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Fermi-LAT SED for J2108.0+5155 (blue) and HS (red) analyzed with the energy threshold of 300 MeV (see the text for details). Fluxes in energy bins with T S > 10 are drawn as flux points, and for lower TS 95% confidence level ULs are shown.
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Context. Several new ultrahigh-energy (UHE) γ -ray sources have recently been discovered by the Large High Altitude Air Shower Observatory (LHAASO) collaboration. These represent a step forward in the search for the so-called Galactic PeVatrons, the enigmatic sources of the Galactic cosmic rays up to PeV energies. However, it has been shown that mu...
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... SED points of J2108.0+5155 and HS shown in Fig. 5 were computed by running a separate independent likelihood analysis in each smaller energy band, replacing the source of interest with a simple PL spectrum. The normalization of this spectrum was let free to vary in the fit, whereas its photon index was fixed to the local slope (α) of the log parabola in the case of J2108.0+5155, and ...
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... LST-1 is currently under commissioning and it is already producing technical and scientific results (see e.g. [2][3][4][5][6] ). The remaining three LSTs (LST-2, LST-3 and LST-4) are being installed at ORM, with an expected date of inauguration by early 2026. ...
The Cherenkov Telescope Array Observatory (CTAO) is the upcoming next-generation ground-based gamma-ray observatory. CTAO will have two sites, one located in the northern hemisphere in the Roque de los Muchachos Observatory, La Palma (Spain) and a sourthern site in Paranal (Chile). CTAO will count on improved sensitivity, angular and spectral resolution with respect to the current generation of imaging atmospheric Cherenkov telescopes (IACTs) and will cover a broader energy range. In this contribution, we review the current status of CTAO and address the scientific questions that CTAO aims to answer. We outline the science perspectives of CTAO and the timeline of the observatory.
... Recently, in many papers, the Fermi-LAT data have been analyzed to investigate the emission from extended teraelectronvolt halos (M. Di Mauro et al. 2021;J. Li et al. 2021;S. Abe et al. 2023;X. Guo & Y. Xin 2024;Y. Xiao et al. 2024). Fermi-LAT data analysis is very useful in exploring the gigaelectronvolt counterparts of the teraelectronvolt sources and subsequently identifying their origin. If both an SNR and pulsar are present within the teraelectronvolt halo, in some cases with the spatial position and morphology of the e ...
The extended ultra-high-energy (UHE) gamma-ray source HAWC J1844–034 is closely associated with two other sources, HAWC J1843–032 and HWC J1846–025. Moreover, other gamma-ray observatories like HESS, LHAASO, and Tibet AS γ have detected UHE gamma-ray sources whose spatial positions coincide with the position of HAWC J1844–034. The UHE gamma-ray data from several observatories aid analysis of the spectral features of this source in detail at teraelectronvolt energies. Of the four pulsars near HAWC J1844–034, PSR J1844–0346 is closest to it and possibly supplies the cosmic-ray leptons to power this source. We have analyzed the Fermi–Large Area Telescope (LAT) data to explore this source’s morphology and identify its spectral features in the Fermi-LAT energy band. After removing the contribution of the pulsar to the gamma-ray spectral energy distribution (SED) by pulsar-phased analysis, we obtained upper limits on the photon flux and identified the gigaelectronvolt counterpart PS J1844.2–0342 in the Fermi-LAT energy band with more than 5 σ significance, which may be a pulsar wind nebula (PWN). Finally, the multiwavelength SED is modeled, assuming HAWC J1844–034 is a PWN.
... a with the "source" event class (evclass = 128 & evtype = 3) are selected from 2008 August 4 (MET 239557418) to 2024 August 31 (MET 746775603). γ-ray pulsars are characterized by a soft spectrum, with the flux steeply falling above a few GeV, and γ-ray pulsations from pulsars have usually not been seen above 10 GeV (MAGIC Collaboration et al. 2020;S. Abe et al. 2023). Therefore, the energy of the event was cut between 30 GeV and 1 TeV to avoid contamination of PSR J0248 +6021, allowing for a better test of whether the γ-rays emission could have come from the PWN scenario (Z. Cao et al. 2021). In the Fermi-LAT data analysis of PWN, there are cases where data with an energy range above 30 GeV are used ...
1LHAASO J0249+6022 is an extended very-high-energy γ -ray source discovered by the Large High-Altitude Air Shower Observatory. Based on nearly 16.1 yr of data from the Fermi Large Area Telescope, we report the probable γ -ray emission from 1LHAASO J0249+6022 in the 0.03–1 TeV energy range. The results show that its γ -ray spectrum can be well fitted by a single power law with an index of 1.54 ± 0.17, and integral photon flux is (4.28 ± 1.03) × 10 ⁻¹¹ photons cm ⁻² s ⁻¹ . We also considered theoretically whether the nonthermal emission could originate from a pulsar wind nebula (PWN) scenario. Assuming that the particles injected into the nebula have a power-law distribution, the resulting spectrum from the inverse Compton scattering is consistent with the detected GeV and TeV γ -ray fluxes. Our study shows that the PWN scenario is reasonable for 1LHAASO J0249+6022.
... al. 2021; Abe et al. 2023). Therefore, the energy of the event was cut between 30 GeV and 1 TeV to avoid contamination of PSR J0248+6021, allowing a better test of whether the γ-rays emission could have come from the PWN scenario (Cao et al. 2021). ...
1LHAASO J0249+6022 is an extended very-high-energy gamma-ray source discovered by the Large High-Altitude Air Shower Observatory. Based on nearly 16.1 years of data from the Fermi Large Area Telescope, we report the probable gamma-ray emission from 1LHAASO J0249+6022 in the 0.03-1 TeV energy range. The results show that its gamma-ray spectrum can be well fitted by a single power law with an index of 1.54 0.17, and integral photon flux is (4.28 1.03) 10 photons cm s. We also considered theoretically whether the non-thermal emission could originate from a pulsar wind nebula (PWN) scenario. Assuming that the particles injected into the nebula have a power-law distribution, the resulting spectrum from the inverse Compton scattering is consistent with the detected GeV and TeV gamma-ray fluxes. Our study shows that the PWN scenario is reasonable for 1LHAASO J0249+6022.
... Recently, in many papers, the Fermi-LAT data have been analysed to investigate the emission from extended TeV halos (Li et al. 2021;Di Mauro et al. 2021;Abe et al. 2023;Guo & Xin 2024;Xiao et al. 2024). Fermi-LAT data analysis is very useful in exploring the GeV counterparts of the TeV sources and subsequently identifying their origin. ...
The extended ultra-high-energy gamma-ray source HAWC J1844-034 is closely associated with two other sources, HAWC J1843-032 and HWC J1846-025. Moreover, other gamma-ray observatories like H.E.S.S., LHAASO, and Tibet AS have detected ultra-high-energy gamma-ray sources whose spatial positions coincide with the position of HAWC J1844-034. The ultra-high-energy gamma-ray data from several observatories help analyse the spectral features of this source in detail at TeV energies. Of the four pulsars near HAWC J1844-034, PSR J1844-0346 is closest to it and possibly supplies the cosmic-ray leptons to power this source. We have analysed the Fermi-LAT data to explore this source's morphology and identify its spectral feature in the Fermi-LAT energy band. After removing the contribution of the pulsar to the gamma-ray spectral energy distribution by pulsar phased analysis, we have obtained upper limits on the photon flux and identified the GeV counterpart PS J1844.2-0342 in the Fermi-LAT energy band with more than 5 significance, which may be a pulsar wind nebula. Finally, the multi-wavelength spectral energy distribution has been modelled, assuming HAWC J1844-034 is a pulsar wind nebula.
... A large number of studies have been conducted to understand the origin of cosmic rays (CRs) since their discovery Banik & Ghosh 2022;Abe et al. 2023). Radio synchrotron radiation from supernova remnants (SNRs) proves that there are relativistic electrons that have accelerated in SNRs (Ginzburg et al. 1954), which means SNRs might be the potential source of Galactic CRs. ...
Red dwarfs have been suggested to be among the possible astrophysical species accelerating particles and emitting TeV γ -rays. In an effort to search for the GeV γ -ray counterparts of the suggested TeV emission from eight red dwarfs, we analyze the 0.2–500 GeV γ -ray emission of the regions covering them, exploiting the ∼13.6 yr Pass 8 data from the Fermi Large Area Telescope (LAT). A GeV γ -ray emission excess with a significance of 3.8 σ is detected in the direction of the red dwarf V962 Tau. This emission contains V962 Tau in a 1 σ error radius and is independent of the catalog source. However, the stellar flare scenario can hardly explain the total energy and lightcurve (LC) derived from the γ -ray emission in view of the spectral analysis. We also analyze the LCs in the positions of the eight red dwarfs, and no time bin with a significance >5 σ is found. Therefore, no significant emission from the red dwarfs could be concluded to have been detected by Fermi-LAT.
... This telescope, together with three others of the same design to be put in operation in the coming years, will form the group of LSTs [72] that will be part of the future CTAO (Cherenkov Telescope Array Observatory [141]). LST-1 has already achieved results in the observation of the gamma-ray source LHAASO J2108+5157 [142]. As for the study of AGNs, it has recently discovered the FSRQ OP 313 [73] in the VHE gamma-ray range. ...
The MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) Florian Goebel telescopes are a system of two Cherenkov telescopes located on the Canary island of La Palma (Spain), at the Roque de Los Muchachos Observatory, which have been operating in stereo mode since 2009. Their low energy threshold (down to 15 GeV) allows the investigation of Active Galactic Nuclei (AGNs) in the very-high-energy (VHE, E > 100 GeV) gamma-ray range with a sensitivity up to the redshift limit of the existing IACT (Imaging Atmospheric Cherenkov Telescopes) systems. The MAGIC telescopes discovered 36 extragalactic objects emitting VHE gamma-rays and performed comprehensive studies of galaxies and their AGNs, also in a multi-wavelength (MWL) and multi-messenger (MM) context, expanding the knowledge of our Universe. Here, we report on the highlights achieved by the MAGIC collaboration since the beginning of their operations.
... The Cherenkov Telescope Array (CTA) aims to go beyond by improving the sensitivity by a factor of five to ten compared to the current-generation instruments and provide an energy coverage from 20 GeV to more than 300 TeV. Although the project is currently in the construction phase, the first Large-Sized Telescope (LST-1, portrayed in Figure 1) prototype is under commissioning yet operational and has already made its first detections [Abe et al. 2021;Jurysek et al. 2023]. Similarly to all IACTs, the detection of gamma rays with CTA is not straightforward as the principle of detection is indirect and relies on using the atmosphere as a calorimeter. ...
The Cherenkov Telescope Array is the next generation of observatory using imaging air Cherenkov technique for very-high-energy gamma-ray astronomy. Its first prototype telescope is operational on-site at La Palma and its data acquisitions allowed to detect known sources, study new ones, and to confirm the performance expectations. The application of deep learning for the reconstruction of the incident particle physical properties (energy, direction of arrival and type) have shown promising results when conducted on simulations. Nevertheless, its application to real observational data is challenging because deep-learning-based models can suffer from domain shifts. In the present article, we address this issue by implementing domain adaptation methods into state-of-art deep learning models for Imaging Atmospheric Cherenkov Telescopes event reconstruction to reduce the domain discrepancies, and we shed light on the gain in performance that they bring along.
... We will also show the results of a multi-instrument analysis including XMM-Newton data and 12 years of Fermi-LAT data, as well as the multi-wavelength modeling and consequent interpretation of different possible scenarios of emission. The results discussed in this contribution have been recently published [6]. ...
... Multi-wavlength analysis of the galactic PeVatron candidate LHAASO J2108+5157 G. Pirola The green line and band represent the best-fit PL spectral model of LST-1 data and its statistical uncertainties, whereas the blue line corresponds to the joint likelihood fit of the LST-1 data and LHAASO flux points with an ECPL spectral model. Together with the ECPL model, the plot also shows the 95% confidence level ULs on differential flux [6]. In the table are reported the best-fit parameters for the two aforementioned spectral analyses [6]. ...
... Together with the ECPL model, the plot also shows the 95% confidence level ULs on differential flux [6]. In the table are reported the best-fit parameters for the two aforementioned spectral analyses [6]. Right: statistical significance map in a region of 2 • × 2 • around LHAASO J2108+5157, in the energy range between 3 TeV and 100 TeV. ...
... Two sources that do not appear to have a known energetic pulsar counterpart are LHAASO J1843-0338, plausibly associated with the SNR G28.6-0.1, and the enigmatic source LHAASO J2108+5157; the only source to be first discovered at the highest energies. To date, coincident molecular material as been found at the location of the latter [205,206], potentially indicating that energetic particles are hadronic in nature, yet no accelerator has as yet been identified in the vicinity [207]. 11 Within a scenario whereby the particles accelerated to the highest energies escape the accelerator, travel through the intervening ISM and subsequently interact with target material such as molecular clouds, one may anticipate a population of such 'passive' sources emerging at the highest energies. ...
Galaxy evolution is an important topic, and our physical understanding must be complete to establish a correct picture. This includes a thorough treatment of feedback. The effects of thermal–mechanical and radiative feedback have been widely considered; however, cosmic rays (CRs) are also powerful energy carriers in galactic ecosystems. Resolving the capability of CRs to operate as a feedback agent is therefore essential to advance our understanding of the processes regulating galaxies. The effects of CRs are yet to be fully understood, and their complex multi-channel feedback mechanisms operating across the hierarchy of galaxy structures pose a significant technical challenge. This review examines the role of CRs in galaxies, from the scale of molecular clouds to the circumgalactic medium. An overview of their interaction processes, their implications for galaxy evolution, and their observable signatures is provided and their capability to modify the thermal and hydrodynamic configuration of galactic ecosystems is discussed. We present recent advancements in our understanding of CR processes and interpretation of their signatures, and highlight where technical challenges and unresolved questions persist. We discuss how these may be addressed with upcoming opportunities.
