89 research outputs found
Cyclotron line formation in the magnetized atmospheres of compact stars: I. The transfer equations for polarized radiation
We find the forms of the transfer equations for polarized cyclotron radiation
in the atmospheres of compact stars, which are simple enough to allow practical
implementation and still preserve all important physical effects. We take into
account a frequency redistribution of radiation within the cyclotron line as
well as the relativistic and quantum-electrodynamic effects. Our analysis is
valid for the magnetic fields up to G and for temperatures well below
500keV.} We present and compare two forms of the radiation transfer equations.
The first form, for the intensities of ordinary and extraordinary modes, is
applicable for the compact stars with a moderate magnetic field strength up to
G for typical neutron star and up to G for magnetic white
dwarfs. The second form, for the Stokes parameters, is more complex, but
applicable even if a linear mode coupling takes place somewhere in the
scattering-dominated atmosphere. Analysing dispersion properties of a
magnetized plasma {in the latter case, we describe a range of parameters where
the linear mode coupling is possible and essential.Comment: 12 pages, 3 figures, MNRA
Off-axis emission from relativistic plasma flows
We show that there is no universal law describing how the spectra and
luminosity of synchrotron and inverse Compton radiation from relativistic jets
change with increasing observation angle. Instead, the physics of particle
acceleration leaves pronounced imprints in the observed spectra and allows for
a freedom in numerous modifications of them. The impact of these effects is the
largest for high-energy radiation and depends on the details of particle
acceleration mechanism(s), what can be used to discriminate between different
models. Generally, the beam patterns of relativistic jets in GeV-TeV spectral
domain are much wider than the inverse Lorentz factor. The off-axis emission in
this energy range appear to be brighter, have much harder spectra and a much
higher cut-off frequency compared to the values derived from Doppler boosting
considerations alone.
The implications include the possibility to explain high-latitude
unidentified EGRET sources as off-axis but otherwise typical relativistic-jet
sources, such as blazars, and the prediction of GeV-TeV afterglow from
transient jet sources, such as Gamma-Ray Bursts. We also discuss the phenomenon
of beam-pattern broadening in application to neutrino emission.Comment: Submitted to the Astrophysical Journa
High-energy emission from off-axis relativistic jets
We analyze how the spectrum of synchrotron and inverse Compton radiation from
a narrow relativistic jet changes with the observation angle. It is shown that
diversity of acceleration mechanisms (in particular, taking the converter
mechanism (Derishev et al. 2003) into account) allows for numerous
modifications of the observed spectrum. In general, the off-axis emission in
GeV-TeV energy range appears to be brighter, has a much harder spectrum and a
much higher cut-off frequency compared to the values derived from Doppler
boosting considerations alone. The magnitude of these effects depends on the
details of particle acceleration mechanisms, what can be used to discriminate
between different models.
One of the implications is the possibility to explain high-latitude
unidentified EGRET sources as off-axis but otherwise typical relativistic-jet
sources, such as blazars. We also discuss the broadening of beam pattern in
application to bright transient jet sources, such as Gamma-Ray Bursts.Comment: 6 pages, Proceedings of the International Symposium "High Energy
Gamma-Ray Astronomy", 26-30 July 2004, Heidelberg, German
Higher order correction to the neutrino self-energy in a medium and its astrophysical applications
We have calculated the 1/M^4 (M the vector boson mass) order correction to
the neutrino self-energy in a medium. The possible application of this higher
order contribution to the neutrino effective potential is considered in the
context of the Early Universe hot plasma and of the cosmological Gamma Ray
Burst fireball. We found that, depending on the medium parameters and on the
neutrino properties (mixing angle and mass square difference) the resonant
oscillation of active to active neutrinos is possible.Comment: 10 pages, revtex style, uses axodraw.sty, 1 figur
MeV-GeV emission from neutron-loaded short gamma-ray burst jets
Recent discovery of the afterglow emission from short gamma-ray bursts
suggests that binary neutron star or black hole-neutron star binary mergers are
the likely progenitors of these short bursts. The accretion of neutron star
material and its subsequent ejection by the central engine implies a
neutron-rich outflow. We consider here a neutron-rich relativistic jet model of
short bursts, and investigate the high energy neutrino and photon emission as
neutrons and protons decouple from each other. We find that upcoming neutrino
telescopes are unlikley to detect the 50 GeV neutrinos expected in this model.
For bursts at z~0.1, we find that GLAST and ground-based Cherenkov telescopes
should be able to detect prompt 100 MeV and 100 GeV photon signatures,
respectively, which may help test the neutron star merger progenitor
identification.Comment: 13 pages, 2 figures. 1 figure added, minor changes, ApJ accepte
The Ultraviolet flash accompanying GRBs from neutron-rich internal shocks
In the neutron-rich internal shocks model for Gamma-ray Burts (GRBs), the
Lorentz factors (LFs) of ions shells are variable, so are the LFs of
accompanying neutron shells. For slow neutron shells with a typical LF tens,
the typical beta-decay radius reads R_{\beta,s} several 10^{14} cm, which is
much larger than the typical internal shocks radius 10^{13} cm, so their impact
on the internal shocks may be unimportant. However, as GRBs last long enough
(T_{90}>20(1+z) s), one earlier but slower ejected neutron shell will be swept
successively by later ejected ion shells in the range 10^{13}-10^{15} cm, where
slow neutrons have decayed significantly. We show in this work that ion shells
interacting with the beta-decay products of slow neutron shells can power a
ultraviolet (UV) flash bright to 12th magnitude during the prompt gamma-ray
emission phase or slightly delayed, which can be detected by the upcoming
Satellite SWIFT in the near future.Comment: 6 pages (2 eps figures), accepted for publication in ApJ
- …