arXiv subjects

R. Campana

Publications and source records attributed to R. Campana.

At least 55 records · Page 3Linked to original sources

arXiv2018

The e-ASTROGAM gamma-ray space observatory for the multimessenger astronomy of the 2030s

e-ASTROGAM is a concept for a breakthrough observatory space mission carrying a gamma-ray telescope dedicated to the study of the non-thermal Universe in the photon energy range from 0.15 MeV to 3 GeV. The lower energy limit can be pushed down to energies as low as 30 keV for gamma-ray burst detection with the calorimeter. The mission is based on an advanced space-proven detector technology, with unprecedented sensitivity, angular and energy resolution, combined with remarkable polarimetric capability. Thanks to its performance in the MeV-GeV domain, substantially improving its predecessors, e-ASTROGAM will open a new window on the non-thermal Universe, making pioneering observations of the most powerful Galactic and extragalactic sources, elucidating the nature of their relativistic outflows and their effects on the surroundings. With a line sensitivity in the MeV energy range one to two orders of magnitude better than previous and current generation instruments, e-ASTROGAM will determine the origin of key isotopes fundamental for the understanding of supernova explosion and the chemical evolution of our Galaxy. The mission will be a major player of the multiwavelength, multimessenger time-domain astronomy of the 2030s, and provide unique data of significant interest to a broad astronomical community, complementary to powerful observatories such as LISA, LIGO, Virgo, KAGRA, the Einstein Telescope and the Cosmic Explorer, IceCube-Gen2 and KM3NeT, SKA, ALMA, JWST, E-ELT, LSST, Athena, and the Cherenkov Telescope Array.

astro-ph.HE↗

arXiv2018

Minimum Spanning Tree cluster analysis of the LMC region above 10 GeV: detection of the SNRs N 49B and N 63A

We present the results of a cluster search in the gamma-ray sky images of the Large Magellanic Cloud region by means of the Minimum Spanning Tree algorithm at energies higher than 10 GeV, using 9 years of Fermi-LAT data. Several significant clusters were found, the majority of which associated with previously known gamma-ray sources. New significant clusters associated with the supernova remnants N 49B and N 63A are also found, and confirmed with a Maximum Likelihood analysis of the Fermi-LAT data.

astro-ph.HE↗

arXiv2018

The THESEUS space mission concept: science case, design and expected performances

THESEUS is a space mission concept aimed at exploiting Gamma-Ray Bursts for investigating the early Universe and at providing a substantial advancement of multi-messenger and time-domain astrophysics. These goals will be achieved through a unique combination of instruments allowing GRB and X-ray transient detection over a broad field of view (more than 1sr) with 0.5-1 arcmin localization, an energy band extending from several MeV down to 0.3 keV and high sensitivity to transient sources in the soft X-ray domain, as well as on-board prompt (few minutes) follow-up with a 0.7 m class IR telescope with both imaging and spectroscopic capabilities. THESEUS will be perfectly suited for addressing the main open issues in cosmology such as, e.g., star formation rate and metallicity evolution of the inter-stellar and intra-galactic medium up to redshift $\sim$10, signatures of Pop III stars, sources and physics of re-ionization, and the faint end of the galaxy luminosity function. In addition, it will provide unprecedented capability to monitor the X-ray variable sky, thus detecting, localizing, and identifying the electromagnetic counterparts to sources of gravitational radiation, which may be routinely detected in the late '20s / early '30s by next generation facilities like aLIGO/ aVirgo, eLISA, KAGRA, and Einstein Telescope. THESEUS will also provide powerful synergies with the next generation of multi-wavelength observatories (e.g., LSST, ELT, SKA, CTA, ATHENA).

astro-ph.IM↗

arXiv2018

THESEUS: a key space mission concept for Multi-Messenger Astrophysics

The recent discovery of the electromagnetic counterpart of the gravitational wave source GW170817, has demonstrated the huge informative power of multi-messenger observations. During the next decade the nascent field of multi-messenger astronomy will mature significantly. Around 2030, third generation gravitational wave detectors will be roughly ten times more sensitive than the current ones. At the same time, neutrino detectors currently upgrading to multi km^3 telescopes, will include a 10 km^3 facility in the Southern hemisphere that is expected to be operational around 2030. In this review, we describe the most promising high frequency gravitational wave and neutrino sources that will be detected in the next two decades. In this context, we show the important role of the Transient High Energy Sky and Early Universe Surveyor (THESEUS), a mission concept proposed to ESA by a large international collaboration in response to the call for the Cosmic Vision Programme M5 missions. THESEUS aims at providing a substantial advancement in early Universe science as well as playing a fundamental role in multi-messenger and time-domain astrophysics, operating in strong synergy with future gravitational wave and neutrino detectors as well as major ground- and space-based telescopes. This review is an extension of the THESEUS white paper (Amati et al. 2017), also in light of the discovery of GW170817/GRB170817A that was announced on October 16th, 2017.

astro-ph.HE↗

arXiv2018

The X-Gamma Imaging Spectrometer (XGIS) onboard THESEUS

A compact and modular X and gamma-ray imaging spectrometer (XGIS) has been designed as one of the instruments foreseen on-board the THESEUS mission proposed in response to the ESA M5 call. The experiment envisages the use of CsI scintillator bars read out at both ends by single-cell 25 mm 2 Silicon Drift Detectors. Events absorbed in the Silicon layer (lower energy X rays) and events absorbed in the scintillator crystal (higher energy X rays and Gamma-rays) are discriminated using the on-board electronics. A coded mask provides imaging capabilities at low energies, thus allowing a compact and sensitive instrument in a wide energy band (~2 keV up to ~20 MeV). The instrument design, expected performance and the characterization performed on a series of laboratory prototypes are discussed.

astro-ph.IM↗

arXiv2018

Observing strategy of the THESEUS mission

We will discuss the observing strategy of the Transient High Energy Sky and Early Universe Surveyor (THESEUS) mission proposed to ESA as a response to the M5 call for proposals. The description of THESEUS and its science goals can be found in the white paper by Amati et al. (2017).

astro-ph.HE↗

arXiv2017

A compact and modular X and gamma-ray detector with a CsI scintillator and double-readout Silicon Drift Detectors

A future compact and modular X and gamma-ray spectrometer (XGS) has been designed and a series of prototypes have been developed and tested. The experiment envisages the use of CsI scintillator bars read out at both ends by single-cell 25 mm2 Silicon Drift Detectors. Digital algorithms are used to discriminate between events absorbed in the Silicon layer (lower energy X rays) and events absorbed in the scintillator crystal (higher energy X rays and gamma-rays). The prototype characterization is shown and the modular design for future experiments with possible astrophysical applications (e.g. for the THESEUS mission proposed for the ESA M5 call) are discussed.

astro-ph.IM↗

arXiv2017

The e-ASTROGAM gamma-ray space mission

The e-ASTROGAM is a gamma-ray space mission to be proposed as the M5 Medium-size mission of the European Space Agency. It is dedicated to the observation of the Universe with unprecedented sensitivity in the energy range 0.2 - 100 MeV, extending up to GeV energies, together with a groundbreaking polarization capability. It is designed to substantially improve the COMPTEL and Fermi sensitivities in the MeV-GeV energy range and to open new windows of opportunity for astrophysical and fundamental physics space research. e-ASTROGAM will operate as an open astronomical observatory, with a core science focused on (1) the activity from extreme particle accelerators, including gamma-ray bursts and active galactic nuclei and the link of jet astrophysics to the new astronomy of gravitational waves, neutrinos, ultra-high energy cosmic rays, (2) the high-energy mysteries of the Galactic center and inner Galaxy, including the activity of the supermassive black hole, the Fermi Bubbles, the origin of the Galactic positrons, and the search for dark matter signatures in a new energy window; (3) nucleosynthesis and chemical evolution, including the life cycle of elements produced by supernovae in the Milky Way and the Local Group of galaxies. e-ASTROGAM will be ideal for the study of high-energy sources in general, including pulsars and pulsar wind nebulae, accreting neutron stars and black holes, novae, supernova remnants, and magnetars. And it will also provide important contributions to solar and terrestrial physics. The e-ASTROGAM telescope is optimized for the simultaneous detection of Compton and pair-producing gamma-ray events over a large spectral band. It is based on a very high technology readiness level for all subsystems and includes many innovative features for the detectors and associated electronics.

astro-ph.IM↗

arXiv2016

Two new high energy gamma-ray blazar candidates

We report the detection of two new gamma-ray sources in the Fermi-LAT sky (Pass 8) at energies higher than 20 GeV, and confirmed at lower energies, using a source detection tool based on the Minimum Spanning Tree algorithm. One of these sources, at a Galactic latitude of about -4°, is a new discovery, while the other was previously reported above 50 GeV in the 2FHL catalogue. We searched for archival multi-wavelength data of possible counterparts and found interesting candidates. Both objects are radio sources and their WISE infrared colours are typical of blazars. While for the former source no optical spectra are available, for the latter a puzzling optical spectrum corresponding to a white dwarf star is found in the 6dF database. We discuss the spectral energy distributions of both sources and possible interpretations.

astro-ph.HE↗

arXiv2016

Application of the MST clustering to the high energy gamma-ray sky. IV - Blazar candidates found as possible counterparts of photon clusters

We present the results of a cluster search in the Fermi-LAT Pass 8 gamma-ray sky by means of the Minimum Spanning Tree algorithm, at energies higher than 10 GeV and at Galactic latitudes higher than 25 degrees. The selected clusters have a minimum number of photons higher than or equal to 5, a high degree of concentration, and are without a clear corresponding counterpart in blazar catalogues. A sample of 30 possible gamma-ray sources was obtained. These objects were verified by applying the standard Maximum Likelihood analysis on the Fermi-LAT data. A search for possible radio counterparts in a circle having a radius of 6 arcmin was performed, finding several interesting objects, the majority of them without optical spectroscopical data. These can be considered as new blazar candidates. Some of them were already noticed as possible blazars or Active Galactic Nuclei in previous surveys, but never associated with high energy emission. These possible counterparts are reported and their properties are discussed.

astro-ph.HE↗

arXiv2016

eXTP -- enhanced X-ray Timing and Polarimetry Mission

eXTP is a science mission designed to study the state of matter under extreme conditions of density, gravity and magnetism. Primary targets include isolated and binary neutron stars, strong magnetic field systems like magnetars, and stellar-mass and supermassive black holes. The mission carries a unique and unprecedented suite of state-of-the-art scientific instruments enabling for the first time ever the simultaneous spectral-timing-polarimetry studies of cosmic sources in the energy range from 0.5-30 keV (and beyond). Key elements of the payload are: the Spectroscopic Focusing Array (SFA) - a set of 11 X-ray optics for a total effective area of about 0.9 m^2 and 0.6 m^2 at 2 keV and 6 keV respectively, equipped with Silicon Drift Detectors offering <180 eV spectral resolution; the Large Area Detector (LAD) - a deployable set of 640 Silicon Drift Detectors, for a total effective area of about 3.4 m^2, between 6 and 10 keV, and spectral resolution <250 eV; the Polarimetry Focusing Array (PFA) - a set of 2 X-ray telescope, for a total effective area of 250 cm^2 at 2 keV, equipped with imaging gas pixel photoelectric polarimeters; the Wide Field Monitor (WFM) - a set of 3 coded mask wide field units, equipped with position-sensitive Silicon Drift Detectors, each covering a 90 degrees x 90 degrees FoV. The eXTP international consortium includes mostly major institutions of the Chinese Academy of Sciences and Universities in China, as well as major institutions in several European countries and the United States. The predecessor of eXTP, the XTP mission concept, has been selected and funded as one of the so-called background missions in the Strategic Priority Space Science Program of the Chinese Academy of Sciences since 2011. The strong European participation has significantly enhanced the scientific capabilities of eXTP. The planned launch date of the mission is earlier than 2025.

astro-ph.IM↗

arXiv2016

Steps towards the hyperfine splitting measurement of the muonic hydrogen ground state: pulsed muon beam and detection system characterization

The high precision measurement of the hyperfine splitting of the muonic-hydrogen atom ground state with pulsed and intense muon beam requires careful technological choices both in the construction of a gas target and of the detectors. In June 2014, the pressurized gas target of the FAMU experiment was exposed to the low energy pulsed muon beam at the RIKEN RAL muon facility. The objectives of the test were the characterization of the target, the hodoscope and the X-ray detectors. The apparatus consisted of a beam hodoscope and X-rays detectors made with high purity Germanium and Lanthanum Bromide crystals. In this paper the experimental setup is described and the results of the detector characterization are presented.

physics.ins-det↗

arXiv2016

Enhanced detection of terrestrial gamma-ray flashes by AGILE

At the end of March 2015 the onboard software configuration of the AGILE satellite was modified in order to disable the veto signal of the anticoincidence shield for the minicalorimeter instrument. The motivation for such a change was the understanding that the dead time induced by the anticoincidence prevented the detection of a large fraction of Terrestrial Gamma-Ray Flashes (TGFs). The configuration change was highly successful resulting in an increase of one order of magnitude in TGF detection rate. As expected, the largest fraction of the new events has short duration ($< 100 \mathrm {μs}$), and part of them has simultaneous association with lightning sferics detected by the World Wide Lightning Location Network (WWLLN). The new configuration provides the largest TGF detection rate surface density (TGFs/$\mathrm{km^2}$/year) to date, opening prospects for improved correlation studies with lightning and atmospheric parameters on short spatial and temporal scales along the equatorial region.

physics.space-ph↗

arXiv2016

Application of the MST clustering to the high energy gamma-ray sky. III - New detections of gamma-ray emission from blazars

We present the results of a photon cluster search in the gamma-ray sky observed by the Fermi Large Area Telescope, using the new Pass 8 dataset, at energies higher than 10 GeV. By means of the Minimum Spanning Tree (MST) algorithm, we found 25 clusters associated with catalogued blazars not previously known as gamma-ray emitters. The properties of these sources are discussed.

astro-ph.HE↗

arXiv2016

Application of the MST clustering to the high energy gamma-ray sky. II - Possible detection of gamma-ray emission from blazar candidates in the 1WHSP sample

We present the results of a photon cluster search in the 7-years Fermi-Large Area Telescope extragalactic Pass 8 gamma-ray sky by means of the Minimum Spanning Tree (MST) algorithm, at energies higher than 10 GeV. We found 16 clusters of photons, corresponding to candidate gamma-ray sources, located very close to infrared-selected sources in the 1WHSP (WISE High Synchrotron Peaked) sample, and therein classified as either "new" or "candidate" blazars. In this paper some properties of the MST clusters and of the associated sources are presented.

astro-ph.HE↗

arXiv2015

Application of the MST clustering to the high energy gamma-ray sky. I - New possible detection of high-energy gamma-ray emission associated with BL Lac objects

In this paper we show an application of the Minimum Spanning Tree (MST) clustering method to the high-energy gamma-ray sky observed at energies higher than 10 GeV in 6.3 years by the Fermi-Large Area Telescope. We report the detection of 19 new high-energy gamma-ray clusters with good selection parameters whose centroid coordinates were found matching the positions of known BL Lac objects in the 5th Edition of the Roma-BZCAT catalogue. A brief summary of the properties of these sources is presented.

astro-ph.HE↗

arXiv2015

Missing hard states and regular outbursts: the puzzling case of the black hole candidate 4U 1630-472

4U 1630-472 is a recurrent X-ray transient classified as a black-hole candidate from its spectral and timing properties. One of the peculiarities of this source is the presence of regular outbursts with a recurrence period between 600 and 730 d that has been observed since the discovery of the source in 1969. We report on a comparative study on the spectral and timing behaviour of three consecutive outbursts occurred in 2006, 2008 and 2010. We analysed all the data collected by the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) and the Rossi X-ray timing Explorer (RXTE) during these three years of activity. We show that, in spite of having a similar spectral and timing behaviour in the energy range between 3 and 30 keV, these three outbursts show pronounced differences above 30 keV. In fact, the 2010 outburst extends at high energies without any detectable cut-off until 150-200 keV, while the two previous outbursts that occurred in 2006 and 2008 are not detected at all above 30 keV. Thus, in spite of a very similar accretion disk evolution, these three outbursts exhibit totally different characteristics of the Compton electron corona, showing a softening in their evolution rarely observed before in a low mass X-ray binary hosting a black hole. We argue the possibility that the unknown perturbation that causes the outbursts to be equally spaced in time could be at the origin of this particular behaviour. Finally we describe several possible scenarios that could explain the regularity of the outbursts, identifying the most plausible, such as a third body orbiting around the binary system.

astro-ph.HE↗

arXiv2015

High-energy radiation from thunderstorms and lightning with LOFT

This is a White Paper in support of the mission concept of the Large Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We discuss the potential of LOFT for the study of high-energy radiation from thunderstorms and lightning. For a summary, we refer to the paper.

astro-ph.HE↗