1,086 research outputs found
Extended GeV-TeV Emission around Gamma-Ray Burst Remnants, and the Case of W49B
We investigate the high-energy photon emission around Gamma-Ray Burst (GRB)
remnants caused by ultrahigh-energy cosmic rays (UHECRs) from the GRBs. We
apply the results to the recent report that the supernova remnant W49B is a GRB
remnant in our Galaxy. If this is correct, and if GRBs are sources of UHECRs, a
natural consequence of this identification would be a detectable TeV photon
emission around the GRB remnant. The imaging of the surrounding emission could
provide new constraints on the jet structure of the GRB.Comment: 12 pages, 2 figures, accepted for publication in ApJ
A Crazy Question: Can Apparently Brighter Gamma-ray Bursts Be Farther Away?
The cosmological relationships between observed and emitted quantities are determined for gamma-ray bursts (GRBs). The relationship shows that apparently fainter bursts need not, in general, lie at larger redshifts.This is possible when the luminosities (or emitted energies) in a sample of bursts increase faster than the dimming of the observed values with redshift. Four different samples of long bursts suggest that this is what really happens
Gamma-ray bursts: optical afterglows in the deep Newtonian phase
Gamma-ray burst remnants become trans-relativistic typically in days to tens
of days, and they enter the deep Newtonian phase in tens of days to months,
during which the majority of shock-accelerated electrons will no longer be
highly relativistic. However, a small portion of electrons are still
accelerated to ultra-relativistic speeds and capable of emitting synchrotron
radiation. The distribution function for electrons is re-derived here so that
synchrotron emission from these relativistic electrons can be calculated. Based
on the revised model, optical afterglows from both isotropic fireballs and
highly collimated jets are studied numerically, and compared to analytical
results. In the beamed cases, it is found that, in addition to the steepening
due to the edge effect and the lateral expansion effect, the light curves are
universally characterized by a flattening during the deep Newtonian phase.Comment: MNRAS in press (originally submitted in October 2002), 8 pages with 8
eps figures embedded, references update
Large scale magnetic fields and their dissipation in GRB fireballs
We consider possible geometries of magnetic fields in GRB outflows, and their
evolution with distance from the source. For magnetically driven outflows, with
an assumed ratio of magnetic to kinetic energy density of order unity, the
field strengths are sufficient for efficient production of gamma-rays by
synchrotron emission in the standard internal shock scenario, without the need
for local generation of small scale fields. In these conditions, the MHD
approximation is valid to large distances (>10^19cm). In outflows driven by
nonaxisymmetric magnetic fields, changes of direction of the field cause
dissipation of magnetic energy by reconnection. This dissipation takes place
outside the photosphere of the outflow, and can convert a significant fraction
of the magnetic energy flux into radiation.Comment: 12 pages including 3 figures, submitted to A&
Fungal diversity in floral and honeydew honeys
Studying fungal diversity in various environmental samples provides us with valuable knowledge about the occurrence of fungi of medical and ecological importance. Moreover, fungal composition may also characterise well the botanical and geographical source of food products, such as the origin of the spore enriched honeydew honeys. Thereby, we identified a wide spectrum of fungi found in 100 of honey samples from various geographical sources â most of them were from Italy, Greece and Hungary. Our honeydew honeys had a higher mean of the number of spore types found in them than floral honeys had. Statistically significant differences in diversity were found regarding the botanical source (p = 1.29 Ă 10â9) and the climatic classification (p = 2.28 Ă 10â2) according to Kruskalâ Wallis rank sum tests. Most frequently encountered genera included ubiquitous saprotrophic species (Alternaria, Cladosporium, Epicoccum nigrum, Stemphylium), both in floral and honeydew honeys. On the other hand, certain sooty moulds like Aureobasidium pullulans, Tripospermum and Capnobotrys were rather present in different types of honeydew honeys. Metschnikowia reukaufii, the nectar inhabiting yeast reached considerably high quantities in floral honey samples. Present findings encourage further studies on quantifying the occurrence and the indicator value of specific fungal elements in honey, concerning its origin
On the detectability of gravitational waves background produced by gamma ray bursts
In this paper we discuss a new strategy for the detection of gravitational
radiation likely emitted by cosmological gamma ray burst. Robust and
conservative estimates lead to the conclusion that the uncorrelated
superimposition of bursts of gravitational waves can be detected by
interferometric detectors like VIRGO or LIGO. The expected signal is predicted
to carry two very distinctive signatures: the cosmological dipole anisotropy
and a characteristic time scale in the auto correlation spectrum, which might
be exploited, perhaps with ad hoc modifications and/or upgrading of the planned
experiments, to confirm the non-instrumental origin of the signal.Comment: 9 pages, 2 figures, LATEX2e, Accepted for pubblications as a Letter
to the Editor in Journal of Physics G: Nuclear and Particle Physic
A hagyomĂĄnyos kĂnai orvoslĂĄs magyarorszĂĄgi szabalyozĂĄsĂĄnak egyes problĂ©mĂĄi Ă©s lehetsĂ©ges megoldĂĄsai az EgyesĂŒlt KirĂĄlysĂĄg pĂ©ldĂĄjĂĄn keresztĂŒl
This paper aims to present factual information and to suggest possible solutions regarding some of the recent questions which have arisen regarding the regulation of traditional Chinese medicine in Hungary. According to current legislation "traditional Chinese doctors", who are the most highly trained professionals in this field, are not allowed to practice Chinese medicine and acupuncture in Hungary. This situation cannot be explained by their educational background, as they receive thorough training in both Chinese medicine and modern medical sciences. Furthermore, this legislation is not supported by any EU standard: Traditional Chinese medicine professionals can practice Chinese medicine and acupuncture in a number of European countries within a legal and regulated framework. Different kinds of healthcare professionals may practice Chinese medicine and acupuncture in the UK - this could be a good example for Hungarian regulation. The five-year bachelor level traditional Chinese medicine training at the Faculty of Health Sciences, Semmelweis University and the increasing number of locally trained traditional Chinese medicine professionals could be a good basis for laying the groundwork of the new system. Orv., Hetil., 2014, 155(15), 575-581
TeV Neutrinos from Successful and Choked Gamma-Ray Bursts
Core collapse of massive stars resulting in a relativistic fireball jet which
breaks through the stellar envelope is a widely discussed scenario for
gamma-ray burst production. For very extended or slow rotating stars, the
fireball may be unable to break through the envelope. Both penetrating and
choked jets will produce, by photo-meson interactions of accelerated protons, a
burst of neutrinos with energies in excess of 5 TeV while propagating in the
envelope. The predicted flux, from both penetrating and chocked fireballs,
should be easily detectable by planned cubic kilometer neutrino telescopes.Comment: Phys.Rev.Letters, in press, final version accepted 8/31/01 (orig.
3/17/01
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