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The ASTRI Mini-Array is an international collaboration led by the Italian National Institute for Astrophysics (INAF) that will operate nine telescopes to perform Cherenkov and optical stellar intensity interferometry (SII) observations. At the focal plane of these telescopes, we are planning to install a stellar intensity interferometry instrument. Here we present the selected design, based on Silicon Photomultiplier (SiPM) detectors matching the telescope point spread function together with dedicated front-end electronics.

Blazars: model behaviour Blazars are the most extreme active galactic nuclei, possessing oppositely directed plasma jets emanating from accreting supermassive black holes at near-light speeds. The jets have been modelled as being propelled by magnetic fields twisted by differential rotation of the black hole's accretion disk or inertial-frame-dragging ergosphere. Until now, this general picture of jet formation, and the exact location of the outbursts, had not been verified. Marscher et al . now report high-resolution radio images and optical polarization measurements of the blazar BL Lacertae. The new measurements reveal a bright feature in the jet that causes a double flare of radiation from optical frequencies to TeV γ-ray energies. This suggests that the event begins in a region with a helical magnetic field, in line with model predictions. Sequences of high-resolution radio images and optical polarization measurements of the blazar BL Lacertae are reported. The data reveal a bright feature in the jet that causes a double flare of radiation from optical frequencies to TeV γ-ray energies. It is concluded that the event starts in a region with a helical magnetic field as envisaged by the theories. Blazars are the most extreme active galactic nuclei. They possess oppositely directed plasma jets emanating at near light speeds from accreting supermassive black holes. According to theoretical models, such jets are propelled by magnetic fields twisted by differential rotation of the black hole’s accretion disk or inertial-frame-dragging ergosphere 1 , 2 , 3 . The flow velocity increases outward along the jet in an acceleration and collimation zone containing a coiled magnetic field 4 , 5 . Detailed observations of outbursts of electromagnetic radiation, for which blazars are famous, can potentially probe the zone. It has hitherto not been possible to either specify the location of the outbursts or verify the general picture of jet formation. Here we report sequences of high-resolution radio images and optical polarization measurements of the blazar BL Lacertae. The data reveal a bright feature in the jet that causes a double flare of radiation from optical frequencies to TeV γ-ray energies, as well as a delayed outburst at radio wavelengths. We conclude that the event starts in a region with a helical magnetic field that we identify with the acceleration and collimation zone predicted by the theories. The feature brightens again when it crosses a standing shock wave corresponding to the bright ‘core’ seen on the images.

The ASTRI Mini-Array is an international project led by the Italian National Institute for Astrophysics (INAF) to deploy an array of nine Imaging Atmospheric Cherenkov Telescopes at the Teide Observatory in Tenerife. The system will study astronomical sources emitting in the very high-energy band above 1 TeV up to 200 TeV. The telescope array is an improved version of the ASTRI-Horn telescope (Mt. Etna, Italy), a 4 m diameter small-sized telescope (SST) prototype, developed by INAF in the initial phase of the ASTRI Project in the CTA context. The Cherenkov camera for the Mini-Array, based on Silicon Photo-Multiplier (SiPM) detectors, is an evolution of the ASTRI-Horn telescope camera. Its electronics is based on a peak detection circuit and is designed to perform self-trigger of the whole focal plane. This allows to detect the Cherenkov signal while reducing the amount of raw data. Its electronics, based on a peak detection circuit, is designed to perform self-trigger of the whole focal plane in order to detect Cherenkov signal while ensuring a small amount of data transfer. In this contribution we present the camera calibration strategy and tools developed thanks to the lessons learned with the ASTRI-Horn telescope. These calibration procedures are essential to extract the SiPMs calibration coefficients, which are needed for the Cherenkov data analysis, as well as camera configuration parameters, that ensure system stability and a uniform trigger efficiency over the whole focal plane. Moreover, thanks to the internal calibration system, these procedures allow to monitor the system performance and camera health during the regular data taking period.

We present the result of a year-long effort to think, design, build, realize, and manage the robotic, autonomous REM observatory, placed since June 2003 on the cerro La Silla, ESO Chile. The various aspects of the management and control are here surveyed, with the nice ideas and the wrong dead ends we encountered under way. Now REM is offered to the international astronomical community, a real, schedulable telescope, automatic for the People.

The Rapid Eye Mount (REM) is a 60 cm robotic telescope located at La Silla, Chile. Its Observing Software (REMOS) is constituted by a set of distributed intercommunicating processes organized around a central manager. Together they grant the system safety, automatically schedule and perform observations with two simultaneous cameras of user-defined targets, and drive fast reaction to satellite alerts. Subsequent data reduction is left to pipelines managed by each camera.

In this paper we describe the hardware and software architecture of the Automatic Imaging Telescope (AIT), recently developed at the Perugia University Observatory. It is based on an existing 0.4-m telescope which was transformed into an automatic device. During the night, all the observatory functions are controlled by two PCs in an unattended mode. The system is equipped with an autoguider and the software was designed to allow the automatic reduction of the data at the end of the night. Since 1994 October the AIT has been collecting a large amount of BVR C I C data for about 30 blazars.

During the last years, a number of telescopes have been dedicated to the followup of the GRBs. But after the Swift launch, the average observed intensity of the GRBs showed to be lower than thought before. Our experience with the robotic 60 cm REM telescope confirmed this evidence, with a large number of lost GRBs. Then, we proposed to study the feasibility of a 4 m fast pointing class telescope, equipped with a multichannel imagers, from Visible to Near Infrared. In this paper, we present the main result of the feasibility study we performed so far.

We present a list of photometricVRIcomparison sequences in the fields of 16 blazars. For six of these objects, comparison stars were calibrated for the first time during the present work. For most of the other 10 blazars, we improved the old sequences by either calibrating stars in theRandIbands or adding new comparison stars. Finding charts for 15 of these sequences are also reported.

This study presents a Normal Behavior Model (NBM) developed to forecast monitoring time-series data from the ASTRI-Horn Cherenkov telescope under normal operating conditions. The analysis focused on 15 physical variables acquired by the Telescope Control Unit between September 2022 and July 2024, representing sensor measurements from the Azimuth and Elevation motors. After data cleaning, resampling, feature selection, and correlation analysis, the dataset was segmented into fixed-length intervals, in which the first I samples represented the input sequence provided to the model, while the forecast length, T, indicated the number of future time steps to be predicted. A sliding-window technique was then applied to increase the number of intervals. A Multi-Layer Perceptron (MLP) was trained to perform multivariate forecasting across all features simultaneously. Model performance was evaluated using the Mean Squared Error (MSE) and the Normalized Median Absolute Deviation (NMAD), and it was also benchmarked against a Long Short-Term Memory (LSTM) network. The MLP model demonstrated consistent results across different features and I-T configurations, and matched the performance of the LSTM while converging faster. It achieved an MSE of 0.019+/-0.003 and an NMAD of 0.032+/-0.009 on the test set under its best configuration (4 hidden layers, 720 units per layer, and I-T lengths of 300 samples each, corresponding to 5 hours at 1-minute resolution). Extending the forecast horizon up to 6.5 hours-the maximum allowed by this configuration-did not degrade performance, confirming the model's effectiveness in providing reliable hour-scale predictions. The proposed NBM provides a powerful tool for enabling early anomaly detection in online ASTRI-Horn monitoring time series, offering a basis for the future development of a prognostics and health management system that supports predictive maintenance.

We present a list of photometric VRI comparison sequences in the fields of 16 blazars. For six of these objects, comparison stars were calibrated for the first time during the present work. For most of the other 10 blazars, we improved the old sequences by either calibrating stars in the R and I bands or adding new comparison stars. Finding charts for 15 of these sequences are also reported. (Author)