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| ESA SP-1296: ESA's Report to the 36th COSPAR Meeting |
Scientific editor: R. Marsden
Editor: A. Wilson
The report for the 36th COSPAR Meeting covers, as in previous issues, the missions of the Scientific Programme of ESA in the areas of astronomy, Solar System science and fundamental physics. This year's COSPAR meeting will take place only weeks before the end of the SMART-1 mission to the Moon, a technology project that provided the first European look at our natural satellite from lunar orbit.In October of this year, a new mission will be launched: COROT. ESA, together with a number of countries, is contributing to this unique, French-led project that will provide an insight into the interior of the stars, by means of the asteroseismology technique successfully applied by SOHO. COROT will also perform a systematic search for new extrasolar planets using photometric transits.
The record number of ESA Science Programme missions in operation established at the time of the last report was maintained in 2006 (Huygens having been replaced in the list by Venus Express). Eleven different missions, involving 14 operating spacecraft, are providing excellent science to the worldwide scientific community. The Research and Scientific Support Department (RSSD) is responsible for the science operations of these missions and makes every effort to ensure the best possible science return. The Department also supports the realisation of approved projects in all phases of their development. |
| Publication date: 15 Jun 2006 |
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| GRB 030406 - 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 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 GRB 030406. The burst is localized with the Compton events, and the location is consistent with the previous Interplanetary Network position. A spectral analysis is possible by detailed modeling of the detector response for such a far off-axis source with an 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 a 90% confidence level. |
| Publication date: 15 Jun 2006 |
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| INTEGRAL and XMM-Newton observations of the low-luminosity and Xray rich burst GRB 040223 |
| GRB 040223 was observed by INTEGRAL and XMM-Newton. GRB 040223 has a peak flux of (1.6+/-0.13) x10^-8 ergs cm^-2 s^-1, a fluence of (4.4+/-0.4)x10^-7 ergs cm^-2 and a steep photon power law index of -2.3+/-0.2, in the energy range 20-200 keV. The steep spectrum implies it is an x- ray rich GRB with emission up to 200 keV and E_peak < 20 keV. If E_peak is < 10 keV, it would qualify as an x-ray flash with high energy emission. The x-ray data has a spectral index beta_x = -1.7+/-0.2, a temporal decay of t^(-0.75+/-0.25) and a large column density of (1.8 x 10^22) cm^-2. The luminosity-lag relationship was used to obtain a redshift (z = 0.3+/-0.06). The isotropic energy radiated in gamma-rays and x-ray luminosity after 10 hours are factors of 1000 and 100 less than classical GRBs. GRB 040223 is consistent with the extrapolation of the Amati relation into the region that includes XRF 030723 and XRF 020903. |
| Publication date: 01 Jun 2006 |
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| The 2nd IBIS/ISGRI soft gamma-ray survey catalogue |
| In this paper we report the second soft gamma-ray source catalog obtained with the IBIS/ISGRI gamma-ray imager
on board the INTEGRAL satellite. The scientific data set is based on more than 10 Ms of high-quality observations
performed during the first 2 years of Core Program and public IBIS/ISGRI observations, and covers ~50% of the
whole sky. The main aim of the first survey was to scan systematically, for the first time at energies above 20 keV, the
whole Galactic plane to achieve a limiting sensitivity of ~1 mcrab in the central radian. The target of the second year
of the INTEGRAL mission lifetime was to expand as much as possible our knowledge of the soft gamma-ray sky, with
the same limiting sensitivity, to at least 50% of the whole sky, mainly by including a substantial coverage of extragalactic
fields. This catalog comprises more than 200 high-energy sources detected in the energy range 20-100 keV,
including new transients not active during the first year of operation, faint persistent objects revealed with longer
exposure time, and several Galactic and extragalactic sources in sky regions not observed in the first survey. The mean
position error for all the sources detected with significance above 10 sigma is ~40", enough to identify most of them with a
known X-ray counterpart and to unveil the nature of most of the strongly absorbed ones, even though they are very
difficult to detect in X-rays.
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| Publication date: 10 Jan 2006 |
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| Radioactive 26Al from massive stars in the Galaxy |
| Gamma-rays from radioactive 26Al (half-life ,7.2 x 105 years)
provide a 'snapshot' view of continuing nucleosynthesis in the
Galaxy. The Galaxy is relatively transparent to such gamma-rays, and
emission has been found concentrated along its plane. This led
to the conclusion1 that massive stars throughout the Galaxy
dominate the production of 26Al. On the other hand, meteoritic
data show evidence for locally produced 26Al, perhaps from
spallation reactions in the protosolar disk. Furthermore, prominent
gamma-ray emission from the Cygnus region suggests that a
substantial fraction of Galactic 26Al could originate in localized
star-forming regions. Here we report high spectral resolution
measurements of 26Al emission at 1808.65 keV, which demonstrate
that the 26Al source regions corotate with the Galaxy, supporting
its Galaxy-wide origin. We determine a present-day equilibrium
mass of 2.8 (±0.8) solar masses of 26Al. We use this to determine
that the frequency of core collapse (that is, type Ib/c and type II)
supernovae is 1.9 (±1.1) events per century. |
| Publication date: 05 Jan 2006 |
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| Two years of INTEGRAL monitoring of the Soft Gamma-Ray repeater SGR 1806-20, from quiescence to frenzy |
| SGR 1806-20 has been observed for more than 2 years with the INTEGRAL satellite. In this period
the source went from a quiescent state into a very active one culminating in a giant flare on December 27 2004. Here we report on the properties of all the short bursts detected with INTEGRAL before the giant flare. We derive their number-intensity distribution and confirm the hardness-intensity correlation for the bursts found by Götz et al. (2004a). Our sample includes a very bright outburst that occurred on October 5 2004, during which over one hundred bursts were emitted in 10 minutes, involving an energy release of 3x1042 erg. We present a
detailed analysis of it and discuss our results in the framework of the magnetar model. |
| Publication date: 15 Dec 2005 |
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| ISOC Newsletter #15 |
Contents
- Foreword
- 4th Announcement of Opportunity (AO-4)
- The INTEGRAL Users Group
- INTEGRAL Mission Status
- Science Highlights
- Galactic Bulge Monitoring Program
- Science Operations - Highlights
- The ISOC Science Data Archive
- The 6th INTEGRAL workshop
- Outreach
- ISOC now at ESAC
- Contact INTEGRAL science operations
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| Publication date: 15 Nov 2005 |
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| Resolving the hard X-ray emission of GX 5-1 with INTEGRAL |
| We present the study of one year of INTEGRAL data on the neutron star low mass X-ray binary GX 5-1. Thanks to the excellent angular
resolution and sensitivity of INTEGRAL, we are able to obtain a high quality spectrum of GX 5-1 from ~5 keV to ~100 keV, for the first time
without contamination from the nearby black hole candidate GRS 1758-258 above 20 keV. During our observations, GX 5-1 was mostly found
in the horizontal and normal branch of its hardness intensity diagram. A clear hard X-ray emission is observed above ~30 keV which exceeds the
exponential cut-off spectrum expected from lower energies. This spectral flattening may have the same origin of the hard components observed
in other Z sources as it shares the property of being characteristic to the horizontal branch. The hard excess is explained by introducing
Compton up-scattering of soft photons from the neutron star surface due to a thin hot plasma expected in the boundary layer. The spectral
changes of GX 5-1 downward along the 'Z' pattern in the hardness intensity diagram can be well described in terms of monotonical decrease
of the neutron star surface temperature. This may be a consequence of the gradual expansion of the boundary layer as the mass accretion rate
increases. |
| Publication date: 01 Nov 2005 |
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| Scientific highlights from INTEGRAL |
| In proceeding of "Workshop Astronomy with Radioactivities V", Clemson SC, USA, Sep 5-9 2005, Editors R. Diehl, D. Hartmann, E. Zinner, in New Reviews in Astronomy, Elsevier
The gamma-ray observatory INTEGRAL was launched in October 2002 and produces since then a wealth of discoveries and important new results. I will present a selection of scientific highlights obtained during the first 2.5 years of the mission. |
| Publication date: 05 Sep 2005 |
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| A Persistent High-Energy Flux from the Heart of the Milky Way : Integral's view of the Galactic Center |
| The IBIS/ISGRI imager on Integral detected for the first time a hard X-ray source, IGR J17456-2901, located within 1' of Sgr A* over the energy range 20-100 keV. Here we present the results of a detailed analysis of ~7x106s of Integral observations of the Galactic Centre. With an effective exposure of 4.7x106s we have obtained more stringent positional constraints on this high-energy (HE) source and constructed its spectrum in the range 20-400 keV. Furthermore, by combining the Isgri spectrum with the total X-ray spectrum corresponding to the same physical region around SgrA* from XMM data, and collected during part of the Integral observations, we constructed and present the first accurate wide band HE spectrum for the central arcmins of the Galaxy. Our complete analysis of the emission properties of IGR shows that it is faint but persistent with no variability above 3 sigma contrary to what was alluded to in our first paper. This result, in conjunction with the spectral characteristics of the X-ray emission from this region, suggests that the source is most likely not point-like but, rather, that it is a compact, yet diffuse, non-thermal emission region. The centroid of IGR is estimated to be R.A.=17h45m42.5s, decl.=-28°59'28'', offset by 1' from the radio position of Sgr A* and with a positional uncertainty of 1'. Its 20-400 keV luminosity at 8 kpc is L=5.4x1035 erg/sec. Very recently, Hess detected of a source of ~TeV gamma-rays also located within 1' of Sgr A*. We present arguments in favor of an interpretation according to which the photons detected by Integral and Hess arise from the same compact region of diffuse emission near the central black hole and that the supernova remnant Sgr A East could play an important role as a contributor of very HE gamma-rays to the overall spectrum from this region. |
| Publication date: 04 Aug 2005 |
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| 26Al production in gamma-2 Velorum |
The closest Wolf-Rayet star, WR 11 in the binary system 2 Velorum, is the only star for
which the spectral signature of the 26Al produced in its core is expected to be detectable with current gamma-ray instruments, through the 1.8 MeV decay of that radioactive nucleus.
We present here the current status of both model predictions, from calculations of
massive star evolution including rotation of stellar interior, and from data on 2 Velorum
obtained by the ESA's gamma-ray satellite INTEGRAL over the first year of its mission. |
| Publication date: 25 Jul 2005 |
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| INTEGRAL spectroscopy of the accreting millisecond pulsar XTE J1807-294 in outburst |
| The transient X-ray accreting millisecond pulsar XTE J1807-294 was observed during its February/March 2003 outburst by INTEGRAL, partly simultaneously with the XMM-Newton and RXTE satellites. We present here the first study of the 0.5-200 keV broad-band spectra of the source. On February 28, the source spectrum was consistent with thermal Comptonization by electrons of temperature ~40 keV, considerably higher than the value (~10 keV) previously derived from the low energy XMM-Newton data alone. The source is detected by INTEGRAL up to 200 keV with a luminosity in the energy band (0.1-200) keV of 1.3 x 1037 erg s-1 (assuming a distance of 8 kpc). 22 days later the luminosity dropped to 3.6 x 1036 erg s-1. A re-analysis of XMM-Newton data yields the orbital Doppler variations of the pulse period and refines the previous ephemeris. For this source, with shortest orbital period of any known binary radio or X-ray millisecond pulsar, we constrain the companion mass MC < 0.022~MSun, assuming minimum mass transfer driven by gravitational radiation. Only evolved dwarfs with a C/O composition are consistent with the Roche lobe and gravitational radiation constraints, while He dwarfs require an unlikely low inclination. |
| Publication date: 15 Jun 2005 |
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| Extragalactic Source Counts in the 20-50 keV Energy Band from the Deep Observation of the Coma Region by INTEGRAL IBIS |
| We present the analysis of serendipitous sources in a deep, 500 ks, hard X-ray observation of the Coma Cluster region with the IBIS instrument on board INTEGRAL. In addition to the Coma Cluster, the final 20-50 keV image contains 12 serendipitous sources with statistical significance >4 sigma. We use these data (after correcting for expected number of false detections) to extend the extragalactic source counts in the 20-50 keV energy band down to a limiting flux of 1.0x10-11 ergs s-1 cm-2 (~=1 mcrab). This is a more than a factor of 10 improvement in sensitivity compared to the previous results in this energy band obtained with the HEAO 1 A-4 instrument. The derived source counts are consistent with the Euclidean relation N(>f)~f-3/2. A large fraction of identified serendipitous sources are low-redshift, z<0.02, active galactic nuclei (AGNs), mostly of Seyfert 1 type. The surface density of hard X-ray sources is (1.4+/-0.5)x10-2 deg-2 above a flux threshold of 10-11 ergs s-1 cm-2. These sources directly account for ~3% of the cosmic X-ray background in the 20-50 keV energy band. Given the low redshift depth of our sample, we expect that similar sources at higher redshifts account for a significant fraction of the hard X-ray background. Our field covers only 3% of the sky; a systematic analysis of other extragalactic INTEGRAL observations can produce much larger source samples and is, therefore, critically important. |
| Publication date: 20 May 2005 |
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| A link between prompt optical and prompt gamma-ray emission in gamma-ray bursts |
| The prompt optical emission that arrives with the gamma-rays from a cosmic gamma-ray burst (GRB) is a signature of the engine powering the burst, the properties of the ultra-relativistic ejecta of the explosion, and the ejecta's interactions with the surroundings. Until now, only GRB 990123 had been detected at optical wavelengths during the burst phase. Its prompt optical emission was variable and uncorrelated with the prompt gamma-ray emission, suggesting that the optical emission was generated by a reverse shock arising from the ejecta's collision with surrounding material. Here we report prompt optical emission from GRB 041219a. It is variable and correlated with the prompt gamma-rays, indicating a common origin for the optical light and the gamma-rays. Within the context of the standard fireball model of GRBs, we attribute this new optical component to internal shocks driven into the burst ejecta by variations of the inner engine. The correlated optical emission is a direct probe of the jet isolated from the medium. The timing of the uncorrelated optical emission is strongly dependent on the nature of the medium. |
| Publication date: 12 May 2005 |
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| An infrared flash contemporaneous with the gamma-rays of GRB 041219a |
| The explosion that results in a cosmic gamma-ray burst (GRB) is thought to produce emission from two physical processes: the central engine gives rise to the high-energy emission of the burst through internal shocking, and the subsequent interaction of the flow with the external environment produces long-wavelength afterglows. Although observations of afterglows continue to refine our understanding of GRB progenitors and relativistic shocks, gamma-ray observations alone have not yielded a clear picture of the origin of the prompt emission nor details of the central engine. Only one concurrent visible-light transient has been found and it was associated with emission from an external shock. Here we report the discovery of infrared emission contemporaneous with a GRB, beginning 7.2 minutes after the onset of GRB 041219a. We acquired 21 images during the active phase of the burst, yielding early multi-colour observations. Our analysis of the initial infrared pulse suggests an origin consistent with internal shocks.
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| Publication date: 12 May 2005 |
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| Detection of gamma-ray lines from interstellar 60Fe by the high resolution spectrometer SPI |
| It is believed that core-collapse supernovae (CCSN), occurring at a rate ~once per century, have seeded the interstellar medium with long-lived radioisotopes such as 60Fe (half-life 1.5 Myr), which can be detected by the gamma-rays emitted when they beta-decay. Here we report the detection of the 60Fe decay lines at 1173 keV and 1333 keV with fluxes 3.7 ± 1.1 × 10-5 photons cm-2 s-1 per line, in spectra taken by the SPI spectrometer on board INTEGRAL during its first year. The same analysis applied to the 1809 keV line of 26Al yielded a line flux ratio 60Fe/26Al = 0.11 ± 0.03. This supports the hypothesis that there is an extra source of 26Al in addition to CCSN. |
| Publication date: 01 Apr 2005 |
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| GRB 040403: A faint X-ray rich gamma-ray burst discovered by INTEGRAL |
| GRB 040403 is one of the faintest gamma-ray bursts for which a rapid and accurate localization has been obtained. Here we report on the gamma-ray properties of this burst, based on observations with the IBIS instrument aboard INTEGRAL, and the results of searches for its optical afterglow. The steep spectrum (power law photon index = 1.9 in the 20-200 keV range) implies that GRB 040403 is most likely an X-ray rich burst. Our optical limit of R > 24.2 at 16.5 h after the burst, indicates a rather faint afterglow, similar to those seen in other relatively soft and faint bursts. |
| Publication date: 01 Apr 2005 |
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| INTEGRAL discovery of persistent hard X-ray emission from the Soft Gamma-ray Repeater SGR 1806-20* |
| We report the discovery of persistent hard X-ray emission extending up to 150 keV from the soft gamma-ray repeater SGR 1806-20 using data obtained with the INTEGRAL satellite in 2003-2004. Previous observations of hard X-rays from objects of this class were limited to short duration bursts and rare transient episodes of strongly enhanced luminosity ("flares''). The emission observed with the IBIS instrument above 20 keV has a power law spectrum with photon index in the range 1.5-1.9 and a flux of 3 milliCrabs, corresponding to a 20-100 keV luminosity of ~1036 erg s-1 (for a distance of 15 kpc). The spectral hardness and the luminosity correlate with the level of source activity as measured from the number of emitted bursts. |
| Publication date: 01 Apr 2005 |
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| A New Population of Very High Energy Gamma-Ray Sources in the Milky Way |
| Very high energy gamma-rays probe the long-standing mystery of the origin of cosmic rays. Produced in the interactions of accelerated particles in astrophysical objects, they can be used to image cosmic particle accelerators. A first sensitive survey of the inner part of the Milky Way with the High Energy Stereoscopic System (HESS) reveals a population of eight previously unknown firmly detected sources of very high energy gamma-rays. At least two have no known radio or x-ray counterpart and may be representative of a new class of "dark" nucleonic cosmic ray sources. |
| Publication date: 25 Mar 2005 |
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| INTEGRAL SPI Limits on Electron-Positron Annihilation Radiation from the Galactic Plane |
| The center of our Galaxy is a known strong source of electron-positron 511 keV annihilation radiation. Thus far, however, there have been no reliable detections of annihilation radiation outside of the central radian of our Galaxy. One of the primary objectives of the INTEGRAL (International Gamma-Ray Astrophysics Laboratory) mission, launched in 2002 October, is the detailed study of this radiation. The Spectrometer on INTEGRAL (SPI) is a high-resolution, coded-aperture gamma-ray telescope with an unprecedented combination of sensitivity, angular resolution, and energy resolution. We report results from the first 10 months of observation. During this period a significant fraction of the observing time was spent in or near the Galactic plane. No positive annihilation flux was detected outside of the central region (|l|>40°) of our Galaxy. In this paper we describe the observations and data analysis methods and give limits on the 511 keV flux. |
| Publication date: 01 Mar 2005 |
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