The detection of very-high-energy gamma rays from supernova remnant shells testifies of the acceleration of particles at strong shocks. Many aspects of the particle acceleration remain however unclear. The study of individual objects is very helpful, but the study of the entire population of SNRs detected in this range and its characteristics can also bring valuable science. Using Monte-Carlo simulations, the population of shells bright in the TeV and multi-TeV range can be simulated. The results of these simulations aim at being compared with observations of in struments operating in these ranges, such as the Cherenkov Telescope Array (CTA). Our results suggest that CTA should be able to effectively constrain the slope of particles accelerated at SNRs and the electron-to-proton ratio.
We discuss the prospects for indirect detection of dark matter (DM) with the Cherenkov Telescope Array (CTA), a future ground-based gamma-ray observatory that will be sensitive to gamma rays in the energy range from a few tens of GeV to 100 TeV. We consider the detectability of DM annihilation in different astrophysical targets with a focus on the Galactic Center (GC) region. With a deep observation of the GC, CTA will be sensitive to DM particles with mass greater than 100 GeV and an annihilation cross section close to the thermal relic value.
Very high energy (VHE, i.e. $\gtrsim 10$ GeV) photons from Gamma-Ray Bursts (GRBs), as high as 90 GeV in rest frame energy, have been detected by the $Fermi$ Large Area Telescope (LAT). This provides hope for a high statistics GRB detection by a ground-based instrument in the VHE domain. We here report on our estimates of the expected GRB detection rate and $γ$-ray rate (in case of detection) for the next generation ground-based Imaging Air Cherenkov Telescopes (IACTs): the Cherenkov Telescope Array (CTA). Moreover, we investigated the effect critical design parameters of CTA have on our predi…
The Cherenkov Telescope Array (CTA) is planned to serve as a ground-based observatory for (very-)high-energy gamma-ray astronomy, open to a wide astrophysics community, providing a deep insight into the non-thermal high-energy universe. It foresees a factor of ~10 improvement in sensitivity above 100 GeV, with substantially better angular and spectral resolutions and wider field-of-view in comparison with currently operational experiments. The CTA consortium is investigating the different physics cases for different proposed array configurations and subsets. Pulsar Wind Nebulae (PWNe), the mos…
The Cherenkov Telescope Array (CTA) will have a unique chance of discovery for a large range of masses in Weakly Interacting Massive Particles models of dark matter. The principal target for dark matter searches with CTA is the centre of the Galactic Halo. The best strategy is to perform CTA observations within a few degrees of the Galactic Centre, with the Galactic Centre itself and the most intense diffuse emission regions removed from the analysis. Assuming a cuspy dark matter density profile for the Milky Way, 500 hours of observations in this region provide sensitivities to and below the …
The Fermi Large Area Telescope (LAT) discovered the time signature of a radio-silent pulsar coincident with RX J0007.0+7302, a plerion-like X-ray source at the centre of the CTA 1 supernova remnant. The inferred timing parameters of the gamma-ray pulsar PSR J0007+7303 (P=315.8 ms; dot{P}\sim3.6 10^{-13} s s^{-1}) point to a Vela-like neutron star, with an age comparable to that of CTA 1. The PSR J0007+7303 low distance (\sim 1.4 kpc), interstellar absorption (A_V\sim 1.6), and relatively high energy loss rate (dot{E} \sim4.5 10^{35} erg s^{-1}), make it a suitable candidate for an optical foll…
The Cherenkov Telescope Array (CTA) will be the next generation instrument for the very high energy gamma-ray astrophysics domain. With its enhanced sensitivity in comparison with the current facilities, CTA is expected to shed light on a varied population of sources. In particular, we will achieve a deeper knowledge of the Crab nebula and pulsar, which are the best characterized pulsar wind nebula and rotation powered pulsar, respectively. We aim at studying the capabilities of CTA regarding these objects through simulations, using the main tools currently in development for the CTA future da…
Radio galaxies host relativistic jets oriented away from our line of sight, making them challenging targets for Very High Energy (VHE, E$>$100 GeV) $γ$-ray detectors. Indeed, out of $\sim100$ extragalactic sources detected at $E>100$ GeV, only six are radio galaxies. The new Cherenkov Telescope Array (CTA) will provide order-of-magnitude improvements in sensitivity with respect to the present generation of ground-based $γ$-ray observatories, opening new frontiers for high-energy studies of radio galaxies. In a previous paper, we studied the CTA detection prospects of misaligned jets from the T…
We present a likelihood profile stacking technique based on the {\it Fermi}-Large Area Telescope (LAT) data to explore the $γ$-ray characteristics of {\it Fermi}-LAT undetected astrophysical populations. The pipeline is applied to a sample of $γ$-ray unresolved extreme blazars, i.e., sources with the highest synchrotron peak frequencies ($ν_{\rm Syn}^{\rm peak}\geqslant 10^{17}$ Hz), and we report a cumulative $γ$-ray detection with more than 32$σ$ confidence for 2 degrees of freedom. Comparing the generated stacked $γ$-ray spectrum with the sensitivity limits of the upcoming Cherenkov Telesco…
Around 160 gamma-ray pulsars were discovered by the Fermi Large Area Telescope (LAT) since 2008. The most energetic of them, 12 objects with emission above 25 GeV, are suitable candidates for the detection with the current and future Imaging Atmospheric Cherenkov Telescopes above few tens of GeV. We perform an analysis of the Fermi-LAT data of these high-energy pulsars in order to determine if such objects can be detected with the Cherenkov Telescope Array (CTA). Our goal is to forecast the significance of their point source detection with CTA. We analyze 5 years of the Fermi-LAT data fitting …
CTA 1 (G119.5+10.2) is a composite supernova remnant (SNR) with a shell-type structure, visible in the radio band, surrounding a smaller pulsar wind nebula. Fermi detected a radio-quiet pulsar PSR J0007+7303 within the radio shell. 26.5 hours of VERITAS observation revealed extended TeV emission from CTA 1. The centroid of the TeV emission is located near the Fermi pulsar. The integral flux of the emission was ~4% of the Crab Nebula flux (>1TeV). We present an update on the source analysis with additional exposure and possible interpretations.
CTA 1 (G119.5+10.2) is a composite supernova remnant (SNR) with a shell-type structure in the radio band and a center filled morphology at X-ray energies. Fermi has detected a radio-quiet pulsar PSR J0007+7303 within the radio shell of CTA 1 in a blind search within its first months of operation. Located within an X-ray synchrotron pulsar wind nebula (PWN), the Fermi source is spatially coincident with the EGRET source 3EG J0010+7309. We present the the detection of the system in very-high-energy (VHE) gamma rays by VERITAS, with a preliminary comparison to other TeV-detected PWNe.
We simulate the spectral behaviour of the non-transient gamma-ray binaries using archival observations as a reference. With this we test the CTA capability to measure the sources' spectral parameters and detect variability on various time scales. We review the known properties of gamma-ray binaries and the theoretical models that have been used to describe their spectral and timing characteristics. We show that CTA is capable of studying these sources on time scales comparable to their characteristic variability time scales. For most of the binaries, the unprecedented sensitivity of CTA will a…
The discovery of novae as sources of ~GeV gamma-rays highlights the key role of shocks and relativistic particle acceleration in these transient systems. Although there is evidence for a spectral cut-off above energies ~1-100 GeV at particular epochs in some novae, the maximum particle energy achieved in these accelerators has remained an open question. The high densities of the nova ejecta (~10 orders of magnitude larger than in supernova remnants) render the gas far upstream of the shock neutral and shielded from ionizing radiation. The amplification of the magnetic field needed for diffusiv…
Ap Librae is one out of a handful of low-frequency peaked blazars to be detected at TeV $γ$-rays and the only one with an identified X-ray jet. Combined observations of Fermi-LAT at high energies (HE) and of H.E.S.S at very high energies (VHE) revealed a striking spectral property of Ap Librae; the presence of a broad high-energy component that extends more than nine orders of magnitude in energy and is, therefore, hard to be explained by the usual single-zone synchrotron self-Compton model. We show that the superposition of different emission components related to photohadronic interactions c…
TeV-scale particles that couple to the standard model through the weak force represent a compelling class of dark matter candidates. The search for such Weakly Interacting Massive Particles (WIMPs) has already spanned multiple decades, and whilst it has yet to provide any definitive evidence for their existence, viable parameter space remains. In this paper, we show that the upcoming Cherenkov Telescope Array (CTA) has significant sensitivity to uncharted parameter space at the TeV mass scale. To do so, we focus on two prototypical dark matter candidates, the Wino and Higgsino. Sensitivity for…
The development and construction of the Cherenkov Telescope Array (CTA) opens up new opportunities for the study of very high energy (VHE, E>100 GeV) sources. As a part of CTA, the ASTRI project, led by INAF, has one of the main goals to develop one of the mini-arrays of CTA pre-production telescopes, proposed to be installed at the CTA southern site. Thanks to the innovative dual-mirror optical design of its small-sized telescopes, the ASTRI mini-array will be characterized by a large field of view, an excellent angular resolutioerrorn and a good sensitivity up to energies of several tens of …
Gamma-ray emitting narrow-line Seyfert 1 ($γ$-NLSy1) galaxies are thought to harbour relatively low-mass black holes (10$^6$-10$^8$ M$_{\odot}$) accreting close to the Eddington limit. They show characteristics similar to those of blazars, such as flux and spectral variability in the gamma-ray energy band and radio properties which point toward the presence of a relativistic jet. These characteristics make them an intriguing class of sources to be investigated with the Cherenkov Telescope Array (CTA), the next-generation ground-based gamma-ray observatory. We present our extensive set of simul…
We investigate the prospects for detection of neutralino dark matter in the 19-parameter phenomenological MSSM (pMSSM). We explore very wide ranges of the pMSSM parameters but pay particular attention to the higgsino-like neutralino at the ~ 1 TeV scale, which has been shown to be a well motivated solution in many constrained supersymmetric models, as well as to a wino-dominated solution with the mass in the range of 2-3 TeV. After summarising the present bounds on the parameter space from direct and indirect detection experiments, we focus on prospects for detection of the Cherenkov Telescope…
Gamma-ray emitting narrow-line Seyfert 1 ($γ$-NLS1) galaxies possibly harbour relatively low-mass black holes (10$^6$-10$^8$ M$_{\odot}$) accreting close to the Eddington limit, and share many characteristics with their sibling sources, flat-spectrum radio quasars. Although they have been detected in the MeV--GeV band with Fermi-LAT, they have never been seen in the very high energy band with current imaging atmospheric Cherenkov telescopes (IACTs). Thus, they are key targets for the next-generation IACT, the Cherenkov Telescope Array (CTA). In a previous work we selected, by means of extensiv…
The last few years have seen a revolution in very-high gamma-ray astronomy (VHE; E>100 GeV) driven largely by a new generation of Cherenkov telescopes (namely the H.E.S.S. telescope array, the MAGIC and MAGIC-II large telescopes and the VERITAS telescope array). The Cherenkov Telescope Array (CTA) project foresees a factor of 5 to 10 improvement in sensitivity above 0.1 TeV, extending the accessible energy range to higher energies up to 100 TeV, in the Galactic cut-off regime, and down to a few tens GeV, covering the VHE photon spectrum with good energy and angular resolution. As a result of t…
Ground-based gamma-ray astronomy has experienced a major breakthrough in the last decade thanks to the advent of new generation instruments such as H.E.S.S., MAGIC, Milagro and VERITAS. A large variety of cosmic particle accelerators has been unveiled, comprising supermassive black holes in the centres of active galaxies, nearby star forming galaxies, Galactic supernova remnants and pulsar wind nebulae, and stellar binary systems housing a compact object. While current instruments revealed the tips of the non-thermal icebergs in our Universe, a factor of 10 increase in sensitivity, improved an…
The Cherenkov Telescope Array is expected to lead to the detection of many new supernova remnants in the TeV and multi-TeV range. In addition to the individual study of each SNR, the study of these objects as a population can help constraining the parameters describing the acceleration of particles and increasing our understanding of the mechanisms involved. We present Monte Carlo simulations of the population of Galactic SNRs emitting TeV gamma rays. We also discuss how the simulated population can be confronted with future observations to provide a novel test for the SNR hypothesis of cosmic…
We investigate escape of cosmic ray (CR) electrons from a supernova remnant (SNR) to interstellar space. We show that CR electrons escape in order from high energies to low energies like CR nuclei, while the escape starts later than the beginning of the Sedov phase at an SNR age of 10^3 - 7*10^3 yrs and the maximum energy of runaway CR electrons is below the knee about 0.3 - 50 TeV because unlike CR nuclei, CR electrons lose their energy due to synchrotron radiation. Highest energy CR electrons will be directly probed by AMS-02, CALET, CTA and LHAASO experiments, or have been already detected …
We compute the sensitivity to dark matter annihilations for the forthcoming large Cherenkov Telescope Array (CTA) in several primary channels and over a range of dark matter masses from 30 GeV up to 80 TeV. For all channels, we include inverse Compton scattering of e$^\pm$ by dark matter annihilations on the ambient photon background, which yields substantial contributions to the overall gamma-ray flux. We improve the analysis over previous work by: i) implementing a spectral and morphological analysis of the gamma-ray emission; ii) taking into account the most up-to-date cosmic ray background…
Supernova remnants (SNRs) are thought to be one of the major acceleration sites of galactic cosmic rays (CRs) and an important class of objects for high-energy astrophysics. SNRs produce multi-wavelength, non-thermal emission via accelerated particles at collisionless shocks generated by the interactions between the SN ejecta and the circumstellar medium (CSM). Although it is expected that the rich diversities observed in supernovae (SNe) and their CSM can result in distinct very-high-energy (VHE) electromagnetic signals in the SNR phase, there are only a handful of SNRs observed in both GeV a…
The excess of positrons in cosmic rays above $\sim$10 GeV has been a puzzle since it was discovered. Possible interpretations of the excess have been suggested, including acceleration in a local supernova remnant or annihilation of dark matter particles. To discriminate between these scenarios, the positron fraction must be measured at higher energies. One technique to perform this measurement is using the Earth-Moon spectrometer: observing the deflection of positron and electron moon shadows by the Earth's magnetic field. The measurement has been attempted by previous imaging atmospheric Cher…
We discuss the prospects for the detection of gamma-ray bursts (GRBs) by the Cherenkov Telescope Array (CTA), the next generation, ground-based facility of imaging atmospheric Cherenkov telescopes (IACTs) operating above a few tens of GeV. By virtue of its fast slewing capabilities, the lower energy threshold compared to current IACTs, and the much larger effective area compared to satellite instruments, CTA can measure the spectra and variability of GRBs with excellent photon statistics at multi-GeV energies. Employing a model of the GRB population whose properties are broadly consistent with…
We estimate the molecular mass around CTA 1 using data from Planck and the Harvard CO survey. We observe that the molecular mass in the vicinity of the complex is not enough to explain the TeV emission observed by VERITAS, even under favorable assumptions for the cosmic-ray acceleration properties of the supernova remnant. This supports the idea that the TeV emission comes from the PWN. Here, we model the spectrum of the PWN at possible different stages of its evolution, including both the dynamics of the PWN and the SNR and their interaction via the reverse shock. We have included in the mode…
We derive the Cherenkov Telescope Array (CTA) sensitivity to dark matter (DM) annihilation in several primary channels, over a broad range of DM masses. These sensitivities are estimated when CTA is pointed towards a large sample of Milky Way's dwarf spheroidal galaxies (dSphs) with promising $J$-factors and small statistical uncertainties. This analysis neglects systematic uncertainties, which we estimate at the level of at least 1 dex. We also present sensitivities on the annihilation cross section from a combined analysis of 4 dSphs. We assess the CTA sensitivity by: $i)$ using, for each dS…
The recent discovery of TeV emission from gamma-ray bursts (GRBs) by the MAGIC and H.E.S.S. Cherenkov telescopes confirmed that emission from these transients can extend to very high energies. The TeV energy domain reaches the most sensitive band of the Cherenkov Telescope Array (CTA). This newly anticipated, improved sensitivity will enhance the prospects of gravitational-wave follow-up observations by CTA to probe particle acceleration and high-energy emission from binary black hole and neutron star mergers, and stellar core-collapse events. Here we discuss the implications of TeV emission o…
Very high-energy gamma-ray measurements of distant blazars can be well explained by secondary gamma rays emitted by cascades induced by ultra-high-energy cosmic rays. The secondary gamma rays will enable one to detect a large number of blazars with future ground based gamma-ray telescopes such as Cherenkov Telescope Array (CTA). We show that the secondary emission process will allow CTA to detect 100, 130, 150, 87, and 8 blazars above 30 GeV, 100 GeV, 300 GeV, 1 TeV, and 10 TeV, respectively, up to $z\sim8$ assuming the intergalactic magnetic field (IGMF) strength $B=10^{-17}$ G and an unbiase…
Gamma rays at rest frame energies as high as 90 GeV have been reported from gamma-ray bursts (GRBs) by the Fermi Large Area Telescope (LAT). There is considerable hope that a confirmed GRB detection will be possible with the upcoming Cherenkov Telescope Array (CTA), which will have a larger effective area and better low-energy sensitivity than current-generation imaging atmospheric Cherenkov telescopes (IACTs). To estimate the likelihood of such a detection, we have developed a phenomenological model for GRB emission between 1 GeV and 1 TeV that is motivated by the high-energy GRB detections o…
Galactic cosmic rays are commonly believed to be accelerated at supernova remnants via diffusive shock acceleration. Despite the popularity of this idea, a conclusive proof for its validity is still missing. Gamma-ray astronomy provides us with a powerful tool to tackle this problem, because gamma rays are produced during cosmic ray interactions with the ambient gas. The detection of gamma rays from several supernova remnants is encouraging, but still does not constitute a proof of the scenario, the main problem being the difficulty in disentangling the hadronic and leptonic contributions to t…
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 th…
A gamma-ray burst (GRB) jet running into an external medium is expected to generate luminous GeV-TeV emission lasting from minutes to several hours. The high-energy emission results from inverse Compton upscattering of prompt and afterglow photons by shock-heated {\it thermal} plasma. At its peak the high-energy radiation carries a significant fraction of the power dissipated at the forward shock. We discuss in detail the expected TeV luminosity, using a robust "minimal" emission model. Then, using the statistical properties of the GRB population (luminosity function, redshift distribution, af…
The assumption of Lorentz invariance is one of the founding principles of modern physics and violation of that would have deep consequences to our understanding of the universe. Potential signatures of such a violation could range from energy dependent dispersion introduced into a light curve to a change in the photon-photon pair production threshold that changes the expected opacity of the universe. Astronomical sources of Very High Energy (VHE) photons can be used as test beams to probe fundamental physics phenomena, however, such effects would likely be small and need to be disentangled fro…
It is widely believe that galactic cosmic rays are originated in supernova remnants (SNRs) where they are accelerated by diffusive shock acceleration process at supernova blast waves driven by expanding SNRs. In recent theoretical developments of the diffusive shock acceleration theory in SNRs, protons are expected to accelerate in SNRs at least up to the knee energy. If SNRs are true generator of cosmic rays, they should accelerate not only protons but also heavier nuclei with right proportion and the maximum energy of heavier nuclei should be atomic mass (Z) times that of protons. In this wo…
The prospects for future blazar surveys by next-generation very high energy (VHE) gamma-ray telescopes, such as Advanced Gamma-ray Imaging System (AGIS) and Cherenkov Telescope Array (CTA), are investigated using the latest model of blazar luminosity function and its evolution which is in good agreement with the flux and redshift distribution of observed blazars as well as the extragalactic gamma-ray background. We extend and improve the template of spectral energy distributions (SEDs) based on the blazar SED sequence paradigm, to make it reliable also in the VHE bands (above 100 GeV) by compa…
In this paper, we review the prospects for studies of active galactic nuclei (AGN) using the envisioned future Cherenkov Telescope Array (CTA). This review focuses on jetted AGN, which constitute the vast majority of AGN detected at gamma-ray energies. Future progress will be driven by the planned lower energy threshold for very high energy (VHE) gamma-ray detections to ~10 GeV and improved flux sensitivity compared to current-generation Cherenkov Telescope facilities. We argue that CTA will enable substantial progress on gamma-ray population studies by deepening existing surveys both through …
In this contribution, CTAs potential role in detection of particle dark matter in the context of other detection approaches is briefly discussed for an audience of gamma-ray astronomers. In particular searches for new particles at the large hadron collider and detection of dark matter particles in deep underground detectors are considered. We will focus on Weakly Interacting Massive Particles (WIMP). Approaches will be compared in terms of (a) robustness of sensitivity predictions, (b) timeline and (c) reach. The estimate of the reach will be model-dependent. Given our ignorance about the natu…
In this work, we compare the $γ$-ray spectra available in literature from 11 middle aged supernova remnants (SNRs) interacting with molecular clouds (MCs). It is found that 5 remnants prefer a smoothly broken power law proton spectrum with similar power law index but different break energy. The rest of the SNRs need updated data to test whether a spectral break is preferred in the proton spectrum. Then we compare the $γ$-ray spectra from all 11 SNRs with the prediction from widely accepted escaping scenario and direct interaction scenario. We show that current $γ$-ray data is inconsistent with…
The Cherenkov Telescope Array (CTA), currently in its Preparatory Phase, will be the first open observatory for very high energy gamma-rays from galactic and extragalactic sources. The international consortium behind CTA is preparing the construction of two large arrays of Cherenkov telescopes in the Northern and Southern Hemispheres with a performance that will be significantly improved compared to the current generation of arrays. Its increased sensitivity and energy range will give CTA access to a large population of Active Galactic Nuclei (AGN) not yet detected at very high energies and pr…
We compare the $γ$-ray spectra from 10 middle-aged supernova remnants (SNRs), which are interacting with molecular clouds (MCs), with the model prediction from widely used escaping scenario and direct interaction scenario. It is found that the $γ$-ray data is inconsistent with the escaping scenario statistically, as it predicts a diversity of spectral shape which is not observed. The inconsistency suggests that the free escape boundary adopted in the escaping model is not a good approximation, which challenges our understanding of cosmic ray (CR) escaping in SNRs. In addition, we show that amb…
Interstellar clouds can act as target material for hadronic cosmic rays; gamma-rays produced through inelastic proton-proton collisions and spatially associated with the clouds provide a key indicator of efficient particle acceleration. However, even for PeVatron sources reaching PeV energies, the system of cloud and accelerator must fulfil several conditions in order to produce a detectable gamma-ray flux. In this contribution, we characterise the necessary properties of both cloud and accelerator. Using available Supernova Remnant (SNR) and interstellar cloud catalogues, and assuming particl…
We investigate $^{60}$Fe in massive stars and core-collapse supernovae focussing on uncertainties that influence its production in 15, 20 and 25 $M_\odot$ stars at solar metallicity. We find that the $^{60}$Fe yield is a monotonic increasing function of the uncertain $^{59}$Fe$(n,γ)^{60}$Fe cross section and that a factor of 10 reduction in the reaction rate results in a factor 8-10 reduction in the $^{60}$Fe yield; while a factor of 10 increase in the rate increases the yield by a factor 4-7. We find that none of the 189 simulations we have performed are consistent with a core-collapse supern…
QUIJOTE scientific results -- XIII. Intensity and polarization study of supernova remnants in the QUIJOTE-MFI wide survey: CTB 80, Cygnus Loop, HB 21, CTA 1, Tycho and HB 9
The gravitational wave data of GW170817 favor the equation of state (EoS) models that predict compact neutron stars (NSs), consistent with the radius constraints from X-ray observations. Motivated by such a remarkable progress, we examine the fate of the remnants formed in NS mergers and focus on the roles of the angular momentum and the mass distribution of the binary NSs. In the mass shedding limit (for which the dimensionless angular momentum equals to the Keplerian value, i.e., $j=j_{\rm Kep}$), the adopted { seven EoS models, except H4 and ALF2,} yield supramassive NSs in more than half o…
