700 research outputs found
Gamma rays from Nebulae around Recurrent Novae
Novae were discovered to emit transient gamma rays during the period of
several days to a few weeks after initial explosion, indicating presence of
acceleration processes of particles in their expanding shells. In the case of
recurrent novae, electrons can be in principle accelerated in the nova shells
for the whole recurrence period of nova producing delayed ray emission
as considered in Bednarek (2022). Here we extend the ideas presented in this
article by considering the fate of electrons which diffuse out of the shells of
novae supplying fresh relativistic electrons to the recurrent nova
super-remnants during the whole active period of nova ( yrs). We
develop a model for the acceleration of electrons and their escape from the
nova shells. The electrons within the recurrent nova super-remnants produce
rays in the comptonization process of the radiation from the red giant
companion and the Cosmic Microwave Background Radiation. As an example, the
case of a symbiotic nova RS Oph (with the recurrence period estimated on
10-50 yrs) is considered in more detail. Predicted -ray emission
from the nova super-remnant around RS Oph is discussed in the context of its
observability by satellite experiments (i.e. Fermi-LAT) as well as current and
future Cherenkov telescopes.Comment: 17 pages, 9 figures, Journal of High Energy Astrophysics, accepte
Geomagnetic field and altitude effects on the performance of future IACT arrays
The performance of IACT's arrays is sensitive to the altitude and geomagnetic
field (GF) of the observatory site. Both effects play important role in the
region of the sub-TeV gamma-ray measurements. We investigate the influence of
GF on detection rates and the energy thresholds for five possible locations of
the future CTA observatory using the Monte Carlo simulations. We conclude that
the detection rates of gamma rays and the energy thresholds of the arrays can
be fitted with linear functions of the altitude and the component of the GF
perpendicular to the shower axis core. These results can be directly
extrapolated for any possible localization of the CTA. In this paper we also
show the influence of both geophysical effects on the images of shower and
gamma/hadron separation.Comment: 4 pages, 6 figures, two-column. Contribution to ICRC 2013 proceeding
Time dependent gamma-ray production in the anisotropic IC pair cascade initiated by electrons in active galaxies
New high energy emission features have been recently discovered by the
Cherenkov telescopes from active galaxies e.g., a few minutes variability time
scale of TeV emission from Mrk 501 and PKS 2155-304, sub-TeV -ray
emission from GeV peaked blazar 3C 279, and TeV emission from two nearby active
galaxies, M87 and Cen A, which jets are inclined at a relatively large angle to
the line of sight. These results have put a new light on the high energy
processes occurring in central parts of active galaxies stimulating more
detailed studies of -ray emission models. Here we report the results of
a detailed analysis concerning the most general version of the model for the
-ray production by leptons injected in the jet which interact with the
thermal radiation from an accretion disk (the so called {\it external inverse
Compton model}). We investigate the -ray spectra produced in an
anisotropic Inverse Compton (IC) pair cascade in the whole volume above
the accretion disk. The cascade -ray spectra are obtained for different
locations of the observer in respect to the direction of the jet. We also study
the time evolution of this -ray emission caused by the propagation of
the relativistic leptons along the jet and the delays resulting from different
places of the origin of -rays above the accretion disk. We discuss the
main features of such a cascade model assuming constant injection rate of
electrons along the jet. We are investigating two models for their different
maximum energies: constant value independent on the distance along the jet or
limited by the synchrotron energy losses considered locally in the jet. The
model is discussed in the context of blazars observed at small and large
inclination angles taking as an example the parameters of the two famous
sources Cen A and 3C 279.Comment: 16 pages, 18 figures, accepted for publication in MNRA
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