Physics and astrophysics with gamma-ray telescopes
J. Vandenbroucke
备注：
invited review at Neutrino 2010, Athens, Greece, June 2010, 2 figures, 1 table, 7 pages; v2 has "references" title fixed in formatting and clarified table 1 in caption
In the past few years gamma-ray astronomy has entered a golden age. A modern suite of telescopes is now scanning the sky over both hemispheres and over six orders of magnitude in energy. At $\sim$TeV energies, only a handful of sources were known a decade ago, but the current generation of ground-based imaging atmospheric Cherenkov telescopes (H.E.S.S., MAGIC, and VERITAS) has increased this number to nearly one hundred. With a large field of view and duty cycle, the Tibet and Milagro air shower detectors have demonstrated the promise of the direct particle detection technique for TeV gamma rays. At $\sim$GeV energies, the Fermi Gamma-ray Space Telescope has increased the number of known sources by nearly an order of magnitude in its first year of operation. New classes of sources that were previously theorized to be gamma-ray emitters have now been confirmed observationally. Moreover, there have been surprise discoveries of GeV gamma-ray emission from source classes for which no theory predicted it was possible. In addition to elucidating the processes of high-energy astrophysics, gamma-ray telescopes are making essential contributions to fundamental physics topics including quantum gravity, gravitational waves, and dark matter. I summarize the current census of astrophysical gamma-ray sources, highlight some recent discoveries relevant to fundamental physics, and describe the synergetic connections between gamma-ray and neutrino astronomy. This is a brief overview intended in particular for particle physicists and neutrino astronomers, based on a presentation at the Neutrino 2010 conference in Athens, Greece. I focus in particular on results from Fermi (which was launched soon after Neutrino 2008), and conclude with a description of the next generation of instruments, namely HAWC and the Cherenkov Telescope Array.
Several projects planned or proposed can significantly expand our knowledge of the high-energy Universe in gamma rays. Construction of the Cherenkov telescope array CTA is started, and other detectors are planned which will use the reconstruction of extensive air showers. This report explores the near future, and possible evolutions in a longer term.
The last half-century has seen dramatic developments in gamma-ray telescopes, from their initial conception and development through to their blossoming into full maturity as a potent research tool in astronomy. Gamma-ray telescopes are leading research in diverse areas such as gamma-ray bursts, blazars, Galactic transients, and the Galactic distribution of aluminum-26.
High-energy photons are a powerful probe for astrophysics and for fundamental physics in extreme conditions. During the recent years, our knowledge of the most violent phenomena in the Universe has impressively progressed thanks to the advent of new detectors for gamma rays, both at ground and on satellites. This article reviews the present status of high-energy gamma-ray astrophysics, with emphasis on the recent results and a look to the future.
By detecting the beginning of electron pairs with nuclear emulsion, precise gamma-ray direction and gamma-ray polarization can be detected. With recent advancement in emulsion scanning system, emulsion analyzing capability is becoming powerful. Now we are developing the balloon-borne gamma-ray telescope with nuclear emulsion. Overview and status of our telescope is described.
A cluster of galaxies is a huge system bounded by gravitation, and cosmic rays are thought to be confined in the system, thus it should contain much non-thermal components. Many theories predict significant gamma-ray emission that could be detectable by state-of-the-art gamma-ray telescopes. Some clusters have already been studied by using Fermi gamma-ray space telescope in the GeV band and Cherenkov telescopes in the TeV band, but most clusters are not studied in both energy bands. Here I present results on GeV gamma-ray emission from clusters of galaxies which have been given upper limits by…
Towards a foundation model for astrophysical source detection: An End-to-End Gamma-Ray Data Analysis Pipeline Using Deep Learning
University of Nova Gorica（新戈里察大学）；Nikhef, Dutch National Institute for Subatomic Physics（荷兰国家亚原子物理研究所）；Radboud University Nijmegen（奈梅亨拉德堡德大学）；Erlangen Centre for Astroparticle Physics（埃尔朗根天体粒子物理中心）；Università di Trieste（的里雅斯特大学）；University of Ljubljana（卢布尔雅那大学）；Instituto de Física Corpuscular, IFIC-UV/CSIC（粒子物理研究所）；Faculty of Computer and Information Science, University of Ljubljana（卢布尔雅那大学计算机与信息科学 faculties）；University of Oxford（牛津大学）
Gamma-ray astronomy provides a direct window into the most violent, dynamic processes in the Universe. MeV gamma-ray astronomy in particular allows us to directly observe the process of chemical enrichment of the interstellar medium (ISM) through the decay of radioactive isotopes synthesized by stars and compact objects during their lives, in their death throes and after their deaths. Moreover, gamma-ray lines such as the positron annihilation line can give us a unique view into the propagation of cosmic rays in the Galaxy, as well as hints about unusual transient phenomena that may be respons…
This paper explores the potential of AstroPix, a project to develop Complementary Metal Oxide Semiconductor (CMOS) pixels for the next generation of space-based high-energy astrophysics experiments. Multimessenger astrophysics is a rapidly developing field whose upcoming missions need support from new detector technology such as AstroPix. ATLASPix, a monolithic silicon detector optimized for the ATLAS particle detector at CERN, is the beginning of the larger AstroPix project. Energy resolution is a driving parameter in the reconstruction of gamma-ray events, and therefore the characterization …
Neutrinos with energies in the PeV to EeV range produce upgoing extensive air showers when they interact underground close enough to the surface of the Earth. We study the possibility for detection of such showers with a system of very wide field-of-view imaging atmospheric Cherenkov telescopes, named CHANT for CHerenkov from Astrophysical Neutrinos Telescope, pointing down to a strip below the Earth's horizon from space. We find that CHANT provides sufficient sensitivity for the study of the astrophysical neutrino flux in a wide energy range, from 10 PeV to 10 EeV. A space-based CHANT system …
A large sample of blazar from the Candidate Gamma Ray Blazar Survey (CGRaBS) has been observed with the Owens Valley Radio Observatory (OVRO) 40-Meter Telescope at 15GHz. Using these quasi-simultaneous observations, we study the connection between the gamma-ray behavior of blazars as detected by Fermi-LAT and the cm band as observed by the F-GAMMA project with the OVRO 40-Meter Telescope. Comparing the light curves for a large number of sources, it is possible to study in detail the relation between the gamma-ray and radio activity of Fermi-LAT detected gamma-ray blazars. We present first resu…
The Fermi Gamma-ray Space Telescope (formerly known as Gamma-ray Large Area Space Telescope, GLAST) was successfully launched on June 11 2008. Its main instrument is the Large Area Telescope (LAT), which detects gamma rays from 20 MeV to more than 300 GeV. It is a pair-conversion telescope with 16 identical towers (tracker and calorimeter), covered by an anti-coincidence detector to reject charged particles. The calorimeter is a hodoscopic array of CsI(Tl) crystals, arranged in 8 alternating orthogonal layers, with a total thickness of 8.6 radiation lengths. In this paper we will present the p…
Sensipy: simulate gamma-ray observations of transient astrophysical sources
Max-Planck-Institut für Physik（马克斯·普朗克物理研究所）；Technische Universität München（慕尼黑工业大学）；University of Pisa（比萨大学）；INAF - Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）；Cherenkov Telescope Array Observatory（切伦科夫望远镜阵列观测站）；Institut de Física d’Altes Energies (IFAE)（高能物理研究所）
Satellites that are capable of detecting gamma-ray bursts can trigger the Antares neutrino telescope via the real-time gamma-ray bursts coordinates network. Thanks to the "all-data-to-shore" concept that is implemented in the data acquisition system of Antares, the sensitivity to neutrinos from gamma-ray bursts is significantly increased when a gamma-ray burst is detected by these satellites. The performance of the satellite-triggered data taking is shown, as well as the resulting gain in detection efficiency. Different search methods can be applied to the data taken in coincidence with gamma-…
We study the conditions for the adiabatic resonant conversion of the cold dark matter (CDM) axions into photons in existence of the astrophysically sourced strong magnetic fields such as those in the neutron star magnetosphere. We demonstrate the possibility that the forthcoming radio telescopes such as the SKA (Square Kilometre Array) can probe those photon signals from the CDM axions.
We explore potential of current and next-generation gamma-ray telescopes for the detection of weak magnetic fields in the intergalactic medium. We demonstrate that using two complementary techniques, observation of extended emission around point sources and observation of time delays in gamma-ray flares, one would be able to probe most of the cosmologically and astrophysically interesting part of the "magnetic field strength" vs. "correlation length" parameter space. This implies that gamma-ray observations with Fermi and ground-based Cherenkov telescopes will allow to (a) strongly constrain t…
Tau neutrinos with energies in the PeV-EeV range produce up-going extensive air showers (UEAS) if they interact underground close enough to the surface of the Earth. This work studies detectability of the UEAS with a system of fluorescence telescopes overlooking dark, low reflectivity, area on the ground up to the distances 20-30 km from mountain top(s). Such system could provide sensitivity sufficient for accumulation of the astrophysical neutrino signal statistics at the rate ten(s) events per year in the energy range beyond 10 PeV, thus allowing to extend the energy frontier of neutrino ast…
We spectrally fit the GeV gamma-ray flares recently-observed in the Crab Nebula by considering a small blob Lorentz-boosted towards us. We point out that the corresponding inverse-Compton flare at TeV--PeV region is more enhanced than synchrotron by a Lorentz factor square \sim Γ^2, which is already excluding Γ\gtrsim 200 and will be detected by future TeV - PeV observatories, CTA, Tibet AS + MD and LHAASO for Γ\gtrsim 30. We also show that PeV photons emitted from the Crab Nebula are absorbed by Cosmic Microwave Background radiation through electron-positron pair creation.
Astrophysical explosions result from the release of magnetic, gravitational, or thermonuclear energy on dynamical timescales, typically the sound-crossing time for the system. These explosions include solar and stellar flares, eruptive phenomena in accretion disks, thermonuclear combustion on the surfaces of white dwarfs and neutron stars, violent magnetic reconnection in neutron stars, thermonuclear and gravitational collapse supernovae and cosmic gamma-ray bursts, each representing a different type and amount of energy release. This paper summarizes the properties of these explosions and des…
Several classes of astrophysical sources contribute to the approximately isotropic gamma-ray background measured by the Fermi Gamma-Ray Space Telescope. In this paper, we use Fermi's catalog of gamma-ray sources (along with corresponding source catalogs at infrared and radio wavelengths) to build and constrain a model for the contributions to the extragalactic gamma-ray background from astrophysical sources, including radio galaxies, star-forming galaxies, and blazars. We then combine our model with Fermi's measurement of the gamma-ray background to derive constraints on the dark matter annihi…
Gamma rays are the best probes to study high-energy particle interactions occurring in astrophysical environments. Space based instruments such as Fermi Large Area Telescope (Fermi LAT) and ground based experiments such as VERITAS, H.E.S.S. and MAGIC have provided us with valuable data on various production mechanisms of gamma rays within our Galaxy and beyond. Depending on astronomical conditions, gamma rays can be produced either by hadronic or leptonic interactions. In this paper, we probe the production of gamma rays by the hadronic channel where gamma rays are primarily produced by the de…
We propose to explore the so-far poorly measured cosmic ray and gamma-ray sky (accelerator sky) in the energy range from 10 TeV to 1 EeV. New physics questions might be addressed in this last remaining observation window of gamma-ray astronomy. The very high beam-energies provided by Cosmic accelerators and the air-shower detection technique naturally imply an entanglement between fundamental questions of astroparticle physics and particle physics. The new large-area (10 km$^2$) wide-angle (1 sr) air Cherenkov detector SCORE (Study for a Cosmic ORigin Explorer) is based on non-imaging Cherenko…
Space-based gamma-ray telescopes such as the Fermi Large Area Telescope have used single sided silicon strip detectors to track secondary charged particles produced by primary gamma-rays with high resolution. At the lower energies targeted by keV-MeV telescopes, two dimensional position information within a single detector is required for event reconstruction - especially in the Compton regime. This work describes the development of monolithic CMOS active pixel silicon sensors - AstroPix - as a novel technology for use in future gamma-ray telescopes. Based upon sensors (ATLASPix) designed for …
In recent years, observational $γ$-ray astronomy has seen a remarkable range of exciting new results in the high-energy and very-high energy regimes. Coupled with extensive theoretical and phenomenological studies of non-thermal processes in the Universe these observations have provided a deep insight into a number of fundamental problems of high energy astrophysics and astroparticle physics. Although the main moti- vations of $γ$-ray astronomy remain unchanged, recent observational results have contributed significantly towards our understanding of many related phenomena. This article aims to…
The 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.
Ultra-long gamma-ray bursts (ULGRBs) have very atypical durations of more than 2000 seconds. Even if their origins are discussed, the SVOM mission with its soft gamma-ray telescope ECLAIRs could detect ULGRBs and increase the sample of the few which have been detected so far by the Burst Alert Telescope aboard the Neil Gehrels Swift Observatory and some other instruments. In this paper, after a short description of the SVOM mission, we present methods developed to clean detector images from non-flat background and known source contributions in the onboard imaging process. We present an estimat…
The Gamma-ray Cherenkov Telescope (GCT) is one of the Small Size Telescopes (SSTs) proposed for the Cherenkov Telescope Array (CTA) aimed at the 1 TeV to 300 TeV energy range. GCT will be equipped with a Compact High-Energy Camera (CHEC) containing 2048 pixels of physical size about 6$\times$6~mm$^2$, leading to a field of view of over 8 degrees. Electronics based on custom TARGET ASICs and FPGAs sample incoming signals at a gigasample per second and provide a flexible triggering scheme. Waveforms for every pixel in every event are read out are on demand without loss at over 600 events per sec…
The last few years have seen gamma-ray astronomy maturing and advancing in the field of time-domain astronomy, utilizing source variability on timescales over many orders of magnitudes, from a decade down to a few minutes and shorter, depending on the source. This review focuses on some of the key science issues and conceptual developments concerning the timing characteristics of active galactic nuclei (AGN) at gamma-ray energies. It highlights the relevance of adequate statistical tools and illustrates that the developments in the gamma-ray domain bear the potential to fundamentally deepen ou…
High-energy photons are a powerful probe for astrophysics and for fundamental physics under extreme conditions. During the recent years, our knowledge of the most violent phenomena in the universe has impressively progressed thanks to the advent of new detectors for very-high-energy (VHE) gamma rays (above 100 GeV). Ground-based detectors like the Cherenkov telescopes (H.E.S.S., MAGIC and VERITAS) recently discovered more than 80 new sources. This talk reviews the present status of VHE gamma astrophysics, with emphasis on the recent results and on the experimental developments, keeping an eye …
While large neutrino telescopes have so far mainly focused on the detection of TeV-PeV astrophysical neutrinos, several efforts are ongoing to extend the sensitivity down to the GeV level for transient sources. Only a handful of neutrino searches have been carried out at the moment leaving the signature of astrophysical transients poorly known in this energy range. In this contribution, we discuss the motivations for high-energy neutrino telescopes to explore the GeV energy range and summarize the current limitations of detectors, such as IceCube and KM3NeT. We then present and compare differe…
The propagation of a relativistic electron-positron beam in a magnetized electron-ion plasma is studied, focusing on the polarization of the radiation generated in this case. Special emphasis is laid on investigating the polarization of the generated radiation for a range of beam-plasma parameters, transverse and longitudinal beam sizes, and the external magnetic fields. Our results not only help in understanding the high degrees of circular polarization observed in gamma-rays bursts but they also help in distinguishing the different modes associated with the filamentation dynamics of the pair…
We present the first interpretation of the new isotropic diffuse gamma-ray background (IGRB), measured by the Fermi Large Area Telescope (LAT), based on a statistical analysis. We demonstrate that the gamma-ray emission from unresolved active galactic nuclei and star forming galaxies is consistent with the Fermi-LAT IGRB data within the uncertainties both on the choice of the Galactic diffuse emission model and on the gamma-ray emission mechanism of these sources. Furthermore, adding to the extragalactic sources the contribution from a smooth Galactic halo of annihilating weakly interacting da…
The Fermi Gamma-ray Space Telescope, as an all-sky survey and monitoring mission, is producing daily/weekly sampled gamma-ray light curves for dozens of blazars and other high-energy sources. Highlights on MeV-GeV gamma-ray variability properties of these sources are reported together with a few remarks about some multi-waveband observing campaigns led by Fermi and targeted to known or newly discovered gamma-ray blazars.
We investigate looking for black hole starships using very high energy gamma ray telescopes. We find they would be above the threshhold of visibility although there are many unknown factors.
Advances in X-ray and gamma-ray astronomy have opened a new window on our universe and revealed a wide variety of binaries composed of a compact object and a Be star. In Be X-ray binaries, a neutron star accretes the Be disk and truncates it through tidal interactions. Such systems have important X-ray outbursts, some related to the disk structure. In other systems, strong gamma ray emission is observed. In gamma-ray binaries, the neutron star is not accreting but driving a highly relativistic wind. The wind collision region presents similarities to colliding wind binaries composed of massive …
Lorentz invariance (LI) has a central role in science and its violation (LIV) at some high-energy scale has been related to possible solutions for several of the most intriguing puzzles in nature such as dark matter, dark energy, cosmic rays generation in extreme astrophysical objects and quantum gravity. We report on a search for LIV signal based on the propagation of gamma rays from astrophysical sources to Earth. An innovative data analysis is presented which allowed us to extract unprecedented information from the most updated data set composed of 111 energy spectra of 38 different sources…
We present a range of unbroken power-law fits to the astrophysical-neutrino spectrum consistent with the most recent published IceCube data at the 68\% confidence level. Assuming that the neutrinos originate in decays of pi mesons, we estimate accompanying gamma-ray fluxes for various distributions of sources, taking propagation effects into account. We then briefly discuss existing experimental results constraining PeV to EeV diffuse gamma-ray flux and their systematic uncertainties. Several scenarios are marginally consistent both with the KASKADE and CASA-MIA upper limits at (10^15-10^16) e…
Following its launch in June 2008, the Fermi Gamma-ray Space Telescope (Fermi) began a sky survey in August. The Large Area Telescope (LAT) on Fermi in 3 months produced a deeper and better-resolved map of the gamma-ray sky than any previous space mission. We present here initial results for energies above 100 MeV for the 205 most significant (statistical significance greater than ~10-sigma) gamma-ray sources in these data. These are the best-characterized and best-localized point-like (i.e., spatially unresolved) gamma-ray sources in the early-mission data.
The detection of an astrophysical flux of high-energy neutrinos by IceCube is a major step forward in the search for the origin of cosmic rays, as this emission is expected to originate in hadronic interactions taking place in or near cosmic-ray accelerators. No neutrino point sources, or a significant correlation with known astrophysical objects, have been identified in the IceCube data so far that could reveal the location of the neutrino emission sites. The hadronic interactions responsible for the neutrino emission should also lead to the production of high-energy gamma rays from neutral p…
The Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope provides both direct and indirect measurements of Galactic cosmic rays (CR). The LAT high-statistics observations of the 7 GeV - 1 TeV electron plus positron spectrum and limits on spatial anisotropy constrain models for this cosmic-ray component. On a Galactic scale, the LAT observations indicate that cosmic- ray sources may be more plentiful in the outer Galaxy than expected or that the scale height of the cosmic-ray diffusive halo is larger than conventional models. Production of cosmic rays in supernova remnants (SNR) is…
We discuss the potential for the detection of dark matter and the characterization of its particle nature via the observation of dark matter subhalos. Specifically, we discuss the search for dark matter Galactic subhalos in the gamma-ray band with the Large Area Telescope on-board the Fermi gamma-ray Space Telescope, and the future generation of imaging atmospheric Cherenkov telescopes, best represented by the planned Cherenkov Telescope Array.
Presently there are several classes of detected gamma-ray extragalatic sources. They are mostly associated to active galactic nuclei (AGN) and (at soft gamma rays) to gamma-ray bursts (GRB), but not only. Active galactic nuclei consist of accreting supermassive black holes hosted by a galaxy that present in some cases powerful relativistic jet activity. These sources, which have been studied in gamma rays for several decades, are probably the most energetic astrophysical objects, and their appearance depends much on whether their jets point to us. Gamma-ray bursts, thought to be associated to …
We use likelihood approach for search for local astrophysical neutrino sources in unbinned versus binned methods with Baikal deep underwater telescopes. We analyze neutrino data sample selected with NT200 telescope for 1038 live days by scanning a celestial map with different nets and for listed gamma ray sources. Significance of most probable location of enhance in measured number of events is found to be less than one sigma. We obtain the upper limits and a sensitivity at 90\% C.L. on neutrino fluxes from listed sources for NT200 and NT1000 correspondingly.
Very high energy (VHE; E > 100 GeV) gamma-rays provide a unique probe into the non-thermal processes in the universe. The ground-based Imaging Air Cherenkov telescopes (IACTs) for detecting VHE gamma-rays have been perfected, so a relatively fast and inexpensive assembly of IACTs is now possible. Next generation instruments will have a sensitivity about 10 times better than current facilities, and will extend the accessible gamma-ray bandwidth at both energy ends (down to 30 GeV and up to 300 TeV) with improved angular and energy resolutions. Some key physics drivers, that are discussed here, …
The ANTARES neutrino telescope is installed at a depth of 2.5 km of the Mediterranean Sea and consists of a three-dimensional array of 885 photomultipliers arranged on twelve detector lines. The prime objective is to detect high-energy neutrinos from extraterrestrial origin. Relativistic muons emerging from charged-current muon neutrino interactions in the detector surroundings produce a cone of Cerenkov light which allows the reconstruction of the original neutrino direction. The collaboration has implemented different methods to search for neutrino point sources in the data collected since 2…
The diffuse Galactic gamma-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess gamma-ray emission > 1 GeV relative to diffuse Galactic gamma-ray emission models consistent with directly measured CR spectra (the so-called ``EGRET GeV excess''). The excess emission was observed in all directions on the sky, and a variety of explanations have been proposed, including beyond-the-Standard-Model scenarios like annih…
We report the detection of high-energy gamma-ray emission from two starburst galaxies using data obtained with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. Steady point-like emission above 200 MeV has been detected at significance levels of 6.8 sigma and 4.8 sigma respectively, from sources positionally coincident with locations of the starburst galaxies M82 and NGC 253. The total fluxes of the sources are consistent with gamma-ray emission originating from the interaction of cosmic rays with local interstellar gas and radiation fields and constitute evidence for a li…
Recently the IceCube collaboration has reported the observation of 28 contained events with a visible energy in the interval between 60 TeV and 1.5 PeV, and has argued that this detection is evidence, with a statistical significance of more than four standard deviations, for the existence of an astrophysical neutrino flux that accounts for a large fraction of the events. In this work we analyze the arguments that allow to identify a component of astrophysical origin in the high energy neutrino flux separating it from atmospheric neutrinos. An astrophysical origin for a large fraction of the Ic…
Very hot plasmas with ion temperature exceeding $10^{10}$ K can be formed in certain astrophysical environments. The distinct radiation signature of such plasmas is the $γ$-ray emission dominated by the prompt de-excitation nuclear lines and $π^0$-decay $γ$-rays. Using a large nuclear reaction network, we compute the time evolution of the chemical composition of such hot plasmas and their $γ$-ray line emissivity. At higher energies, we provide simple but accurate analytical presentations for the $π^0$-meson production rate and the corresponding $π^0\to2γ$ emissivity derived for the Maxwellian …
We assess the capabilities of a ground-based gamma-ray observatory to detect astrophysical neutrinos with energies in the $100\,{\rm TeV}$ to $100\,{\rm PeV}$ range. The identification of these events would be done through the measurement of very inclined extensive air showers induced by downward-going and upward-going neutrinos. The discrimination of neutrino-induced showers in the overwhelming cosmic-ray background is achieved by analysing the balance of the total electromagnetic and muonic signals of the shower at the ground. We demonstrate that a ${\rm km^2}$-scale wide field-of-view groun…
Supernovae and their remnants have long been favored as cosmic ray ac- celerators. Recent data from the Fermi Gamma-ray Space Telescope has given us an improved window into such sources, including the remnant CTB 37A. Using the Fermi Large Area Telescope, we found significant gamma-ray emission coincident with the remnant, which also emits in radio, X-ray, and very high energy gamma-rays. We modeled the multiwavelength spectrum using a combination of hadronic and leptonic emission with reasonable parameter values and determined that CTB 37A is a potential cosmic ray accelerator commensurate wi…
The LAT instrument on the Fermi Gamma-Ray Space Telescope is performing an all-sky survey from 20 MeV to 300 GeV with unprecedented statistics and angular resolution. This is providing a wealth of new information on the non-thermal emission from the Galactic interstellar medium with implications for cosmic rays and Galactic structure. First results at intermediate latitudes have already shown good agreement with predictions based on direct measurements of cosmic rays, suggesting that at least the local (within about 1 kpc from the Sun) gamma-ray emission is understood. We will present the firs…
We report the discovery of GeV emission at the position of supernova remnant Kes 17 by using the data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. Kes 17 can be clearly detected with a significance of ~12 sigma in the 1 - 20 GeV range. Moreover, a number of gamma-ray sources were detected in its vicinity. The gamma-ray spectrum of Kes 17 can be well described by a simple power-law with a photon index of ~ 2.4. Together with the multi-wavelength evidence for its interactions with the nearby molecular cloud, the gamma-ray detection suggests that Kes 17 is a candida…
We report on measurements of the cosmic-ray induced gamma-ray emission of Earth's atmosphere by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope. The LAT has observed the Earth during its commissioning phase and with a dedicated Earth-limb following observation in September 2008. These measurements yielded 6.4 x 10^6 photons with energies >100MeV and ~250hours total livetime for the highest quality data selection. This allows the study of the spatial and spectral distributions of these photons with unprecedented detail. The spectrum of the emission - often referred to as Ea…
