AGILE development and silicon detector Barbiellini, Guido
Atti della Accademia nazionale dei Lincei. Rendiconti Lincei. Scienze fisiche e naturali,
12/2019, Letnik:
30, Številka:
Suppl 1
Journal Article
Recenzirano
In the years 1980s and 1990s, a very fast and important progress on position and energy loss measurements of elementary particles was obtained by the use of Si strip detector in high energy (HE) ...experiments. The number of strips has been increasing at any improvement of the tracker device. The high number of strip density also pushed the power reduction of the readout electronic amplifiers. The Si tracker became at certain moment a challenging substitute of the classical spark chambers (Fichtel et al. NASA-TM-X-70761,
1995
; Thompson
arXiv:e:0811.0738
,
2008
), in use for tracking particles in space experiments. In particular in HE
γ
-strophysics, the photon direction was derived by measuring that of the positron electron pair produced in high
Z
material interlaid in the planes of the spark chamber. See for instance the EGRET figure in the text. AGILE and GLAST (renamed Fermi after launch) are the most successful examples of the Si revolution.
Context. The nearby Large Magellanic Cloud (LMC) provides a rare opportunity of a spatially resolved view of an external star-forming galaxy in γ-rays. The LMC was detected at 0.1–100 GeV as an ...extended source with CGRO/EGRET and using early observations with the Fermi-LAT. The emission was found to correlate with massive star-forming regions and to be particularly bright towards 30 Doradus. Aims. Studies of the origin and transport of cosmic rays (CRs) in the Milky Way are frequently hampered by line-of-sight confusion and poor distance determination. The LMC offers a complementary way to address these questions by revealing whether and how the γ-ray emission is connected to specific objects, populations of objects, and structures in the galaxy. Methods. We revisited the γ-ray emission from the LMC using about 73 months of Fermi-LAT P7REP data in the 0.2–100 GeV range. We developed a complete spatial and spectral model of the LMC emission, for which we tested several approaches: a simple geometrical description, template-fitting, and a physically driven model for CR-induced interstellar emission. Results. In addition to identifying PSR J0540−6919 through its pulsations, we find two hard sources positionally coincident with plerion N 157B and supernova remnant N 132D, which were also detected at TeV energies with H.E.S.S. We detect an additional soft source that is currently unidentified. Extended emission dominates the total flux from the LMC. It consists of an extended component of about the size of the galaxy and additional emission from three to four regions with degree-scale sizes. If it is interpreted as CRs interacting with interstellar gas, the large-scale emission implies a large-scale population of ~1–100 GeV CRs with a density of ~30% of the local Galactic value. On top of that, the three to four small-scale emission regions would correspond to enhancements of the CR density by factors 2 to 6 or higher, possibly more energetic and younger populations of CRs compared to the large-scale population. An alternative explanation is that this is emission from an unresolved population of at least two dozen objects, such as pulsars and their nebulae or supernova remnants. This small-scale extended emission has a spatial distribution that does not clearly correlate with known components of the LMC, except for a possible relation to cavities and supergiant shells. Conclusions. The Fermi-LAT GeV observations allowed us to detect individual sources in the LMC. Three of the newly discovered sources are associated with rare and extreme objects. The 30 Doradus region is prominent in GeV γ-rays because PSR J0540−6919 and N 157B are strong emitters. The extended emission from the galaxy has an unexpected spatial distribution, and observations at higher energies and in radio may help to clarify its origin.
Abstract
Gamma-ray emission in the MeV–GeV range from explosive cosmic events is of invaluable relevance to understanding physical processes related to the formation of neutron stars and black holes. ...Here we report on the detection by the AGILE satellite in the MeV–GeV energy range of the remarkable long-duration gamma-ray burst GRB 221009A. The AGILE onboard detectors have good exposure to GRB 221009A during its initial crucial phases. Hard X-ray/MeV emission in the prompt phase lasted hundreds of seconds, with the brightest radiation being emitted between 200 and 300 s after the initial trigger. Very intense GeV gamma-ray emission is detected by AGILE in the prompt and early afterglow phase up to 10,000 s. Time-resolved spectral analysis shows time-variable MeV-peaked emission simultaneous with intense power-law GeV radiation that persists in the afterglow phase. The coexistence during the prompt phase of very intense MeV emission together with highly nonthermal and hardening GeV radiation is a remarkable feature of GRB 221009A. During the prompt phase, the event shows spectrally different MeV and GeV emissions that are most likely generated by physical mechanisms occurring in different locations. AGILE observations provide crucial flux and spectral gamma-ray information regarding the early phases of GRB 221009A during which emission in the TeV range was reported.
The AGILE silicon tracker: an innovative γ-ray instrument for space Prest, M; Barbiellini, G; Bordignon, G ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2003, Letnik:
501, Številka:
1
Journal Article
Recenzirano
AGILE (Light Imager for Gamma-ray Astrophysics) is the first small scientific mission of ASI, the Italian Space Agency. It is a light (
100
kg
for the scientific instrument) satellite for the ...detection of γ-ray sources in the energy range
30
MeV
–
50
GeV
within a large field of view (
1
4
of the sky). It is planned to be operational in the years 2003–2006, a period in which no other gamma-ray mission in the same energy range is foreseen.
AGILE is made of a silicon tungsten tracker, a CsI(Tl) minicalorimeter (1.5
X
0), an anticoincidence system of segmented plastic scintillators and a X-ray imaging detector sensitive in the 10–
40
keV
range. The tracker consists of 14 planes, each of them made of two layers of 16 single-sided, AC coupled,
410
μm
thick,
9.5×9.5
cm
2
silicon detectors with a readout pitch of
242
μm
and a floating strip. The readout ASIC is the TAA1, an analog-digital, low noise, self-triggering ASIC used in a very low power configuration
(<400
μW/
channel)
with full analog readout. The trigger of the satellite is given by the tracker. The total number of readout channels is around 43
000.
We present a detailed description of the tracker, its trigger and readout logic, its assembly procedures and the prototype performance in several testbeam periods at the CERN PS.
ABSTRACT We report the discovery of PSR J1906+0722, a gamma-ray pulsar detected as part of a blind survey of unidentified Fermi Large Area Telescope (LAT) sources being carried out on the volunteer ...distributed computing system, Einstein@Home. This newly discovered pulsar previously appeared as the most significant remaining unidentified gamma-ray source without a known association in the second Fermi-LAT source catalog (2FGL) and was among the top 10 most significant unassociated sources in the recent third catalog (3FGL). PSR J1906+0722 is a young, energetic, isolated pulsar, with a spin frequency of 8.9 Hz, a characteristic age of 49 kyr, and spin-down power erg s−1. In 2009 August it suffered one of the largest glitches detected from a gamma-ray pulsar ( ). Remaining undetected in dedicated radio follow-up observations, the pulsar is likely radio-quiet. An off-pulse analysis of the gamma-ray flux from the location of PSR J1906+0722 revealed the presence of an additional nearby source, which may be emission from the interaction between a neighboring supernova remnant and a molecular cloud. We discuss possible effects which may have hindered the detection of PSR J1906+0722 in previous searches and describe the methods by which these effects were mitigated in this survey. We also demonstrate the use of advanced timing methods for estimating the positional, spin and glitch parameters of difficult-to-time pulsars such as this.
Possible interpretation of highest energy neutrino never detected by IceCube as cosmological neutrinos boosted by the first accelerated protons in the Universe: the Inverse Fermi scattering ...\(p\nu\rightarrow p'\nu'\).
AGILE (Light Imager for Gamma-ray Astrophysics) is a small scientific satellite for the detection of cosmic γ-ray sources in the energy range
30
MeV
–
50
GeV
with a very large field of view (1/4 of ...the sky). It is planned to be operational in the years 2003–2006, a period in which no other γ-ray mission in the same energy range is foreseen.
The heart of the AGILE scientific instrument is a silicon–tungsten tracker made of 14 planes of single sided silicon detectors for a total of 43
000 readout channels. Each detector has a dimension of
9.5×9.5
cm
2
and a thickness of
410
μm
.
We present here a detailed description of the performance of the detector prototype during a testbeam period at the CERN PS in May 2000. The Tracker performance is described in terms of position resolution and signal-to-noise ratio for on and off-axis incident charged particles. The measured
40
μm
resolution for a large range of incident angles will provide an excellent angular resolution for cosmic γ-ray imaging.
We present the Fermi Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) observations of the LIGO binary black hole merger event GW151226 and candidate LVT151012. At the time of the LIGO ...triggers on LVT151012 and GW151226, GBM was observing 68% and 83% of the localization regions, and LAT was observing 47% and 32%, respectively. No candidate electromagnetic counterparts were detected by either the GBM or LAT. We present a detailed analysis of the GBM and LAT data over a range of timescales from seconds to years, using automated pipelines and new techniques for characterizing the flux upper bounds across large areas of the sky. Due to the partial GBM and LAT coverage of the large LIGO localization regions at the trigger times for both events, differences in source distances and masses, as well as the uncertain degree to which emission from these sources could be beamed, these non-detections cannot be used to constrain the variety of theoretical models recently applied to explain the candidate GBM counterpart to GW150914.
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