Highlights from TeV Extragalactic Sources Prandini, E. (2017)
Abstract: The number of discovered TeV sources populating the extragalactic sky in 2017 is nearly 70, mostly blazars located up to a redshift ~1. Ten years ago, in 2007, less than 20 TeV emitters were known, up to a maximum redshift of 0.2. This is a major achievement of current generation of Cherenkov telescopes operating in synergy with optical, X-ray, and GeV gamma-ray telescopes. A review of selected results from the extragalactic TeV sky is presented, with particular emphasis on recently detected distant sources.
TeV Astrophysics: Probing the Relativistic Universe Barres de Almeida, U. (2017)
Abstract: We focus our contribution to this volume on the relativistic Universe and on present and future experimental efforts in Teraelectronvolt Astronomy, i.e., the observation of cosmic gamma-ray photons above 100 GeV, employing ground-based imaging atmospheric Cherenkov telescopes. The main topics of our contribution are directed to the discussion of the importance of TeV observations for a better understanding of the cosmic-ray content of the galaxy and of the Universe’s most energetic astrophysical objects. In particular, we are concerned with cosmic ray accelerators: supernova remnants, pulsars and their environments, active galaxies and black holes in general. In perspective, we will briefly discuss the role of the Cherenkov Telescope Array (CTA) in the current revolution that astroparticle physics is undergoing, emphasising the key position occupied by South America in this context. The 21st Century promises to be a golden age for astroparticle physics, and it is expected that much of the frontier research in relativistic astrophysics in next decades will be associated to advances in this growing field of observational astronomy.
Introduction to high-energy gamma-ray astronomy Degrange, B. & Fontaine, G. (2016)
Abstract: The present issue is the first of a two-volume reviewdevoted to gamma-ray astronomy above 100 MeV, which has witnessedconsiderable progress over the last 20 years. The motivations forresearch in this area are explained, the follow-on articles of thesetwo issues are introduced and a brief history of the field isgiven.
Ground-based detectors in very-high-energy gamma-ray astronomy de Naurois, M. & Mazin, D. (2015)
Abstract: Following the discovery of the cosmic rays by Victor Hessin 1912, more than 70 years and numerous technological developmentswere needed before an unambiguous detection of the firstvery-high-energy gamma-ray source in 1989 was made. Since thisdiscovery the field on very-high-energy gamma-ray astronomyexperienced a true revolution: A second, then a third generation ofinstruments were built, observing the atmospheric cascades from theground, either through the atmospheric Cherenkov light they comprise,or via the direct detection of the charged particles theycarry. Present arrays, 100 times more sensitive than the pioneeringexperiments, have detected a large number of astrophysical sources ofvarious types, thus opening a new window on the non-thermalUniverse. New, even more sensitive instruments are currently beingbuilt; these will allow us to explore further this fascinatingdomain. In this article we describe the detection techniques, thehistory of the field and the prospects for the future of ground-basedvery-high-energy gamma-ray astronomy.
Atmospheric Cherenkov Gamma-ray Telescopes Holder, J. (2015)
Abstract: The stereoscopic imaging atmospheric Cherenkov technique,developed in the 1980s and 1990s, is now used by a number of existingand planned gamma-ray observatories around the world. It provides themost sensitive view of the very high energy gamma-ray sky (above 30GeV), coupled with relatively good angular and spectral resolutionover a wide field-of-view. This Chapter summarizes the details of thetechnique, including descriptions of the telescope optical systems andcameras, as well as the most common approaches to data analysis andgamma-ray reconstruction.
Status of ground-based gamma-ray astronomy Lemoine-Goumard, M. (2015)
Abstract: This article is the write-up of a rapporteur talk givenat the 34th ICRC in The Hague, Netherlands. It attempts to review theresults and developments presented at the conference and associated tothe vibrant field of ground-based gamma-ray astronomy. In total, itaims to give an overview of the 19 gamma-ray sessions, 84 talks and176 posters presented at the 34th ICRC on this topic. New technicaladvances and projects will be described with an emphasis given on thecosmic-ray related studies of the Universe.
The Very High Energy Sky from ~20 GeV to Hundreds of TeV - SelectedHighlights de Naurois, M. (2015)
Abstract: After nearly a decade of operation, the three majorarrays of atmospheric Cherenkov telescopes have revolutionized ourview of the Very High Energy Universe, unveiling more than 100 sourcesof various types. MAGIC, consisting of two 17 m diameter telescopes onthe Canary island of La Palma, and VERITAS, with four 12 m telescopesinstalled in southern Arizona, USA, have primarily explored theextragalactic sky, where the majority of the sources are activegalactic nuclei (AGN), with gamma-ray emission originating in theirrelativistic jets. ...... Highlights of these observations withH.E.S.S., MAGIC and VERITAS have been presented and discussed at theconference.
Space- and Ground-Based Gamma-Ray Astrophysics Funk, S. (2015)
Abstract: In recent years, observational gamma-ray astronomy hasseen a remarkable range of exciting new results in the high-energy andvery-high energy regimes. Coupled with extensive theoretical andphenomenological studies of non-thermal processes in the Universethese observations have provided a deep insight into a number offundamental problems of high energy astrophysics and astroparticlephysics. Although the main moti- vations of gamma-ray astronomy remainunchanged, recent observational results have contributed significantlytowards our understanding of many related phenomena. This article aimsto review the most important results in the young and rapidlydeveloping field of gamma-ray astrophysics.
Ground-Based Gamma Ray Astronomy Holder, J. (2014)
Abstract: This paper is the write-up of a rapporteur talk given bythe author at the 33rd International Cosmic Ray Conference in Rio deJaneiro, Brazil, in 2013. It attempts to summarize results anddevelopments in ground-based gamma-ray observations andinstrumentation from among the ˜300 submissions to the gamma-raysessions of the meeting. Satellite observations and theoreticaldevelopments were covered by a companion rapporteur (Stawarz, L., 33rdICRC, Rio de Janeiro, Brazil, Rapporteur talk: Space-based Gamma-RayAstronomy, 2013). Any review of this nature is unavoidably subjectiveand incomplete. Nevertheless, the article should provide a usefulstatus report for those seeking an overview of this exciting andfast-moving field.
High energy astrophysics Zhang, B. & Meszaros, P. (2014)
Abstract: High energy astrophysics is one of the most activebranches in the contemporary astrophysics. It studies astrophysicalobjects that emit X-ray and γ-ray photons, such as accretingsuper-massive and stellar-size black holes, and various species ofneutron stars. With the operations of many space-borne andground-based observational facilities, high energy astrophysics hasenjoyed rapid development in the past decades. It is foreseen that thefield will continue to advance rapidly in the coming decade, withpossible ground-breaking discoveries of astrophysical sources in thehigh-energy neutrino and gravitational wave channels. This SpecialIssue of Frontiers of Physics is dedicated to a systematic survey ofthe field of high energy astrophysics as it stands in 2013.
Evolution of ground-based gamma-ray astronomy from the early days tothe Cherenkov Telescope Arrays Hillas, A. M. (2013)
Abstract: Most of what we know of cosmic gamma rays has come fromspacecraft, but at energies above tens of GeV it has become possibleto make observations with ground-based detectors of enormously greatercollecting area. In recent years one such detector type, the clusterof imaging air Cherenkov telescopes, has reached a very productivestate, whilst several alternative approaches have been explored,including converted solar power collectors and novel high-altitudeparticle shower detectors which promised to extend the energy rangecovered. Key examples of development from 1952 to 2011 are followed,noting the problems and discoveries that stimulated the current work,explaining the logic of the alternative approaches that weretaken. The merits of the current major Cherenkov observatories and ofother viable detectors are examined and compared, with examples of theastrophysical information they are beginning to provide. The detectorsare still evolving, as we still do not understand the processes ontowhich the gamma rays provide a window. These include the accelerationof Galactic cosmic rays (in particular, the wide-band spectra ofradiation from some individual supernova remnants are still hard tointerpret), the highly relativistic and variable jets from activegalactic nuclei, and aspects of the electrodynamics of pulsars. Largergroups of Cherenkov telescopes still offer the possibility of anincrease in power of the technique for resolvable Galactic sourcesespecially.
TeV Astronomy Riger, F. M., de Ona-Wilhelmi, E. & Aharonian,F. A. (2013)
Abstract: With the successful realization of the current-generationof ground-based detectors, TeV Astronomy has entered into a newera. We review recent advances in VHE astronomy, focusing on thepotential of Imaging Atmospheric Cherenkov Telescopes (IACTs), andhighlight astrophysical implications of the results obtained withinrecent years.
Very-high energy gamma-ray astronomy: A 23-year success story inhigh-energy astroparticle physics Lorenz, E. & Wagner,R. (2012)
Abstract: Very-high energy (VHE) gamma quanta contribute only aminuscule fraction - below one per million - to the flux of cosmicrays. Nevertheless, being neutral particles they are currently thebest "messengers" of processes from therelativistic/ultra-relativistic Universe because they can beextrapolated back to their origin. The window of VHE gamma rays wasopened only in 1989 by the Whipple collaboration, reporting theobservation of TeV gamma rays from the Crab nebula. After a slowstart, this new field of research is now rapidly expanding with thediscovery of more than 150 VHE gamma-ray emitting sources. Progress isintimately related with the steady improvement of detectors andrapidly increasing computing power. We give an overview of the earlyattempts before and around 1989 and the progress after the pioneeringwork of the Whipple collaboration. The main focus of this article ison the development of experimental techniques for Earth-boundgamma-ray detectors; consequently, more emphasis is given to thoseexperiments that made an initial breakthrough rather than to thesuccessors which often had and have a similar (sometimes even higher)scientific output as the pioneering experiments. The considered energythreshold is about 30 GeV. At lower energies, observations canpresently only be performed with balloon or satellite-bornedetectors. Irrespective of the stormy experimental progress, thesuccess story could not have been called a success story without abroad scientific output. Therefore we conclude this article with asummary of the scientific rationales and main results achieved overthe last two decades.
Experimental Gamma-Ray Astronomy Paneque, D. (2012)
Abstract: Our knowledge of the gamma-ray sky has dramaticallychanged due to the advent of the new ground-based Imaging AtmosphericCherenkov Telescopes (H.E.S.S., MAGIC and VERITAS) and thesatellite-borne instruments (AGILE and Fermi). These facilitiesboosted the number of gamma-ray sources by one order of magnitude inthe last 6 years, providing us with about 2000 sources detected above100 MeV (from space) and about 100 sources detected above 100 GeV(from the ground). The combination of this large leap in experimentalcapabilities together with the fact that the Universe is still quiteunexplored at these extreme energies is evidence of a large scientificdiscovery potential that will surely make the decade 2010-2020 agolden age for gamma-ray astronomy. In this manuscript I provide asubjective review of some of the most exciting observations from thisrapidly evolving field during the last two years.
The status of gamma-ray astronomy Funk, S. (2012)
Abstract: Gamma-ray studies are an essential tool in our search forthe origin of cosmic rays. Instruments like the Fermi-LAT, H.E.S.S.,MAGIC and VERITAS have revolutionized our understanding of the highenergy Universe. This paper describes the status of the very richfield of gamma-ray astrophysics that contains a wealth of data onGalactic and extragalactic particle accelerators. It is the write-upof a rapporteur talk given at the 32nd ICRC in Beijing, China in whichnew results were presented with an emphasis on the cosmic-ray relatedstudies of the Universe.
TeV Gamma-ray Astronomy: A Summary Holder, J. (2012)
Abstract: The field of TeV gamma-ray astronomy has produced manyexciting results over the last decade. Both the source catalogue, andthe range of astrophysical questions which can be addressed, continueto expand. This article presents a topical review of the field, with afocus on the observational results of the imaging atmosphericCherenkov telescope arrays. The results encompass pulsars and theirnebulae, supernova remnants, gamma-ray binary systems, star formingregions and starburst and active galaxies.
The Galactic Sky seen by H.E.S.S de Naurois,M. for the H.E.S.S. collaboration (2011)
Abstract: The H.E.S.S. experiment is an array of four imagingCherenkov telescopes located in the Khomas Highlands of Namibia. Ithas been operating in its full configuration since December 2003 anddetects very-high-energy (VHE) gamma rays ranging from 100 GeV to 50TeV. Since 2004, the continuous observation of the Galactic Plane bythe H.E.S.S. array of telescopes has yielded the discovery of morethan 50 sources, belonging to the classes of pulsar wind nebulae(PWN), supernova remnants (SNR), gamma ray binaries and, morerecently, a stellar cluster and molecular clouds in the vicinity ofshell-type SNRs. Galactic emission seen by H.E.S.S. and itsimplications for particle acceleration in our Galaxy arediscussed.
Physics and astrophysics with gamma-ray telescopes Vandenbroucke,J. for the Fermi LAT collaboration (2010)
Abstract: In the past few years gamma-ray astronomy has entered agolden age. A modern suite of telescopes is now scanning the sky overboth hemispheres and over six orders of magnitude in energy. At ~TeVenergies, only a handful of sources were known a decade ago, but thecurrent generation of ground-based imaging atmospheric Cherenkovtelescopes (H.E.S.S., MAGIC, and VERITAS) has increased this number tonearly one hundred. With a large field of view and duty cycle, theTibet and Milagro air shower detectors have demonstrated the promiseof the direct particle detection technique for TeV gamma rays. At ~GeVenergies, the Fermi Gamma-ray Space Telescope has increased the numberof known sources by nearly an order of magnitude in its first year ofoperation. New classes of sources that were previously theorized to begamma-ray emitters have now been confirmed observationally. Moreover,there have been surprise discoveries of GeV gamma-ray emission fromsource classes for which no theory predicted it was possible. Inaddition to elucidating the processes of high-energy astrophysics,gamma-ray telescopes are making essential contributions to fundamentalphysics topics including quantum gravity, gravitational waves, anddark matter. I summarize the current census of astrophysical gamma-raysources, highlight some recent discoveries relevant to fundamentalphysics, and describe the synergetic connections between gamma-ray andneutrino astronomy. This is a brief overview intended in particularfor particle physicists and neutrino astronomers, based on apresentation at the Neutrino 2010 conference in Athens, Greece. Ifocus in particular on results from Fermi (which was launched soonafter Neutrino 2008), and conclude with a description of the nextgeneration of instruments, namely HAWC and the Cherenkov TelescopeArray.
Teraelectronvolt Astronomy Hinton, J. A. & Hoffman, W. (2009)
Abstract: Ground-based gamma-ray astronomy, which provides accessto the TeV energy range, is a young and rapidly developingdiscipline. Recent discoveries in this waveband have importantconsequences for a wide range of topics in astrophysics andastroparticle physics. This article is an attempt to review theexperimental status of this field and to provide the basic formulaeand concepts required to begin the interpretation of TeVobservations.
Gamma-ray astronomy in the summer of 2009 Torres, D. F. (2009)
Abstract: This paper presents a snapshot of the field of gamma-rayastrophysics in the early summer of 2009, as it was discussed in about200 presentations at the International Cosmic Ray Conference (ICRC)held in Lodz, Poland. This is the written wrap up of a Rapporteur,one-hour talk and as such it is thus an atypical review, a stillpicture in a moment of great advancement in an observationally drivenfield, led by the full operation of ground-based arrays and the launchand operations of Fermi and Agile.
Latest results on Galactic sources as seen in VHE gamma-rays Renaud, M. (2009)
Abstract: As of early 2009, latest results on Galactic sources(mainly shell-type and plerionic supernova remnants), as observed inthe very-high-energy gamma-ray domain, are reviewed. A particularattention is given to those obtained with the H.E.S.S experimentduring its Galactic Plane Survey which now covers the inner part ofthe Milky Way. From the well identified gamma-ray sources to thosewithout any obvious counterpart and the putative Galactic diffuseemission, this observational window fully deserves to be celebratedduring this International Year of Astronomy, as a new mean to imagethe Galaxy and reveal sites of particle acceleration, potentially atthe origin of Galactic cosmic rays.
Imaging Very High Energy Gamma-Ray Telescopes Voelk, H. J. and Bernloehr, K. (2008)
Abstract: The technique of gamma-ray astronomy at very highenergies (VHE: > 100 GeV) with ground-based imaging atmosphericCherenkov telescopes is described, the H.E.S.S. array in Namibiaserving as example. Mainly a discussion of the physical principles ofthe atmospheric Cherenkov technique is given, emphasizing its rapiddevelopment during the last decade. The present status is illustratedby two examples: the spectral and morphological characterization inVHE gamma-rays of a shell-type supernova remnant together with itstheoretical interpretation, and the results of a survey of theGalactic Plane that shows a large variety of non-thermal sources. Thefinal part is devoted to an overview of the ongoing and futureinstrumental developments.
TeV Gamma-ray Astronomy: The Story So Far Weekes,T. C. (2008)
Abstract: A snapshot is presented of the present status of ourknowledge of the TeV gamma-ray universe. Emphasis is put onobservations made using the imaging atmospheric Cherenkovtechnique. The capabilities of the present generation of telescopes islisted. Progress has been dramatic and several features have beendifferent from what was anticipated. The catalog of sources includessome 78 objects and these are tabulated as extragalactic sources (24),supernovae remnants (11), pulsar wind nebulae (10), binaries (4),miscellaneous (9), diffuse high energy sources (3) and unidentifiedsources (20). Some comments are made on the factors influencing thepast and future development of the field.
Gamma Ray Astronomy and the Origin of Galactic Cosmic Rays Gabici,S. (2008)
Abstract: Diffusive shock acceleration operating at expandingsupernova remnant shells is by far the most popular model for theorigin of galactic cosmic rays. Despite the general consensus receivedby this model, an unambiguous and conclusive proof of the supernovaremnant hypothesis is still missing. In this context, the recentdevelopments in gamma ray astronomy provide us with precious insightsinto the problem of the origin of galactic cosmic rays, sinceproduction of gamma rays is expected both during the acceleration ofcosmic rays at supernova remnant shocks and during their subsequentpropagation in the interstellar medium. In particular, the recentdetection of a number of supernova remnants at TeV energies nicelyfits with the model, but it still does not constitute a conclusiveproof of it, mainly due to the difficulty of disentangling thehadronic and leptonic contributions to the observed gamma rayemission. In this paper, the most relevant cosmic-ray-related resultsof gamma ray astronomy are briefly summarized, and the foreseeablecontribution of future gamma ray observations to the final solution ofthe problem of cosmic ray origin is discussed.
Gammaray astrophysics: the EGRET results Thompson, D. J. (2008)
Abstract: Cosmic gamma rays provide insight into some of the mostdynamic processes in the Universe. At the dawn of a new generation ofgamma-ray telescopes, this review summarizes results from theEnergetic Gamma Ray Experiment Telescope (EGRET) on the Compton GammaRay Observatory, the principal predecessor mission studyinghigh-energy photons in the 100 MeV energy range. EGRET viewed agamma-ray sky dominated by prominent emission from the Milky Way, butfeaturing an array of other sources, including quasars, pulsars,gamma-ray bursts, and many sources that remain unidentified. A centralfeature of the EGRET results was the high degree of variability seenin many gamma-ray sources, indicative of the powerful forces at workin objects visible to gamma-ray telescopes.
TheStatus and future of ground-based TeV gamma-ray astronomy. A WhitePaper prepared for the Division of Astrophysics of the AmericanPhysical Society Buckley, J. H. (2008)
Abstract: In recent years, ground-based TeV gamma-ray observatorieshave made spectacular discoveries including imaging spectroscopyobservations of galactic sources of different classes, and thediscovery of rapid gamma-ray flares from radio galaxies and activegalactic nuclei containing supermassive black holes. Thesediscoveries, and the fact that gamma-ray astronomy has the potentialto map the radiation from dark matter annihilation in our Galaxy andin extragalactic systems, have attracted the attention of the widerscientific community. The Division of Astrophysics of the AmericanPhysical Society requested the preparation of a white paper on thestatus and future of ground-based gamma-ray astronomy to define thescience goals of a future observatory, to determine the performancespecifications, to identify the areas of necessary technologydevelopment, and to lay out a clear path for proceeding beyond thenear term. The white paper was written with broad community input,including discussions on several dedicated open meetings, and a numberof APS or other conferences. It contains an executive summary,detailed reports from the science working groups, and appendices withsupplementary material including the full author lists for thedifferent sections of the white paper and a glossary.
High energy astrophysics with ground-based gamma ray detectors Aharonian, F., Buckley, J., Kifune, T. and Sinnis, G. (2008)
Abstract: Recent advances in ground-based gamma ray astronomy haveled to the discovery of more than 70 sources of very high energy (E >=100 GeV) gamma rays, falling into a number of source populationsincluding pulsar wind nebulae, shell type supernova remnants,Wolf-Rayet stars, giant molecular clouds, binary systems, the GalacticCenter, active galactic nuclei and 'dark' (yet unidentified) galacticobjects. We summarize the history of TeV gamma ray astronomy up to thecurrent status of the field including a description of experimentaltechniques and highlight recent astrophysical results. We also discussthe potential of ground-based gamma ray astronomy for futurediscoveries and describe possible directions for future instrumentaldevelopments.
High-(Energy)-Lights -- The Very High Energy Gamma-Ray Sky Horns, D. (2008)
Abstract: The high-lights of ground-based very-high-energy (VHE,E>100 GeV) gamma-ray astronomy are reviewed. The summary covers bothGalactic and extra-galactic sources. A total of at least 70 sourcesare currently known. Implications for our understanding of thenon-thermal Universe are discussed. The next generation of groundbased gamma-ray instruments aims to cover the entire accessible energyrange from as low as ~10 GeV up to 10e5 GeV and to improve thesensitivity by an order of magnitude in comparison with currentinstruments.
Recent Topics on Very High Energy Gamma-ray Astronomy Mori, M. (2008)
Abstract: With the advent of imaging atmospheric Cherenkovtelescopes in late 1980's, ground-based observation of TeV gamma-rayscame into reality after struggling trials by pioneers for twentyyears, and the number of gamma-ray sources detected at TeV energieshas increased to be over seventy now. In this review, recent findingsfrom ground-based very-high-energy gamma-ray observations aresummarized (as of 2008 March), and up-to-date problems in thisresearch field are presented.
High energy astrophysics with ground-based gamma ray detectors Aharonian, F., Buckley, J., Kifune T. & Sinnis, G. (2008)
Abstract: Recent advances in ground-based gamma ray astronomy haveled to the discovery of more than 70 sources of very high energy (Eγ>= 100 GeV) gamma rays, falling into a number of source populationsincluding pulsar wind nebulae, shell type supernova remnants,Wolf-Rayet stars, giant molecular clouds, binary systems, the GalacticCenter, active galactic nuclei and 'dark' (yet unidentified) galacticobjects. We summarize the history of TeV gamma ray astronomy up to thecurrent status of the field including a description of experimentaltechniques and highlight recent astrophysical results. We also discussthe potential of ground-based gamma ray astronomy for futurediscoveries and describe possible directions for future instrumentaldevelopments.
Status of Very High Energy gamma-ray Astronomy as of early2008 Djannati-Atai, A. (2008)
Abstract: Data obtained in the very high energy gamma-ray band withthe new generation of imaging telescopes, in particular through thegalactic plane survey undertaken by H.E.S.S., low thresholdobservations with MAGIC and more recently by operation of VERITAS,have revealed dozens of galactic and extragalactic sources, providinga wealth of information on a variety of high energy acceleration sitesin our universe. Also, the water Cherenkov instrument Milagro hasprovided several extended sources after seven years of dataintegration. An overview of these results with focus on some of themost recent highlights is given.
Abstract: This report is based on a rapporteur talk presented atthe 30th International Cosmic Ray Conference held in Merida, Mexico(July 2007), and covers three of the OG sessions devoted to neutrino,gravitational wave, and gamma-ray detection.
TeV Gamma-Ray Astrophysics Ribo, M. (2008)
Abstract: The window of TeV Gamma-Ray Astrophysics was opened lessthan two decades ago, when the Crab Nebula was detected for the firsttime. After several years of development, the technique used byimaging atmospheric Cherenkov telescopes like HESS, MAGIC or VERITAS,is now allowing to conduct sensitive observations in the TeVregime. Water Cherenkov instruments like Milagro are also providingthe first results after years of integration time. Different types ofextragalactic and galactic sources have been detected, showing avariety of interesting phenomena that are boosting theory in very highenergy gamma-ray astrophysics. Here I review some of the mostinteresting results obtained up to now, making special emphasis in thefield of X-ray/gamma-ray binaries.
Gamma-ray Astronomy Hinton, J. (2007)
Abstract: The relevance of gamma-ray astronomy to the search forthe origin of the galactic and, to a lesser extent, theultra-high-energy cosmic rays has long been recognised. The currentrenaissance in the TeV gamma-ray field has resulted in a wealth of newdata on galactic and extragalactic particle accelerators, and almostall the new results in this field were presented at the recentInternational Cosmic Ray Conference (ICRC). Here I summarise the 175papers submitted on the topic of gamma-ray astronomy to the 30th ICRCin Merida, Mexico in July 2007.
Very-High Energy GammaAstrophysics De Angelis, A., Mansutti, O. & Persic,M. (2008)
Abstract: High-energy photons are a powerful probe for astrophysicsand for fundamental physics under extreme conditions. During therecent years, our knowledge of the most violent phenomena in theUniverse has impressively progressed thanks to the advent of newdetectors for high-energy gamma-rays. Observation of gamma-rays givesan exciting view of the high-energy universe thanks to satellite-basedtelescopes (AGILE, GLAST) and to ground-based detectors like theCherenkov telescopes (H.E.S.S. and MAGIC in particular), whichrecently discovered more than 60 new very-high-energy sources. Theprogress achieved with the last generation of Cherenkov telescopes iscomparable to the one drawn by EGRET with respect to the previousgamma-ray satellite detectors. This article reviews the present statusof high-energy gamma astrophysics, with emphasis on the recent resultsand on the experimental developments.
VHEastrophysics: recent developments Persic, M. & De Angelis,A. (2007)
Abstract: We review the current status, and some open issues, ofVHE astrophysics.
TheStatus of VHE Gamma-Ray Astronomy Ong, R. A. (2006)
Abstract: This paper presents a summary of the status of the fieldof very high-energy (VHE) gamma-ray astronomy, as of early 2006. Thepaper is based on the Rapporteur Talk given at the 29th InternationalCosmic Ray Conference in Pune, India (ICRC 2005). It coversastrophysical results from observations made by high-energy and veryhigh-energy telescopes operating at photon energies above 1 GeV. Themajority of recent observations in this field have been made byground-based telescopes using the atmospheric Cherenkov or air showertechniques.
TeVAstrophysics, A Review Cui, W. (2006)
Abstract: In this paper I briefly review recent progress in thefield of ground-based gamma ray astrophysics.
AirCherenkov methods in cosmic rays: Review and some historyLidvansky, A. S. (2006)
Abstract: The history of application of the Cherenkov lightemission in the atmosphere to cosmic ray and gamma-ray astronomystudies is briefly outlined with an emphasis on the pioneeringactivity of A.E. Chudakov. The present-day situation and some newideas are also discussed.
TheAtmospheric Cherenkov Imaging Technique for Very High Energy Gamma-rayAstronomy Weekes, T. C. (2005)
Abstract: The Atmospheric Cherenkov Imaging Technique has opened upthe gamma-ray spectrumfrom 100 GeV to 50 TeV to astrophysicalexploration. The development of the technique is described as are thebasic principles underlying its use. The current generation of arraysof telescopes is briefly described and the early results aresummarized.
Extragalacticsources of TeV gamma rays: a summary Horan, D. & Weekes,T. C. (2004)
Abstract: The development of techniques whereby gamma rays ofenergy 100 GeV and above can be studied from the ground, usingindirect, but sensitive, techniques has opened up a new area of highenergy photon astronomy. The most exciting result that has come fromthese is the detection of highly variable fluxes of TeV gamma raysfrom the relativistic jets in nearby AGN. The recent detection ofsignals from a starburst galaxy and from a radio galaxy opens thepossibility that the extragalactic emission of TeV gamma rays is aubiquitous phenomenon. Here we attempt to summarize the properties ofthe sources detected so far.
TheStatus of VHE Astronomy Ong, R. A. (2003)
Abstract: This paper summarizes the status of very high-energy(VHE) astronomy, as of early 2003. It concentrates on observationsmade by gamma-ray telescopes operating at energies above 10 GeV. Thisfield is an exciting one to be working in, with a growing and variedlist of established sources that includes plerions, supernovaremnants, and active galactic nuclei. New results include thediscovery of the first unidentified source at these energies and thedetection of gamma rays from a nearby starburst galaxy (NGC 253). Thearrival of a new generation of telescopes, both on the ground and inspace, argues that we can anticipate a wealth of exciting results inthe near future.
Multi-messengerastronomy: cosmic rays, gamma-rays and neutrinos Halzen,F. (2002)
Abstract: Although cosmic rays were discovered a century ago, we donot know where or how they are accelerated. There is a realistic hopethat the oldest problem in astronomy will be solved soon by ambitiousexperimentation: air shower arrays of 10,000 kilometer-square area,arrays of air Cerenkov telescopes and kilometer-scale neutrinoobservatories. Their predecessors are producing science. We willreview the highlights: 1) Cosmic rays: the highest energy particlesand the GZK cutoff, the search for cosmic accelerators and the Cygnusregion, top-down mechanisms: photons versus protons? 2) TeV-energygamma rays: blazars, how molecular clouds may have revealed protonbeams, fist hints of the diffuse infrared background? 3) Neutrinos:first results and proof of concept for technologies to constructkilometer-scale observatories.
TeVGamma-ray Observations and the Origin of Cosmic Rays: I Weekes,T. C. (2003)
Abstract: This is the first of three plenary talks with the sametitle given at the 28th ICRC in Tsukuba, Japan in August, 2003. Abrief description of the techniques for detecting gamma rays at TeVenergies is followed by a summary of the observational status of thefield. The expectations of the field from a cosmic ray perspective arecompared with these early results. The majority of sources detectedwith some certainty are extragalactic; the observational status ofthese sources is summarized. The most complete set of observations arethose dealing with the detection of blazars for which a catalog ispresented. This discipline is now established as a new branch ofobservational astronomy.
Veryhigh energy gamma-ray astronomy Weekes, T. C. (2003)
Book Description: High energy gamma-ray photons are the primeprobes of the relativistic or high-energy universe, populated by blackholes, neutron stars, supernovae, quasars, and matter-antimatterannihilations. Through studying the gamma-ray sky, astrophysicists areable to better understand the formation and behavior of these exoticand energetic bodies. Very High Energy Gamma-Ray Astronomy summarizesthe status of gamma-ray astronomy at energies between 30MeV and 50TeVat a critical point in the development of the discipline: the hiatusbetween the demise of the EGRET telescope and the launch of the nextgeneration of space telescopes. Starting with an overview of theastrophysics of the bodies that generate high energy gamma rays, itproceeds to discuss the latest developments in observationaltechniques and equipment. By presenting the techniques, observations,and theories of this expanding frontier, Very High Energy Gamma-RayAstronomy aids experimentalists and theoreticians in detecting andexplaining gamma rays of the highest energies..
Gamma-RaySummary Report Buckley, J. B., et al. (2002)
Abstract: This paper reviews the field of gamma-ray astronomy anddescribes future experiments and prospects for advances in fundamentalphysics and high-energy astrophysics through gamma-raymeasurements. We concentrate on recent progress in the understandingof active galaxies, and the use of these sources as probes ofintergalactic space. We also describe prospects for future experimentsin a number of areas of fundamental physics, including: searches foran annihilation line from neutralino dark matter, understanding theenergetics of supermassive black holes, using AGNs as cosmologicalprobes of the primordial radiation fields, constraints on quantumgravity, detection of a new spectral component from GRBs, and theprospects for detecting primordial black holes.
Statusof VHE Astronomy c. 2000 Weekes, T. C. (2001)
Abstract: The status of VHE Astronomy is reviewed.
GeV-TeVGamma-ray Astronomy Mori, M. (2001)
Abstract: Recent results of GeV and TeV observations of gamma-raysfrom the Universe are briefly reviewed. Topics include observationaltechnique, diffuse gamma-rays, pulsars, unidentified sources,plerions, supernova remnants and AGNs.
GammaRay Astronomy Pohl, M. (2001)
Abstract: This paper summarizes recents results in gamma-rayastronomy, most of which were derived with data from groundbasedgamma-ray detectors. Many of the contributions presented at thisconference involve multiwavelength studies which combine ground-basedgamma-ray measurements with optical data or space-based X-ray andgamma-ray measurements. Besides measurements of the diffuse emissionfrom the Galaxy, observations of blazars, gamma-ray bursts, andsupernova remnants this paper also covers theoretical models for theacceleration of radiating particles and their emission mechanisms inthese sources.
Gammaray astronomy Buckley, J. H. (2000)
Abstract: This paper summarizes recent results in X-ray andgamma-ray stronomy including measurements of galactic andextragalactic sources from 0.1 keV to 20 GeV from space, measurementsof gamma-rays at energies above 70 GeV from the ground as well astheoretical models for the emission of gamma-rays and X-rays ingalactic and extragalactic sources. The majority of the new resultspresented at this conference were made with ground-based gamma-raydetectors, with relatively few new results from the Compton Gamma-rayObservatory (CGRO) and other space-based instruments. Many of theresults involve multiwavelength studies which combine ground-basedgamma-ray measurements with space based X-ray and gamma-raymeasurements. The main topics covered in this paper includeobservations of diffuse gamma-ray emission from the galaxy,observations of blazars, gamma-ray bursts, supernova remnants andpulsars as well as theoretical models for the emission mechanisms ofthese sources.
ParticleAstrophysics with High Energy Photons Weekes, T. C. (2000)
Abstract: Not Available.
VHEAstronomy Before the New Millennium Weekes, T. C. (2000)
Abstract: A report on the observational status of VHE astronomy isgiven.
HighEnergy Gamma Rays Mukherjee, R. (2000)
Abstract: This article reviews the present status of high energygamma-ray astronomy at energies above 30 MeV. Observations in the pastdecade using both space- and ground-based experiments have beenprimarily responsible for giving a tremendous boost to our knowledgeof the high energy Universe. High energy gamma-rays have been detectedfrom a wide range of Galactic and extragalactic astrophysical sources,such as gamma-ray bursters, pulsars, and active galaxies. Theseobservations have established high energy gamma-ray astronomy as avital and exciting field, that has a bright future. This reviewsummarizes the experimental techniques, observations and resultsobtained with recent experiments, and concludes with a shortdescription of future prospects.
Gamma-rayastronomy at high energies Hoffman, C. M., Sinnis, C., Fleury,P. & Punch, M. (1999)
Abstract: Progress in high-energy gamma-ray astronomy has dependedupon the development of sophisticated detectors and analysistechniques. Observations in this decade using space-based andground-based detectors have observed gamma-ray emission from a varietyof sources. For the first time a consistent picture of the gamma-raysky has emerged. This article describes the detection techniques ingamma-ray astronomy, the nature of the astrophysical objects studied,and the present state of the observations. Several possible newdirections in the field are also described.
VeryHigh Energy Gamma-Ray Astronomy Catanese, M. & Weekes,T. C. (1999)
Abstract: We present a review of the current status of very highenergy gamma-ray stronomy has led to a rapid growth in the number ofobservatories. The detection of TeV gamma-rays from active galacticnuclei was unexpected and is providing new insights into the emissionmechanisms in the jets. Next-generation telescopes are underconstruction and will increase dramatically the knowledge available atthis extreme end of the cosmic electromagnetic spectrum.
AGeneral Gamma-Ray Source Catalog Macomb, D. J. & Gehrels,N. (1999)
Abstract: The past several years have seen unprecedented growth inthe field of gamma-ray astronomy. Highly successful missions such asthe Compton Gamma-Ray Observatory (CGRO) have led to both a greatincrease in the number of detected gamma-ray sources and a morefundamental understanding of the basic physical processes involved forthose sources. New ground-based observatories, the Rossi X-Ray TimingExplorer (RXTE), and the SIGMA instrument aboard the GRANAT spacecrafthave all contributed to this explosion. Detailed observations ofactive galaxies, pulsars, accreting binaries, and diffuse emissionhave had a tremendous impact on our view of the universe. Given thatnew experiments that will provide a similar increase in source numbersare several years away, it is a good time to take inventory of thestate of gamma-ray astronomy. To this end, we have developed a generalgamma-ray point-source catalog containing 309 objects that summarizethe field. Gamma-ray astronomy, as we define it, includes photonenergies from 50 keV to about 1 TeV. While many catalogs concentrateon a single type of astronomical object and/or a very restrictedenergy range, the nature of this catalog is somewhat different. Thelarge variety of objects and the many orders of magnitude in energyspace covered by gamma-ray astronomy presents an organizationalchallenge. We focus on two main types of information: a generallisting of the basic characteristics of each source, and detailedtables of a representative sample of high-energy observations. We alsosummarize the gamma-ray instruments whose observations are included inthe catalog.
Veryhigh-energy gamma-ray astronomy Ong, R. A.
Abstract: Very high-energy gamma-ray astronomy has emerged as anexciting and vital field. In the last seven years, major discoverieshave been made by experiments in space and on the ground. In space,instruments on the Compton Gamma Ray Observatory have identifiedhigh-energy emission from a variety of astrophysical sources,including gamma-ray bursts, spin-down pulsars, and active galaxies ofthe blazar type. Remarkably, a number of these sources have now beendetected at much higher energies by ground-based instruments. Thisreview will concentrate on the methodology and results from theseground-based experiments, currently operating at energies above 250GeV. The ground-based detections are for the first time statisticallycompelling and stand in direct contrast to earlier results reported inthe 1980s. The future scientific and experimental prospects for thefield appear excellent and are summarized.
Veryhigh-energy gamma-ray astronomy Ong, R. A. (1998)
Abstract: Very high-energy gamma-ray astronomy has emerged as anexciting and vital field. In the last seven years, major discoverieshave been made by experiments in space and on the ground. In space,instruments on the Compton Gamma Ray Observatory have identifiedhigh-energy emission from a variety of astrophysical sources,including gamma-ray bursts, spin-down pulsars, and active galaxies ofthe blazar type. Remarkably, a number of these sources have now beendetected at much higher energies by ground-based instruments. Thisreview will concentrate on the methodology and results from theseground-based experiments, currently operating at energies above 250GeV. The ground-based detections are for the first time statisticallycompelling and stand in direct contrast to earlier results reported inthe 1980s. The future scientific and experimental prospects for thefield appear excellent and are summarized..
TeVGamma-ray Astronomy: New Light from the Dark Sky Weekes,T. C. (1997)
Abstract: High energy astrophysics, in particular high energygamma-ray astronomy, has generally been considered as in the domain ofspace astronomy. Somewhat surprisingly, very high energy gamma rayastronomy can be pursued using ground-based techniques. The airshowers generated by the interaction of gamma rays in the atmospherecan be detected using rather simple optical detectors to register theCherenkov radiation in the atmosphere. In recent years the atmosphericCherenkov imaging technique, which has been mostly developed at theWhipple Observatory, has been shown to be extremely sensitive togamma-ray fluxes in the 200 GeV to 10 TeV energy region. The majorbreakthrough came with the detection of the Crab Nebula which has nowbeen established as the standard candle for the newdiscipline. Although other supernova remnants have been detected, itappears that in all cases the gamma rays come from Compton scatteringby electrons in the synchrotron nebula surrounding the pulsar. TeVgamma-ray astronomy has not yet provided the "smoking gun" for shockacceleration of hadrons in supernova remnants, the canonical pictureof cosmic ray production in the Galaxy. BL Lac objects are alsopowerful sources of TeV gamma rays; in this case the observed gammarays are almost certainly associated with the relativistic particlesin the jets. Doubling times as short as 15 minutes have been observedin Markarian 421. In 1997 Markarian 501 has been in a state of highemission making it the brightest TeV source in the sky. A newgeneration of telescopes (e.g. VERITAS) is now at an advanced state ofplanning and will complement the next generation of high energygamma-ray space telescopes (e.g. GLAST).
TheAtmospheric Cherenkov Technique in Very High Energy Gamma-RayAstronomy Weekes, T. C. (1996)
Abstract: Not available.
TeVGamma-Ray Astronomy in South Africa Raubenheimer,B. C. (1995)
Abstract: Not Available.
GammaRay Astronomy at TeV Energies Weekes, T. C. (1994)
Abstract: Cosmic sources of gamma-rays of energy in excess of 0.25TeV are now well-established using the ground-based atmosphericCherenkov technique. Recently high resolution cameras (arrays ofphototubes) on large optical reflectors have achieved significantimprovements in flux sensitivity. Observations with the Compton GammaRay Observatory have shown that many sources have significant fluxesat the highest useful energy of EGRET (30 GeV); at least three ofthese sources have been detected in the TeV energy range. The CrabNebula is the best established source; its spectrum extends beyond 10TeV and is well understood in terms of a Compton-synchrotronmodel. PSR1706-044 is one of five pulsars seen by EGRET but at TeVenergies it is seen as a steady (unpulsed) source. Markarian 421 isclosest AGN seen by EGRET; at TeV energies it is a strong and variablesource. The failure to detect emission from other stronger, but moredistant, AGN's has led to speculation that the intergalactic infraredbackground is responsible for significant absorption causingphoton-photon pair production. It is thus possible to derive an upperlimit to the intergalactic infrared background. New telescopes areunder development which will reduce the energy threshold of theatmospheric Cherenkov technique and bridge the gap to space gamma-raytelescopes. Supported in part by the U.S. Dept. of Energy.
Thesearch for discrete astrophysical sources of energetic gammaradiation Cronin, J. W., Gibbs, K. & Weekes, T. C. (1993)
Abstract: Not Available
TeVradiation from galactic sources Weekes, T. C. (1992)
Abstract: The detection of the Crab Nebula as a steady source ofTeV gamma rays puts the field of Very High Energy Gamma-Ray Astronomyon a firm observational basis and permits a critical reassessment ofthe claims for the detection of a multitude of episodic binarysources. A new generation of detectors in the TeV and PeV energyregions is coming on-line; together with the telescopes of theGamma-Ray Observatory, these instruments will present a newperspective on one of the last frontiers of astronomy.
TOPICALREVIEW: Very high energy gamma rays from x-ray binary pulsarsChadwick, P. M., McComb, T. J. & Turver, K. E. (1990)
Abstract: Not Available
Veryhigh energy gamma-ray astronomy Weekes, T. C. (1988)
Abstract: Not Available
CerenkovRadiation from the Night Sky, and its Application to Gamma-RayAstronomy Jelley, J. V. & Porter, N. A. (1963)
Abstract: Not Available.
Note: If the Abstract section reads "Not Available", this meansthat the abstract was not posted on ADS. If the abstract of a paper issubmitted to us, we will post it here.