417 research outputs found
IBIS/PICsIT in-flight performances
PICsIT (Pixellated Imaging CaeSium Iodide Telescope) is the high energy
detector of the IBIS telescope on-board the INTEGRAL satellite. PICsIT operates
in the gamma-ray energy range between 175 keV and 10 MeV, with a typical energy
resolution of 10% at 1 MeV, and an angular resolution of 12 arcmin within a
\~100 square degree field of view, with the possibility to locate intense point
sources in the MeV region at the few arcmin level. PICsIT is based upon a
modular array of 4096 independent CsI(Tl) pixels, ~0.70 cm^2 in cross-section
and 3 cm thick. In this work, the PICsIT on-board data handling and science
operative modes are described. This work presents the in-flight performances in
terms of background count spectra, sensitivity limit, and imaging capabilities.Comment: 8 pages, 4 figures. Accepted for publication on A&A, special issue on
First Science with INTEGRA
Imaging extended sources with coded mask telescopes: Application to the INTEGRAL IBIS/ISGRI instrument
Context. In coded mask techniques, reconstructed sky images are
pseudo-images: they are maps of the correlation between the image recorded on a
detector and an array derived from the coded mask pattern. Aims. The
INTEGRAL/IBIS telescope provides images where the flux of each detected source
is given by the height of the local peak in the correlation map. As such, it
cannot provide an estimate of the flux of an extended source. What is needed is
intensity sky images giving the flux per solide angle as typically done at
other wavelengths. Methods. In this paper, we present the response of the
INTEGRAL IBIS/ISGRI coded mask instrument to extended sources. We develop a
general method based on analytical calculations in order to measure the
intensity and the associated error of any celestial source and validated with
Monte-Carlo simulations. Results. We find that the sensitivity degrades almost
linearly with the source extent. Analytical formulae are given as well as an
easy-to-use recipe for the INTEGRAL user. We check this method on IBIS/ISGRI
data but these results are general and applicable to any coded mask telescope.Comment: 9 pages, 6 figures, Accepted for publication in A&
Outburst of the X-ray transient SAX J1818.6-1703 detected by INTEGRAL in September 2003
During the observation of the Galactic-center field by the INTEGRAL
observatory on September 9, 2003, the IBIS/ISGRI gamma-ray telescope detected a
short (several-hours-long) intense (~380 mCrab at the peak) outburst of hard
radiation from the X-ray transient SAX J1818.6-1703. Previously, this source
was observed only once in 1998 during a similar short outburst. We present the
results of our localization, spectral and timing analyses of the object and
briefly discuss the possible causes of the outburst. The release time of the
bulk of the energy in such an outburst is appreciably shorter than the
accretion (viscous) time that characterizes the flow of matter through a
standard accretion disk.Comment: 16 pages, 7 figures, to be published in Astronomy Letters, v. 31, n.
10, p. 672 (2005
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.Comment: To be published in the Proceedings of the THESEUS Workshop 2017
(http://www.isdc.unige.ch/theseus/workshop2017.html), Journal of the Italian
Astronomical Society (Mem.SAIt), Editors L. Amati, E. Bozzo, M. Della Valle,
D. Gotz, P. O'Brien. Details on the THESEUS mission concept can be found in
the white paper Amati et al. 2017 (arXiv:171004638) and Stratta et al. 2017
(arXiv:1712.08153
GRB030406 an extremely hard burst outside of the INTEGRAL field of view
Using the IBIS Compton mode, the INTEGRAL satellite is able to detect and
localize bright and hard GRBs, which happen outside of the nominal INTEGRAL
telescopes field of view. We have developed a method of analyzing such INTEGRAL
data to obtain the burst location and spectra. We present the results for the
case of GRB030406. The burst is localized with the Compton events, and the
location is consistent with the previous Interplanetary Network position. A
spectral analysis is possible with the detailed modeling of the detector
response for such a far off-axis source with the offset of 36.9 . The
average spectrum of the burst is extremely hard: the photon index above 400
\kev is -1.7, with no evidence of a break up to 1.1 \mev at 90% confidence
level.Comment: Astronomy and Astrophysics in pres
Coma revealed as an extended hard X-rays source by INTEGRAL IBIS/ISGRI
Aims. We report the INTEGRAL/IBIS observations of the Coma Cluster in the
hard X-ray/soft-ray domain. Methods. Since the Coma Cluster appears as an
extended source, its global intensity and significance cannot be directly
extracted with standard coded mask analysis. We used the method of imaging the
extended sources with a coded mask telescope developed by Renaud et al. (2006).
Results. The imaging capabilities and the sensitivity of the IBIS/ISGRI coded
mask instrument allows us to identify for the first time the site of the
emission above ~ 15 keV. We have studied the Coma Cluster morphology in the
18-30keV band and found that it follows the prediction based on X-ray
observations.We also bring constraints on the non-thermal mechanism
contribution at higher energies.Comment: 4 pages, 4 figures, Accepted for publication in A&A Letter
INTEGRAL/IBIS search for e-e+ annihilation radiation from the Galactic Center Region
Electron-positron annihilation radiation from the Galactic Center region has
been detected since the seventies, but its astrophysical origin is still a
topic of a scientific debate. We have analyzed data of the gamma-ray imager
IBIS/ISGRI onboard of ESA's INTEGRAL platform in the ee line.
During the first year of the missions Galactic Center Deep Exposure no evidence
for point sources at 511 keV has been found in the ISGRI data; the
upper limit for resolved single point sources is estimated to be .Comment: 6 pages, 3 figures; Cospar 2004. To be published in: Advances in
Space Researc
Measurement of the non-linearity in the gamma-ray response of the GAGG:Ce inorganic scintillator
A characteristic of every inorganic scintillator crystal is its light yield,
i.e., the amount of emitted scintillation photons per unit of energy deposited
in the crystal. Light yield is known to be usually non-linear with energy,
which impacts the spectroscopic properties of the scintillator. Cerium-doped
gadolinium-aluminium-gallium garnet (GAGG:Ce) is a recently developed
scintillator with several interesting properties, which make it very promising
for space-based gamma-ray detectors, such as in the HERMES nanosatellite
mission. In this paper we report an accurate measurement of the GAGG:Ce
non-linearity in the 20-662 keV gamma-ray energy interval, using a setup
composed of three samples of GAGG:Ce crystals read out by Silicon Drift
Detectors (SDDs).Comment: 22 pages, 11 figures. Accepted for publication in NIM
A large spin-up rate measured with INTEGRAL in the High Mass X-ray Binary Pulsar SAXJ2103.5+4545
The High Mass X-ray Binary Pulsar SAXJ2103.5+4545 has been observed with
INTEGRAL several times during the last outburst in 2002-2004. We report a
comprehensive study of all INTEGRAL observations, allowing a study of the pulse
period evolution during the recent outburst. We measured a very rapid spin-up
episode, lasting 130days, which decreased the pulse period by 1.8s. The spin-up
rate, pdot=-1.5e-7 s/s, is the largest ever measured for SAXJ2103.5+4545, and
it is among the fastest for an accreting pulsar. The pulse profile shows
evidence for temporal variability, apparently not related to the source flux or
to the orbital phase. The X-ray spectrum is hard and there is significant
emission up to 150keV. A new derivation of the orbital period, based on RXTE
data, is also reported.Comment: 8 pages, 7 figures, accepted for publication in A&
IBIS preliminary results on Cygnus X-1 spectral and temporal characteristics
We report preliminary results of a broadband spectral and temporal study of
the black-hole binary Cyg X-1 performed with the IBIS telescope. Cyg X-1 was
the first pointed celestial target of IBIS during the INTEGRAL Performance and
Verification Phase, 2002 Nov.-Dec., for a total observing time of 2 Ms in both
staring and dithering mode. Here, we report on only the staring, on-axis,
observation performed in a stable instrument configuration. During the
observing period the source was in its characteristic low/hard state, in which
a few flares and dips have been detected. The IBIS/ISGRI results demonstrate
that the INTEGRAL observatory offers a unique capability for studying
correlations between hardness and/or flux in different bands over a wide photon
energy range. One of our new results is finding that the hardness-flux
correlation changes the sign twice over the 20-220 keV; first from positive to
negative at 50 keV, and then back to positive at 120 keV. The former change
appears to be due to the spectral curvature introduced by variable Compton
reflection. The latter may be due spectral pivoting.Comment: 7 pages, 8 figures (4 in color), accepted for publication in A&A,
INTEGRAL special issu
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