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

Polarization of the Crab pulsar and nebula as observed by the Integral/IBIS telescope

15 pages, 2 figuresInternational audienceNeutron stars generate powerful winds of relativistic particles that form bright synchrotron nebulae around them. Polarimetry provides a unique insight into the geometry and magnetic configuration of the wind, but high-energy measurements have failed until recently. The Integral-IBIS telescope has been used in its Compton mode to search for linearly polarized emission for energies above 200 keV from the Crab nebula. The asymmetries in the instrument response are small and we obtain evidences for a strongly polarized signal at an angle parallel to the pulsar rotation axis. This result confirms the detection recently reported by Dean et al. (2008), and extends the polarization measure for all the pulsar's phases. The hard X-ray/soft $\gamma$-ray observations therefore probe the inner jets or equatorial flow of the wind. The achieved sensitivity opens a new window for polarimetric studies at energies above 200 keV

Spatially resolved XMM-Newton analysis and a model of the nonthermal emission of MSH 15-52

We present an X-ray analysis and a model of the nonthermal emission of the pulsar wind nebula (PWN) MSH15-52. We analyzed XMM-Newton data to obtain the spatially resolved spectral parameters around the pulsar PSRB1509-58. A steepening of the fitted power-law spectra and decrease in the surface brightness is observed with increasing distance from the pulsar. In the second part of this paper, we introduce a model for the nonthermal emission, based on assuming the ideal magnetohydrodynamic limit. This model is used to constrain the parameters of the termination shock and the bulk velocity of the leptons in the PWN. Our model is able to reproduce the spatial variation of the X-ray spectra. The parameter ranges that we found agree well with the parameter estimates found by other authors with different approaches. In the last part of this paper, we calculate the inverse Compton emission from our model and compare it to the emission detected with the H.E.S.S. telescope system. Our model is able to reproduce the flux level observed with H.E.S.S., but not the spectral shape of the observed TeV {\gamma}-ray emission.Comment: Accepted for publication in A&A, 9 pages, 15 figure

INTEGRAL observations of TeV plerions

Amongst the sources seen in very high gamma-rays several are associated with Pulsar Wind Nebulae (``TeV plerions''). The study of hard X-ray/soft gamma-ray emission is providing an important insight into the energetic particle population present in these objects. The unpulsed emission from pulsar/pulsar wind nebula systems in the energy range accessible to the INTEGRAL satellite is mainly synchrotron emission from energetic and fast cooling electrons close to their acceleration site. Our analyses of public INTEGRAL data of known TeV plerions detected by ground based Cherenkov telescopes indicate a deeper link between these TeV plerions and INTEGRAL detected pulsar wind nebulae. The newly discovered TeV plerion in the northern wing of the Kookaburra region (G313.3+0.6 powered by the middle aged PSR J1420-6048) is found to have a previously unknown INTEGRAL counterpart which is besides the Vela pulsar the only middle aged pulsar detected with INTEGRAL. We do not find an INTEGRAL counterpart of the TeV plerion associated with the X-ray PWN ``Rabbit'' G313.3+0.1 which is possibly powered by a young pulsar.Comment: 4 pages, 6 figures, proceedings of conference "The Multi-Messenger Approach to High-Energy Gamma-ray Sources" Barcelona/Spain (2006

INTEGRAL long-term monitoring of the Supergiant Fast X-ray Transient XTE J1739-302

In the past few years, a new class of High Mass X-Ray Binaries (HMXRB) has been claimed to exist, the Supergiant Fast X-ray Transients (SFXT). These are X-ray binary systems with a compact companion orbiting a supergiant star which show very short and bright outbursts in a series of activity periods overimposed on longer quiescent periods. Only very recently the first attempts to model the behaviour of these sources have been published, some of them within the framework of accretion from clumpy stellar winds.Our goal is to analyze the properties of XTE J1739-302/IGR J17391-3021 within the context of the clumpy structure of the supergiant wind. We have used INTEGRAL and RXTE/PCA observations in order to obtain broad band (1-200 keV) spectra and light curves of XTE J1739-302 and investigate its X-ray spectrum and temporal variability. We have found that XTE J1739-302 follows a much more complex behaviour than expected. Far from presenting a regular variability pattern, XTE J1739-302 shows periods of high, intermediate, and low flaring activity.Comment: 9 pages, 7 figures, accepted for publication in A&

A Model of Polarized X-ray Emission from Twinkling Synchrotron Supernova Shells

Synchrotron X-ray emission components were recently detected in many young supernova remnants (SNRs). There is even an emerging class - SN1006, RXJ1713.72-3946, Vela Jr, and others - that is dominated by non-thermal emission in X-rays, also probably of synchrotron origin. Such emission results from electrons/positrons accelerated well above TeV energies in the spectral cut-off regime. In the case of diffusive shock acceleration, which is the most promising acceleration mechanism in SNRs, very strong magnetic fluctuations with amplitudes well above the mean magnetic field must be present. Starting from such a fluctuating field, we have simulated images of polarized X-ray emission of SNR shells and show that these are highly clumpy with high polarizations up to 50%. Another distinct characteristic of this emission is the strong intermittency, resulting from the fluctuating field amplifications. The details of this "twinkling" polarized X-ray emission of SNRs depend strongly on the magnetic-field fluctuation spectra, providing a potentially sensitive diagnostic tool. We demonstrate that the predicted characteristics can be studied with instruments that are currently being considered. These can give unique information on magnetic-field characteristics and high-energy particle acceleration in SNRs.Comment: 7 pages, 8 figures, MNRAS (in press

Optical polarisation of the Crab pulsar: precision measurements and comparison to the radio emission

The linear polarisation of the Crab pulsar and its close environment was derived from observations with the high-speed photo-polarimeter OPTIMA at the 2.56-m Nordic Optical Telescope in the optical spectral range (400 - 750 nm). Time resolution as short as 11 microseconds, which corresponds to a phase interval of 1/3000 of the pulsar rotation, and high statistics allow the derivation of polarisation details never achieved before. The degree of optical polarisation and the position angle correlate in surprising details with the light curves at optical wavelengths and at radio frequencies of 610 and 1400 MHz. Our observations show that there exists a subtle connection between presumed non-coherent (optical) and coherent (radio) emissions. This finding supports previously detected correlations between the optical intensity of the Crab and the occurrence of giant radio pulses. Interpretation of our observations require more elaborate theoretical models than those currently available in the literature.Comment: 21 pages, 13 figures, uses AMS.sty, mn2e.cls, mn2e.bst and natbib.sty, submitted to MNRA

Detection of the energetic pulsar PSR B1509-58 and its pulsar wind nebula in MSH 15-52 using the Fermi-Large Area Telescope

We report the detection of high energy gamma-ray emission from the young and energetic pulsar PSR B1509$-$58 and its pulsar wind nebula (PWN) in the composite supernova remnant SNR G320.4-1.2 (aka MSH 15-52). Using 1 year of survey data with the Fermi-Large Area Telescope (LAT), we detected pulsations from PSR B1509-58 up to 1 GeV and extended gamma-ray emission above 1 GeV spatially coincident with the PWN. The pulsar light curve presents two peaks offset from the radio peak by phases 0.96 $\pm$ 0.01 and 0.33 $\pm$ 0.02. New constraining upper limits on the pulsar emission are derived below 1 GeV and confirm a severe spectral break at a few tens of MeV. The nebular spectrum in the 1 - 100 GeV energy range is well described by a power-law with a spectral index of (1.57 $\pm$ 0.17 $\pm$ 0.13) and a flux above 1 GeV of (2.91 $\pm$ 0.79 $\pm$ 1.35) 10^{-9} cm^{-2} s^{-1}. The first errors represent the statistical errors on the fit parameters, while the second ones are the systematic uncertainties. The LAT spectrum of the nebula connects nicely with Cherenkov observations, and indicates a spectral break between GeV and TeV energies.Comment: 14 pages, 6 figures, accepted for publication by Ap

A pair production telescope for medium-energy gamma-ray polarimetry

We describe the science motivation and development of a pair production telescope for medium-energy (∼5–200 MeV) gamma-ray polarimetry. Our instrument concept, the Advanced Energetic Pair Telescope (AdEPT), takes advantage of the Three-Dimensional Track Imager, a low-density gaseous time projection chamber, to achieve angular resolution within a factor of two of the pair production kinematics limit (∼0.6° at 70 MeV), continuum sensitivity comparable with the Fermi-LAT front detector (<3 × 10−6 MeV cm−2 s−1 at 70 MeV), and minimum detectable polarization less than 10% for a 10 mCrab source in 106 s.submittedVersionFil: Hunter, Stanley D. National Aeronautics and Space Administration. Goddard Space Flight Center; Estados Unidos de América.Fil: Bloser, Peter F. University of New Hampshire. Institute for the Study of Earth, Oceans, and Space. Space Science Center; Estados Unidos de América.Fil: Depaola, Gerardo Osvaldo. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.Fil: Dion, Michael P. Department of Energy. Office of Science. Pacific Northwest National Laboratory; Estados Unidos de América.Fil: DeNolfo, Georgia A. National Aeronautics and Space Administration. Goddard Space Flight Center; Estados Unidos de América.Fil: Hanu, Andrei. National Aeronautics and Space Administration. Goddard Space Flight Center; Estados Unidos de América.Fil: Iparraguirre, Lorenzo Marcos. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.Fil: Legere, Jason. University of New Hampshire. Institute for the Study of Earth, Oceans, and Space. Space Science Center; Estados Unidos de América.Fil: Longo, Francesco. Università Degli Studi de Trieste. Dipartimento di fisica; Italia.Fil: McConnell, Mark L. University of New Hampshire. Institute for the Study of Earth, Oceans, and Space. Space Science Center; Estados Unidos de América.Fil: Nowicki, Suzanne F. National Aeronautics and Space Administration. Goddard Space Flight Center; Estados Unidos de América.Fil: Nowicki, Suzanne F. University of Maryland, Baltimore County. Department of Physics; Estados Unidos de América.Fil: Ryan, James M. University of New Hampshire. Institute for the Study of Earth, Oceans, and Space. Space Science Center; Estados Unidos de América.Fil: Son, Seunghee. National Aeronautics and Space Administration. Goddard Space Flight Center; Estados Unidos de América.Fil: Son, Seunghee. University of Maryland, Baltimore County. Department of Physics; Estados Unidos de América.Fil: Stecker, Floyd W. National Aeronautics and Space Administration. Goddard Space Flight Center; Estados Unidos de América.Física de Partículas y Campo

Scientific Prospects for Hard X-ray Polarimetry

X-ray polarimetry promises to give qualitatively new information about high-energy sources. Examples of interesting source classes are binary black hole systems, rotation and accretion powered neutron stars, Microquasars, Active Galactic Nuclei and Gamma-Ray Bursts. Furthermore, X-ray polarimetry affords the possibility for testing fundamental physics, e.g. to observe signatures of light bending in the strong gravitational field of a black hole, to detect third order Quantum Electrodynamic effects in the magnetosphere of Magnetars, and to perform sensitive tests of Lorentz Invariance. In this paper we discuss scientific drivers of hard (>10 keV) X-ray polarimetry emphasizing how observations in the hard band can complement observations at lower energies (0.1 - 10 keV). Subsequently, we describe four different technical realizations of hard X-ray polarimeters suitable for small to medium sized space borne missions, and study their performance in the signal-dominated case based on Monte Carlo simulations. We end with confronting the instrument requirements for accomplishing the science goals with the capabilities of the four polarimeters.Comment: Accepted for publication in Astroparticle Physic