53583135
Three-dimensional two-layer outer gap model: Fermi energy-dependent light curves of the Vela pulsar
We extend the two-dimensional two-layer outer gap model to a three-dimensional geometry and use it to study the high-energy emission of the Vela pulsar. In this model, the outer gap is divided into two parts, i.e. the main acceleration region on the top of last-open field lines and the screening region around the upper boundary of the gap. In the main acceleration region, the charge density is much lower than the Goldreich–Julian charge density, and the charged particles are accelerated by the electric field along the magnetic field to emit multi-GeV photons. In the screening region, the charge density is larger than the Goldreich–Julian value to close the gap, and particles in this region are responsible for multi-100 MeV photon emission. We apply this three-dimensional two-layer model to the Vela pulsar and compare the model light curves, the phase-averaged spectrum and the phase-resolved spectra with the recent Fermi observations, which also reveals the existence of the third peak between two main peaks. The phase position of the third peak moves with the photon energy, which cannot be explained by the geometry of magnetic field structure and the caustic effects of the photon propagation. We suggest that the existence of the third peak and its energy-dependent movement results from the azimuthal structure of the outer gap.
118889930
POPULATION STUDY FOR γ-RAY PULSARS WITH THE OUTER GAP MODEL
Inspired by the increase of the population of {gamma}-ray emitting pulsars by the Fermi telescope, we perform a population study for {gamma}-ray emitting canonical pulsars. We use a Monte Carlo technique to simulate the Galactic population of neutron stars and the radio pulsars. For each simulated neutron star, we consider the {gamma}-ray emission from the outer gap accelerator in the magnetosphere. In our outer gap model, we apply the gap closure mechanism proposed by Takata et al., in which both photon-photon pair-creation and magnetic pair-creation processes are considered. Simulating the sensitivities of previous major radio surveys, our simulation predicts that there are {approx}18-23 radio-loud and {approx}26-34 {gamma}-ray-selected {gamma}-ray pulsars, which can be detected with a {gamma}-ray flux F{sub {gamma}} {>=} 10{sup -10} erg cm{sup -2} s{sup -1}. Applying the sensitivity of the six month observation of the Fermi telescope, 40-61 radio-selected and 36-75 {gamma}-ray selected pulsars are detected within our simulation. We show that the distributions of various pulsar parameters for the simulated {gamma}-ray pulsars can be consistent with the observed distribution of the {gamma}-ray pulsars detected by the Fermi telescope. We also predict that {approx}64 radio-loud and {approx}340 {gamma}-ray-selected pulsars irradiate the Earth with a flux F{sub {gamma}} {>=}more » 10{sup -11} erg cm{sup -2} s{sup -1}, and most of those {gamma}-ray pulsars are distributed with a distance greater than 1 kpc and a flux F{sub {gamma}} {approx} 10{sup -11} erg cm{sup -2} s{sup -1}. The ratio between the radio-selected and {gamma}-ray-selected pulsars depends on the sensitivity of the radio surveys. We also discuss the Galactic distribution of the unidentified Fermi sources and the canonical {gamma}-ray pulsars.« less
119299391
Outer gap accelerator closed by magnetic pair-creation process
We discuss outer gap closure mechanism in the trans-field direction with the magnetic pair-creation process near the stellar surface. The gap closure by the magnetic pair-creation is possible if some fraction of the pairs are produced with an outgoing momentum. By assuming that multiple magnetic field will affect the local field near the stellar surface, we show a specific magnetic field geometry near the stellar surface resulting in the outflow of the pairs. Together with the fact that the electric field is weak below null charge surface, the characteristic curvature photon energy emitted by incoming particles, which were accelerated in the outer gap, decreases drastically to ∼ 100MeV near the stellar surface. We estimate the height measured from the last-open field line, above which 100 MeV photons is converted into pairs by the magnetic pair-creation. We also show the resultant multiplicity due to the magnetic pair-creation process could acquire Me± ∼ 10− 10. In this model the fractional outer gap size is proportional to P. The predicted gamma-ray luminosity (Lγ) and the characteristic curvature photon energy (Ec) emitted from the outer gap are proportional to B P and BP respectively. This model also predicts that Lγ and Ec are related to the spin down power (Lsd) or the spin down age of pulsars (τ) as Lγ ∝ L 5/8 sd or Lγ ∝ τ , and Ec ∝ L 1/4 sd or Ec ∝ τ −1/2 respectively. Subject headings: pulsars: general– radiation mechanisms:non-thermal– -gamma rays:theory–magnetic field
118161430
Population study for gamma-ray pulsars; II Millisecond pulsars
The population of $\gamma$-ray emitting millisecond pulsars (MSPs) is studied by using Monte-Carlo techniques. We simulate the Galactic distributions of the MSPs, and apply the outer gap model for the $\gamma$-ray emission from each simulated MSP. We take into account the dependence of the observed $\gamma$-ray flux on the viewing angle and inclination angle, which is the angle between the rotation axis and the magnetic axis, respectively. Using the sensitivity of the six-month long observation of the $Fermi$ telescope and radio sensitivities of existing pulsar surveys, 9-13 radio-selected and 22-35 $\gamma$-ray-selected pulsars are detected within our simulation. The statistical properties of the simulated population are consistent with the $Fermi$ observations. Scaling the observed sensitivity $\propto \sqrt{T}$, where $T$ is the length of observation time, the present model predicts that over the 5-year mission $Fermi$ would detect 15-22 radio-selected $\gamma$-ray MSPs, and 95-152 $\gamma$-ray-selected MSPs. Our simulation also predicts that about 100 (or 200-300) $\gamma$-ray MSPs with a flux larger $F\ge 10^{-11}~\mathrm{erg/cm^2 s}$ (or $5\times 10^{-12}~\mathrm{erg/cm^2 s}$) irradiate the Earth. With the present sensitivities of the radio surveys, most of them are categorized as $\gamma$-ray-selected pulsars, indicating that most of the $\gamma$-ray MSPs have been missed by the present $Fermi$ observations. We argue that the Galactic $Fermi$ unidentified sources located at high latitudes should be dominated by MSPs, whereas the sources in the galactic plane are dominated by radio-quiet canonical pulsars.
53631567
Probing deviations from general relativity with the Euclid spectroscopic survey
We discuss the ability of the planned Euclid mission to detect deviations from General Relativity using its extensive redshift survey of more than 50 Mi llion galaxies. Constraints on the gravity theory are placed measuring the growth rate of struc ture within 14 redshift bins betweenz = 0.7 andz = 2. The growth rate is measured from redshift-space distortio ns, i.e. the anisotropy of the clustering pattern induced by coherent pe culiar motions. This is performed in the overall context of the Euclid spectroscopic survey, w hich will simultaneously measure the expansion history of the universe, using the power spect rum and its baryonic features as a standard ruler, accounting for the relative degeneracies of expansion and growth parameters. The resulting expected errors on the growth rate in the different redshift bins, expressed through the quantity fσ8, range between 1.3% and 4.4%. We discuss the optimisation of the survey configuration and investigate the important depende nce on the growth parameterisation and the assumed cosmological model. We show how a specifi c parameterisation could actually drive the design towards artificially restricted r egions of the parameter space. Finally, in the framework of the popular “γ parameterisation”, we show that the Euclid spectroscopic survey alone will already be able to provide substantial evidence (in Bayesian terms) if the growth index differs from the GR value γ = 0.55 by at least � 0.13. This will combine with the comparable inference power provided by the Euclid weak lensing survey, resulting in Euclid’s unique ability to provide a decisive test of modi fied gravity.
15483575
Energy Loss of Particles in Pulsar Radio Emission Region
Extremely relativistic particles play an important role in various radiative mechanisms of pulsar radio as well as high-energy emission. It is thus very essential to estimate the Lorentz factor of these particles in the radiation regions both observationally and theoretically. In this paper, according to the frequency dependence of component separation and considering some radiation processes, we obtain the Lorentz factor and its variation in the radiation region observationally for seven multi-frequency observed pulsars. It is found that the Lorentz factor decays substantially in the emission region, and the decay can not be well understood by all known energy loss processes. This result hints that there are some unknown processes which are responsible to loosing energy effectively.
121485651
Aging test of a real-size high rate MRPC for CBM-TOF wall
A new kind of low-resistivity glass has been developed. Its volume resistivity is on the order of 1010 Ω cm and multi-gap resistive plate chambers (MRPCs), once assembled with it, can be operated at a charged particle flux in excess of 25 kHz/cm2, with very small charge build-up at the plates. This new technology has a wide range of application in high energy physics experiments such as FAIR-CBM, LHC-ATLAS or Jlab-SOLID, to mention some. In this paper we report on results related to its long-term behavior (aging). A 6 × 2-pad CBM module has been irradiated by X-rays at a mips-equivalent flux of 15 kHz/cm2, for 300 hours and for a released charge totaling 0.22 C (50 mC/cm2). Tested in an electron beam before and after exposure, no degradation of the detector performances could be appreciated. As expected, compared to common glass MRPCs, the newly developed high rate counter also responds faster to sudden irradiation.
121363939
Guidelines for a supercollider experiment: the magnetic system
Abstract We try to give some general guidelines for optimizing the magnetic system of a general-purpose detector with a high momentum resolution for muons at a supercollider experiment. Solenoidal and toroidal schemes are investigated, with the possibility of using calorimeter material as the coil.
118398936
Top Hypercharge
We propose a top hypercharge model with gauge symmetry SU(3)C ×SU(2)L × U(1)1 ×U(1)2 where the first two families of the Standard Model (SM) fermions are charged under U(1)1 while the third family is charged under U(1)2. The U(1)1×U(1)2 gauge symmetry is broken down to the U(1)Y gauge symmetry, when a SM singlet Higgs field acquires a vacuum expectation value. We consider the electroweak constraints, and compare the fit to experimental observables to that of the SM. We study the quark CKM mixing between the first two families and the third family, the neutrino masses and mixing, the flavour changing neutral current effects in meson mixing and decays, the Z ′ discovery potential at the Large Hadron Collider, the dark matter with a gauged Z2 symmetry, and the Higgs boson masses.