 INTEGRAL Offline Scientific Analysis 9 |
 INTEGRAL in HEAVENS |
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INTEGRAL Offline Scientific Analysis 9 |
INTEGRAL in HEAVENS |
| INTEGRAL Off-line Scientific Analysis version 9 |
The INTEGRAL Off-line Scientific Analysis (OSA) software package provides tools to analyse data from the four INTEGRAL instruments - IBIS, SPI, JEMX and OMC - and some generic tools.
OSA version 9.0 provides crucial improvements of the ISGRI imaging software, decreasing the systematics in the image reconstruction by a factor of about 10.
OSA runs on Linux and Mac OS X Intel platforms and is provided in binary and source format, together with documentation, calibration files and catalogues.
OSA 9 improves very significantly the quality of the results of the ISGRI image, lightcurve and spectral analysis by taking into account the effect of bright sources when subtracting the background and cleaning the ghost images. These improvements are particularly important for the analysis of faint sources when many Ms of data need to be combined together. The effective exposure time at which systematics are becoming a problem has more than doubled.
ISGRI images around bright sources were affected by systematics at the level of a few percent of the count rate of the brightest source. These systematics come from an imperfect modeling of the instrument and limit the capability to clean ghost images and result in an effective loss of sensitivity (or usable exposure time) in the areas of the sky within 10 degrees of bright sources.
Thanks to an extensive in-flight calibration effort, the source of these artifacts became clearer. The main problem is likely coming from the glue applied between the coded mask elements and the NOMEX supporting structure. A small amount of that glue leaked in some open elements of the mask during the manufacturing process and is absorbing hard X-rays efficiently at low energy. This additional absorption is not yet included in the mask model.
Fortunately most of the effects concentrate on some specific areas of the mask. When a bright source illuminates the detector through the mask, only a small fraction of the detector pixels will be affected by the glue. OSA 9 includes a new executable to filter out these pixels before performing the analysis. This is enough to decrease the systematics by a factor of almost 10.
This filtering executable uses a catalogue of bright sources. This catalogue should not be unnecessarily large to avoid filtering out too many pixels. The bright source catalogue provided with OSA, used by default, produces good results in most cases.
The picture highlights the improvement of the image quality for a field centered on the black-hole candidate Cygnus X-1 (left panel). The circular structures (middle panel) in the background are artifacts. Their intensity is of the order of 0.2% of that of the brightest source in the field of view. The filtering software reduces these artifacts by a factor of 10 (right panel). In the latter image, new faint hard X-ray sources could be detected for the first time. The source in the green circle is two thousands times fainter than Cygnus X-1.
During the analysis background images are subtracted from ISGRI detector images. These images are normalized using the observed data to account for background variability. As the derived background normalization could be affected by the presence a strong source is in the FOV, the background subtraction software now uses a bright source catalogue to exclude pixels illuminated by these sources from the background normalization determination. A default catalogue is provided.
The bright source catalogues mentioned above for the source cleaning and background normalization are derived from the ISDC reference catalogue using specific selection flags. The meaning of these flags is explained on ISDC Source Catalogues web page and can be modified manually e.g. if a bright transient appears in the field of view during an observation. This catalogue information will be taken into account by the analysis only for specific source search modes (SearchMode=1|3).
OSA9 has also been modified to use uniformity gain maps for the ISGRI pixels. These maps are being calibrated and should be provided as calibration files in the future. Finally three new ISGRI ancillary response files are provided to cover the latest observation periods.
The main improvements come from the introduction of updated calibration files.
The pipeline scripts have been corrected for marginal bugs in the parameter handling and the user is now given the opportunity to have the flat-field template automatically selected, based on temporal proximity.
No new functionality has been added. Stability of the software has been improved in several places. This is visible in particular in the imaging step when performing analyses with very narrow energy bins and/or very short time intervals, leading to shadowgrams with few or even zero counts. Documentation has also been consolidated.
The source detection algorithm in the imaging step has been improved, so that it does not stop anymore after the first rejected detection (which usually occurs in the edges of the image, which are the noisiest parts). As a result, the imaging step is now able to recover all significant sources in the field of view.
The most important change in OSA 9 is the correction of a bug that made the gain correction only partially used in some recent revolutions. This could generate spurious effects in the flux determination in some cases. It is advised to check any unexpected OSA 8 result that makes uses of data in revolution beyond ~700 by performing an identical OSA 9 analysis.
| INTEGRAL in HEAVENS |
High-energy astrophysics space missions have pioneered and demonstrated the power of legacy data sets for generating new discoveries, especially when analysed in ways the original researchers could not have anticipated.
HEAVENS query parameters. Besides the source name or position the selected products could be generated for specific time interval, energy band and time binning.
The new HEAVENS interface provides on-the fly analysis services for a number of instruments. These services are designed to produce straightforwardly high-level scientific products for any sky position, time and energy intervals without requiring mission specific software or detailed instrumental knowledge.
A first version of HEAVENS is released today providing on-the fly analysis of INTEGRAL ISGRI and JEM-X data with OSA9. About 30% of the ISGRI data and 10% of the JEM-X data are accessible, the complete public archive will be accessible through HEAVENS by the end of May 2010. The scientific products are state of the art and of publication quality. Average PICSIT and SPI spectra are also provided for the brightest sources.
HEAVENS results for a specific source are displayed per instrument. Source images, lightcurves and spectra, generated on-the-fly, can be visualized and downloaded in various formats.
Source lightcurves can be visualized, zoomed, rebinned on-the-fly and can be obtained in ASCII or FITS formats. Here the extraordinary variability of Vela X-1 is probing the stellar wind structure.
Using HEAVENS is straightforward: just select a source or a position in the sky, a time interval, energy band and time binning, the corresponding sky images, spectra and lightcurves will be generated on the fly within few tens of seconds and available in graphical, ASCII or FITS format ready to be used with ds9, xspec or many other software packages. HEAVENS products are also available in the Virtual Observatory, however withe less flexibility.
A second release of HEAVENS will occur by the end of June 2010 providing similar interfaces to OMC, SPI-ACS and IREM results, plus a few more instruments and some new analysis capabilities.
| INTEGRAL Archive revision 3 |
The ISDC is preparing the third revision of the complete INTEGRAL archive, regenerated starting from INTEGRAL telemetry, including a much improved time correlation and the improved data selection and calibrations used in OSA9.
The time correlation includes all published corrections and fixes many other problems discovered in the past years. Users of the archive revision 3 are not expected to further correct their data for any known mission specific timing effect.
The new INTEGRAL archive will be freely accessible through anonymous ftp or through W3Browse at the end of May 2010. High level products are accessible through the HEAVENS interface.
| Other news and announcements |
Since astroparticle physics is a young domain developing very dynamically, new research structures are required to support it. The Rectorate of the University of Geneva recently approved the creation of the Center for Astroparticle Physics, CAP Genève. Its purpose is to federate local expertise in observational and theoretical cosmology, particle physics and high energy astrophysics.
CAP Genève will create a forum where participating groups can enhance their scientific dialogue, find new fields of collaboration and thus liberate synergies. Its initial research subjects will include dark matter and energy, physics of supernovae, GRB and black holes, gravitational waves, CMB and large scale structure formation. It will also regroup local competence in instrument definition, design and construction as well as data analysis. Research groups from ISDC, DPT and DPNC of University of Geneva will initially form the nucleus of CAP Genève, joint by two additional professors appointed in the near future. CAP Genève will be open to all interested scientists in the Lake Geneva area and collaborate closely with colleagues at University of Geneva, CERN, EPF Lausanne and LAPP Annecy.
The Cherenkov Telescope Array (CTA) is an international project conducted by many countries worldwide.
With its unprecedented energy coverage and sensitivity, it will uncover the Universe in the most extreme window of the electromagnetic spectrum: the very high energy gamma-rays. Such energetic photons are emitted by the annihilation or disintegration of particles and from the acceleration of electrons, positrons and atomic nuclei in the most extreme sources of the Universe.
The ISDC is seeking a high-energy physicist/software engineer for its growing team working on the CTA project. The successful candidate will be responsible for the design and early implementation of the on-site real-time data acquisition system for the CTA telescopes and will participate in the development of the infrastructure for the CTA data analysis. The selected candidate will as well strengthen the System Administration team at the ISDC.
More details on the position and the related responsibilities and tasks can be found here.
Euclid is a candidate Class "M" mission of the European Space Agency in the Cosmic Vision programme. The goal of Euclid is to perform an extremely deep imaging all-sky survey with very high spatial resolution in the optical and near-infrared, and to acquire spectra for a large subset of the objects. This unprecedented survey will allow very significant progress in the understanding of our Universe, by combining several cosmological probes, in particular the cosmic shear. Because of the huge size and tremendous complexity of the cosmological data set, the Euclid ground segment presents some unprecedented data analysis challenges, making it of direct interest to the ISDC. The ISDC has participated to the Euclid ground segment in the assessment phase and is very interested in pursuing its participation at a significant level in the subsequent phases in both the science and data analysis aspects.
A collaboration has been established at the Swiss level to develop the scientific and data analysis instruments that will be required for the successful exploitation of the Euclid data set (a so-called Sinergia program). As part of this collaboration, a post-doc position has been opened at ISDC. The candidate will work on the definition of the science requirements of the Euclid ground segment. In addition, the candidate is expected to conduct an active research program in observational cosmology.
POLAR is a detector concept to measure GRB polarization.
In December 2009, one module of POLAR (the full POLAR instrument will consists of 25 identical modules) was exposed to polarized photons in the Grenoble synchrotron light source facility (ESRF).
The module design was close to final concerning mechanics, but the data were read with laboratory electronic and a discrete trigger system. The energy of the beam was selected between 50 and 511 keV.
Photons from a synchrotron source are naturally 100% linearly polarized in the plane of the machine, which is perfect for measuring properties of polarimeters.
In a week, we collected more then 8 million events. The goal was to prove the concept of the polarization measurement by using asymmetry of the Compton scattering direction and to compare the measurements with GEANT 4 Monte-Carlo simulations. The concept was seen to work already during data acquisition. Fine comparison with Monte-Carlo are being analyzed right now. The results will be published this year.
We plan to perform further test beam measurements this year with lower energy photons and using multiple modules. The aim will be to check the final electronic performance and the trigger strategy.
INTEGRAL has shown the importance of an observatory with capabilities from the medium to the hard X-rays. To improve hard X-ray sensitivity two orders of magnitude beyond what INTEGRAL can do, however, requires a change in technology, namely the ability to focus hard X-rays.
The Japanese ASTRO-H mission, which is scheduled to be launched early 2014, will be an observatory with such capability.
It will also include three other instruments extending the energy range from the soft X-ray band to the soft gamma-ray band. One of these instruments will be the first operational micro-calorimeter on a satellite, the Soft X-ray Spectrometer (SXS). ASTRO-H is extremely important for many of the science topics that are studied at ISDC. We therefore took the opportunity offered to us to participate to this mission.
Together with SRON, the ISDC is co-responsible for the development of a filter wheel and calibration source system for the SXS.
We started a Phase B preliminary design early 2009. Mid-April 2010 the ASTRO-H filter wheel subsystem passed successfully the Preliminary Design Review, marking the end of Phase B. The development of the filter wheel will continue in phase C/D, with a goal of delivering the flight model to JAXA by the end of 2012.
Gaia is an ambitious mission of the European Space Agency. Gaia will chart a three-dimensional map of our Galaxy, the Milky Way, in the process revealing the composition, formation and evolution of the Galaxy. Gaia will provide unprecedented positional and radial velocity measurements with the accuracies needed to produce a stereoscopic and kinematic census of about one billion stars in our Galaxy and throughout the Local Group. This amounts to about 1 per cent of the Galactic stellar population.
With Gaia's launch set for 2012 the consortium for the on ground data processing (DPAC) is now preparing an extensive end-to-end test campaign. This will be the first time in the existence of the DPAC that data will be processed and exchanged between all six data processing centers. Over a period of one year simulated data of some 10 million stars will be flowing around all over Europe. Geneva is in charge of the software development and processing of the Gaia data for the variability analysis and will enter the scene later in 2011 when the required calibration of the data is available.
More information on Gaia is available in the Gaia DPAC newsletters.
Because it will allow to pursue most of the science addressed by INTEGRAL, ESA's Cosmic Vision Class "L" candidate mission International X-ray Observatory (IXO) is one of the long-term science goals of the ISDC. However, many of the favorite INTEGRAL targets will prove to be exceedingly bright when observed with IXO. This drives the need for an instrument to be able to handle efficiently sources up to 10 Crab, i.e. more than one million counts per second. The High Time Resolution Spectrometer (HTRS), an IXO baseline payload instrument, which is led by the CESR in Toulouse, is such instrument. The ISDC participates to the HTRS instrument team by developing a filter wheel.
After completion of the Phase A study, the HTRS collaboration will organize a scientific conference dedicated to the science of the HTRS, from the current observations with Rossi-XTE, XMM-Newton, Suzaku or Chandra to the future HTRS/IXO observations. The ISDC is the lead organizer of the conference.
The HTRS conference: "Fast X-ray timing and spectroscopy with the High Time Resolution Spectrometer" will take place from February 7 until February 11, 2011, in Champéry, Switzerland. Champéry is a small town in the Swiss Alps and is part of one of the largest ski areas in the world, the "Portes du Soleil", providing ample opportunities for outdoor winter activities in addition to a very pleasant working environment.