Microblazars should exist and be
found with the developement of new tools in astronomy.
Mirabel &
Rodríguez (1999)
proposed that for objects with angles between the
line of sight and the jet axis
10° one expects the
timescales to be shortened by
2
2
and the flux densities to be boosted by
83
with respect to the values in the rest frame
of the condensation. For instance, for motions with v = 0.98c
( = 5), the
time-scale will shorten by a factor of ~ 50 and
the flux densities will be boosted by a factor of ~ 103. Then,
for a galactic source with relativistic jets and small
we
expected fast and intense variations in the observed flux.
Microblazars are hard to detect in practice, both because of
the low probability of small
values and because of
the fast decline in the flux.
Recently, several flares were detected with Konus from a region that
contains Cygnus X-1
(Golenetskii et
al. 2002),
later confirmed with the BATSE data base as gamma-ray transients
(Schmidt, 2002).
These events have been interpreted
by Romero, Kaufman
Bernadó & Mirabel (2002)
in the context of the ideas of
Georganopoulos, Aharonian,
& Kirk (2002),
as non-thermal emission by inverse Compton interaction between
relativistic electrons in a precessing jet
and external photon fields, with a dominant contribution from the companion
star field
(Kaufman Bernadó,
Romero & Mirabel, 2002).
Another microblazar
could be V4641 Sgr, which exhibits outbursts with rapid optical variations
(Uemura et al. 2002)
and seems to be a source of jets with apparent speeds
10
(Orosz et al. 2001).
Paredes et al. (2000) found that the runaway persistent microquasar LS 5039 (Ribó et al. 2002) is inside the error box of the unidentified Egret source 3EG J1824-1514. In addition, a TeV source inside the core of the OB association Cygnus OB2 and at the edge of the 95% error circle of the EGRET source 3EG J2033+4118 has been reported by Aharonian et al (2002). No counterpart for the TeV source at other wavelengths has so far been identified, and one could envisage gamma -ray production via a jet-driven termination shock. Although most may be isolated neutron stars, a microquasar sub-population of EGRET sources is at this time a working hypothesis.
I point out that Cygnus X-1, V4641 Sgr, and LS 5039 are all three confirmed sources of relativistic jets in high mass X-ray binaries. In this class of sources the jets initially move inside the UV photon field of the massive donor stars and inverse Compton of the jets with the UV photons is unavoidable.
INTEGRAL and other space and ground based observatories for gamma-rays as well as km2 neutrino telescopes will in the next decade enhance the number of known microquasars providing unprecedented insights into the physics of high energy processes and phenomena in accreting stellar-mass black holes.