U 1755-33

Abstract

A number of microquasars exhibit parsec-scale jets, which in some cases are known to interact with the interstellar medium (ISM). A famous example is the SS-433 system. Here, we summarise H.E.S.S. observations of three further examples in this category with arc-minute scale jets and/or jet/ISM interaction features. The small line-of-sight angle in the Cir X-l jet makes this source a potential 'microblazar'. An arc-minute bow-shock radio feature has been blown out by the Cyg X-1 jet, and the MAGIC telescope has also detected a VHE flare on 24 Sept. 2006 from Cyg X-1 (H.E.S.S. obs. were taken ∼1 month earlier). Persistent bi-lobal (∼7 arcmin long) 'fossil' jets of 4U1755-33 have been seen in X-rays. This report summarises our observations, searching for pointlike VHE emission at the central sources and for extended emission from their jets and/or jet/ISM interaction regions. © 2009 American Institute of Physics.