Title: New Black Hole X-ray Novae in the Glactic Halo


Proposal ID: 0120098
Subject category: Compact Object
Principal investigator: Mirabel
Institute: CEA/Saclay


Abstract

Black Holes (BH) in the thick disk and/or halo of the Milky Way galaxy appear sporadically as X-ray Novae with very hard spectra. The origin and nature of these objects is one of the most intriguing problems in high energy astrophysics. They could have been shot out from the galactic plane, or be pristine BHs formed in the Galactic Halo before the Milky Way disk. At galactic latitudes |b|>5 degrees BH X-ray Novae are likely to be close to the Sun, bright, optically unobscured, and the compact radio counterpart subject to low interstellar scattering. This will allow to: 1) probe the connection between accretion disk instabilities and the formation of relativistic jets in all wavelength bands, 2) know whether the radio, infrared, and optical non-thermal component and the gamma-ray events originate - as recently found in quasars - within the same shocked area downstream the relativistic jet, and 3) determine the space velocity of the binary centre of mass, and therefore know where these BHs come from. The recent discovery of XTEJ1118+48, which is 62 degrees off hte galactic plane, and had its peak at L(X) < 1e36 erg/s, rises the suspicion that we may have so far missed a large population of BHs in the galactic thick disk and/or the Milky Way disk. Furtehrmore, some of these accreting BHs in Low MAss Binaries could be micro-blazars and it is an open question their possbile relation to a subset of soft and variable unidentified EGRET sources that are spread at medium and high latitude, most assembled within 30 degrees from the galactic centre. We will perform Multiwavelength Target of Opportunity (ToO) observations, from space with INTEGRAL and HST and from ground with opt/IR/radio telescopes, of new BH X-ray Novae at |b| > 5 degrees (which at the galactic centre would correspond to a distance > 700 pc above the plane not subject to INTEGRAL Core Program ToO.