4,022 research outputs found
Compton telescope with coded aperture mask: Imaging with the INTEGRAL/IBIS Compton mode
Compton telescopes provide a good sensitivity over a wide field of view in
the difficult energy range running from a few hundred keV to several MeV. Their
angular resolution is, however, poor and strongly energy dependent. We present
a novel experimental design associating a coded mask and a Compton detection
unit to overcome these pitfalls. It maintains the Compton performance while
improving the angular resolution by at least an order of magnitude in the field
of view subtended by the mask. This improvement is obtained only at the expense
of the efficiency that is reduced by a factor of two. In addition, the
background corrections benefit from the coded mask technique, i.e. a
simultaneous measurement of the source and background. This design is
implemented and tested using the IBIS telescope on board the INTEGRAL satellite
to construct images with a 12' resolution over a 29 degrees x 29 degrees field
of view in the energy range from 200 keV to a few MeV. The details of the
analysis method and the resulting telescope performance, particularly in terms
of sensitivity, are presented
INTEGRAL discovery of a bright highly obscured galactic X-ray binary source IGR J16318-4848
INTEGRAL regularly scans the Galactic plane to search for new objects and in
particular for absorbed sources with the bulk of their emission above 10-20
keV. The first new INTEGRAL source was discovered on 2003 January 29, 0.5
degree from the Galactic plane and was further observed in the X-rays with
XMM-Newton. This source, IGR J16318-4848, is intrinsically strongly absorbed by
cold matter and displays exceptionally strong fluorescence emission lines. The
likely infrared/optical counterpart indicates that IGR J16318-4848 is probably
a High Mass X-Ray Binary neutron star or black hole enshrouded in a Compton
thick environment. Strongly absorbed sources, not detected in previous surveys,
could contribute significantly to the Galactic hard X-ray background between 10
and 200 keV.Comment: 6 pages, 4 figures (fig 1 quality lowered), accepted for publication
in A&A letters (INTEGRAL special issue
INTEGRAL and Swift/XRT observations of IGR~J16460+0849
IGR J16460+0849 is reported in the 3rd IBIS catalog with the shortest
exposure of about 10 ks among all the detected sources, which makes it the most
interesting target to be investigated with a deeper exposure. We analyze all
available observations carried out by the International Gamma-Ray Astrophysics
Laboratory (INTEGRAL) on the unidentified source IGR J16460+0849. The data
were processed by using the latest version OSA 7.0. In addition we analyze also
all the available Swift/XRT data on this source. We find that IGR J16460+0849
has a detection significance of ~ 4.4 sigma in the 20-100 keV band during the
observational period between March 2003 and September 2004, when it was exposed
by ~ 19 ks. Thereafter the source was not detected anymore, despite an
additional exposure of ~ 271 ks. This suggests a flux variability on a
timescale of years. The spectral analysis shows that the IBIS/ISGRI data are
well presented by a power-law shape, with a photon index obtained as
1.45+-0.86. So far, the source has been detected consistently by IBIS/ISGRI in
the subsequent observations and in the adjacent energy bands. We have analyzed
the Swift/XRT observations on IGR J16460+0849 as well, and found no source
inside the IBIS/ISGRI error circle. The non-detection during the Swift/XRT
observation is consistent with the source having a variable nature.Comment: published in A&
SPI Measurements of the Diffuse Galactic Hard X-ray Continuum
INTEGRAL Spectrometer SPI data from the first year of the Galactic Centre
Deep Exposure has been analysed for the diffuse continuum from the Galactic
ridge. A new catalogue of sources from the INTEGRAL Imager IBIS has been used
to account for their contribution to the celestial signal. Apparently diffuse
emission is detected at a level ~10% of the total source flux. A comparison of
the spectrum of diffuse emission with that from an analysis of IBIS data alone
shows that they are consistent. The question of the contribution of unresolved
sources to this ridge emission is still open.Comment: Proceedings of the 5th INTEGRAL Workshop, Munich 16-20 February 2004.
ESA SP-552. Reference to Terrier et al. (2004) updated to include astro-ph
versio
The signature of 44Ti in Cassiopeia A revealed by IBIS/ISGRI on INTEGRAL
We report the detection of both the 67.9 and 78.4 keV 44Sc gamma-ray lines in
Cassiopeia A with the INTEGRAL IBIS/ISGRI instrument. Besides the robustness
provided by spectro-imaging observations, the main improvements compared to
previous measurements are a clear separation of the two 44Sc lines together
with an improved significance of the detection of the hard X-ray continuum up
to 100 keV. These allow us to refine the determination of the 44Ti yield and to
constrain the nature of the nonthermal continuum emission. By combining
COMPTEL, BeppoSAX/PDS and ISGRI measurements, we find a line flux of (2.5 +/-
0.3)*10(-5) cm(-2) s(-1) leading to a synthesized 44Ti mass of 1.6
(+0.6-0.3)*10(-4) solar mass. This high value suggests that Cas A is peculiar
in comparison to other young supernova remnants, from which so far no line
emission from 44Ti decay has been unambiguously detected.Comment: 5 pages, 4 figures, Accepted for publication in ApJ
Land and sea BRDF laboratory measurements at 360 nm in view of ground reflected Cherenkov light detection in EUSO
Detection and period measurements of GX1+4 at hard x ray energies with the SIGMA telescope
The galactic Low Mass X ray Binary GX1+4 was detected by the coded aperture hard X ray gamma ray SIGMA telescope during the Feb. to April 1991 observations of the galactic center regions. The source, whose emission varied during the survey of a factor greater than 40 pct., reached a maximum luminosity in the 40 to 140 energy range of 1.03 x 10(exp 37) erg/s (D = 8.5 kpc), thus approaching the emission level of the 1970 to 1980 high state. Two minute flux pulsations were detected on Mar. 22 and on Mar. 31 and Apr. 1. Comparison with the last period measurements shows that the current spin-down phase of GX1+4 is ending. Concerning the proposed association of this source with the galactic center 511 keV annihilation emission, upper limits were derived
Innovative methodology to transfer conventional GC-MS heroin profiling to UHPLC-MS/MS
Nowadays, in forensic laboratories, heroin profiling is frequently carried out by gas chromatography coupled with mass spectrometry (GC-MS). This analytical technique is well established, provides good sensitivity and reproducibility, and allows the use of large databases. Despite those benefits, recently introduced analytical techniques, such as ultra-high-pressure liquid chromatography (UHPLC), could offer better chromatographic performance, which needs to be considered to increase the analysis throughput for heroin profiling. With the latter, chromatographic conditions were optimized through commercial modeling software and two atmospheric pressure ionization sources were evaluated. Data obtained from UHPLC-MS/MS were thus transferred, thanks to mathematical models to mimic GC-MS data. A calibration and a validation set of representative heroin samples were selected among the database to establish a transfer methodology and assess the models' abilities to transfer using principal component analysis and hierarchical classification analysis. These abilities were evaluated by computing the frequency of successful classification of UHPLC-MS/MS data among GC-MS database. Seven mathematical models were tested to adjust UHPLC-MS/MS data to GC-MS data. A simplified mathematical model was finally selected and offered a frequency of successful transfer equal to 95%. Figur
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