11,100 research outputs found
Leptonic emission from microquasar jets: from radio to very high-energy gamma-rays
Microquasars are sources of very high-energy gamma-rays and, very probably,
high-energy gamma-ray emitters. We propose a model for a jet that can allow to
give accurate observational predictions for jet emission at different energies
and provide with physical information of the object using multiwavelength data.Comment: 2 pages, 1 figure. Proceedings of the conference: "International
Astronomical Union Symposium No. 230: Populations of High Energy Sources in
Galaxies". Edited by Evert J.A. Meurs & Giuseppina Fabbian
Extreme intranight variability in the BL Lacertae object AO 0235+164
We present results of two-colour photometry with high time resolution of the
violently variable BL Lac object AO 0235+164. We have found extreme intranight
variability with amplitudes of ~ 100 % over time scales of 24 hours. Changes of
0.5 magnitudes in both R and V bands were measured within a single night, and
variations up to 1.2 magnitudes occurred from night to night. A complete
outburst with an amplitude ~ 30 % was observed during one of the nights, while
the spectrum remained unchanged. This seems to support an origin based on a
thin relativistic shock propagating in such a way that it changes the viewing
angle, as recently suggested by Kraus et al. (1999) and Qian et al. (2000).Comment: 4 pages, 3 figures, to appear in Astronomy & Astrophysics (Letters
Parity-dependent State Engineering and Tomography in the ultrastrong coupling regime
Reaching the strong coupling regime of light-matter interaction has led to an
impressive development in fundamental quantum physics and applications to
quantum information processing. Latests advances in different quantum
technologies, like superconducting circuits or semiconductor quantum wells,
show that the ultrastrong coupling regime (USC) can also be achieved, where
novel physical phenomena and potential computational benefits have been
predicted. Nevertheless, the lack of effective decoupling mechanism in this
regime has so far hindered control and measurement processes. Here, we propose
a method based on parity symmetry conservation that allows for the generation
and reconstruction of arbitrary states in the ultrastrong coupling regime of
light-matter interactions. Our protocol requires minimal external resources by
making use of the coupling between the USC system and an ancillary two-level
quantum system.Comment: Improved version. 9 pages, 5 figure
Recurrent microblazar activity in Cygnus X-1?
Recurrent flaring events at X- and soft gamma-ray energies have been recently
reported for the galactic black hole candidate Cygnus X-1. The observed fluxes
during these transient outbursts are far higher than what is observed in
``normal'' episodes. Here we suggest that the origin of this radiation is
non-thermal and produced by inverse Compton interactions between relativistic
electrons in the jet and external photon fields, with a dominant contribution
from the companion star field. The recurrent and relatively rapid variability
could be explained by the precession of the jet, which results in a variable
Doppler amplification.Comment: 4 pages, 5 figures, Accepted for publication in Astronomy &
Astrophysics Letter
Nonthermal processes and neutrino emission from the black hole GRO J0422+32 in a bursting state
GRO J0422+32 is a member of the class of low-mass X-ray binaries (LMXBs). It
was discovered during an outburst in 1992. During the entire episode a
persistent power-law spectral component extending up to MeV was
observed, which suggests that nonthermal processes should have occurred in the
system. We study relativistic particle interactions and the neutrino production
in the corona of GRO J0422+32, and explain the behavior of GRO J0422+32 during
its recorded flaring phase. We have developed a magnetized corona model to fit
the spectrum of GRO J0422+32 during the low-hard state. We also estimate
neutrino emission and study the detectability of neutrinos with 1 km
detectors, such as IceCube. The short duration of the flares ( hours) and
an energy cutoff around a few TeV in the neutrino spectrum make neutrino
detection difficult. There are, however, many factors that can enhance neutrino
emission. The northern-sky coverage and full duty cycle of IceCube make it
possible to detect neutrino bursts from objects of this kind through
time-dependent analysis.Comment: 12 pages, 11 figures, accepted for publication in A&
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