V. Reglero

IBIS: The Imager on-board INTEGRAL

The IBIS telescope is the high angular resolution gamma-ray imager on-board the INTEGRAL Observatory, suc- cessfully launched from Baikonur (Kazakhstan) the 17th of October 2002. This medium size ESA project, planned for a 2 year mission with possible extension to 5, is devoted to the observation of the gamma-ray sky in the energy range from 3 keV to 10 MeV (Winkler 2001). The IBIS imaging system is based on two independent solid state detector arrays optimised for low (15 1000 keV) and high (0:175 10:0 MeV) energies surrounded by an active VETO System. This high eciency shield is essential to minimise the background induced by high energy particles in the highly excentric out of van Allen belt orbit. A Tungsten Coded Aperture Mask, 16 mm thick and1 squared meter in dimension is the imaging device. The IBIS telescope will serve the scientific community at large providing a unique combination of unprecedented high energy wide field imaging capability coupled with broad band spectroscopy and high resolution timing over the energy range from X to gamma rays. To date the IBIS telescope is working nominally in orbit since more than 9 month.

JEM-X: The X-ray monitor aboard INTEGRAL ?

The JEM-X monitor provides X-ray spectra and imaging with arcminute angular resolution in the 3 to 35 keV band. The good angular resolution and the low energy response of JEM-X plays an important role in the identification of gamma ray sources and in the analysis and scientific interpretation of the combined X-ray and gamma ray data. JEM-X is a coded aperture instrument consisting of two identical, coaligned telescopes. Each of the detectors has a sensitive area of 500 cm 2 , and views the sky through its own coded aperture mask. The two coded masks are inverted with respect to each other and provides an angular resolution of 3 0 across an eective field of view of about 10 diameter.

XIPE: the X-ray imaging polarimetry explorer

Abstract X-ray polarimetry, sometimes alone, and sometimes coupled to spectral and temporal variability measurements and to imaging, allows a wealth of physical phenomena in astrophysics to be studied. X-ray polarimetry investigates the acceleration process, for example, including those typical of magnetic reconnection in solar flares, but also emission in the strong magnetic fields of neutron stars and white dwarfs. It detects scattering in asymmetric structures such as accretion disks and columns, and in the so-called molecular torus and ionization cones. In addition, it allows fundamental physics in regimes of gravity and of magnetic field intensity not accessible to experiments on the Earth to be probed. Finally, models that describe fundamental interactions (e.g. quantum gravity and the extension of the Standard Model) can be tested. We describe in this paper the X-ray Imaging Polarimetry Explorer (XIPE), proposed in June 2012 to the first ESA call for a small mission with a launch in 2017. The proposal was, unfortunately, not selected. To be compliant with this schedule, we designed the payload mostly with existing items. The XIPE proposal takes advantage of the completed phase A of POLARIX for an ASI small mission program that was cancelled, but is different in many aspects: the detectors, the presence of a solar flare polarimeter and photometer and the use of a light platform derived by a mass production for a cluster of satellites. XIPE is composed of two out of the three existing JET-X telescopes with two Gas Pixel Detectors (GPD) filled with a He-DME mixture at their focus. Two additional GPDs filled with a 3-bar Ar-DME mixture always face the Sun to detect polarization from solar flares. The Minimum Detectable Polarization of a 1 mCrab source reaches 14 % in the 2–10 keV band in 105 s for pointed observations, and 0.6 % for an X10 class solar flare in the 15–35 keV energy band. The imaging capability is 24 arcsec Half Energy Width (HEW) in a Field of View of 14.7 arcmin × 14.7 arcmin. The spectral resolution is 20 % at 6 keV and the time resolution is 8 μs. The imaging capabilities of the JET-X optics and of the GPD have been demonstrated by a recent calibration campaign at PANTER X-ray test facility of the Max-Planck-Institut für extraterrestrische Physik (MPE, Germany). XIPE takes advantage of a low-earth equatorial orbit with Malindi as down-link station and of a Mission Operation Center (MOC) at INPE (Brazil). The data policy is organized with a Core Program that comprises three months of Science Verification Phase and 25 % of net observing time in the following 2 years. A competitive Guest Observer program covers the remaining 75 % of the net observing time.

Further evidence for the presence of a neutron star in 4U 2206+54. INTEGRAL and VLA observations

The majority of High Mass X-ray Binaries (HMXBs) behave as X-ray pulsars, revealing that they contain a magne- tised neutron star. Among the four HMXBs not showing pulsations, and that do not show the characteristics of accreting bl ack holes, there is the unusual HMXB 4U 2206+54. Here we present contemporaneous high-energy and radio observations of this system conducted with INTEGRALand the VLA in order to unveil its nature. The high-energy spectra show clear indications of the presence of an absorption feature at∼32 keV. This is the third high-energy observatory which reveals marginal evidence of this feature, giving strong support to the existence of a cyc lotron resonance scattering feature, which implies a magnetic field of 3.6×10 12 G. On the other hand, the source is not detected at centimetre radio wavelengths with a 3σ upper limit of 0.039 mJy. The expected radio emission for an accreting black hole in the low/hard state, inferred from X-ray flux measurements, would be at least 60 times greater than the measured upper limit. Both results firmly indicate that, in spite of the absence of pul sations, 4U 2206+54 hosts a magnetic accreting neutron star, the first one not t o be observed as an X-ray pulsar.

GRB 030227: The first multiwavelength afterglow of an INTEGRAL GRB

We present multiwavelength observations of a gamma-ray burst detected byINTEGRAL (GRB 030227) between 5.3 hours and ~ 1.7days after the event. Here we report the discovery of a dim opticalafterglow (OA) that would not have been detected by many previoussearches due to its faintess (R ~ 23). This OA was seen to declinefollowing a power law decay with index alpha R = -0.95 +/-0.16. The spectral index beta_ opt/NIR yielded -1.25 +/- 0.14. Thesevalues may be explained by a relativistic expansion of a fireball (withp = 2.0) in the cooling regime. We also find evidence for inverseCompton scattering in X-rays.Based on observations with INTEGRAL, an ESA project with instruments andscience data centre funded by ESA member states (especially the PIcountries: Denmark, France, Germany, Italy, Switzerland, Spain), CzechRepublic and Poland, and with the participation of Russia and the USA.Also partially based on observations collected by the Gamma-Ray BurstCollaboration at ESO (GRACE) at the European Southern Observatory, Chile(ESO Large Programme 165.H-0464). (Less)

INTEGRAL observations of the Be/X-ray binary EXO 2030+375 during outburst

We present a type-I outburst of the high-mass X-ray binary EXO 2030+375, detected during INTEGRALs Performance and Verification phase in December 2002 (on-source time about 10 6 s). In addition, six more outbursts have been observed during INTEGRALs Galactic Plane Scans. X-ray pulsations have been detected with a pulse period of 41.691798 ± 0.000016 s. The X-ray luminosity in the 5-300keV energy range was 9.7 x 10 36 erg s -1 , for a distance of 7.1 kpc. Two unusual features were found in the light curve, with an initial peak before the main outburst and another possible spike after the maximum. RXTE observations confirm only the existence of the initial spike. Although the initial peak appears to be a recurrent feature, the physical mechanisms producing it and the possible second spike are unknown. Moreover, a four-day delay between periastron passage and the peak of the outburst is observed. We present for the first time a 5-300 keV broad-band spectrum of this source. It can be modelled by the sum of a disk black body (kT BB ∼ 8 keV) with either a power law model with r = 2.04 ± 0.11 keV or a Comptonized component (spherical geometry, kT e = 30 keV, r = 2.64, kT w = 1.5 keV).

JEM-X inflight performance

We summarize the inflight performance of JEM-X, the X-ray monitor on the INTEGRAL mission during the initial ten months of operations. The JEM-X instruments have now been tuned to stable operational conditions. The performance is found to be close to the pre-launch expectations. The ground calibrations and the inflight calibration data permit to determine the instruments characteristics to fully support the scientific data analysis.

Production rate of proton-induced isotopes in different materials

Abstract High background counting rates are the main limitation on sensitivity of satellite borne gamma-ray instrumentations. The observed background comes from different sources: cosmic diffuse, charged particles and high energetic photons. Among the different background components, that due to the activation of the telescope and satellite passive materials by cosmic protons is the most difficult component to evaluate. In the framework of background studies and sensitivity estimations for the INTEGRAL and MINISAT-01 projects, a wide range of materials has been irradiated with proton beams at different energies to identify the induced unstable isotopes and their production cross-sections. In this paper we present experimental results obtained from the analysis of such irradiation experiments. These values are compared to those obtained by means of the two frequently used prediction methods: GEANT/GCALOR Monte-Carlo code and Silberberg and Tsao semiempirical expressions.

INTEGRAL observations of the peculiar BeX System SAX J2103.5+4545

We present an INTEGRAL data analysis of the X-ray transient SAX J2103.5+4545 during two outbursts detected in December 2002. The INTEGRAL coordinates and error circle agree with the position of the recently proposed optical counterpart. A power-law plus cut-off model provided a good fit to the 4–150 keV spectrum yielding a photon index of

The RTS2 protocol

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