Galactic Gamma-ray Bursts Research Articles

New Approach to the Breaking of Space Symmetry in the Masses Spectrum Problem in the Aspect of Spontaneous Breaking of Space Symmetry

It is examined some analogy between properties of hypernucleus and supernucleus with properties of elementary particles and resonances electroproduction by spin shock-waves in ions beams. The serial theory considered processes of hypernucleus and supernucleus electroproduction for medium nuclei is complicated given the collective effects. All these calculations can be done in the t-channel reactions of hypernucleus and supernucleus electroproduction. So when deep inelastic scattering of leptons on a deuteron main contribution in the t-channel give the triangular diagram of anomalous Landau poles below of the two nucleon production threshold, containing in addition to nucleons and the particles insertion per a nucleon lines. Their admixture in the scattering cross-section is known, is low and the contribution of these charts in the scattering amplitude does not exceed 1%. The properties of the deuteron vertex demonstrate that hypernucleus electroproduction not only Δ⁺, but also all other particles of this set in two nucleon systems are small. A similar approach in the t-channel has been developed and for heavy particles and resonances. In all cases, in particular for a deuteron and helium-3, a deviation of a parameter “a” as the masses ratio froma_x=0.412 accompanied by the suppression of contribution of the triangular anomalous Landau charts and as a consequence to a regarding smaller hypernucleus and supernucleus electroproduction. In the field of high-energy was studied formation of Galactic spin shock-waves. In all cases above 20° Galactic longitude intensity of diffuse gamma radiation quickly subsides, so that the theory of Eight spin model profile compared with the intensity of Galactic diffuse gamma radiation from large gamma-ray space telescope (GLAST) is an experimental distribution of diffuse Galactic Gamma-ray bursts very accurately, in all range of the Galactic longitude within the accuracy of measurements in the presence of extra-galactic sources, Sails, etc. All of this confirms the conservation low of the spin angular momentum, as a part of a full and the isotropy of space-time across the Galaxy.

Possible role of gamma ray bursts on life extinction in the universe.

As a copious source of gamma rays, a nearby galactic gamma ray burst (GRB) can be a threat to life. Using recent determinations of the rate of GRBs, their luminosity function, and properties of their host galaxies, we estimate the probability that a life-threatening (lethal) GRB would take place. Amongst the different kinds of GRBs, long ones are most dangerous. There is a very good chance (but no certainty) that at least one lethal GRB took place during the past 5 gigayears close enough to Earth as to significantly damage life. There is a 50% chance that such a lethal GRB took place during the last 500×10^{6} years, causing one of the major mass extinction events. Assuming that a similar level of radiation would be lethal to life on other exoplanets hosting life, we explore the potential effects of GRBs to life elsewhere in the Galaxy and the Universe. We find that the probability of a lethal GRB is much larger in the inner MilkyWay (95% within a radius of 4kpc from the galactic center), making it inhospitable to life. Only at the outskirts of the MilkyWay, at more than 10kpc from the galactic center, does this probability drop below 50%. When considering the Universe as a whole, the safest environments for life (similar to the one on Earth) are the lowest density regions in the outskirts of large galaxies, and life can exist in only ≈10% of galaxies. Remarkably, a cosmological constant is essential for such systems to exist. Furthermore, because of both the higher GRB rate and galaxies being smaller, life as it exists on Earth could not take place at z>0.5. Early life forms must have been much more resilient to radiation.

“Isotopic footprints” of gamma-ray and proton events and anomalous signal in radiocarbon in 775 AD

The production of the cosmogenic radionuclides 14C, 10Be, and 36Cl in the Earth’s atmosphere under the action of powerful impulsive proton and gamma-ray events (superpowerful solar flares and Galactic gamma-ray bursts) is considered. The possible “isotopic footprint” in natural archives (the concentrations of these isotopes in dated polar ice cores and annual tree rings) has been calculated by taking into account geophysical processes. The results obtained have been applied to analyzing the anomalous increase in the concentration of radiocarbon measured in tree rings dated 774–775 AD. Arguments for the fact that the most likely cause of this increase is the high-energy emission from a Galactic gamma-ray burst are adduced.

AD 775 pulse of cosmogenic radionuclides production as imprint of a Galactic gamma-ray burst

We suggest an explanation of a sharp increase in the abundance of cosmogenic radiocarbon found in tree rings dated AD 775. The increase could originate from high-energy irradiation of the atmosphere by a galactic gamma-ray burst. We argue that, unlike a cosmic ray event, a gamma-ray burst does not necessarily result in a substantial increase in long-lived 10Be atmospheric production. At the same time, the 36Cl nuclide would be generated in the amounts detectable in the corresponding ice core samples from Greenland and Antarctica. These peculiar features allow experimental discrimination of nuclide effects caused by gamma-ray bursts and by powerful proton events.

Gamma-ray bursts and the production of cosmogenic radionuclides in the Earth’s atmosphere

An explanation is offered for the impulsive increase in the concentration of cosmogenic radiocarbon in annual tree rings (Δ14C ∼ 12‰) from AD ≃775. A possible cause of such an increase could be the high-energy emission from a Galactic gamma-ray burst. It is shown that such an event should not lead to an increase in the total production of 10Be in the atmosphere, as distinct from the effect of cosmic-ray fluxes on the atmosphere. At the same time, the production of an appreciable amount of 36Cl, which can be detected in Greenland and Antarctica ice samples of the corresponding age, should be expected. This allows the effects caused by a gamma-ray burst and anomalously powerful proton events to be distinguished.

EFFECTS OF GALACTIC GAMMA RAY BURSTS ON PLANETARY BIOSPHERES

We examine the short-term effects that a galactic Gamma Ray Burst would cause on a planetary biosphere. The immediate environmental perturbation would arise due to the emission of an aurora like spectrum in the middle and low atmosphere, delivering at planet's surface a brief but intense ultraviolet flash. We calculated potential damages to both the photosynthetic and DNA apparatuses of unicellular organisms. We conclude that if the progenitor is 1-2 kiloparsec distant in the Milky Way, its main short-term bio-effect will be radiation damage in the photosynthetic machinery rather than in the genome.

EFFECTS OF GALACTIC GAMMA RAYS BURSTS ON PLANETARY ATMOSPHERES

We discuss the potential past incidence of a galactic gamma ray burst on Earth. Rough estimates for the relative frequencies of this kind of event are given, for the different eons of our planet's geological history. Additionally, we explore the effectiveness of the ozone layer of different paleo-atmospheres to shield the surface of the planet from the ultraviolet flash, which arises as a short-term effect after the incidence of a galactic gamma ray burst.

Diffusive and Shock-Drift Acceleration in Relativistic Shocks

It is accepted that the shock acceleration mechanism can explain the non-thermal cosmic rays in supernova remnants, active galactic nuclei and gamma ray bursts. Especially, the importance of relativistic shock acceleration of cosmic rays in extragalactic sources is an important subject of study. In this work we will discuss the shock acceleration mechanism and will review the properties of non-relativistic and relativistic shocks, particularly focusing on relativistic Monte Carlo simulation studies.

Status and results of the IceCube experiment

IceCube is a 1 km 3 scale detector, deployed in the Antarctic ice, aimed at observing high-energy neutrinos from extraterrestrial sources. Currently, 79 strings of photomultipliers are installed between 1500 m and 2500 m below the ice surface. Completion is planned for January 2011, with a total of 86 strings. Neutrinos above 100 GeV are already being detected, so far identified as atmospheric neutrinos, generated in the interaction of cosmic rays with molecules in the atmosphere. One if the central goals of IceCube is the identification of sources of cosmic rays: when neutrinos are produced in proton-photon or proton-proton interactions in a cosmic ray source, the neutrinos carry unique information about the sources and source region, as they travel straight from the production region to the detection region. Cosmic rays do not provide this information, since they are deflected and scrambled by cosmic magnetic fields. In this talk, the status of the IceCube experiment will be presented. Further, the prospects of IceCube detecting extragalactic sources like supernova remnants, Active Galactic Nuclei and gamma-ray bursts will be reviewed.

Lorentz invariance under scrutiny of recent high-energy gamma-ray observations

The postulate that all observers measure the same speed of light in vacuum leads to one of the fundamental consequences of the so far very successful Theory of Relativity: Lorentz invariance. However, at and below the so-called Planck scale, the fundamental scale where quantum gravity effects may affect the nature of spacetime, some quantum gravity scenarios allow for the violation of Lorentz invariance, and the photon's speed may become dependent on its energy. Under a phenomenological approach one of the key tests is to register the arrival times of (presumably) simultaneously emitted photons from very distant astrophysical sources such as Active Galactic Nuclei (AGN) and Gamma-Ray Bursts (GRBs). Here, tiny variations in photon speed accumulated over cosmological distances, may amplify into observable quantities. I will discuss a summary of recent gamma-ray observations of such sources, both from ground based (Air Cherenkov Telescopes) as well as space based (Fermi Gamma-Ray Space Telescope) observatories that are found constraining for the violation of Lorentz invariance.

LIMITS TO THE PHYSICAL PARAMETERS IN EXTRAGALACTIC GAMMA-RAY SOURCES

We examine several constraints on the physical parameters in active galactic nuclei and gamma-ray burst, originating from the assumption that these sources are efficient in converting their energy into gamma-rays. It is shown that in most cases these constraints may be reformulated in terms of bounds on the jet Lorentz factor, for which both the lower and the upper limits can be evaluated.

PARTICLE ACCELERATION, MAGNETIC FIELD GENERATION, AND ASSOCIATED EMISSION IN COLLISIONLESS RELATIVISTIC JETS

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations using injected relativistic electron-ion (electron-positron) jets show that acceleration occurs within the downstream jet. Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electrons' transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties to synchrotron radiation which assumes a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

A NEW MECHANISM FOR PARTICLE ACCELERATION IN RELATIVISTIC JETS

We compare different acceleration mechanisms in application to relativistic jets and show that the converter mechanism, suggested recently, is the least sensitive to the geometry of the magnetic field in accelerators, and can routinely operate up to cosmic-ray energies close to the fundamental limit. The converter mechanism utilizes multiple conversions of charged particles into neutral ones (protons to neutrons and electrons/positrons to photons) and back by means of photon-induced reactions or inelastic nucleon-nucleon collisions. It works efficiently both in relativistic shocks and in shear flows under the conditions typical for active galactic nuclei, gamma-ray bursts, and microquasars, where it often outperforms the standard diffusive shock acceleration. The main advantages of the converter mechanism in such environments are that it greatly diminishes particle losses downstream and avoids the reduction in the energy gain factor, which normally takes place due to the highly collimated distribution of accelerated particles. We also discuss the properties of gamma-ray radiation, which accompanies acceleration of cosmic rays via the converter mechanism and can provide evidence for the latter. In particular, we point out that the opening angle of the radiation beam-pattern is different at different photon energies, which is relevant to the observability of gamma-ray sources as well as to their timing properties.

The Diffuse Emission of Neutrinos from Young Pulsars in the Galaxy

Young pulsars with ages less than 106 yr are powerful particle accelerators, which can accelerate protons to relativistic energies above the polar cap region if the magnetic moment is antiparallel to the spin axis. The interaction of those protons with the soft X-ray photons coming from the neutron star surface can produce high-energy muon neutrinos through photomeson production. Therefore, those pulsars are promising candidates as high-energy neutrino sources. We produce a sample of young pulsars in our Galaxy using a Monte Carlo method, determine whether they are potential neutrino pulsars, and calculate the total neutrino fluxes from those young pulsars using the Link & Burgio (LB) model. We obtain the upper limit of the diffuse neutrino flux from the young pulsars in the Galaxy, and compare it with predicted results from active galactic nuclei (AGNs) and gamma-ray bursts (GRBs).

On the timescale forcing in astrobiology

We investigate the effects of correlated global regulation mechanisms, especially Galactic gamma-ray bursts (GRBs), on the temporal distribution of hypothetical inhabited planets, using simple Monte Carlo numerical experiments. Starting with recently obtained models of planetary ages in the Galactic Habitable Zone (GHZ), we obtain that the times required for biological evolution on habitable planets of the Milky Way are highly correlated. These results run contrary to the famous anti-SETI anthropic argument of Carter, and give tentative support to the ongoing and future SETI observation projects.

High Energy Cosmic Rays from Local GRBs

We have developed a model that explains cosmic rays with energies E between ∼ 0.1 - 1 PeV and the energy of the second knee at E2 ∼ 3 × 1017 eV as originating from a recent Galactic gamma-ray burst (GRB) that occurred ∼ 1 Myr ago within 1 kpc from Earth. Relativistic shocks from GRBs are assumed to inject power-law distributions of cosmic ray (CR) protons and ions to the highest (≳1020 eV) energies. Diffusive propagation of CRs from a recent (∼ 1 Myr old) GRB explains the CR spectrum near and above the first knee at E1 ∼ 3 × 1015 eV. The first and second knees are explained as being directly connected with the injection of plasma turbulence in the interstellar medium on ∼ 1pc and ∼ 100 pc scales, respectively. Transition to CRs from extragalactic GRBs occurs at E ≳ E2. The origin of the ankle in the CR spectrum at Eank ≃ 4 × 1018 eV is due to photopair energy losses of UHECRs on cosmological timescales, as also suggested by Berezinsky and collaborators. The rate density of extragalactic GRBs is assumed to be proportional to the cosmological starburst activity in the universe. Any significant excess flux of extremely high energy CRs deviating from the exponential cutoff behavior at E > EGZK ≃ 6 × 1019 eV would imply a significant contribution due to recent GRB activity on timescales t ≲ 108 yrs from local extragalactic sources within ∼ 10 Mpc.

Climatic and biogeochemical effects of a galactic gamma ray burst

It is likely that one or more gamma ray bursts within our galaxy have strongly irradiated the Earth in the last Gy. This produces significant atmospheric ionization and dissociation, resulting in ozone depletion and DNA‐damaging ultraviolet solar flux reaching the surface for up to a decade. Here we show the first detailed computation of two other significant effects. Visible opacity of NO2 is sufficient to reduce solar energy at the surface up to a few percent, with the greatest effect at the poles, which may be sufficient to initiate glaciation. Rainout of dilute nitric acid could have been important for a burst nearer than our conservative “nearest burst”. These results support the hypothesis that the characteristics of the Late Ordovician mass extinction are consistent with GRB initiation.

Cosmic Rays from Gamma-Ray Bursts in the Galaxy

The rate of terrestrial irradiation events by galactic gamma-ray bursts (GRBs) is estimated using recent standard-energy results. We assume that GRBs accelerate high-energy cosmic rays, and present results of three-dimensional simulations of cosmic rays moving in the Galactic magnetic field and diffusing through pitch-angle scattering. An on-axis GRB extinction event begins with a powerful prompt gamma-ray and neutron pulse, followed by a longer-lived phase from cosmic-ray protons and neutron-decay protons that diffuse towards Earth. Our results force a reinterpretation of reported ~ 10^{18} eV cosmic-ray anisotropies and offer a rigorous test of the model where high-energy cosmic rays originate from GRBs, which will soon be tested with the Auger Observatory.

The Converter Mechanism of Particle Acceleration and Its Applications to the Unidentified Egret Sources

We discuss the properties of gamma-ray radiation accompanying the acceleration of cosmic rays via the converter mechanism. The mechanism exploits multiple photon-induced conversions of high-energy particles from charged into neutral state (namely, protons to neutrons and electrons to photons) and back. Because a particle in the neutral state can freely cross the magnetic field lines, this allows to avoid both particle losses downstream and reduction in the energy gain factor, which normally takes place due to highly collimated distribution of accelerated particles. The converter mechanism efficiently operates in relativistic outflows under the conditions typical for Active Galactic Nuclei, Gamma-Ray Bursts, and microquasars, where it outperforms the standard diffusive shock acceleration.

POSSIBILITIES OF A QED-BASED VACUUM ENERGY

A QED-based bootstrap mechanism, appearing at sufficiently small space-time scales, is suggested as an explanation for the "dark" vacuum energy that may be able to accelerate the universe. Very small-scale vacuum currents are allowed to generate small-scale electromagnetic fields, which become significant near the light cone. The resulting lepton-pair production, some of which may be tachyonic, has ramifications for the convergence of all QED perturbative processes, as well as providing possible mechanisms for "dark" matter, galactic gamma-ray bursts, and ultra-high-energy cosmic rays.