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Journal articles on the topic 'TeV gamma ray astrophysics'

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Author: Grafiati

Published: 10 December 2022

Last updated: 29 January 2023

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1

SINNIS, GUS. "TeV ASTROPHYSICS WITH THE MILAGRO AND HAWC OBSERVATORIES." International Journal of Modern Physics D 22, no. 11 (September 2013): 1360010. http://dx.doi.org/10.1142/s0218271813600109.

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Ground-based gamma-ray astronomy has historically implemented two dramatically different techniques. One method employs Imaging Atmospheric Cherenkov Telescope(s) (IACT) that detect the Cherenkov light generated in the atmosphere by extensive air showers. The other method employs particle detectors that directly detect the particles that reach ground level — known as Extensive Air Shower (EAS) arrays. Until recently, the IACT method had been the only technique to yield solid detections of TeV gamma-ray sources. Utilizing water Chernkov technology, Milagro, was the first EAS array to discover new gamma-ray sources and demonstrated the power of and need for an all-sky high duty cycle instrument in the TeV energy regime. The transient nature of many TeV sources, the enormous number of potential sources, and the existence of TeV sources that encompass large angular areas all point to the need for an all-sky, high duty-factor instrument with even greater sensitivity than Milagro. The High Altitude Water Cherenkov (HAWC) Observatory will be over an order of magnitude more sensitive than Milagro. In this paper we will discuss the results from Milagro and the design of the HAWC instrument and its experimental sensitivity.

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Cui, Wei. "TeV gamma-ray astronomy." Research in Astronomy and Astrophysics 9, no. 8 (July 24, 2009): 841–60. http://dx.doi.org/10.1088/1674-4527/9/8/001.

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Tanimori, Toru. "Sub-TeV Gamma-Ray Astrophysics Using Large Air Čerenkov Telescopes." Progress of Theoretical Physics Supplement 143 (2001): 78–98. http://dx.doi.org/10.1143/ptps.143.78.

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Dubus, Guillaume, Nicolas Guillard, Pierre-Olivier Petrucci, and Pierrick Martin. "Sizing up the population of gamma-ray binaries." Astronomy & Astrophysics 608 (December 2017): A59. http://dx.doi.org/10.1051/0004-6361/201731084.

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Context. Gamma-ray binaries are thought to be composed of a young pulsar in orbit around a massive O or Be star with their gamma-ray emission powered by pulsar spin-down. The number of such systems in our Galaxy is not known. Aims. We aim to estimate the total number of gamma-ray binaries in our Galaxy and to evaluate the prospects for new detections in the GeV and TeV energy range, taking into account that their gamma-ray emission is modulated on the orbital period. Methods. We modelled the population of gamma-ray binaries and evaluated the fraction of detected systems in surveys with the Fermi-LAT (GeV), H.E.S.S., HAWC and CTA (TeV) using observation-based and synthetic template light curves. Results. The detected fraction depends more on the orbit-average flux than on the light-curve shape. Our best estimate for the number of gamma-ray binaries is 101\hbox{$_{-52}^{+89}$} systems. A handful of discoveries are expected by pursuing the Fermi-LAT survey. Discoveries in TeV surveys are less likely. However, this depends on the relative amounts of power emitted in GeV and TeV domains. There could be as many as ≈ 200 HESS J0632+057-like systems with a high ratio of TeV to GeV emission compared to other gamma-ray binaries. Statistics allow for as many as three discoveries in five years of HAWC observations and five discoveries in the first two years of the CTA Galactic Plane survey. Conclusions. We favour continued Fermi-LAT observations over ground-based TeV surveys to find new gamma-ray binaries. Gamma-ray observations are most sensitive to short orbital period systems with a high spin-down pulsar power. Radio pulsar surveys (SKA) are likely to be more efficient in detecting long orbital period systems, providing a complementary probe into the gamma-ray binary population.

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Noda, Koji, and Robert Daniel Parsons. "Gamma-Ray Bursts at TeV Energies: Observational Status." Galaxies 10, no. 1 (January 5, 2022): 7. http://dx.doi.org/10.3390/galaxies10010007.

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Gamma-ray bursts (GRBs) are some of the most energetic events in the Universe and are potential sites of cosmic ray acceleration up to the highest energies. GRBs have therefore been a target of interest for very high energy gamma-ray observatories for many years, leading to the recent discovery of a number of bursts with photons reaching energies above 100 GeV. We summarize the GRB observational campaigns of the current generation of very high energy gamma-ray observatories as well as describing the observations and properties of the GRBs discovered so far. We compare the properties of the very high energy bursts to the total GRB distribution and make predictions for the next generation of very high energy gamma-ray observations.

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Neronov, A., and D. Semikoz. "Galactic diffuse gamma-ray emission at TeV energy." Astronomy & Astrophysics 633 (January 2020): A94. http://dx.doi.org/10.1051/0004-6361/201936368.

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Context. Measuring the diffuse Galactic γ-ray flux in the TeV range is difficult for ground-based γ-ray telescopes because of the residual cosmic-ray background, which is higher than the γ-ray flux by several orders of magnitude. Its detection is also challenging for space-based telescopes because of low signal statistics. Aims. We characterise the diffuse TeV flux from the Galaxy using decade-long exposures of the Fermi Large Area Telescope. Methods. Considering that the level of diffuse Galactic emission in the TeV band approaches the level of residual cosmic-ray background, we estimated the level of residual cosmic-ray background in the SOURCEVETO event selection and verified that the TeV diffuse Galactic emission flux is well above the residual cosmic-ray background up to high Galactic latitude regions. Results. We study spectral and imaging properties of the diffuse TeV signal from the Galactic plane. We find much stronger emission from the inner Galactic plane than in previous HESS telescope estimates (lower bound). We also find a significant difference in the measurement of the Galactic longitude and latitude profiles of the signal measured by Fermi and HESS. These discrepancies are presumably explained by the fact that regions of background estimate in HESS have non-negligible γ-ray flux. Comparing Fermi measurements with those of ARGO-YBJ, we find better agreement, with the notable exception of the Cygnus region, where we find much higher flux (by a factor 1.5). We also measure the TeV diffuse emission spectrum up to high Galactic latitude and show that the spectra of different regions of the sky have spectral slopes consistent with Γ = 2.34 ± 0.04, which is harder than the slope of the locally observed spectrum of cosmic rays with energies 10–100 TeV, which produce TeV diffuse emission on their way through the interstellar medium. We discuss the possible origin of the hard slope of the TeV diffuse emission. Conclusions. Fermi/LAT provides reliable measurements of the diffuse Galactic emission spectrum in the TeV range, which are almost background free at low Galactic latitudes. The diffuse flux becomes comparable to the residual cosmic-ray background at Galactic latitudes |b| > 50°. Its measurement in these regions might suffer from systematic uncertainty stemming from the uncertainty of our phenomenological model of the residual cosmic-ray background in the Pass 8 Fermi/LAT data.

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Huang, Tian-Qi, and Zhuo Li. "Constraints on Hadronic Contributions to LHAASO Sources with Neutrino Observations." Astrophysical Journal 925, no. 1 (January 1, 2022): 85. http://dx.doi.org/10.3847/1538-4357/ac423d.

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Abstract The Large High Altitude Air Shower Observatory (LHAASO) detected 12 gamma-ray sources above 100 TeV, which are the possible origins of Galactic cosmic-rays. We summarize the neutrino measurements by IceCube and ANTARES in the vicinity of LHAASO sources to constrain the contribution of hadronic gamma-rays in these sources. We find that the current observations constrain hadronic gamma-rays to contribute no more than ∼60% of the gamma-rays from the Crab Nebula. Gamma-rays from two LHAASO sources, LHAASO J1825−1326 and LHAASO J1907+0626, are dominated by leptonic components up to ∼200 TeV, under the hypotheses in the analysis by IceCube. The uncertainties of the constraint on the hadronic gamma-ray emission are discussed. We also constrain the total 100 TeV gamma-ray emission from TeV pulsar wind nebulae by relying on the remarkable sensitivity of LHAASO at that energy.

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Shimono, Naoya, Tomonori Totani, and Takahiro Sudoh. "Prospects of newly detecting nearby star-forming galaxies by the Cherenkov Telescope Array." Monthly Notices of the Royal Astronomical Society 506, no. 4 (July 27, 2021): 6212–22. http://dx.doi.org/10.1093/mnras/stab2118.

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ABSTRACT Prospects of the Cherenkov Telescope Array (CTA) for the study of very high energy gamma-ray emission from nearby star-forming galaxies are investigated. In the previous work, we constructed a model to calculate luminosity and energy spectrum of pion-decay gamma-ray emission produced by cosmic ray interaction with the interstellar medium (ISM), from four physical quantities of galaxies [star formation rate (SFR), gas mass, stellar mass, and effective radius]. The model is in good agreement with the observed GeV–TeV emission of several nearby galaxies. Applying this model to nearby galaxies that are not yet detected in TeV (mainly from the KINGFISH catalogue), their hadronic gamma-ray luminosities and spectra are predicted. We identify galaxies of the highest chance of detection by CTA, including NGC 5236, M33, NGC 6946, and IC 342. Concerning gamma-ray spectra, NGC 1482 is particularly interesting because our model predicts that this galaxy is close to the calorimetric limit and its gamma-ray spectral index in GeV–TeV is close to that of cosmic ray protons injected into ISM. Therefore, this galaxy may be detectable by CTA even though its GeV flux is below the Fermi Large Area Telescope sensitivity limit. In the TeV regime, most galaxies are not in the calorimetric limit, and the predicted TeV flux is lower than that assuming a simple relation between the TeV luminosity and SFR of M82 and NGC 253, typically by a factor of 15. This means that a more sophisticated model beyond the calorimetric limit assumption is necessary to study TeV emission from star-forming galaxies.

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Topchiev, N. P., A. M. Galper, I. V. Arkhangelskaja, A. I. Arkhangelskiy, A. V. Bakaldin, I. V. Chernysheva, O. D. Dalkarov, et al. "High-energy gamma- and cosmic-ray observations with future space-based GAMMA-400 gamma-ray telescope." EPJ Web of Conferences 208 (2019): 14004. http://dx.doi.org/10.1051/epjconf/201920814004.

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The future space-based GAMMA-400 gamma-ray telescope will be installed on the Navigator platform of the Russian Astrophysical Observatory. A highly elliptical orbit will provide observations for 7-10 years of many regions of the celestial sphere continuously for a long time (~ 100 days). GAMMA-400 will measure gamma-ray fluxes in the energy range from ~ 20 MeV to several TeV and electron + positron fluxes up to ~ 20 TeV. GAMMA-400 will have an excellent separation of gamma rays from the background of cosmic rays and electrons + positrons from protons and an unprecedented angular (~ 0.01° at Eγ = 100 GeV) and energy (~ 1% at Eγ = 100 GeV) resolutions better than for Fermi-LAT, as well as ground-based facilities, by a factor of 5-10. Observations of GAMMA-400 will provide new fundamental data on discrete sources and spectra of gamma-ray emission and electrons + positrons, as well as the nature of dark matter.

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Carramiñana, Alberto. "Black hole astrophysics with HAWC, the High Altitude Water Cherenkov γ-ray observatory." Proceedings of the International Astronomical Union 12, S324 (September 2016): 309–16. http://dx.doi.org/10.1017/s1743921317002289.

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AbstractThe HAWC gamma-ray observatory is a wide field of view and high duty cycle γ-ray detector investigating the 0.1 - 100 TeV energy range. It has detected supermassive black holes in the near Universe, and is seeking to detect black hole related objects like gamma-ray bursts, Galactic binary systems, primordial black holes and gravitational wave mergers. Daily light curves of the BL Lac objects Mrk 421 and Mrk 501 are presented here, together with a compilation of studies of black hole related objects.

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Skrzypek, B., M. Chianese, and C. A. Argüelles. "Multi-messenger high-energy signatures of decaying dark matter and the effect of background light." Journal of Cosmology and Astroparticle Physics 2023, no. 01 (January 1, 2023): 037. http://dx.doi.org/10.1088/1475-7516/2023/01/037.

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Abstract The IceCube Neutrino Observatory at the South Pole has measured astrophysical neutrinos using through-going and starting events in the TeV to PeV energy range. The origin of these astrophysical neutrinos is still largely unresolved, and among their potential sources could be dark matter decay. Measurements of the astrophysical flux using muon neutrinos are in slight tension with starting event measurements. This tension is driven by an excess observed in the energy range of 40–200 TeV with respect to the through-going expectation. Previous works have considered the possibility that this excess may be due to heavy dark matter decay and have placed constraints using gamma-ray and neutrino data. However, these constraints are not without caveats, since they rely on the modeling of the astrophysical neutrino flux and the sources of gamma-ray emission. In this work, we derive background-agnostic galactic and extragalactic constraints on decaying dark matter by considering Tibet-ASγ data, Fermi-LAT diffuse data, and the IceCube high-energy starting event sample. For the gamma-ray limits, we investigate the uncertainties on secondary emission from electromagnetic cascades during propagation arising from the unknown intensity of the extragalactic background light. We find that such uncertainties amount to a variation of up to ∼ 55% in the gamma-ray limits derived with extragalactic data. Our results imply that a significant fraction of the astrophysical neutrino flux could be due to dark matter and that ruling it out depends on the assumptions on the gamma-ray and neutrino background. The latter depends on the yet unidentified sources.

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Cataldo, M., G. Pagliaroli, V. Vecchiotti, and F. L. Villante. "Probing galactic cosmic ray distribution with TeV gamma-ray sky." Journal of Cosmology and Astroparticle Physics 2019, no. 12 (December 16, 2019): 050. http://dx.doi.org/10.1088/1475-7516/2019/12/050.

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Albert, A., R. Alfaro, C. Alvarez, J. D. Álvarez, J. R. Angeles Camacho, J. C. Arteaga-Velázquez, D. Avila Rojas, et al. "HAWC Study of the Ultra-high-energy Spectrum of MGRO J1908+06." Astrophysical Journal 928, no. 2 (March 31, 2022): 116. http://dx.doi.org/10.3847/1538-4357/ac56e5.

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Abstract We report TeV gamma-ray observations of the ultra-high-energy source MGRO J1908+06 using data from the High Altitude Water Cherenkov Observatory. This source is one of the highest-energy known gamma-ray sources, with emission extending past 200 TeV. Modeling suggests that the bulk of the TeV gamma-ray emission is leptonic in nature, driven by the energetic radio-faint pulsar PSR J1907+0602. Depending on what assumptions are included in the model, a hadronic component may also be allowed. Using the results of the modeling, we discuss implications for detection prospects by multi-messenger campaigns.

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BEILICKE, MATTHIAS. "M 87 — TEN YEARS OF TEV GAMMA-RAY OBSERVATIONS." International Journal of Modern Physics D 19, no. 06 (June 2010): 849–57. http://dx.doi.org/10.1142/s0218271810017093.

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The giant radio galaxy M 87 is located 16.7 Mpc away and harbours a supermassive black hole in its center. Structures of its relativistic plasma jet are resolved at radio, optical and X–ray energies. M 87 belongs to the class of active galactic nuclei and is one of only a few radio galaxies detected at very-high energies (E > 100 GeV ). This makes it a unique laboratory to study jet physics and the corresponding emission processes. The results obtained from TeV gamma-ray observations during the last decade are discussed.

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Costamante, L. "TeV-peaked candidate BL Lac objects." Monthly Notices of the Royal Astronomical Society 491, no. 2 (November 13, 2019): 2771–78. http://dx.doi.org/10.1093/mnras/stz3018.

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ABSTRACT BL Lac objects can be extreme in two ways: with their synchrotron emission, peaking beyond 1 keV in their spectral energy distribution, or with their gamma-ray emission, peaking at multi-TeV energies up to and beyond 10–20 TeV, like 1ES 0229+200. This second type of extreme BL Lacs – which we can name TeV-peaked BL Lacs – is not well explained by the usual synchrotron self-Compton scenarios for BL Lacs. These sources are also important as probes for the intergalactic diffuse infrared background and cosmic magnetic fields, as well as possible sites of production of ultra-high-energy cosmic rays and neutrinos. However, all these studies are hindered by their still very limited number. Here I propose a new, simple criterium to select the best candidates for TeV observations, specifically aimed at this peculiar type of BL Lac objects by combining X-ray, gamma-ray, and infrared data. It is based on the observation of a clustering towards a high X-ray to GeV gamma-ray flux ratio, and it does not rely on the radio flux or X-ray spectrum. This makes it suitable to find TeV-peaked sources also with very faint radio emission. Taking advantage of the Fermi all-sky gamma-ray survey applied to the ROMA-BZCAT and Sedentary Survey samples, I produce an initial list of 47 TeV-peaked candidates for observations with present and future air-Cherenkov telescopes.

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Gill, Ramandeep, and Jonathan Granot. "Gamma-Ray Bursts at TeV Energies: Theoretical Considerations." Galaxies 10, no. 3 (May 30, 2022): 74. http://dx.doi.org/10.3390/galaxies10030074.

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Gamma-ray bursts (GRBs) are the most luminous explosions in the Universe and are powered by ultra-relativistic jets. Their prompt γ-ray emission briefly outshines the rest of the γ-ray sky, making them detectable from cosmological distances. A burst is followed by, and sometimes partially overlaps with, a similarly energetic but very broadband and longer-lasting afterglow emission. While most GRBs are detected below a few MeV, over 100 have been detected at high (≳0.1 GeV) energies, and several have now been observed up to tens of GeV with the Fermi Large Area Telescope (LAT). A new electromagnetic window in the very-high-energy (VHE) domain (≳0.1 TeV) was recently opened with the detection of an afterglow emission in the (0.1–1)TeV energy band by ground-based imaging atmospheric Cherenkov telescopes. The emission mechanism for the VHE spectral component is not fully understood, and its detection offers important constraints for GRB physics. This review provides a brief overview of the different leptonic and hadronic mechanisms capable of producing a VHE emission in GRBs. The same mechanisms possibly give rise to the high-energy spectral component seen during the prompt emission of many Fermi-LAT GRBs. Possible origins of its delayed onset and long duration well into the afterglow phase, with implications for the emission region and relativistic collisionless shock physics, are discussed. Key results for using GRBs as ideal probes for constraining models of extra-galactic background light and intergalactic magnetic fields, as well as for testing Lorentz invariance violation, are presented.

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McCann, Andrew, Michael Daniel, David J. Fegan, Stephen Gammell, Peter Cogan, and John Quinn. "The Search for pulsed TeV gamma-ray sources." Proceedings of the International Astronomical Union 1, S230 (August 2005): 107–8. http://dx.doi.org/10.1017/s1743921306008027.

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Fragile, P. Chris, Grant J. Mathews, John Poirier, and Tomonori Totani. "Constraints on models for TeV gamma rays from gamma-ray bursts." Astroparticle Physics 20, no. 5 (February 2004): 591–607. http://dx.doi.org/10.1016/j.astropartphys.2003.08.005.

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Amenomori, M., S. Asano, Y. W. Bao, X. J. Bi, D. Chen, T. L. Chen, W. Y. Chen, et al. "Measurement of the Gamma-Ray Energy Spectrum beyond 100 TeV from the HESS J1843–033 Region." Astrophysical Journal 932, no. 2 (June 1, 2022): 120. http://dx.doi.org/10.3847/1538-4357/ac6ef4.

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Abstract HESS J1843–033 is a very high energy gamma-ray source whose origin remains unidentified. This work presents, for the first time, the energy spectrum of gamma rays beyond 100 TeV from the HESS J1843–033 region using the data recorded by the Tibet air shower array and its underground muon detector array. A gamma-ray source with an extension of 0.°34 ± 0.°12 is successfully detected above 25 TeV at (α, δ) = (281.°09 ± 0.°10, −3.°76 ± 0.°09) near HESS J1843–033 with a statistical significance of 6.2σ, and the source is named TASG J1844–038. The position of TASG J1844–038 is consistent with those of HESS J1843–033, eHWC J1842–035, and LHAASO J1843–0338. The measured gamma-ray energy spectrum in 25 TeV < E < 130 TeV is described with dN / dE = ( 9.70 ± 1.89 ) × 10 − 16 (E/40 TeV)−3.26±0.30 TeV−1 cm−2 s−1, and the spectral fit to the combined spectra of HESS J1843–033, LHAASO J1843–0338, and TASG J1844–038 implies the existence of a cutoff at 49.5 ± 9.0 TeV. Associations of TASG J1844–038 with SNR G28.6–0.1 and PSR J1844–0346 are also discussed in detail for the first time.

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de Gouveia Dal Pino, Elisabete M. "Cherenkov Telescope Array: Unveiling the Gamma Ray Universe and its Cosmic Particle Accelerators." Proceedings of the International Astronomical Union 11, A29A (August 2015): 337–39. http://dx.doi.org/10.1017/s1743921316003227.

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AbstractGamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. The Cherenkov Telescope Array (CTA) is an international initiative to build the next-generation ground-based gamma-ray observatory which will have a factor of 5-10 improvement in sensitivity in the 100 GeV - 10 TeV range and an extension to energies well below 100 GeV and above 100 TeV. CTA is planned to consist of two arrays (one in the North and another in the South Hemisphere) and will provide the deepest insight ever reached into the non-thermal high-energy Universe and its particle accelerators.

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Raubenheimer, B. Christo. "Tev gamma-ray astronomy in South Africa." Astrophysics and Space Science 230, no. 1-2 (August 1995): 263–77. http://dx.doi.org/10.1007/bf00658185.

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Cassé, Michel, Bruno Mansoulié, and Joseph Silk. "From diffuse extragalactic and galactic gamma-rays to limits on extra dimensions." Monthly Notices of the Royal Astronomical Society: Letters 492, no. 1 (October 15, 2019): L66—L68. http://dx.doi.org/10.1093/mnrasl/slz155.

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ABSTRACT We derive the maximum fraction of energy emitted in the form of massive (Kaluza–Klein) gravitons by core collapse supernovae, and the corresponding minimal extra-dimensional Planck mass M* in the ADD gravity framework at TeV scales. Our constraints arise (a) from the extragalactic gamma-ray background observed by Fermi-LAT after astrophysical sources have been removed and (b) via the residual galactic emission left after astrophysical and potentially dark matter emission have been removed. We focus on a number of extra dimensions 3 and 4, since M* is then in the TeV range, where astrophysical and collider constraints compete. Lower limits on M* are derived in the case (a) of 8.0 and 1.1 TeV for n = 3 and n = 4, respectively, and in the case (b) of 16 and 1.9 TeV. These limits are especially robust and insensitive to the various uncertainties involved.

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Alvarez‐Muniz, J., and F. Halzen. "Muon Detection of TeV Gamma Rays from Gamma‐Ray Bursts." Astrophysical Journal 521, no. 2 (August 20, 1999): 928–33. http://dx.doi.org/10.1086/307591.

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Yamazaki, Ryo, Yuri Sato, Takanori Sakamoto, and Motoko Serino. "Less noticeable shallow decay phase in early X-ray afterglows of GeV/TeV-detected gamma-ray bursts." Monthly Notices of the Royal Astronomical Society 494, no. 4 (April 24, 2020): 5259–69. http://dx.doi.org/10.1093/mnras/staa1095.

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ABSTRACT The nature of the shallow decay phase in the X-ray afterglow of the gamma-ray burst (GRB) is not yet clarified. We analyse the data of early X-ray afterglows of 26 GRBs triggered by Burst Alert Telescope onboard Neil Gehrels Swift Observatory and subsequently detected by Fermi Large Area Telescope (LAT) and/or Imaging Atmospheric Cherenkov Telescopes. It is found that nine events (including two out of three very-high-energy gamma-ray events) have no shallow decay phase and that their X-ray afterglow light curves are well described by single power-law model except for the jet break at later epoch. The rest are fitted by double power-law model and have a break in the early epoch (around ks), however, eight events (including a very-high-energy gamma-ray event) have the pre-break decay index larger than 0.7. We also analyse the data of well-sampled X-ray afterglows of GRBs without LAT detection and compare their decay properties with those of high-energy and very-high-energy gamma-ray events. It is found that for the GeV/TeV bursts, the fraction of events whose X-ray afterglows are described by single power law is significantly larger than those for non-GeV/TeV GRBs. Even if the GeV/TeV GRBs have shallow decay phase, their decay slope tends to be steeper than non-GeV/TeV bursts, that is, they have less noticeable shallow decay phase in the early X-ray afterglow. A possible interpretation along with the energy injection model is briefly discussed.

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Miceli, Davide, and Lara Nava. "Gamma-Ray Bursts Afterglow Physics and the VHE Domain." Galaxies 10, no. 3 (May 5, 2022): 66. http://dx.doi.org/10.3390/galaxies10030066.

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Afterglow radiation in gamma-ray bursts (GRB), extending from the radio band to GeV energies, is produced as a result of the interaction between the relativistic jet and the ambient medium. Although in general the origin of the emission is robustly identified as synchrotron radiation from the shock-accelerated electrons, many aspects remain poorly constrained, such as the role of inverse Compton emission, the particle acceleration mechanism, the properties of the environment and of the GRB jet itself. The extension of the afterglow emission into the TeV band has been discussed and theorized for years, but has eluded for a long time the observations. Recently, the Cherenkov telescopes, MAGIC and H.E.S.S., have unequivocally proven that afterglow radiation is also produced above 100 GeV, up to at least a few TeV. The accessibility of the TeV spectral window will largely improve with the upcoming facility CTA (the Cherenkov Telescope Array). In this review article, we first revise the current model for afterglow emission in GRBs, its limitations and open issues. Then, we describe the recent detections of very high energy emission from GRBs and the origin of this radiation. Implications on the understanding of afterglow radiation and constraints on the physics of the involved processes will be deeply investigated, demonstrating how future observations, especially by the CTA Observatory, are expected to give a key contribution in improving our comprehension of such elusive sources.

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Pais, Matteo, Christoph Pfrommer, Kristian Ehlert, Maria Werhahn, and Georg Winner. "Constraining the coherence scale of the interstellar magnetic field using TeV gamma-ray observations of supernova remnants." Monthly Notices of the Royal Astronomical Society 496, no. 2 (June 12, 2020): 2448–61. http://dx.doi.org/10.1093/mnras/staa1678.

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ABSTRACT Galactic cosmic rays (CRs) are believed to be accelerated at supernova remnant (SNR) shocks. In the hadronic scenario, the TeV gamma-ray emission from SNRs originates from decaying pions that are produced in collisions of the interstellar gas and CRs. Using CR-magnetohydrodynamic simulations, we show that magnetic obliquity-dependent shock acceleration is able to reproduce the observed TeV gamma-ray morphology of SNRs such as Vela Jr and SN1006 solely by varying the magnetic morphology. This implies that gamma-ray bright regions result from quasi-parallel shocks (i.e. when the shock propagates at a narrow angle to the upstream magnetic field), which are known to efficiently accelerate CR protons, and that gamma-ray dark regions point to quasi-perpendicular shock configurations. Comparison of the simulated gamma-ray morphology to observations allows us to constrain the magnetic coherence scale λB around Vela Jr and SN1006 to $\lambda _B \simeq 13_{-4.3}^{+13}$ pc and $\lambda _B \gt 200_{-40}^{+50}$ pc, respectively, where the ambient magnetic field of SN1006 is consistent with being largely homogeneous. We find consistent pure hadronic and mixed hadronic-leptonic models that both reproduce the multifrequency spectra from the radio to TeV gamma-rays and match the observed gamma-ray morphology. Finally, to capture the propagation of an SNR shock in a clumpy interstellar medium, we study the interaction of a shock with a dense cloud with numerical simulations and analytics. We construct an analytical gamma-ray model for a core collapse SNR propagating through a structured interstellar medium, and show that the gamma-ray luminosity is only biased by 30 per cent for realistic parameters.

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Wang, Xiang-Yu, Zhuo Li, and Peter Mészáros. "GeV-TeV and X-Ray Flares from Gamma-Ray Bursts." Astrophysical Journal 641, no. 2 (April 3, 2006): L89—L92. http://dx.doi.org/10.1086/504151.

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Liang, Yun-Feng, Xing-Fu Zhang, Ji-Gui Cheng, Hou-Dun Zeng, Yi-Zhong Fan, and En-Wei Liang. "Effect of axion-like particles on the spectrum of the extragalactic gamma-ray background." Journal of Cosmology and Astroparticle Physics 2021, no. 11 (November 1, 2021): 030. http://dx.doi.org/10.1088/1475-7516/2021/11/030.

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Abstract Axion-like particles (ALPs) provide a feasible explanation for the observed lower TeV opacity of the Universe. If the anomaly TeV transparency is caused by ALPs, then the fluxes of distant extragalactic sources will be enhanced at photon energies beyond TeV, resulting in an enhancement of the observed extragalactic gamma-ray background (EGB) spectrum. In this work, we have investigated the ALP modulation on the EGB spectrum at TeV energies. Our results show that in the most optimistic case, the existence of ALPs can cause the EGB spectrum to greatly deviate from the prediction of a pure extragalactic-background-light (EBL) absorption scenario. The deviation occurs at approximately ≳1 TeV, and the current EGB measurements by Fermi-LAT cannot identify such an effect. We also find that most of the sensitive ALP parameters have been ruled out by existing constraints, leaving only a small region of unrestricted parameters that can be probed using the EGB effect investigated in this work. Observations from forthcoming very-high-energy instruments like LHAASO and CTA may be beneficial for the study of this effect.

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Acciari, V. A., S. Ansoldi, L. A. Antonelli, A. Arbet Engels, K. Asano, D. Baack, A. Babić, et al. "Studying the nature of the unidentified gamma-ray source HESS J1841−055 with the MAGIC telescopes." Monthly Notices of the Royal Astronomical Society 497, no. 3 (July 24, 2020): 3734–45. http://dx.doi.org/10.1093/mnras/staa2135.

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ABSTRACT We investigate the physical nature and origin of the gamma-ray emission from the extended source HESS J1841−055 observed at TeV and GeV energies. We observed HESS J1841−055 at TeV energies for a total effective time of 43 h with the MAGIC telescopes, in 2012 and 2013. Additionally, we analysed the GeV counterpart making use of about 10 yr of Fermi-LAT data. Using both Fermi-LAT and MAGIC, we study both the spectral and energy-dependent morphology of the source for almost four decades of energy. The origin of the gamma-ray emission from this region is investigated using multiwaveband information on sources present in this region, suggested to be associated with this unidentified gamma-ray source. We find that the extended emission at GeV–TeV energies is best described by more than one source model. We also perform the first energy-dependent analysis of the HESS J1841−055 region at GeV–TeV. We find that the emission at lower energies comes from a diffuse or extended component, while the major contribution of gamma rays above 1 TeV arises from the southern part of the source. Moreover, we find that a significant curvature is present in the combined observed spectrum of MAGIC and Fermi-LAT. The first multiwavelength spectral energy distribution of this unidentified source shows that the emission at GeV–TeV energies can be well explained with both leptonic and hadronic models. For the leptonic scenario, bremsstrahlung is the dominant emission compared to inverse Compton. On the other hand, for the hadronic model, gamma-ray resulting from the decay of neutral pions (π0) can explain the observed spectrum. The presence of dense molecular clouds overlapping with HESS J1841−055 makes both bremsstrahlung and π0-decay processes the dominant emission mechanisms for the source.

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30

PAREDES, J. M. "VHE GAMMA-RAYS FROM GALACTIC X-RAY BINARY SYSTEMS." International Journal of Modern Physics D 17, no. 10 (September 2008): 1849–58. http://dx.doi.org/10.1142/s0218271808013480.

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The detection of TeV gamma-rays from LS 5039 and the binary pulsar PSR B1259–63 by HESS, and from LS I +61 303 and the stellar-mass black hole Cygnus X-1 by MAGIC, provides clear evidence of very efficient acceleration of particles to multi-TeV energies in X-ray binaries. These observations demonstrate the richness of nonthermal phenomena in compact galactic objects containing relativistic outflows or winds produced near black holes and neutron stars. I review here some of the main observational results on very high energy (VHE) γ-ray emission from X-ray binaries, as well as some of the proposed scenarios to explain the production of VHE γ-rays. I put special emphasis on the flare TeV emission, suggesting that the flaring activity might be a common phenomena in X-ray binaries.

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31

Bicknell, G. V., and S. J. Wagner. "TeV gamma ray opacity in PKS 2155-304." Astronomy & Astrophysics 526 (December 22, 2010): A61. http://dx.doi.org/10.1051/0004-6361/200913267.

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32

Raubenheimer, B. C., A. R. North, O. C. de Jager, P. J. Meintjes, and H. I. Nel. "TeV gamma-ray properties of VELA X-1." Astrophysical Journal 428 (June 1994): 777. http://dx.doi.org/10.1086/174286.

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33

Delahaye, T., A. Fiasson, M. Pohl, and P. Salati. "The GeV-TeV Galactic gamma-ray diffuse emission." Astronomy & Astrophysics 531 (June 7, 2011): A37. http://dx.doi.org/10.1051/0004-6361/201116647.

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34

Arlen, T., T. Aune, M. Beilicke, W. Benbow, A. Bouvier, J. H. Buckley, V. Bugaev, et al. "RAPID TeV GAMMA-RAY FLARING OF BL LACERTAE." Astrophysical Journal 762, no. 2 (December 19, 2012): 92. http://dx.doi.org/10.1088/0004-637x/762/2/92.

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35

Şentürk, G. D., M. Errando, M. Böttcher, and R. Mukherjee. "GAMMA-RAY OBSERVATIONAL PROPERTIES OF TeV-DETECTED BLAZARS." Astrophysical Journal 764, no. 2 (January 30, 2013): 119. http://dx.doi.org/10.1088/0004-637x/764/2/119.

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36

Kosack, K., H. M. Badran, I. H. Bond, P. J. Boyle, S. M. Bradbury, J. H. Buckley, D. A. Carter-Lewis, et al. "TeV Gamma-Ray Observations of the Galactic Center." Astrophysical Journal 608, no. 2 (May 18, 2004): L97—L100. http://dx.doi.org/10.1086/422469.

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37

Adriani, O., Y. Akaike, K. Asano, Y. Asaoka, E. Berti, G. Bigongiari, W. R. Binns, et al. "CALET Search for Electromagnetic Counterparts of Gravitational Waves during the LIGO/Virgo O3 Run." Astrophysical Journal 933, no. 1 (July 1, 2022): 85. http://dx.doi.org/10.3847/1538-4357/ac6f53.

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Abstract The CALorimetric Electron Telescope (CALET) on the International Space Station consists of a high-energy cosmic-ray CALorimeter (CAL) and a lower-energy CALET Gamma-ray Burst Monitor (CGBM). CAL is sensitive to electrons up to 20 TeV, cosmic-ray nuclei from Z = 1 through Z ∼ 40, and gamma rays over the range 1 GeV–10 TeV. CGBM observes gamma rays from 7 keV to 20 MeV. The combined CAL-CGBM instrument has conducted a search for gamma-ray bursts (GRBs) since 2015 October. We report here on the results of a search for X-ray/gamma-ray counterparts to gravitational-wave events reported during the LIGO/Virgo observing run O3. No events have been detected that pass all acceptance criteria. We describe the components, performance, and triggering algorithms of the CGBM—the two Hard X-ray Monitors consisting of LaBr3(Ce) scintillators sensitive to 7 keV–1 MeV gamma rays and a Soft Gamma-ray Monitor BGO scintillator sensitive to 40 keV–20 MeV—and the high-energy CAL consisting of a charge detection module, imaging calorimeter, and the fully active total absorption calorimeter. The analysis procedure is described and upper limits to the time-averaged fluxes are presented.

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38

Banik, Prabir, Arunava Bhadra, and Abhijit Bhattacharyya. "Interpreting correlated observations of cosmic rays and gamma-rays from Centaurus A with a proton blazar inspired model." Monthly Notices of the Royal Astronomical Society 500, no. 1 (October 28, 2020): 1087–94. http://dx.doi.org/10.1093/mnras/staa3343.

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ABSTRACT The nearest active radio galaxy Centaurus (Cen) A is a gamma-ray emitter in GeV–TeV energy scale. The high energy stereoscopic system (HESS) and non-simultaneous Fermi–Large Area Telescope observation indicate an unusual spectral hardening above few GeV energies in the gamma-ray spectrum of Cen A. Very recently the HESS observatory resolved the kilo parsec (kpc)-scale jets in Centaurus A at TeV energies. On the other hand, the Pierre Auger Observatory (PAO) detects a few ultrahigh energy cosmic ray (UHECR) events from Cen-A. The proton blazar inspired model, which considers acceleration of both electrons and hadronic cosmic rays in active galactic nuclei (AGN) jet, can explain the observed coincident high-energy neutrinos and gamma-rays from Ice-cube detected AGN jets. Here, we have employed the proton blazar inspired model to explain the observed GeV–TeV gamma-ray spectrum features including the spectrum hardening at GeV energies along with the PAO observation on cosmic rays from Cen-A. Our findings suggest that the model can explain consistently the observed electromagnetic spectrum in combination with the appropriate number of UHECRs from Cen A.

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39

MÉSZÁROS, PETER. "GAMMA-RAY BURSTS AS VHE-UHE SOURCES." International Journal of Modern Physics D 17, no. 09 (September 2008): 1319–32. http://dx.doi.org/10.1142/s0218271808012875.

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Gamma-ray bursts are capable of accelerating cosmic rays up to GZK energies Ep ~ 1020 eV, which can lead to a flux at Earth comparable to that observed by large EAS arrays such as Auger. The semi-relativistic outflows inferred in GRB-related hypernovae are also likely sources of somewhat lower energy cosmic rays. Leptonic processes, such as synchrotron and inverse Compton, as well as hadronic processes, can lead to GeV-TeV gamma-rays measurable by GLAST, AGILE, or ACTs, providing useful probes of the burst physics and model parameters. Photo-meson interactions also produce neutrinos at energies ranging from sub-TeV to EeV, which will be probed with forthcoming experiments such as IceCube, ANITA and KM3NeT. This would provide information about the fundamental interaction physics, the acceleration mechanism, the nature of the sources and their environment.

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40

Kisaka, Shota, and Norita Kawanaka. "TeV cosmic-ray electrons from millisecond pulsars." Proceedings of the International Astronomical Union 8, S291 (August 2012): 419–21. http://dx.doi.org/10.1017/s1743921312024350.

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AbstractRecent γ-ray observations by the Fermi Gamma-Ray Space Telescope suggest that the γ-ray millisecond pulsar (MSP) population is separated into two subclasses with respect to pair multiplicity. Here, we calculate the cosmic-ray electron/positron spectra from MSPs. Based on the assumption of equipartition in the pulsar-wind region, the typical energy of electrons/positrons ejected by an MSP with pair multiplicity of the order of unity is ~50 TeV. In this case, we find that a large peak in the 10-50 TeV energy range would be observed in the cosmic-ray electron/positron spectrum. Even if the fraction of pair-starved MSPs is 10%, a large peak would be detectable with future missions such as CALET and CTA.

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41

Foffano, L., E. Prandini, A. Franceschini, and S. Paiano. "A new hard X-ray-selected sample of extreme high-energy peaked BL Lac objects and their TeV gamma-ray properties." Monthly Notices of the Royal Astronomical Society 486, no. 2 (March 20, 2019): 1741–62. http://dx.doi.org/10.1093/mnras/stz812.

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ABSTRACT Extreme high-energy peaked BL Lac objects (EHBLs) are an emerging class of blazars with exceptional spectral properties. The non-thermal emission of the relativistic jet peaks in the spectral energy distribution (SED) plot with the synchrotron emission in X-rays and with the gamma-ray emission in the TeV range or above. These high photon energies may represent a challenge for the standard modelling of these sources. They are important for the implications on the indirect measurements of the extragalactic background light, the intergalactic magnetic field estimate, and the possible origin of extragalactic high-energy neutrinos. In this paper, we perform a comparative study of the multiwavelength spectra of 32 EHBL objects detected by the Swift-BAT telescope in the hard X-ray band and by the Fermi-LAT telescope in the high-energy gamma-ray band. The source sample presents uniform spectral properties in the broad-band SEDs, except for the TeV gamma-ray band where an interesting bimodality seems to emerge. This suggests that the EHBL class is not homogeneous, and a possible subclassification of the EHBLs may be unveiled. Furthermore, in order to increase the number of EHBLs and settle their statistics, we discuss the potential detectability of the 14 currently TeV gamma-ray undetected sources in our sample by the Cherenkov telescopes.

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42

Morselli, Aldo. "Latest Results from the Fermi Gamma-Ray Telescope." Acta Polytechnica CTU Proceedings 1, no. 1 (December 4, 2014): 139–45. http://dx.doi.org/10.14311/app.2014.01.0139.

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Can we learn about New Physics with astronomical and astro-particle data? Since its launch in 2008, the Large Area Telescope, onboard of the Fermi Gamma-ray Space Telescope, has detected the largest amount of gamma rays in the 20 MeV - 300 GeV energy range and electrons + positrons in the 7 GeV- 1 TeV range, opening a new observational window on a wide variety of astrophysical objects.

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43

Kohri, Kazunori, Yutaka Ohira, and Kunihito Ioka. "Gamma-ray flare and absorption in the Crab nebula: lovely TeV-PeV astrophysics." Monthly Notices of the Royal Astronomical Society 424, no. 3 (July 13, 2012): 2249–54. http://dx.doi.org/10.1111/j.1365-2966.2012.21388.x.

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44

Cristofari, P., M. Renaud, A. Marcowith, V. V. Dwarkadas, and V. Tatischeff. "Time-dependent high-energy gamma-ray signal from accelerated particles in core-collapse supernovae: the case of SN 1993J." Monthly Notices of the Royal Astronomical Society 494, no. 2 (April 13, 2020): 2760–65. http://dx.doi.org/10.1093/mnras/staa984.

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ABSTRACT Some core-collapse supernovae are likely to be efficient cosmic ray accelerators up to the PeV range, and therefore, to potentially play an important role in the overall Galactic cosmic ray population. The TeV gamma-ray domain can be used to study particle acceleration in the multi-TeV and PeV range. This motivates the study of the detectability of such supernovae by current and future gamma-ray facilities. The gamma-ray emission of core-collapse supernovae strongly depends on the level of the two-photon annihilation process: high-energy gamma-ray photons emitted at the expanding shock wave following the supernova explosion can interact with soft photons from the supernova photosphere through the pair production channel, thereby strongly suppressing the flux of gamma-rays leaving the system. In the case of SN 1993J, whose photospheric and shock-related parameters are well measured, we calculate the temporal evolution of the expected gamma-ray attenuation by accounting for the temporal and geometrical effects. We find the attenuation to be of about 10 orders of magnitude in the first few days after the supernova explosion. The probability of detection of a supernova similar to SN 1993J with the Cherenkov Telescope Array is highest if observations are performed either earlier than 1 d, or later than 10 d after the explosion, when the gamma-ray attenuation decreases to about two orders of magnitude.

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45

Sitarek, Julian. "TeV Instrumentation: Current and Future." Galaxies 10, no. 1 (January 27, 2022): 21. http://dx.doi.org/10.3390/galaxies10010021.

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During the last 20 years, TeV astronomy has turned from a fledgling field, with only a handful of sources, into a fully-developed astronomy discipline, broadening our knowledge on a variety of types of TeV gamma-ray sources. This progress has been mainly achieved due to the currently operating instruments: imaging atmospheric Cherenkov telescopes, surface arrays and water Cherenkov detectors. Moreover, we are at the brink of a next generation of instruments, with a considerable leap in performance parameters. This review summarizes the current status of the TeV astronomy instrumentation, mainly focusing on the comparison of the different types of instruments and analysis challenges, as well as providing an outlook into the future installations. The capabilities and limitations of different techniques of observations of TeV gamma rays are discussed, as well as synergies to other bands and messengers.

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46

Thomas, Brian C., Dimitra Atri, and Adrian L. Melott. "Gamma-ray bursts: not so much deadlier than we thought." Monthly Notices of the Royal Astronomical Society 500, no. 2 (October 30, 2020): 1970–73. http://dx.doi.org/10.1093/mnras/staa3364.

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ABSTRACT We analyse the additional effect on planetary atmospheres of recently detected gamma-ray burst afterglow photons in the range up to 1 TeV. For an Earth-like atmosphere, we find that there is a small additional depletion in ozone versus that modeled for only prompt emission. We also find a small enhancement of muon flux at the planet surface. Overall, we conclude that the additional afterglow emission, even with TeV photons, does not result in a significantly larger impact over that found in past studies.

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47

Finke, Justin D., and Soebur Razzaque. "Possible Evidence for Lorentz Invariance Violation in Gamma-Ray Burst 221009A." Astrophysical Journal Letters 942, no. 1 (January 1, 2023): L21. http://dx.doi.org/10.3847/2041-8213/acade1.

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Abstract The preliminary detections of the gamma-ray burst 221009A up to 18 TeV by LHAASO and up to 251 TeV by Carpet 2 have been reported through Astronomer’s Telegrams and Gamma-ray Coordination Network circulars. Since this burst is at redshift z = 0.1505, these photons may at first seem to have a low probability to avoid pair production off of background radiation fields and survive to reach detectors on Earth. By extrapolating the reported 0.1–1.0 GeV Fermi Large Area Telescope spectrum from this burst to higher energies and using this to limit the intrinsic spectrum of the burst, we show that the survival of the 18 TeV photon detected by LHAASO is not unlikely with many recent extragalactic background light models, although the detection of a 251 TeV event is still very unlikely. This can be resolved if Lorentz invariance is violated at an energy scale E QG ≲ 49E Planck in the linear (n = 1) case, and E QG ≲ 10−6 E Planck in the quadratic (n = 2) case (95% confidence limits), where E Planck is the Planck energy. This could potentially be the first evidence for subluminal Lorentz invariance violation.

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Pais, Matteo, and Christoph Pfrommer. "Simulating TeV gamma-ray morphologies of shell-type supernova remnants." Monthly Notices of the Royal Astronomical Society 498, no. 4 (September 18, 2020): 5557–73. http://dx.doi.org/10.1093/mnras/staa2827.

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ABSTRACT Supernova remnant (SNR) shocks provide favourable sites of cosmic ray (CR) proton acceleration if the local magnetic field direction is quasi-parallel to the shock normal. Using the moving-mesh magnetohydrodynamical (MHD) code arepo we present a suite of SNR simulations with CR acceleration in the Sedov–Taylor phase that combine different magnetic field topologies, density distributions with gradients and large-scale fluctuations, and – for our core-collapse SNRs – a multiphase interstellar medium with dense clumps with a contrast of 104. Assuming the hadronic gamma-ray emission model for the TeV gamma-ray emission, we find that large-amplitude density fluctuations of δρ/ρ0 ≳ 75 per cent are required to strongly modulate the gamma-ray emissivity in a straw man’s model in which the acceleration efficiency is independent of magnetic obliquity. However, this causes strong corrugations of the shock surface that are ruled out by gamma-ray observations. By contrast, magnetic obliquity-dependent acceleration can easily explain the observed variance in gamma-ray morphologies ranging from SN1006 (with a homogeneous magnetic field) to Vela Junior and RX J1713 (with a turbulent field) in a single model that derives from plasma particle-in-cell simulations. Our best-fitting model for SN1006 has a large-scale density gradient of ∇n ≃ 0.0034 cm−3 pc−1 pointing from south-west to north-east and a magnetic inclination with the plane of the sky of ≲10°. Our best-fitting model for Vela Junior and RX J1713 adopts a combination of turbulent magnetic field and dense clumps to explain their TeV gamma-ray morphologies and moderate shock corrugations.

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Levinson, Amir, and Benoît Cerutti. "Particle-in-cell simulations of pair discharges in a starved magnetosphere of a Kerr black hole." Astronomy & Astrophysics 616 (August 2018): A184. http://dx.doi.org/10.1051/0004-6361/201832915.

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We investigate the dynamics and emission of a starved magnetospheric region (gap) formed in the vicinity of a Kerr black hole horizon, using a new, fully general relativistic particle-in-cell code that implements Monte Carlo methods to compute gamma-ray emission and pair production through the interaction of pairs and gamma rays with soft photons emitted by the accretion flow. It is found that when the Thomson length for collision with disk photons exceeds the gap width, screening of the gap occurs through low-amplitude, rapid plasma oscillations that produce self-sustained pair cascades, with quasi-stationary pair and gamma-ray spectra, and with a pair multiplicity that increases in proportion to the pair production opacity. The gamma-ray spectrum emitted from the gap peaks in the TeV band, with a total luminosity that constitutes a fraction of about 10−5 of the corresponding Blandford−Znajek power. This stage is preceded by a prompt discharge phase of duration ∼rg/c, during which the potential energy initially stored in the gap is released as a flare of curvature TeV photons. We speculate that the TeV emission observed in M87 may be produced by pair discharges in a spark gap.

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50

Torresi, Eleonora. "Gamma-ray emission in radio galaxies, from MeV to TeV." Proceedings of the International Astronomical Union 14, S342 (May 2018): 158–66. http://dx.doi.org/10.1017/s1743921318007895.

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AbstractThanks to the Fermi λ-ray satellite and the current Imaging Atmospheric Cherenkov Telescopes, radio galaxies have arisen as a new class of high- and very-high energy emitters. The favourable orientation of their jets makes radio galaxies extremely relevant in addressing important issues such as: (i) revealing the jet structure complexity; (ii) localising the emitting region(s) of high- and very-high energy radiation; (iii) understanding the physical processes producing these photons. In this review the main results on the λ-ray emission studies of radio galaxies from the MeV to TeV regimes will be presented, and the impact of future Cherenkov Telescope Array observations will be discussed.

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