arXiv subjects

T. Mineo

Publications and source records attributed to T. Mineo.

At least 19 recordsLinked to original sources

arXiv2025

To cut or not to cut: Data-quality evaluation for the ASTRI Mini-Array

The ASTRI Mini-Array consists of nine Cherenkov telescopes under construction at the Observatorio del Teide, with one of them already performing observations since November 2024. Given the complexity of the analysis of gamma-ray data acquired with Cherenkov telescopes, a proper evaluation of the quality of these data is important to avoid a negative impact on the high-level scientific products. There are several factors that can contribute to reducing the quality of the observations, such as clouds, high humidity or a high dust concentration in the air, among others. In order to take all these factors into account and evaluate their impact on the data, a quality check pipeline has been developed for ASTRI. This contribution describes the pipeline, from its inputs at different data levels to the production of outputs in the form of good-quality lists and diagnostic plots. We also show how setting preliminary quality cuts on the Crab Nebula data taken with the first ASTRI telescope can significantly improve the source detection.

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arXiv2025

The New Architecture of the Online Observation Quality System for the ASTRI Mini-Array Project

The ASTRI Mini-Array is an international collaboration led by the Italian National Institute for Astrophysics. The project aims to construct and operate an array of nine Imaging Atmospheric Cherenkov Telescopes to study gamma-ray sources at very high energy (TeV) and perform stellar intensity interferometry observations. We describe the updated Online Observation Quality System (OOQS) software architecture. The OOQS is one of the subsystems of the Supervisory Control and Data Acquisition (SCADA) system. It aims to execute real-time data quality checks on the data acquired by the Cherenkov cameras and intensity interferometry instruments and provide feedback to both SCADA and the Operator about abnormal conditions detected. The data quality results are stored in the Quality Archive for further investigation and sent to the Operator Human Machine Interface (HMI) through Kafka.

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arXiv2025

Unveiling the origin of XMM-Newton soft proton flares II. Systematics in the proton spectral analysis

Low-energy protons entering the field of view of the XMM-Newton telescope scatter with the X-ray mirror surface and might reach the X-ray detectors on the focal plane. They manifest in the form of a sudden increase in the rates, usually referred to as soft proton flares. By knowing the conversion factor between the soft proton energy and the deposited charge on the detector, it is possible to derive the incoming flux and to study the environment of the Earth magnetosphere at different distances. We present the results of testing these matrices with real data for the first time, while also exploring the seasonal and solar activity effect on the proton environment. The selected spectra are relative to 55 simultaneous MOS and PN observations with flares raised in four different temporal windows: December-January and July-August of 2001-2002 (solar maximum) and 2019-2020 (solar minimum). The main result of the spectral analysis is that the physical model representative of the proton spectra at the input of the telescope is a power law. However, a second and phenomenological component is necessary to take into account imprecision in the generation of the matrices at softer energies.

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arXiv2024

The Online Observation Quality System Implementation for the ASTRI Mini-Array Project

The ASTRI Mini-Array project, led by the Italian National Institute for Astrophysics, aims to construct and operate nine Imaging Atmospheric Cherenkov Telescopes for high-energy gamma-ray source study and stellar intensity interferometry. Located at the Teide Astronomical Observatory in Tenerife, the project's software is essential for remote operation, emphasizing the need for prompt feedback on observations. This contribution introduces the Online Observation Quality System (OOQS) as part of the Supervisory Control And Data Acquisition (SCADA) software. OOQS performs real-time data quality checks on data from Cherenkov cameras and Intensity Interferometry instruments. It provides feedback to SCADA and operators, highlighting abnormal conditions and ensuring quick corrective actions for optimal observations. Results are archived for operator visualization and further analysis. The OOQS data quality pipeline prototype utilizes a distributed application with three main components to handle the maximum array data rate of 1.15 Gb/s. The first is a Kafka consumer that manages the data stream from the Array Data Acquisition System through Apache Kafka, handling the data serialization and deserialization involved in the transmission. The data stream is divided into batches of data written in files. The second component monitors new files and conducts analyses using the Slurm workload scheduler, leveraging its parallel processing capabilities and scalability. Finally, the process results are collected by the last component and stored in the Quality Archive.

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arXiv2023

Gain variations as induced by the diffuse night sky background: the ASTRI-Horn experience

ASTRI-Horn is the prototype of the nine telescopes that form the ASTRI Mini-Array, under construction at the Teide Observatory in Tenerife (Spain), devoted to observe the sky in the 1--200 TeV energy band. It adopts an innovative optical design based on a dual-mirror Schwarzschild-Couder configuration, and the camera, composed by a matrix of monolithic multipixel silicon photomultipliers (SiPMs) is managed by ad-hoc tailored front-end electronics based on a peak-detector operation mode. During the Crab Nebula campaign in 2018-2019, ASTRI-Horn was affected by gain variations induced by high levels of night sky background. This paper reports the work performed to detect and quantify the effects of these gain variations in shower images. The analysis requested the use of simultaneous observations of the night sky background flux in the wavelength band 300-650 nm performed with the auxiliary instrument UVscope, a calibrated multi-anode photomultiplier working in single counting mode. As results, a maximum gain reduction of 15% was observed, in agreement with the value previously computed from the variance of the night sky background level in each image. This ASTRI-Horn gain reduction was caused by current limitation of the voltage supply. The analysis presented in this paper provides a method to evaluate possible variations in the nominal response of SiPMs when scientific observations are performed in the presence of high night sky background as in moon conditions.

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arXiv2023

The Online Observation Quality System Software Architecture for the ASTRI Mini-Array Project

The ASTRI Mini-Array is an international collaboration led by the Italian National Institute for Astrophysics. This project aims to construct and operate an array of nine Imaging Atmospheric Cherenkov Telescopes to study gamma-ray sources at very high energy (TeV) and perform stellar intensity interferometry observations. We describe the software architecture and the technologies used to implement the Online Observation Quality System (OOQS) for the ASTRI Mini-Array project. The OOQS aims to execute data quality checks on the data acquired in real-time by the Cherenkov cameras and intensity interferometry instruments, and provides feedback to both the Central Control System and the Operator about abnormal conditions detected. The OOQS can notify other sub-systems, triggering their reaction to promptly correct anomalies. The results from the data quality analyses (e.g. camera plots, histograms, tables, and more) are stored in the Quality Archive for further investigation and they are summarised in reports available to the Operator. Once the OOQS results are stored, the operator can visualize them using the Human Machine Interface. The OOQS is designed to manage the high data rate generated by the instruments (up to 4.5 GB/s) and received from the Array Data Acquisition System through the Kafka service. The data are serialized and deserialized during the transmission using the Avro framework. The Slurm workload scheduler executes the analyses exploiting key features such as parallel analyses and scalability.

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arXiv2023

The ASTRI Cherenkov Camera: from the prototype to the industrial version for the Mini-Array

The observation of energetic astronomical sources emitting very high-energy gamma-rays in the TeV spectral range (as e.g. supernova remnants or blazars) is mainly based on detecting the Cherenkov light induced by relativistic particles in the showers produced by the photon interaction with the Earth atmosphere. The ASTRI Mini-Array is an INAF-led project aimed observing such celestial objects in the 1 - 100 TeV energy range. It consists of an array of nine innovative imaging atmospheric Cherenkov telescopes that are an evolution of the dual-mirror aplanatic ASTRI-Horn telescope operating at the INAF "M.C. Fracastoro" observing station (Serra La Nave, Mount Etna, Italy). The ASTRI Mini-Array is currently under construction at the Observatorio del Teide (Tenerife, Spain). In this paper, we present the compact (diameter 660mm, height 520mm, weight 73kg) ASTRI-Horn prototype Cherenkov Camera based on a modular multipixel Silicon Photon Multiplier (SiPM) detector, has been acquiring data since 2016 and allowing us to obtain both scientific data and essential lessons. In this contribution, we report the main features of the camera and its evolution toward the new Cherenkov camera, which will be installed on each ASTRI Mini-Array telescope to cover an unprecedented field of view of 10.5°.

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arXiv2021

Scattering efficiencies measurements of soft protons at grazing incidence from an Athena Silicon Pore Optics sample

Soft protons are a potential threat for X-ray missions using grazing incidence optics, as once focused onto the detectors they can contribute to increase the background and possibly induce radiation damage as well. The assessment of these undesired effects is especially relevant for the future ESA X-ray mission Athena, due to its large collecting area. To prevent degradation of the instrumental performance, which ultimately could compromise some of the scientific goals of the mission, the adoption of ad-hoc magnetic diverters is envisaged. Dedicated laboratory measurements are fundamental to understand the mechanisms of proton forward scattering, validate the application of the existing physical models to the Athena case and support the design of the diverters. In this paper we report on scattering efficiency measurements of soft protons impinging at grazing incidence onto a Silicon Pore Optics sample, conducted in the framework of the EXACRAD project. Measurements were taken at two different energies, ~470 keV and ~170 keV, and at four different scattering angles between 0.6 deg and 1.2 deg. The results are generally consistent with previous measurements conducted on eROSITA mirror samples, and as expected the peak of the scattering efficiency is found around the angle of specular reflection.

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arXiv2021

The Online Observation Quality System for the ASTRI Mini-Array

The ASTRI Mini-Array is an international collaboration led by the Italian National Institute for Astrophysics (INAF), aiming to construct and operate an array of nine Imaging Atmospheric Cherenkov Telescopes (IACTs) to study gamma-ray sources at very high energy (TeV) and to perform stellar intensity interferometry observations. This contribution describes the design and the technologies used by the ASTRI team to implement the Online Observation Quality System (OOQS). The main objective of the OOQS is to perform data quality analyses in real-time during Cherenkov and intensity interferometry observations to provide feedback to both the Central Control System and the Operator. The OOQS performs the analysis of key data quality parameters and can generate alarms to other sub-systems for a fast reaction to solve critical conditions. The results from the data quality analyses are saved into the Quality Archive for further investigations. The Operator can visualise the OOQS results through the Operator Human Machine Interface as soon as they are produced. The main challenge addressed by the OOQS design is to perform online data quality checks on the data streams produced by nine telescopes, acquired by the Array Data Acquisition System and forwarded to the OOQS. In the current OOQS design, the Redis in-memory database manages the data throughput generated by the telescopes, and the Slurm workload scheduler executes in parallel the high number of data quality analyses.

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arXiv2021

Looking through the photoionisation wake: Vela X-1 at $φ_\mathrm{orb} \approx 0.75$ with Chandra/HETG

The Supergiant X-ray binary Vela X-1 represents one of the best astrophysical sources to investigate the wind environment of a O/B star irradiated by an accreting neutron star. Previous studies and hydrodynamic simulations of the system revealed a clumpy environment and the presence of two wakes: an accretion wake surrounding the compact object and a photoionisation wake trailing it along the orbit. Our goal is to conduct, for the first time, high-resolution spectroscopy on Chandra/HETG data at the orbital phase $φ_\mathrm{orb} \approx 0.75$, when the line of sight is crossing the photoionisation wake. We aim to conduct plasma diagnostics, inferring the structure and the geometry of the wind. We perform a blind search employing a Bayesian Block algorithm to find discrete spectral features and identify them thanks to the most recent laboratory results or through atomic databases. Plasma properties are inferred both with empirical techniques and with photoionisation models within CLOUDY and SPEX. We detect and identify five narrow radiative recombination continua (Mg XI-XII, Ne IX-X, O VIII) and several emission lines from Fe, S, Si, Mg, Ne, Al, and Na, including four He-like triplets (S XV, Si XIII, Mg XI, and Ne IX). Photoionisation models well reproduce the overall spectrum, except for the near-neutral fluorescence lines of Fe, S, and Si. We conclude that the plasma is mainly photoionised, but more than one component is most likely present, consistent with a multi-phase plasma scenario, where denser and colder clumps of matter are embedded in the hot, photoionised wind of the companion star. Simulations with the future X-ray satellites Athena and XRISM show that a few hundred seconds of exposure will be sufficient to disentangle the lines of the Fe K$α$ doublet and the He-like Fe XXV, improving, in general, the determination of the plasma parameters.

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arXiv2020

The INTEGRAL view of the pulsating hard X-ray sky: from accreting and transitional millisecond pulsars to rotation-powered pulsars and magnetars

In the last 25 years, a new generation of X-ray satellites imparted a significant leap forward in our knowledge of X-ray pulsars. The discovery of accreting and transitional millisecond pulsars proved that disk accretion can spin up a neutron star to a very high rotation speed. The detection of MeV-GeV pulsed emission from a few hundreds of rotation-powered pulsars probed particle acceleration in the outer magnetosphere, or even beyond. Also, a population of two dozens of magnetars has emerged. INTEGRAL played a central role to achieve these results by providing instruments with high temporal resolution up to the hard X-ray/soft gamma-ray band and a large field of view imager with good angular resolution to spot hard X-ray transients. In this article, we review the main contributions by INTEGRAL to our understanding of the pulsating hard X-ray sky, such as the discovery and characterization of several accreting and transitional millisecond pulsars, the generation of the first catalog of hard X-ray/soft gamma-ray rotation-powered pulsars, the detection of polarization in the hard X-ray emission from the Crab pulsar, and the discovery of persistent hard X-ray emission from several magnetars.

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arXiv2020

A non-linear mathematical model for the X-ray variability classes of the microquasar GRS 1915+105 -- I: quiescent, spiking states and QPOs

The microquasar GRS 1915+105 is known to exhibit a very variable X-ray emission on different time scales and patterns. We propose a system of two ordinary differential equations, adapted from the Hindmarsh-Rose model, with two dynamical variables x(t), y(t) and an input constant parameter J_0, to which we added a random white noise, whose solutions for the x(t) variable reproduce consistently the X-ray light curves of several variability classes as well as the development of low frequency Quasi-Periodic Oscillations (QPO). We show that changing only the value of J_0 the system moves from stable to unstable solutions and the resulting light curves reproduce those of the quiescent classes like phi and chi, the delta class and the spiking rho class. Moreover, we found that increasing the values of J_0 the system induces high frequency oscillations that evolve to QPO when it moves into another stable region. This system of differential equations gives then a unified view of the variability of GRS 1915+105 in term of transitions between stable and unstable states driven by a single input function J_0. We also present the results of a stability analysis of the equilibrium points and some considerations on the existence of periodic solutions.

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arXiv2020

A non-linear mathematical model for the X-ray variability classes of the microquasar GRS 1915+105 -- II: transition and swaying classes

The complex time evolution in the X-ray light curves of the peculiar black hole binary GRS 1915+105 can be obtained as solutions of a non-linear system of ordinary differential equations derived form the Hindmarsch-Rose model and modified introducing an input function depending on time. In the first paper,assuming a constant input with a superposed white noise, we reproduced light curves of the classes rho, chi, and delta. We use this mathematical model to reproduce light curves, including some interesting details, of other eight GRS 1915+105 variability classes either considering a variable input function or with small changes of the equation parameters. On the basis of this extended model and its equilibrium states, we can arrange most of the classes in three main types: i) stable equilibrium patterns: (classes phi, chi, alpha'', theta, xi, and omega) whose light curve modulation follows the same time scale of the input function, because changes occur around stable equilibrium points; ii) unstable equilibrium patterns: characterised by series of spikes (class rho) originated by a limit cycle around an unstable equilibrium point; iii) transition pattern: (classes delta, gamma, lambda, kappa and alpha'), in which random changes of the input function induce transitions from stable to unstable regions originating either slow changes or spiking, and the occurrence of dips and red noise. We present a possible physical interpretation of the model based on the similarity between an equilibrium curve and literature results obtained by numerical integrations of a slim disc equations.

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arXiv2020

A non-linear mathematical model for the X-ray variability of the microquasar GRS 1515+105 -- III: Low-frequency Quasi Periodic Oscillations

The X-ray emission from the microquasar GRS 1515+105 shows, together with a very complex variability on different time scales, the presence of low-frequency quasi periodic oscillations (LFQPO) at frequencies lower than 30 Hz. In this paper, we demonstrate that these oscillations can be consistently and naturally obtained as solutions of a system of two ordinary differential equations that is able to reproduce almost all variability classes of GRS 1515+105. We modified the Hindmarsh-Rose model and obtained a system with two dynamical variables x(t), y(t), where the first one represents the X-ray flux from the source, and an input function J(t), whose mean level J_0 and its time evolution is responsible of the variability class. We found that for values of J_0 around the boundary between the unstable and the stable interval, where the equilibrium points are of spiral type, one obtain an oscillating behaviour in the model light curve similar to the observed ones with a broad Lorentzian feature in the power density spectrum and, occasionally, with one or two harmonics. Rapid fluctuations of J(t), as those originating from turbulence, stabilize the low-frequency quasi periodic oscillations resulting in a slowly amplitude modulated pattern.To validate the model we compared the results with real RXTE data which resulted remarkably similar to those obtained from the mathematical model. Our results allow us to favour an intrinsic hypothesis on the origin of LFQPOs in accretion discs ultimately related to the same mechanism responsible for the spiking limit cycle.

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arXiv2020

Soft proton scattering at grazing incidence from X-ray mirrors: analysis of experimental data in the framework of the non-elastic approximation

Astronomical X-ray observatories with grazing incidence optics face the problem of pseudo-focusing of low energy protons from the mirrors towards the focal plane. Those protons constitute a variable, unpredictable component of the non X-ray background that strongly affects astronomical observations and a correct estimation of their flux at the focal plane is then essential. For this reason, we investigate how they are scattered from the mirror surfaces when impacting with grazing angles. We compare the non-elastic model of reflectivity of particles at grazing incidence proposed by Remizovich et al. (1980) with the few available experimental measurements of proton scattering from X-ray mirrors. We develop a semi-empirical analytical model based on the fit of those experimental data with the Remizovich solution. We conclude that the scattering probability weakly depends on the energy of the impinging protons and that the relative energy losses are necessary to correctly model the data. The model we propose assumes no dependence on the incident energy and can be implemented in particle transport simulation codes to generate, for instance, proton response matrices for specific X-ray missions. Further laboratory measurements at lower energies and on other mirror samples, such as ATHENA Silicon Pore Optics, will improve the resolution of the model and will allow us to build the proper proton response matrices for a wider sample of X-ray observatories.

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arXiv2020

First detection of the Crab Nebula at TeV energies with a Cherenkov telescope in a dual-mirror Schwarzschild-Couder configuration: the ASTRI-Horn telescope

We report on the first detection of very high-energy (VHE) gamma-ray emission from the Crab Nebula by a Cherenkov telescope in dual-mirror Schwarzschild-Couder (SC) configuration. The result has been achieved by means of the 4 m size ASTRI-Horn telescope, operated on Mt. Etna (Italy) and developed in the context of the Cherenkov Telescope Array Observatory preparatory phase. The dual-mirror SC design is aplanatic and characterized by a small plate scale, allowing us to implement large field of view cameras with small-size pixel sensors and a high compactness. The curved focal plane of the ASTRI camera is covered by silicon photo-multipliers (SiPMs), managed by an unconventional front-end electronics based on a customized peak-sensing detector mode. The system includes internal and external calibration systems, hardware and software for control and acquisition, and the complete data archiving and processing chain. The observations of the Crab Nebula were carried out in December 2018, during the telescope verification phase, for a total observation time (after data selection) of 24.4 h, equally divided into on- and off-axis source exposure. The camera system was still under commissioning and its functionality was not yet completely exploited. Furthermore, due to recent eruptions of the Etna Volcano, the mirror reflection efficiency was reduced. Nevertheless, the observations led to the detection of the source with a statistical significance of 5.4 sigma above an energy threshold of ~3 TeV. This result provides an important step towards the use of dual-mirror systems in Cherenkov gamma-ray astronomy. A pathfinder mini-array based on nine large field-of-view ASTRI-like telescopes is under implementation.

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arXiv2019

Calibration and monitoring of the ASTRI-Horn telescope by using the night-sky background measured by the photon-statistics ("variance") method

ASTRI-Horn is the Cherenkov telescope developed by INAF and operating in Italy on the slopes of Etna volcano. Characterized by a dual-mirror optical system and a focal plane covered by silicon photomultiplier sensors, ASTRI-Horn is a prototype of the telescopes proposed to form one of the pathfinder sub-arrays of the Cherenkov Telescope Array Observatory in Chile. The electronics of the ASTRI-Horn telescope, optimized to detect nanosecond burst of light, is not able to directly measure any continuous or slowly varying flux illuminating its camera. To measure the intensity of the night sky background (NSB) in the field of view of the telescope, the firmware of the ASTRI-Horn camera continuously performs the statistical analysis of its detector signals and periodically provides in output the "variance" of each pixel, which is linearly dependent on the rate of detected photons; in this way, an indirect, but accurate measurement of the NSB flux is obtained without interference with the normal telescope operation. In this contribution we provide an overview of several calibration and monitoring tasks that can be performed in a straightforward way by the analysis of the "variance" data such as the camera astrometry, the actual telescope orientation and the monitoring of its optical point spread function.

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arXiv2019

Muon calibration of the ASTRI-Horn telescope: preliminary results

Astri-Horn is a Small-Sized Telescope (SST) for very-high energy gamma-ray astronomy installed in Italy at the INAF "M.C. Fracastoro" observing station (Mt. Etna, Sicily). The ASTRI-Horn telescope is characterized by a dual-mirror optical system and a curved focal surface covered by SiPM sensors managed by a innovative fast front-end electronics. Dedicated studies were performed to verify the feasibility of the calibration through muons on the relatively small size of the primary mirror (~4 m diameter), as in the case of larger Cherenkov telescopes. A number of tests were performed using simulations of the atmospheric showers with the CORSIKA package and of the telescope response with a dedicated simulator. In this contribution we present a preliminary analysis of muon events detected by ASTRI-Horn during the regular scientific data taking performed in December 2018 and March 2019. These muon events validate the results obtained with the simulations and definitively confirm the feasibility of calibrating the ASTRI-Horn SST telescope with muons.

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