64 research outputs found
Could a multi-PeV neutrino event have as origin the internal shocks inside the GRB progenitor star?
The IceCube Collaboration initially reported the detection of 37
extraterrestrial neutrinos in the TeV - PeV energy range. The reconstructed
neutrino events were obtained during three consecutive years of data taking,
from 2010 to 2013. Although these events have been discussed to have an
extragalactic origin, they have not been correlated to any known source.
Recently, the IceCube Collaboration reported a neutrino-induced muon event with
energy of PeV which corresponds to the highest event ever detected.
Neither the reconstructed direction of this event (J2000.0), detected on June
11 2014 at R.A.=110.34, Dec.=11.48 matches with any familiar
source. Long gamma-ray bursts (lGRBs) are usually associated with the core
collapse of massive stars leading relativistic-collimated jets inside stars
with high-energy neutrino production. These neutrinos have been linked to the
37 events previously detected by IceCube experiment. In this work, we explore
the conditions and values of parameters so that the highest neutrino recently
detected could be generated by proton-photon and proton-hadron interactions at
internal shocks inside lGRB progenitor star and then detected in IceCube
experiment. Considering that internal shocks take place in a relativistic
collimated jet, whose (half) opening angle is 0.1, we found that
lGRBs with total luminosity erg/s and internal shocks on
the surface of progenitors such as Wolf-Rayet (WR) and blue super giant (BSG)
stars favor this multi-PeV neutrino production, although this neutrino could be
associated to () erg/s provided that the
internal shocks occur at () cm for a WR (BSG).Comment: 12 pages, 8 figures. JHEAp, accepted. References were added, typos
were corrected and the subsection "particle acceleration process" was
include
Gamma-ray fluxes from the core emission of Centaurus A: A puzzle solved
A high-energy component in the radio galaxy Centaurus A was reported after
analyzing four years of Fermi data. The spectrum of this component is described
by means of a broken power law with a break energy of 4 GeV and, below and
above spectral indices of =2.740.03 and
=2.090.20, respectively. Also a faint -ray flux at TeV
energies was detected by H.E.S.S.. In this paper we show that the spectrum at
GeV-TeV energies is described through synchrotron self-Compton emission up to a
few GeV ( 4 GeV) and decay products up to TeV energies, although
the emission of synchrotron radiation by muons could contribute to the spectrum
at GeV energies, if they are rapidly accelerated. Muons and s are
generated in the interactions of accelerated protons with two populations of
seed photons which were reported by Compton Gamma-Ray Observatory: one
population at intermediate state emission with energy peak of 0.15 MeV and
another at low state emission with energy peak of 0.59 MeV. In addition, we
show that the reported observations of ultra-high-energy cosmic rays and non
high-energy neutrino detection around Centaurus A can be explained through
these interactions, assuming that proton spectrum is extended up to
ultra-high-energies.Comment: MNRAS, accepte
Propagation and neutrino oscillations in the base of a highly magnetized gamma-ray burst fireball flow
Neutrons play an important role in the dynamics of gamma-ray bursts. The
presence of neutrons in the baryon-loaded fireball is expected. If the neutrons
abundance is comparable to that of protons, important features may be observed
such as quasi-thermal multi-GeV neutrinos in coincidence with a subphotospheric
-ray emission, nucleosynthesis at later times and rebrightening of the
afterglow emission. Additionally, thermal MeV neutrinos are created by
electron-positron annihilation, electron (positron) capture on protons
(neutrons) and nucleonic bremsstrahlung. Although MeV neutrinos are difficult
to detect, quasi-thermal GeV neutrinos are expected in km detectors and/or
DeepCore+IceCube. In this paper, we show that neutrino oscillations have
outstanding implications for the dynamics of the fireball evolution and also
that they can be detected through their flavor ratio on Earth. For that we
derive the resonance and charged-neutrality conditions as well as the neutrino
self-energy and effective potential up to order at strong, moderate
and weak magnetic field approximation to constrain the dynamics of the
fireball. We found important implications: i) resonant oscillations are
suppressed for high baryon densities as well as neutrons abundance larger than
that of protons and ii) the effect of magnetic field is to decrease the
proton-to-neutron ratio aside from the number of multi-GeV neutrinos expected
in DeepCore detector. Also we estimate the GeV neutrino flavor ratios along the
jet and on Earth.Comment: ApJ, accepted. There was not changes with respect to the previous
versio
Could a plasma in quasi-thermal equilibrium be associated to the "orphan" TeV flares ?
TeV -ray detections in flaring states without activity in X-rays from
blazars have attracted much attention due to the irregularity of these "orphan"
flares. Although the synchrotron self-Compton model has been very successful in
explaining the spectral energy distribution and spectral variability of these
sources, it has not been able to describe these atypical flaring events. On the
other hand, an electron-positron pair plasma at the base of the AGN jet was
proposed as the mechanism of bulk acceleration of relativistic outflows. This
plasma in quasi-themal equilibrium called Wein fireball emits radiation at
MeV-peak energies serving as target of accelerated protons. In this work we
describe the "orphan" TeV flares presented in blazars 1ES 1959+650 and Mrk421
assuming geometrical considerations in the jet and evoking the interactions of
Fermi-accelerated protons and MeV-peak target photons coming from the Wein
fireball. After describing successfully these "orphan" TeV flares, we correlate
the TeV -ray, neutrino and UHECR fluxes through p interactions
and calculate the number of high-energy neutrinos and UHECRs expected in
IceCube/AMANDA and TA experiment, respectively. In addition, thermal MeV
neutrinos produced mainly through electron-positron annihilation at the Wein
fireball will be able to propagate through it. By considering two- (solar,
atmospheric and accelerator parameters) and three-neutrino mixing, we study the
resonant oscillations and estimate the neutrino flavor ratios as well as the
number of thermal neutrinos expected on Earth.Comment: Accepted for publication in Astroparticle Physics (31 pages, 14
figures
GRB 110731A: Early afterglow in stellar wind powered by a magnetized outflow
One of the most energetic gamma-ray burst GRB 110731A was observed from
optical to GeV energy range. Previous analysis on the prompt phase revealed
similarities with the Large Area Telescope (LAT) bursts observed by Fermi: i) a
delayed onset of the high-energy emission ( MeV), ii) a short-lasting
bright peak at later times and iii) a temporally extended component from this
phase and lasting hundreds of seconds. Additionally to the prompt phase,
multiwavelength observations over different epochs showed that the spectral
energy distribution was better fitted by a wind afterglow model. We present a
leptonic model based on an early afterglow that evolves in a stellar wind of
its progenitor. We apply this model to interpret the temporally extended LAT
emission and the brightest LAT peak exhibited by the prompt phase of GRB
110731A. Additionally, using the same set of parameters, we describe the
multiwavelength afterglow observations. The origin of the temporally extended
LAT, X-ray and optical flux is explained through synchrotron radiation from the
forward shock and the brightest LAT peak is described evoking the synchrotron
self-Compton emission from the reverse shock. The bulk Lorentz factor required
in this model () lies in the range of values demanded for most
LAT-detected gamma-ray bursts. We show that the strength of the magnetic field
in the reverse-shock region is 50 times stronger than in the
forward-shock region. This result suggests that for GRB 110731A, the central
engine is likely entrained with strong magnetic fields.Comment: Accepted in ApJ (13 Pages, 4 figures
Resonant oscillations of GeV - TeV neutrinos in internal shocks from gamma-ray burst jets inside the stars
High-energy neutrinos generated in collimated jets inside the progenitors of
gamma-ray bursts (GRBs) have been related with the events detected by IceCube.
These neutrinos, produced by hadronic interactions of Fermi-accelerated protons
with thermal photons and hadrons in internal shocks, are the only signature
when jet has not broken out or failed. Taking into account that the photon
field is thermalized at keV energies and the standard assumption that the
magnetic field maintains a steady value throughout the shock region (with a
width of cm in the observed frame), we study the effect of
thermal and magnetized plasma generated in internal shocks on the neutrino
oscillations. We calculate the neutrino effective potential generated by this
plasma, the effects of the envelope of the star, and the vacuum on the path to
Earth. By considering these three effects, the two (solar, atmospheric and
accelerator parameters) and three neutrino mixing, we show that although GeV -
TeV neutrinos can oscillate resonantly from one flavor to another, a
nonsignificant deviation of the standard flavor ratio (1:1:1) could be expected
on Earth.Comment: Accepted in MNRAS (17 Pages, 12 figures
Neutrino, -ray and cosmic ray fluxes from the core of the closest radio galaxies
The closest radio galaxies; Centaurus A, M87 and NGC 1275, have been detected
from radio wavelengths to TeV -rays, and also studied as high-energy
neutrino and ultra-high-energy cosmic ray potential emitters. Their spectral
energy distributions show a double-peak feature, which is explained by
synchrotron self-Compton model. However, TeV -ray measured spectra
could suggest that very-high-energy -rays might have a hadronic origin.
We introduce a lepto-hadronic model to describe the broadband spectral energy
distribution; from radio to sub GeV photons as synchrotron self-Compton
emission and TeV -ray photons as neutral pion decay resulting from
p interactions occurring close to the core. These photo-hadronic
interactions take place when Fermi-accelerated protons interact with the seed
photons around synchrotron self-Compton peaks. Obtaining a good description of
the TeV -ray fluxes, firstly, we compute neutrino fluxes and events
expected in IceCube detector and secondly, we estimate ultra-high-energy cosmic
ray fluxes and event rate expected in Telescope Array, Pierre Auger and HiRes
observatories. Within this scenario we show that the expected high-energy
neutrinos cannot explain the astrophysical flux observed by IceCube, and the
connection with ultra-high-energy cosmic rays observed by Auger experiment
around Centaurus A, might be possible only considering a heavy nuclei
composition in the observed events.Comment: 16 pages and 7 figures. Accepted for publication in Ap
Neutrino Oscillation from Magnetized Strange Stars
Strange-quark matter (SQM) is a likely candidate of the ground state of
nuclear matter. Along with many other equations of state (EoSs), SQM seemed to
be severely constrained by the recent discoveries of the 1.97 PSR
J1614-2230 and the 2.01 PSR J0348+0432. However with new,
, perturbative calculations, SQM seems to be able to accommodate
masses as large as . The literature of SQM stars or strange
stars includes estimates of internal magnetic fields as large as G,
which are unlikely to be formed as they would require erg to be
produced. Nonetheless, if strange stars may hold magnetar-strength fields
( G), their internal fields are likely to reach magnetic fields as
large as G. We consider neutrinos with energies of some MeV and
oscillation parameters from solar, atmospheric and accelerator experiments. We
study the possibility of resonant oscillation of neutrinos in strange stars.Comment: 5 pages, 2 figures. To appear in Magnetic Fields in the Universe IV
(2013
Hypercritical accretion phase and neutrino expectation in the evolution of Cassiopeia A
Cassiopeia A the youngest supernova remnant known in the Milky Way is one of
the brightest radio sources in the sky and a unique laboratory for supernova
physics. Although its compact remnant was discovered in 1999 by the Chandra
X-Ray Observatory, nowadays it is widely accepted that a neutron star lies in
the center of this supernova remnant. In addition, new observations suggest
that such neutron star with a low magnetic field and evidence of a carbon
atmosphere could have suffered a hypercritical accretion phase seconds after
the explosion. Considering this hypercritical accretion episode, we compute the
neutrino cooling effect, the number of events and neutrino flavor ratios
expected on Hyper-Kamiokande Experiment. The neutrino cooling effect (the
emissivity and luminosity of neutrinos) is obtained through numerical
simulations performed in a customized version of the FLASH code. Based on these
simulations, we forecast that the number of events expected on the
Hyper-Kamiokande Experiment is around 3195. Similarly, we estimate the neutrino
flavor ratios to be detected considering the neutrino effective potential due
to the thermal and magnetized plasma and thanks to the envelope of the star. It
is worth noting that our estimates correspond to the only trustworthy method
for verifying the hypercritical phase and although this episode took place 330
years ago, at present supernova remnants with these similarities might occur
thus confirming our predictions for this phase.Comment: Accepted for publication in MNRAS (14 pages, 6 figures
Neutrino Oscillation from Hidden GRB Jets
Collapsars are the likely progenitors of Long Gamma-Ray Burst (lGRBs). lGRBs
have been observed to last for thousands to tens of thousands of seconds, thus
making unlikely the neutrino-driven engine as the main mechanism for driving
the jets. In this context, the Blandford-Znajek mechanism seems likely to
explain the production of rotational-axis directed jets without the need for
large accretion rates. These engines, require magnetic fields between
G G threading the innerdisk, Kerr-BH region to exist. We derive
the neutrino self-energy and the effective potential up to O(1/) in a
weakly and highly magnetized GRB fireball flow which is made up of electrons,
protons, neutrons and their anti-particles. We consider neutrino energies of
1-100 MeV which are produced during stellar collapse, merger events or in the
fireball itself by electron-positron annihilation, inverse beta decay and
nucleonic bremsstrahlung processes. Many of these neutrinos propagate through
the fireball and may oscillate resonantly. Using two-neutrino mixing we study
the possibility of these oscillations.Comment: 5 pages, 2 figures, To appear in MAGNETIC FIELDS IN THE UNIVERSE 4
(2013). arXiv admin note: text overlap with arXiv:1401.378
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