Microquasars as high-energy gamma-ray sources

Galactic microquasars are certainly one of the most recent additions to the field of high energy astrophysics and have attracted increasing interest over the last decade. However, the high energy part of the spectrum of microquasars is the most poorly known, mainly due the lack of sensitive instrumentation in the past. Microquasars are now primary targets for all of the observatories working in the X-ray and gamma-ray domains. They also appear as the possible counterparts for some of the unidentified sources of high-energy gamma-rays detected by the experiment EGRET on board the satellite COMPTON-GRO. This paper provides a general review of the main observational results obtained up to now as well as a summary of the scenarios for production of high-energy gamma-rays at the present moment.Comment: Invited talk presented at the V Microquasar Workshop, Beijing, June 2004. Accepted for publication in the Chinese Journal of Astronomy and Astrophysics. 14 pages, 9 figure

High energy processes in microquasars

Microquasars are X-ray binary stars with the capability to generate relativisticjets. It is expected that microquasars are gamma-ray sources, because of the analogy with quasars and because the theoretical models predict emission at such energy range. In addition, from observational arguments, there are two microquasars that appear as the possible counterparts for two unidentified high-energy gamma-ray sources.Comment: Universitat de Barcelona, Departament d'Astronomia i Meteorologia, 12 pages, 5 figures. Invited talk presented at the International Symposium "High-Energy Gamma-Ray Astronomy", 26-30 July 2004, Heidelberg (Germany). To be published by AIP Proceedings Serie

Stellar radio astrophysics

Radio emission has been detected from all the stages of stellar evolution across the HR Diagram. Its presence reveals both astrophysical phenomena and stellar activity which, otherwise, would not be detectable by other means. The development of large, sensitive interferometers has allowed us to resolve the radio structure of several stellar systems, providing insights into the mass transfer process in close binary systems. I review the main characteristics of the radio emission from several kinds of stars, paying special attention to those cases where such an emission originates in relativistic jets.Comment: 20 pages, 6 figures. Talk presented at the JENAM-2003 Symposium, "Radio Astronomy at 70: from Karl Jansky to microjansky", Budapest, Hungary, 27-30 August 2003. To be published by EDP Sciences, eds. L. Gurvits, S. Frey, and S. Rawling

Detection of radio emission at mas scales from HESS J0632+057 with the e-EVN

HESS J0632+057 is a variable TeV gamma-ray source. The likely low energy counterparts of the source are XMMU J063259.3+054801, the B0pe-type star MWC 148, and a point-like probable non-thermal radio source

Gamma-ray binaries: microquasars and binary systems with pulsar

Several binary systems have been detected at High Energy (HE, E > 100 MeV) and/or Very High Energy (VHE, E > 100 GeV) gamma rays. Some of them are X-ray binaries in which accretion feeds relativistic radio jets and powers the non-thermal emission (i.e., microquasars), whereas in others the power comes from the wind of a young pulsar instead of accretion. Although the power mechanism in these systems is different (accretion vs pulsar wind), all of them are radio, X-ray and gamma-ray emitters, and have a high-mass bright companion (O or B) star that is a source of seed photons for IC scattering and target nuclei for hadronic interactions. I review here some of the main observational results on the non-thermal emission from X-ray binaries as well as some of the proposed scenarios to explain the production of gamma rays.Comment: Invited talk presented at the Workshop "SciNeGHE 2010", September 8-10, 2010, Trieste, Italy; 6 pages, 1 figure. To appear in Il Nuovo Cimento C - Colloquia on physic

AGNs and microquasars as high energy gamma-ray sources

The extragalactic analogs of the microquasars, the quasars, are strong gamma-ray emitters at GeV energies. It is expected that microquasars are also gamma-ray sources, because of the analogy with quasars and because theoretical models predict the high-energy emission. There are two microquasars that appear as the possible counterparts for two unidentified high-energy gamma-ray sources.Comment: 8 pages, 3 figures, to appear in From X-ray Binaries to Quasars: Black Hole Accretion on All Mass Scales, ed. T. J. Maccarone, R. P. Fender, and L. C. Ho (Dordrecht: Kluwer