The γ-ray emission from the Seyfert galaxy NGC 4151

Light curves at X-ray, ultraviolet, optical and infrared wavelengths of NGC 4151 over the period 1977–1980 are presented together with a summary of the large amount of observational data relating to this Seyfert galaxy. Intensity variations in different wavebands are discussed and compared with recent low energy -ray observations of this object. The positive measurement of gamma-radiation in May 1977 is shown to have been characterised by a high optical state and a possible infrared maximum. The data presented are compared with the predictions of some emission mechanisms, which have been proposed to account for the gamma-radiation. In particular, a synchrotron self-Compton model, which relates the infrared/optical emission to the X-ray/low energy -ray emission is discussed.     

Searching for γ-ray emission from LOTAAS pulsars

The LOw-Frequency ARray(LOFAR)has recently conducted a survey(LOFAR Tied-Array Allsky Survey;LOTAAS)for pulsars in the Northern hemisphere that resulted in discoveries of 73 new pulsars.For the purpose of studying the properties of these pulsars,we search for theirγ-ray counterparts using the all-sky survey data obtained with the Large Area Telescope(LAT)onboard the Fermi Gamma-Ray Space Telescope(Fermi).We analyze the LAT data for 70 LOTAAS pulsars(excluding two millisecond pulsars and one with the longest known spin period of 23.5 s).We find one candidate counterpart to PSR J1017+30,which should be searched for theγ-ray pulsation signal once its timing solution is available.For other LOTAAS pulsars,we derive their 0.3-500 GeV flux upper limits.In order to compare the LOTAAS pulsars with the knownγ-ray pulsars,we also derive the 0.3-500 GeVγ-ray fluxes for 112 of the latter contained in the Fermi LAT fourth source catalog.Based on the properties of theγ-ray pulsars,we derive upper limits on the spin-down luminosities of the LOTAAS pulsars.The upper limits are not very constraining but help suggest that most of the LOTAAS pulsars probably have<10³³ erg s^-1 spin-down luminosities and are not expected to be detectable with Fermi LAT.     

Injected spectrum for TeV γ-ray emission from the galactic center

The detection of very high energy γ-ray emission from the Galactic center has been reported by four independent groups. One of these γ-ray sources, the 10 TeV -γ-ray radiation reported by HESS, has been suggested as having a hadronic origin when relativistic protons are injected into and interact with the dense ambient gas. Assuming that such relativistic protons required by the hadronic model come from the tidal disruption of a star by the massive black hole of Sgr A＊, we explore the spectrum of the relativis- tic protons. In the calculations, we investigate cases where different types of stars are tidally disrupted by the black hole of Sgr A＊, and we consider that different diffusion mechanisms are used for the propagation of protons. The initial energy distribution of the injected spectrum of protons is assumed to follow a power-law with an exponential cut-off, and we derive the different indices of the injected spectra for the tidal disruption of different types of stars. For the best fit to the spectrum of photons detected by HESS, the spectral index of the injected relativistic protons is about 2.05 when a red giant is tidally disrupted by the black hole of Sgr A＊ and the diffusion mechanism is the Effective Confinement of Protons.     

On a new class of impulsive flares with no nuclear γ-ray line emission

The new class of -ray spectra from impulsive flares without nuclear -ray lines is compared with bremsstrahlung spectra of energetic electrons undergoing stochastic acceleration, Coulomb and synchrotron losses. The remarkable agreement of both the produced -spectra from the precipitated electrons and the electron spectra measured in the interplanetary space leads to the conclusion that seed population and acceleration process are identical for both classes of electrons. A new estimate of the electron bremsstrahlung contribution in -spectra of impulsive solar flares seems to be necessary.     

TeV γ-ray fluxes from the long campaigns on Mrk 421 as constraints on the emission of TeV–PeV neutrinos and UHECRs

Long TeV γ-ray campaigns have been carried out to study the spectrum, variability and duty cycle of the BL Lac object Markarian 421. These campaigns have given some evidence of the presence of protons in the jet: (i) Its spectral energy distribution which shows two main peaks; one at low energies (∼1 keV) and the other at high energies (hundreds of GeV), has been described by using synchrotron proton blazar model. (ii) The study of the variability at GeV γ-rays and X-rays has indicated no significant correlation. (iii) TeV γ-ray detections without activity in X-rays, called “orphan flares” have been observed in this object.Recently, The Telescope Array Collaboration reported the arrival of 72 ultra-high-energy cosmic rays with some of them possibly related to the direction of Markarian 421. The IceCube Collaboration reported the detection of 37 extraterrestrial neutrinos in the TeV–PeV energy range collected during three consecutive years. In particular, no neutrino track events were associated with this source. In this paper, we consider the proton–photon interactions to correlate the TeV γ-ray fluxes reported by long campaigns with the neutrino and ultra-high-energy cosmic ray observations around this blazar. Considering the results reported by The IceCube and Telescope Array Collaborations, we found that only from ∼25% to 70% of TeV fluxes described with a power law function with exponential cutoff can come from the proton–photon interactions.     

Possible effects of positronium negative ion on 0.511 MeV ψ-ray line in astrophysical sources

The astrophysical importance of the negative positronium ion, detected recently in the laboratory, has been pointed out. It is found that the presence of Ps^– ions will contribute additionally to the width of 0.511 -ray line formed by pair annihilation. The formation of Ps^– ion from an aggregate of electrons, positrons and positronium results in a variable positron population in the 0.511 MeV -ray line source.     

A study of the He λ 10830 line emission from quiescent prominences

Observations of the He 10830 line emission in a number of quiescent prominences are presented. The line shapes are analyzed to obtain values for the Doppler widths and optical thicknesses, leading to a determination of the 2³ P – 2³ S excitation temperature of 4020 K. The results are compared with those of previous observational and theoretical research.     

Possible modulated γ-ray emission from the transitional millisecond pulsar binary PSR J1023+0038

We report the results from our analysis of Fermi Large Area Telescope(LAT) data for the transitional millisecond pulsar binary PSR J1023+0038. The time period of the data is nearly 9 yr, and that after the source's transition, in June 2013 from the disk-free state to the active state of having an accretion disk, is approximately 4 yr. We identify a high-energy 5.5 GeV component in the source's spectrum in the active state, and find this component is only significantly detected in half of the orbital phase centered at the descending node(when the pulsar is moving towards the Earth). Considering the pulsar scenario proposed for multi-frequency emission from the source, in which the pulsar is still active and a cold-relativistic pulsar wind inverse-Compton scatters the photons from the accretion disk, we discuss the origin of the high-energy component. In order to explain the observed spectrum, a power-law distribution of particles, with an index of ～3, in the pulsar wind is required, while the orbital variations are possibly due to changes in power-law index as a function of orbital phase.     

High energy γ-ray emission from compact galactic sources in the context of observations with the next generation Cherenkov Telescope Arrays

The observational progress in the γ-ray astronomy in the last few years has led to the discovery of more than a thousand sources at GeV energies and more than a hundred sources at TeV energies. A few different classes of compact objects in the Galaxy have been established. They show many unexpected features at high energies the physics of which remains mainly unknown. At present it is clear that detailed investigation of these new phenomena can be performed only with the technical equipment which offer an order of magnitude better sensitivity, and a few times better energy, angular and time resolution in the broad energy range staring from a few tens of GeV up to a few hundreds TeV. Such facilities can be realized by the next generation of instruments such as the planned Cherenkov Telescope Array (CTA).The aim of this report is to summarize up to date observational results on the compact galactic sources in the GeV–TeV γ-ray energy range, discuss their theoretical implications, and indicate which hypothesis considered at present might be verified with the next generation of telescopes. We point out which of the observational features of the γ-ray sources are important to investigate with special care with the planned CTA in order to throw new light on physical processes involved. Their knowledge should finally allow us to answer the question on the origin of energetic particles in our Galaxy.     

Possible γ-ray emission of radio intermediate AGN Ⅲ Zw 2 and its implication on the evolution of jets in AGNs

AGNs with hard γ-ray emission identified so far are radio-loud.III Zw 2 is a radio intermediate AGN with a relativistic jet.We study its spectral energy distribution (SED) and find that the broad band emissions are dominated by the non-thermal emissions from the jet.We model its SED through a synchrotron + inverse Compton (IC) model.The results show that the IC component of III Zw 2 peaks at a few MeV, and the flux density drops rapidly at higher energy with photon index Γ≈3.3 above 0.1GeV.The predicted flu...     

Injected spectrum for TeV-γ-ray emission from the galactic center

The detection of very high energy γ-ray emission from the Galactic center has been reported by four independent groups. One of these γ-ray sources, the 10TeV γ-ray radiation reported by HESS, has been suggested as having a hadronic origin when relativistic protons are injected into and interact with the dense ambient gas. Assuming that such relativistic protons required by the hadronic model come from the tidal disruption of a star by the massive black hole of Sgr A*, we explore the spectrum of the relativistic protons. In the calculations, we investigate cases where different types of stars are tidally disrupted by the black hole of Sgr A*, and we consider that different diffusion mechanisms are used for the propagation of protons. The initial energy distribution of the injected spectrum of protons is assumed to follow a power-law with an exponential cut-off, and we derive the different indices of the injected spectra for the tidal disruption of different types of stars. For the best fit to the spectrum of photons detected by HESS, the spectral index of the injected relativistic protons is about 2.05 when a red giant is tidally disrupted by the black hole of Sgr A* and the diffusion mechanism is the Effective Confinement of Protons.     

High-resolution observations of Hα emission line from R Aquarii

We have obtained H emission line profiles from R Aquarii, a Mira variable surrounded by a complex nebulosity, using a very high-resolution Fabry-Pérot spectrometer. A new feature that was seen in our observations is the fact that the line profile shows a splitting which we interpret as due to two expanding shells surrounding the star with velocities of 5 km s^–1 and 15 km s^–1. The expansion velocities show an acceleration outwards due perhaps to the radiation pressure caused momentum transfer. Possible periodic variation of radial velocity derived from observations is discussed.     

Numerical simulations of the K-corona and of the λ 5303 emission line corona

More and more observations tend to prove that the lower corona is very heterogeneous and that the active regions are quite exclusively arch-structured. So, we have attempted to see what would be the result of simulations of a corona structured only with arches. In a previous work we had made the computations for both the K-corona and the 5303 emission line corona, for which we have much observational data. The complexity of computations has led us to make the comparisons with observations for the vertical intensity gradients only. A priori, it seemed impossible to obtain a simulation close to reality with a corona structured only with arches, at least as we have defined them in this paper, the important fact being a conspicuous lack of matter beyond a certain height. We have made new simulations with a different electron density distribution and for a different region. These latter calculations show us that the material can be confined in the feet of very high arches or in open structures as has already been suggested.     

A synchrotron self-Compton scenario for the very high energy γ-ray emission of the intermediate BL Lacertae object W Comae

W Comae has significant variability in multi-wavelengthes, from radio to gamma-ray bands. A bright outburst in optical and X-ray bands was observed in 1998, and most recently, a strong TeV flare was detected by VERITAS in 2008. It is the first TeV intermediate-frequency-peaked BL Lacertae source. I find that both the broadband spectral energy distributions （SEDs） which were quasi-simultaneously obtained during the TeV flare and during the optical/X-ray outburst are well fit by using a single-zone synchrotron ＋ synchrotron-self-Compton model. The satisfactory fitting requires a large beaming factor, i.e., δ- 25 and δ- 20 for the TeV flare and the optical/X-ray outburst, respectively, suggesting that both the optical/X-ray outburst and the TeV flare are from a relativistic jet. The size of the emission region of the TeV flare is three times larger than that of the optical/X-ray outburst, and the strength of the magnetic field for the TeV flare is - 14 times smaller than that of the X-ray/optical outburst, likely indicating that the region of the TeV flare is more distant from the core than that of the X-ray/optical outburst. The inverse Compton component of the TeV flare peaks around 1.3 GeV, but it is around 20 MeV for the X-ray/optical outburst, lower than that for the TeV flare by two orders of magnitude. The model predicts that the optical/X-ray outburst might be accompanied by a strong MeV/GeV emission, but the TeV flare may be not associated with the X-ray/optical outburst. The GeV emission is critical for characterizing the SEDs of the optical/X-ray outburst and the TeV flare. The predicted GeV flux is above the sensitivity of Fermi/LAT, and it could be verified with the observations by Fermi/LAT in the near future.     

Direct demodulation imaging of the γ-ray burst GRB 910601

The COMPTEL observation of the γ-ray burst GRB 910601 has been reanalyzed using a direct demodulation method. The imaging result indicates that the location of GRB 910601 is closer to the annulus obtained by the Ulysses-BATSE system than that with the maximum-likelihood method. This confirms the feasibility of processing γ-ray bursts, a kind of transient source with good signal-to-noise ratio but poor statistics, with a direct demodulation method. The precision of locating γ-ray bursts by imaging can also be improved using this method.     

MeV Properties of the γ-ray Blazars PKS1622-297, 3C454.3 and CTA102

1　IntroductionTheblazarsPKS 1 62 2 2 97,3C 454 .3andCTA 1 0 2werefirstlydetectedasγ raysourcesby　　Fig .1　TheCOMPTELspectraoftheflareandquiescentstate (top)aswellasthecombinedCOMPTEL/EGRETspectrumoftheflarestateforPKS 1 62 2 -2 97(bottom) .EGRET/CGRO [1 ,2 ,3 ] .WehaveconsistentlyanalyzedtheCOMPTELdata (0 .75-3 0MeV)onthese 3blazars.Inouranalysesweselected 2 8CGROviewingperiods (VPs)forPKS 1 62 2 2 97between’91and’97,and 2 2VPsfor 3C 454 .3andCTA 1 0 2between…     

The γ-ray emission produced by protons that escape from supernova remnant G349.7+0.2

G349.7+0.2 is an interacting supernova remnant(SNR) expanding in a dense medium.Recently,a very strong γ-ray source coincident with this SNR has been revealed by Fermi-LAT and H.E.S.S.observations which shows a broken power-law-like spectrum.An escaping-diffusion model,including the power-law and δ-function injection,is applied to this source which can naturally explain the spectral feature in both the GeV and TeV regime.We use the Markov Chain Monte Carlo method to constrain the model parameters and find that the correction factor of slow diffusion around this SNR,χ~0.01 for power-law injection and χ~0.1 for δ-function injection,can fit the data best with reasonable molecular cloud mass.This slow diffusion is also consistent with previous results from both phenomenological models and theoretical predication.