Andrea Comastri: WELCOME

Massimo Cappi: UTG III

Roberta Zanin: CTAO: a new view of the very-high energy sky

• Roberta Zanin (Istituto Nazionale di Astrofisica (INAF))

Very-high-energy (VHE) gamma-ray astroparticle physics is a relatively young field, and observations over the past decade have surprisingly revealed almost 250 VHE emitters which appear to act as cosmic particle accelerators. However, the existing experiments have provided exciting glimpses, but often falling short of supplying the full answer. Fundamental questions such as the origin of the highest energy cosmic rays within our Galaxy remain still open. Answers to this kind of questions require a instrument with a factor 5 to 10 improvement in sensitivity, a sub-arcminute angular resolution and 10% energy resolution. The next generation gamma-ray observatory, the Cherenkov Telescope Array Observatory (CTAO), is the answer to this need. In this talk I will briefly present the status of this upcoming observatory, and its scientific capabilities in terms of key performance parameters. I will also focus on “planned” surveys, the impact they will have on the understanding of the VHE sky, and the status of their preparation. I will then conclude talking about the key role of CTAO in the study of the most extreme transient phenomena.

Salvatore Scuderi: Astri Mini-Array

• Salvatore Scuderi (Istituto Nazionale di Astrofisica (INAF))

The ASTRI Mini-Array is an INAF project to build and operate a facility to study astronomical sources emitting very energy high energy in the TeV spectral band. It consists of a group of nine innovative aplanatic dual mirror Imaging Atmospheric Cherenkov telescopes. The telescopes will be installed at the Teide Astronomical Observatory of the Instituto de Astrofisica de Canarias in Tenerife (Canary Islands, Spain) on the basis of a host agreement with INAF. Thanks to its expected overall performance, better than those of current Cherenkov telescopes' arrays for energies above about 5 TeV and up to 100 TeV and beyond, the ASTRI MA will represent an important instrument to perform deep observations of the Galactic and extra-Galactic sky at these energies. After describing, the expected performances briefly, the characteristics and the architecture of the ASTRI Mini-Array, I will report on the status of the site implementation and of the production of the main ASTRI Mini-Array subsystems.

Stefano Vercellone: ASTRI Mini-Array Core Science Program

• Stefano Vercellone (Istituto Nazionale di Astrofisica (INAF))

The ASTRI Mini-Array, an array of nine Cherenkov dual-mirror telescopes, is under construction at the Observatorio del Teide (Tenerife, Spain). We review the Core Science Program which we plan to perform during the first four observing years, including the origin of cosmic rays, the extra-galactic background light and the study of fundamental physics, and the novel field in the VHE domain of gamma-ray bursts and multi-messenger transients. We also discuss the synergies with current and future VHE facilities in the Northern hemisphere, such as MAGIC, LHAASO, HAWC, Tibet AS-gamma, and CTAO-N.

Andrea Bulgarelli: CTA and ASTRI technological activities @ OAS and the CTA Science Alert Generation system

• Andrea Bulgarelli (Istituto Nazionale di Astrofisica (INAF))

The technological involvement of OAS in the ASTRI, CTA, and LST projects covers many aspects of software development, computing, and software project management including quality assurance, development of automated pipelines for data quality checks and scientific analysis of the mentioned projects, development of deep learning algorithms, and software for data acquisition and control of ASTRI telescopes. In addition, OAS has also the responsibility of the automated pipeline to detect gamma-ray transient and generate science alerts for the CTA Observatory. This contribution gives an overview of these activities.

Barbara Olmi: CTA Galactic Science

• Barbara Olmi (Istituto Nazionale di Astrofisica (INAF))

ASTRI and CTA will give us an unprecedented view of the very high energy properties of our own Galaxy. The widest class of gamma-ray sources is represented by pulsar wind nebulae, with around 300 objects expected from the Galactic Plane Survey simulations, to be compared with 30-40 SNRs and 10 binaries. These sources are known to be efficient particle accelerators, with the class prototype, the Crab nebula, the unique firmly identified leptonic PeVatron of the Galaxy. Last years observations at X-rays and gamma-rays have proved they efficiently release particles in the ambient medium in their late evolutionary phases, being connected to the formation of elongated X-ray jets and extended TeV halos. Almost all the LHAASO's recently detected PeVatrons have a pulsar in their surroundings, leaving open the possibility that all of them are actually illuminated by a pulsar or a pulsar wind nebula that is not resolved by LHAASO. Being able to model and identify these sources through their different evolutionary stages is then extremely important for the interpretation of future gamma-ray data. Here I will discuss where we are in this respect.

Vito Sguera: Forecasts on the potential of the transient Galactic TeV sky during the CTA “diluvian” era: prepare for the flood

• Vito Sguera (Istituto Nazionale di Astrofisica (INAF))

The Cherenkov Telescope Array (CTA) has the potential to transform our understanding of the high-energy sky. In particular, a true revolution could occur in the field of Galactic TeV transients. The CTA promises to perform exceptionally well as a Galactic transient detection factory since it will offer an order of magnitude improvement in the TeV domain in terms of sensitivity and survey speed compared to existing facilities. I will firstly highlight the considerable potential of the Galactic TeV transient sky. Then I will present a  possible specific contribution of the OAS institute to this field of study during the CTA era.

Nicolò Parmiggiani: Automated scientific analysis pipeline and data quality for ASTRI Mini-Array

• Nicolo' Parmiggiani (Istituto Nazionale di Astrofisica (INAF))

The Automated Scientific Analysis Pipeline is a software system that runs in the off-site data center in Rome. It executes analyses on the event list, already reduced by the data reduction pipeline, and produces high-level scientific results (counts maps, light curves, and more). A short-term scientific analysis pipeline starts automatically as soon as the data are received (~ 20 min since data acquisition) and reduced at the data center (~10 min since data receiving) to generate scientific quick-look results that can be visualized using the Human Machine Interface (HMI). A long-term scientific analysis pipeline, without time constraints and based on the best available calibration factors, is also planned to generate scientific results that will be stored in the Science Archive for reference by scientific users. The Online Observation Quality System (OOQS) is part of the ASTRI Mini-Array on-site software systems. It aims to execute real-time data quality checks on the data acquired during the observations to detect abnormal conditions. The results of the data quality checks are stored in the Quality Archive, and the Operator can visualize them using the HMI.

V. Conforti/F.Gianotti: ASTRI and CTA activities on computing, software management and data acquisition

• Vito Conforti (Istituto Nazionale di Astrofisica (INAF))
• Fulvio Gianotti (OAS - Istituto Nazionale di Astrofisica (INAF))

Lorenzo Amati: The synergy of ASTRI and  CTA with next generation space missions for GRBs and high-energy transients

• Lorenzo Amati (Istituto Nazionale di Astrofisica (INAF))

The strong synergy with the very large facilities that are being built in the electro-magnetic (e.g., CTA, ELT, SKA, Athena) and multi-messenger domains (2G+ and 3G GW detectors, as well as  further advanced neutrino detectors)  is a key asset of the next generation space missions dedicated to the detection, accurate localization and multi-wavelength characterization of GRBs and high-energy transients. I will focus in particular on those mission projects, like THESEUS, HERMES, Gamow Explorer, eXTP, in which INAF - OAS Bologna plays a key role on both scientific and technological aspects, showing our their measurements will allow ASTRI and the CTA observatories to fulfill some of their main objectives, thus enhancing substantially their scientific return.

Patrizia Romano: CTAO Extragalactic Science

• Patrizia Romano (Istituto Nazionale di Astrofisica (INAF))

CTAO, the next-generation ground-based gamma-ray observatory, will boast a wide energy range (20 GeV to 300 TeV) and will provide an average differential sensitivity a factor of 5–20 times better with respect to the current IACT arrays; in particular for transients and flaring events (time-scales of ∼1 d or shorter) CTAO will be about two orders of magnitude more sensitive with respect to Fermi-LAT at the overlapping energy of 25 GeV, thus allowing an unprecedented opportunity to investigate gamma-ray-emitting active galactic nuclei. In this talk I will give an up to date overview of the initiatives and activities currently in progress within the CTAO Extragalactic Science Working group, and the highlights of the expected results.

Eleonora Torresi: The GeV to TeV view of Misaligned AGN

• Eleonora Torresi (Istituto Nazionale di Astrofisica (INAF))

Misaligned AGN (MAGN) represents a new GeV and TeV emitters class. Thanks to the favorable orientation of their jets, MAGN proved to be extremely valuable in addressing important issues such as i) revealing the jet structure complexity; ii) localizing the emitting region(s) of very-high-energy radiation; understanding the physical processes producing very-high-energy photons. This talk will present the main results obtained in the last decade by studying MAGN at GeV and TeV energies. In addition, the impact of future Cherenkov Telescope Array observations will be discussed.

Giulia Migliori: The TeV-detected radio galaxy 3C 264

• Giulia Migliori (Istituto Nazionale di Astrofisica (INAF))

Studies of the inner jets of radio galaxies with VLBI techniques provide us with a new perspective on the jet structure and kinematics, probing for the first time the so-called acceleration zone. We use the case study of the radio galaxy 3C 264 to: (i) investigate the implications of these findings for radiative models aimed at explaining the GeV-to-TeV emission of jets, and (ii) discuss the opportunities offered by CTA  to improve over the present knowledge.

Raffaella Landi: INTEGRAL view of TeV sources: a legacy for the CTA project

• Raffaella Landi (INAF-OAS)

In recent years, our knowledge of the most violent phenomena in the Universe has progressed impressively thanks to the advent of new detectors for γ-ray, on both the ground and in orbit. At the furthest extremes of this observational energy window, we have now discovered more than a thousand sources in the soft γ-ray band (20–100 keV) and more than 200 in the TeV band. Connecting the properties of sources that are seen at both these extremes is very important, as it allows us to discriminate between various emission scenarios and, in turn, fully understand their nature.  By employing a spatial cross correlation technique, we compared the INTEGRAL/IBIS catalogue and TeV all-sky data in search of secure or likely associations.  Although this analysis is based on a subset of the INTEGRAL all-sky observations (1000 orbits), we find that there is a significant correlation: 39 objects (∼20% of the VHE γ-ray catalogue) show emission in both soft γ-ray and TeV wavebands. We will briefly show the various typology of the sources resulted from this cross-correlation. The full INTEGRAL database, now comprising almost 20 years of data and available at OAS, will represent an important legacy that will be useful for the Cherenkov Telescope Array (CTA).

Ambra Di Piano: Real-time analysis for the LST-1

• Ambra Di Piano (Istituto Nazionale di Astrofisica (INAF))

The Large-Size Telescope (LST) is one of the three classes of telescopes that will comprise the Cherenkov Telescope Array (CTA). The first of such telescopes, the LST-1 prototype, was inaugurated onsite, at the Observatorio del Roques de los Muchachos, on October 10th, 2018. The telescope is now in the commissioning phase to ensure that all requirements are satisfied, as well as to improve the telescope’s sensitivity and performance. An onsite and online software system will be provided for reconstruction, data quality and scientific analyses of the observations in real-time. The goal is to provide scientific quick-looks for the support astronomer, to produce fast raw scientific results and to generate (as well as react to) science alerts on transient and variable phenomena. The software is based on the framework used by AGILE and is a prototype for the Science Alert Generation (SAG) system of CTA. In this contribution I will present a general overview of the project and report on its status.

Paolo Padovani: Neutrinos from blazar jets: open issues and multi messenger synergies

• Paolo Padovani (ESO)

I will first give an overview of neutrino astrophysics and then introduce the IceCube observatory, which is the largest neutrino detector in the world. I will then address the very hot topic of the astronomical counterparts of IceCube neutrinos, concentrating on the first association with the blazar TXS 0506+056 and then discussing more recent ones, which strengthen the case that at least some blazars should be neutrino sources. I will then talk about the very strong synergies between neutrino astrophysics and very high-energy astrophysics and in particular the role that Astri and CTA will have.

Antonio Marinelli: Cosmic reservoirs: the importance of CTA to understand high-energy neutrino observations Star-forming and starburst galaxies, which are well-known cosmic-ray reservoirs, are expected to emit gamma-rays and neutrinos predominantly via hadronic collisions. The link between diffuse gamma rays and diffuse high-energy neutrinos measured by IceCube goes through the knowledge of this abundant class of sources. Moreover the IceCube point-like searches highlight a possible excess in coincidence with NGC1068, a starburst galaxy which contain also a active galactic nuclei. While Fermi-LAT already measured the spectral energy distribution of 13 nearby starburst galaxies, only 4 of them have been observed by imagine Cherenkov telescopes. The future observations of these nearby sources by the incoming CTA telescope will be crucial to understand their spectral features at TeV energies and better predict their contribution to the diffuse and point-like high-energy neutrino observations. Future CTA measurements will also test the hypothesis that the observed gamma-ray fluxes from starburst galaxies are mostly due to star-forming activity, in agreement with the available star formation rates coming from IR and UV observations.

Cristina Nanci: The parsec-scale regions of candidate neutrino emitter blazar Despite promising results based on samples of blazars already available, TXS 0506+056 remains the only case of a high-confidence association between a neutrino event and a gamma-ray blazar. Thanks to the high angular reso- lution reachable with the very-long-baseline-interferometry (VLBI), it was pos- sible to identify peculiar properties related to the neutrino production in the TXS0506+056 jet, such as, for example, an apparent superluminal expansion of the core after the event and a decrease of the magnetic energy density after the neutrino detection. Both these characteristics have been explained by a conspicuous release of energy which is also likely responsible for the neutrino production in the source. In order to test the scenario of gamma-ray blazars as neutrino emitters, we are carrying out a follow-up program of candidate counter- parts of neutrino events by means of VLBI observations. In doing so, we aim to retrieve any recurring features in the parsec scale regions of the candidates’ jets potentially related to the neutrino production, as observed in TXS0506+056. We present our results for four events: our VLBI observations of the gamma- ray blazars in the neutrino event fields are compared with past archival VLBI data. In this talk, I will show some of the results of our first explorative VLBI follow-up campaign (Nanci et al. 2022) and I will introduce how the VLBI- CTA synergy will help to shed light on the hypothesis of the neutrino-blazar connection.

Giancarlo Ghirlanda: Gamma Ray Bursts at high and very high energies: physical insights

• Giancarlo Ghirlanda (Istituto Nazionale di Astrofisica (INAF))

The study of the emission of GRBs at high and very high energies holds the key to  unveil fundamental properties of their jets and environment, of the leading dissipation and radiation mechanisms. Recent investigation of the sub-MeV prompt emission, while revealing the synchrotron nature of the radiation, poses new challenges to the physical conditions in the emission region. GeV emission of GRBs probes the prompt to afterglow transition disclosing key features of the jet dynamics and of the shock physics. The very recent detections at TeV energies provide new clues to study particle acceleration and shock emission physics. I will review the current detections and understanding of high energy emission from GRBs and discuss the impact of future detections on still open issues.

Barbara Patricelli: Multi-messenger astronomy: synergies between gravitational wave and very high energy gamma-ray observations

• Barbara Patricelli (Istituto Nazionale di Astrofisica (INAF))

The detection of the electromagnetic (EM) emission following the gravitational wave (GW) event GW170817 opened the era of multi-messenger astronomy with GWs and provided the first direct evidence that at least a fraction of binary neutron star (BNS) mergers are progenitors of short Gamma-Ray Bursts (GRBs). GRBs are also expected to emit very-high energy (VHE, > 100 GeV) photons, as proven by the recent MAGIC and H.E.S.S. observations and one of the challenges for future multi-messenger observations will be the detection of such VHE emission from GRBs in association with GWs. In this talk I will review the challenges and the status of the searches for VHE EM counterparts to GWs and discuss the prospects for future detections with next generation instruments such as the Cherenkov Telescope Array. The implications that future joint GW and VHE EM observations could have on the understanding of GRB physics will also be discussed.

Giulia Stratta: Synergies between CTA and Athena

• Giulia Stratta (Istituto Nazionale di Astrofisica (INAF))

Athena (Advanced Telescope for High ENergy Astrophysics) is the X-ray observatory large mission selected by the European Space Agency and it is provisionally due for launch in the early 2030s. By that time the Cherenkov Telescope Array will be completed and routinely observing the gamma-ray sky at its nominal sensitivity, that is about one order of magnitude larger than current Imaging Atmospheric Cherenkov Telescopes. This talk explores the potential synergies between these two outstanding high-energy observatories by providing some examples of sources that will greatly benefit from joint observations.