| No. 20 - 15 January 2007 | Edited by Marc Türler & Jérôme Rodriguez |
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This issue of the ISDC Newsletter announces the release of version 6.0 of the INTEGRAL off-line scientific analysis (OSA). Several calibration and software issues have been solved, respectively have progressed significantly, over the last many months, rendering a new issue of OSA necessary. Most progress has been achieved in the ISGRI data analysis that is continuing to gain in solidity and for which calibrations are progressing and in JEM-X where spectra can now be extracted from images. Additional tools have been implemented in the SPI analysis and a new method to calibrate OMC fluxes has been introduced.
This release is later than we had anticipated because solving calibration issues often leads to further questions. We did not want to release OSA 6.0 while this was in constant flux. We have now reached a level in our understanding that allows us to confidently issue a new release today.
Calibration efforts by the instrument teams and at ISDC will continue in the next months with the aim of further improving the quality of the results until we are confident that we are sufficiently close to the ultimate statistical sensitivity of the instruments.
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| Status of the IBIS/ISGRI data analysis and OSA 6.0 | ||
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R. Walter (ISDC) and the IBIS Teams (CEA Saclay & INAF/IASF-Roma) |
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Since OSA 5.1 a lot of work has been invested to further improve the quality of the ISGRI scientific results. The following improvements have been included in the current release of the software:
Background subtraction involves re-normalization of background maps. This re-normalization now disregards pixels illuminated by very bright sources, which improves significantly the results especially when bright sources are in the border of the FOV. The normalization of the background maps is also performed independently for each module. This improves the quality of the science products in particular by reducing stripes and chessboard structures still present in some sky images and by resulting in a more stable Crab lightcurve.
The mask supporting structure (including the NOMEX honeycomb structure) is absorbing the photons before they hit the detector. This absorption depends on the incident angle and the energy of the photons. A numerical model of this structure has been created and adjusted to flight and ground calibration data (see article below). The images/spectra/count rates are now corrected for the effect of this structure. This correction improves the accuracy of the count rate determination (at various off-axis angle), and improves further the stability of the Crab lightcurve. This more accurate off-axis correction could produce fairly different source spectra when compared with OSA 5.1.
The calculation of good time intervals takes better into account pointings with several periods of stable attitude. More stringent limits on the attitude stability are used by default in OSA 6.0 which improves the cleaning of sources.
A "bad time interval" table has been added as a new file of Instrument Characteristics (IC) and is used by default by the analysis to disregard affected data. It points to periods of time during the mission with peculiar instrument settings used during calibration, solar flares, bad settings of rise time thresholds, problems with the IBIS VETO configuration or passages through the radiation belts.
High energy protons hit continuously the detector cristals and electronics. The meanings of the pulse amplitude and pulse rise-time measured by the detector for each event are therefore affected by the total radiation dose. Despite the progress made in the understanding of the energy calibration and its variation with time (see article in Newsletter No. 19) some problems are not yet understood at the level required for the final implementation. Due to the strong interplay between the energy calibration, low energy thresholds and rise time correction a proper energy calibration is central in characterizing the response of the instrument. Systematic residuals observed in spectra as well as the absolute spectral shape depends on that understanding.
The cleaning of ghosts in sky images is not perfect and this limits the exposure time usable to search for faint sources in the vicinity of bright ones (in particular in the galactic buldge). There are now clear evidences for thermal effects affecting the geometry of the instruments and further work is needed to correct that.
| The new IBIS off-axis correction in OSA 6.0 | ||
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P. Lubinski (CAMK, Warsaw & ISDC) |
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The major part of the IBIS mask support is an 8 cm thick layer of honeycomb
made of aramid paper, which is called the Nomex. A layer of such thickness
absorbs a substantial fraction of the source flux, and, moreover, introduces an
additional dependence of the mask transmission on energy and arrival angles of
the source photons. To obtain consistent ISGRI spectra and light curves for
observations taken at different off-axis angles the transmission of the mask
support has to be modelled. The first model was introduced to the data analysis
software in OSA 4.0 (see article in
Newsletter No. 15). This phenomenological model, based on fitting to the
Crab data from early observations, was used also in OSA 5 releases, after some
corrections. However, the performance of ISGRI was considerably improved in OSA
4 and 5 with many systematic effects corrected. The old off-axis correction was
not precise enough to match that improvement and it was demanding to replace it
with something better and based on increasing amount of calibration data. A
phenomenological approach was followed by the IBIS Team, showing that the new
model should be more complex to account for count rate deviations seen at low
off-axis angles [1].
Figure 2. OSA 6.0 off-axis correction maps based on the Nomex geometrical model in the energy bands at 19.9-20.4 keV (top-left), 29.5-30.0 keV (top-right), 50-55 keV (bottom-left) and 250-300 keV (bottom-right). In these new maps, there is an important non-axisymmetric component characterized by the star-like shape which is due to the hexagonal honeycomb structure of the Nomex.
In parallel, a geometric, ray-tracing model was developed at ISDC to describe
the absorption in the Nomex layer. In the beginning this model had all
parameters fixed according to the technical description of the IBIS mask
support. Later, a single 'blurring' parameter was introduced to account for
small deformations of the honeycomb structure that are unavoidable in real
situations. With this model it was possible to obtain the results being clearly
better that those from the OSA 4/OSA 5 off-axis correction. Nevertheless, at
small off-axis angles the observed scatter was still too large. The correlation
of these deviations with the azimuthal angle of arriving photons suggested that
there is some more global deformation of the honeycomb. The study of this effect
was possible with the new calibration data from Crab observation in Rev. 0422.
During that observation, proposed by the IBIS Team [1], three rings of
pointings at 0.5, 1 and 2 degrees off-axis were made. These new data confirmed
that there is a tilt of the honeycomb structure and helped to determine the
character of this deformation.
Figure 2. Results for the Crab observation in INTEGRAL rev. 422 in the 20-25 keV band. The upper panel shows the OSA 6.0 results, the middle panel the OSA 5.1 results and the bottom panel the raw source light curve without off-axis correction. Note the point with the maximal count rate at 2280.22 IJD, corresponding to a minimum of the absorption at a polar angle of 0.5 deg and an azimuthal angle of 60 deg, which is the direction correponding to the tilt of the hexagonal nomex ``tubes''.
Figure 2 illustrates how the new geometrical model with the tilt included improves the stability of the Crab count rate. The major improvement is that the large deviations in count rates observed below ~3 degrees for observations taken at different azimuthal angle disappears. Also the reference, unabsorbed count rate level is larger now due to the fact that the maximal transmission through the Nomex layer happens for photons not arriving along the IBIS system axis. Final parameters of the geometrical model are: blurring angle (mean uncertainty of the honeycomb walls orientation) 0.3 degrees, tilt polar angle 0.5 degrees and tilt azimuthal angle 60 degrees. Figure 1 presents an example of the new off-axis correction maps, showing the dependence on the photon polar and azimuthal angle. The centre of the map is shifted by 3.5/5 pixels corresponding to the tilt angles.
In summary, the new off-axis absorption model gives much less scattered results when plotted against both photon arrival angles and photon energy. The latter improvement is a consequence of using the physical transmission coefficients for the mask support materials instead of the dependence fitted to the old data. The light curves of the Crab are stable within 2-3% for data taken in similar instrument settings. The Crab hardness ratios also present clearly smaller scatter, only slightly exceeding the statistical uncertainty. Spectra from observations made in different conditions are consistent and do not show large deviations even for pointings with the source being more than 10 degrees off-axis. Finally, the remaining deviations do not shown correlation with angles, therefore, it seems that they correspond to some minor, local deformations of the honeycomb or, more probably, they come from effects not related to the mask support layer.
A more detailed report on the geometrical model can be provided upon request.
References
[1] E. Barlow, A. Bazzano, A.J. Bird, IBIS Off Axis Correction, Report
IN_IB_IASF.RP.0001/06, 3 Feb 2006
| IBIS/PICsIT Novelties in OSA 6.0 | ||
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L. Foschini (INAF/IASF-Bologna) |
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The main difference in OSA 6.0 with respect to OSA 5.1 is the presence of an ``off-axis'' correction in ip_skyimage. This correction is calculated according to studies of the Point Spread Function (PSF) for off-axis sources and therefore takes into account several effects that can generate distortions in the PSF. This correction is something temporary, while detailed studies are on going in order to disentangle the different contributions and to correct them separately.
Another novelty is the release of new response files (RMF and ARF) for single
and multiple events with a proper channel width, in agreement with the on-board
instrument configuration.
| SPI Changes & Improvements in OSA 6.0 | ||
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I. Kreykenbohm (IAA Tübingen & ISDC) |
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The SPI software has been generally improved in OSA 6.0, most importantly the response binner, such that it is now possible to use very narrow and broad bins together in one spectrum and also the spectral slope no longer depends on the number of bins used.
Apart from these general improvements, several new features have been added:
An important change for all users is the introduction of a new background
modeling method: instead of using background tracers, SPI flat fields are now
part of the SPI instrument characteristics (IC files) which are used to model
the background. In depth analysis by the SPI Team showed that this method is
superior to other background estimation methods and is therefore the new
default.
Figure: Pulse phase resolved analysis of the Crab pulsar. The data points of different colors correspond to pulse lightcurves in different energy bands (Courtesy: P. Dubath/ISDC)
To further improve the usability of the SPI software and to ease the analysis, the input data are now screened and bad pointings are automatically excluded from the analysis. This is done by an IC file that is provided by the SPI Team in Toulouse.
A complete new feature is the possibility to perform pulse phase
resolved analysis with SPI. It is possible to use very short periods
down to milli-seconds with a high number of phase bins (see
Figure). For the case of binary systems, double star correction can be
performed to remove the effect of the binary motion.
| JEM-X Analysis Improvements in OSA 6.0 | ||
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S. Paltani (ISDC) |
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The JEM-X analysis software in OSA 6 incorporates two major additional functionalities and many small improvements in most areas. The steps that have benefited from these developments are the correction step, the GTI handling, the imaging step and the mosaicing step. JEM-X team has been actively working on new approaches to spectral and light curve extraction. Unfortunately, these developments have not yet materialized into new tools. Work is still in progress, and we hope that these new approaches will constitute the driving forces in a future OSA release.
A first important improvement in OSA 6 for JEM-X is the determination of the gain calibration for revolutions affected by specific problems, like solar flares. The vast majority of the revolutions are unaffected, and the pre-OSA 6 software was already able to determine the gain correction adequately. Improvements in the software in OSA 6 make that it is now able to treat correctly a large fraction of the problematic revolutions. The remaining ones must be treated manually in an off-line analysis performed at the Danish National Space Center. The results are included in the ISDC's Instrument Characteristics tree, and are used automatically by the analysis script. As of today, all revolutions containing useful data can be processed correctly with OSA 6. Should the need arise, new gain tables will be added to the IC tree, and a new web page gives you at a glance the status of a given revolution and a link to the calibration data eventually needed for the processing.
Several periods in the life of the JEM-X instrument are not straightforwardly
usable for scientific production. This is mainly due to instrument
configurations that are not in agreement with the expectations of the analysis
software, either because of a mistake in the instrumental set-up, or because of
an intentional modification of this set-up for the purpose of calibrations. An
Instrument Characteristics table tracks these periods, and the analysis script
ignores them by default.
The image processing chain has also been improved. Several bug fixes contribute to the increased stability of the tool used to create images, 'j_ima_iros'. Useful functionalities have been added, like the creation of a significance map. for individual Science Windows. Mosaics incorporate full projections, and are not anymore limited in size (see the example image).
Figure. Example of a wide JEM-X mosaic image obtained with OSA 6.0 and covering an area of 20x30 square degrees in the Scutum arm of the Galaxy. Courtesy: J. Chenevez (DNSC, Copenhagen)
The second major improvement is the possibility to extract fluxes and produce
spectra directly from the images and mosaic. Images produced by 'j_ima_iros' are
now corrected for effects like off-axis attenuation. This makes possible the
building of deep mosaics to search for faint sources, and to extract their
fluxes directly. The 'mosaic_spec' tool, which was already used for the same
purpose in the IBIS analysis, can now be used to build the spectrum of these
sources. This approach gives the user some more confidence in the result, since
a detection implies that the source is visible either in the image or in the
mosaic; contamination by nearby sources and systematics, which may happen with
the standard spectral extraction tool are practically eliminated.
| OMC Changes & Improvements in OSA 6.0 | ||
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A. Domingo Garau (LAEFF-INTA, Madrid) |
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A new method to calculate the fluxes by re-centring on WCS positions
(IMA_wcsFlag=yes) instead of the brightest pixel
(IMA_wcsFlag=no) has been implemented. The new method reads the
coordinates from the OMC Input Catalogue, and is able to calculate the fluxes by
re-centring on the catalogued position, after deriving the WCS solution. One
advantage of this method is that it can process the mosaics of sub-windows
successfully if the source coordinates are accurate enough. These mosaics are
found for extended sources or high energy source counterparts with large
uncertainties in their position, for which the OMC planning assigns multiple
adjacent sub-windows to cover the whole area. For typical sub-windows, this new
method should be used in crowded fields and for transient or undetected
sources. Of course, it also allows the user to re-process old data when more
accurate positions are available for re-centring.
In addition, the WCS solution has been improved in those shots without reference stars. In such cases, the solution obtained for the last shot including reference stars is used.
In OSA 6.0 the user can specify the OMC_IDs of the sources he/she is interested in, to extract the fluxes only for the given sources. In OSA 5.1, this was only possible in the imaging tool (o_ima_build).
In OSA 6.0, the IC files have been substantially improved. Using data from the Earth observation, a new calibration method was developed, and it allowed to derive new flatfield matrices covering almost all the mission. The photometric calibration was updated as well.
Figure.
Mean standard deviation (1 sigma) found for the photometric reference
stars in each calibration interval (~ 1.2 months). It represents a measurement
of the flatfield accuracy.
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| High energy emission studies of stellar mass accreting black holes | |
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Marion CADOLLE BEL Service d'Astrophysique CEA-Saclay et APC, Orme des Merisiers, Gif-Sur-Yvette, F-91191 | |
| Ph.D. thesis directed by SAndrea GOLDWURM at the University of Paris 7, Denis Diderot | |
| Ph.D. degree awarded on September, 13 2006 | |
| Summary. The present work is dedicated to the study of various X-ray binary systems harbouring accreting stellar mass black holes (or candidates) associated in X-ray binary systems mainly through the spectral and timing properties of the high energy 3 keV-1 MeV emission, sometimes completed by observations performed in radio, near-infrared and optical. The first part is devoted to accretion physics phenomena and the challenges of understanding the X-ray/gamma emission produced with the modelisations of such high energy processes. Then I will define in a second part the instruments on board INTEGRAL and the way coded masked aperture is employed. In a third part, I will develop the standard data reduction analysis and my own contribution in improving the usual software before detailing the specific informatics tools I have developed for my own analysis. In the fourth part I will turn towards the deep analysis and interpretations I have performed on several black hole X-ray binary systems chosen properly: the persistent black hole source Cygnus X-1 which has been studied since several years and surprised us by a high-energy excess detected; two new transient sources which provide interesting informations, XTE J1720-318 located in the galactic bulge and SWIFT J1753.5-0127, probably situated in the halo. I will also detail my work on H 1743-322, recently identified by INTEGRAL as the HEAO source discovered in 1977, and on three (almost) persistent microquasars with superluminal jets, 1E 1740.7-2942, GRS 1758-258 and GRS 1915+105. I will analyze for each source spectral parameter evolutions and their links with each other during state transitions. I will then discuss the presence of two different X/gamma-ray emitting media with a relatively changing geometry. While establishing a cyclic order for the different variability classes of GRS 1915+105 observed during ten years, I will propose an interpretation for such behaviour, compatible with the theoretical predictions of the Accretion-Ejection Instability. As a conclusion I will discuss my results in the framework of theoretical models to explain the observations presented and I will derive some caveats to the general (well understood) physical processes occurring in X-ray binary systems. I will discuss two important phenomena recently observed. I will conclude with my perspectives of future research work. | |
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E-mail contact | |
| The Hard X-ray 20-40 keV AGN Luminosity Function | |
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V. Beckmann 1,2, S. Soldi 3, C. R. Shrader 1, N. Gehrels 1 & N. Produit 3 1. NASA Goddard Space Flight Center, Exploration of the Universe Division, Code 661, Greenbelt, MD 20771, USA 2. Joint Center for Astrophysics, Department of Physics, University of Maryland Baltimore County, MD 21250, USA 3. INTEGRAL Science Data Centre, ch. d' Ecogia 16, CH-1290 Versoix, Switzerland | |
| Accepted for publication in ApJ on June 28, 2006 | |
| Abstract. We have compiled a complete extragalactic sample based on 25,000 deg2 to a limiting flux of 3x10-11 ergs cm-2 s-1 (7,000 deg2 to a flux limit of 10-11 ergs cm-2 s-1) in the 20 - 40 keV band with INTEGRAL. We have constructed a detailed exposure map to compensate for effects of non-uniform exposure. The flux-number relation is best described by a power-law with a slope of α = 1.66 ± 0.11. The integration of the cumulative flux per unit area leads to f= 2.6 x 10-10 ergs cm-2 s-1 sr-1, which is about 1% of the known 20 - 40 keV X-ray background. We present the first luminosity function of AGN in the 20-40 keV energy range, based on 38 extragalactic objects detected by the imager IBIS/ISGRI on-board INTEGRAL. The luminosity function shows a smoothly connected two power-law form, with an index of γ1 = 0.8 below, and γ2 = 2.1 above the turn-over luminosity of L* = 2.4 x 1043 ergs s-1. The emissivity of all INTEGRAL AGNs per unit volume is W(> 1041 ergs s-1) = 2.8 x 1038 ergs s-1 Mpc-3. These results are consistent with those derived in the 2 - 20 keV energy band and do not show a significant contribution by Compton-thick objects. Because the sample used in this study is truly local (< z > = 0.022), only limited conclusions can be drawn for the evolution of AGNs in this energy band. | |
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E-mail contact | Preprint access |
| Magnetars as persistent hard X-ray sources: INTEGRAL discovery of a hard tail in SGR 1900+14 | |
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D. Götz1, S. Mereghetti2, A. Tiengo,2 P. Esposito2 1. CEA-Service d'Astrophysique, Saclay 2. INAF - IASF Milano | |
| Accepted for publication in A&A 449, L31 on Feb 20, 2006 | |
| Abstract. Using 2.5 Ms of data obtained by the INTEGRAL satellite in 2003-2004, we discovered persistent hard X-ray emission from the soft gamma-ray repeater SGR 1900+14. Its 20-100 keV spectrum is well described by a steep power law with photon index Γ=3.1±0.5 and flux 1.5×10-11 erg cm-2 s-1. Contrary to SGR 1806-20, the only other soft gamma-ray repeater for which persistent emission above 20 keV was reported, SGR 1900+14 has been detected in the hard X-ray range while it was in a quiescent state (the last bursts from this source were observed in 2002). By comparing the broad band spectra (1-100 keV) of all the magnetars detected by INTEGRAL (the two SGRs and three anomalous X-ray pulsars) we find evidence for a different spectral behaviour of these two classes of sources. | |
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| Average hard X-ray emission from NS LMXBs: Observational evidence of different spectral states in NS LMXBs | |
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A. Paizis1, R. Farinelli2, L. Titarchuk3, T.J.-L Courvoisier et al. 1. INAF - IASF, Via Bassini 15, 20133, Milano, Italy 2. Dipartimento di Fisica, Universitá di Ferrara, Via Saragat 1, 44100 Ferrara, Italy 3. NASA GSFC, Greenbelt, MD 20771, USA | |
| Accepted for publication in A&A on August 10, 2006 | |
| Abstract. We studied and compared the long-term average hard X-ray (above 20 keV) spectra of a sample of twelve bright low-mass X-ray binaries hosting a neutron star (NS). Our sample comprises the six well studied Galactic Z sources and six Atoll sources, four of which are bright ("GX") bulge sources while two are weaker ones in the 2-10 keV range (H1750-440 and H1608-55). For all the sources of our sample, we analysed available public data and extracted average spectra from the IBIS/ISGRI detector on board INTEGRAL. We can describe all the spectral states in terms of the bulk motion Comptonisation scenario. We find evidence that bulk motion is always present, its strength is related to the accretion rate and it is suppressed only in the presence of high local luminosity. The two low-dim Atoll source spectra are dominated by photons up-scattered presumably due to dynamical and thermal Comptonisation in an optically thin, hot plasma. For the first time, we extend the detection of H1750-440 up to 150keV. The Z and bright "GX" Atoll source spectra are very similar and are dominated by Comptonised blackbody radiation of seed photons, presumably coming from the accretion disc and NS surface, in an optically thick cloud with plasma temperature in the range of 2.5-3 keV. Six sources show a hard tail in their average spectrum: Cyg X-2 (Z), GX 340+0 (Z), GX 17+2 (Z), GX 5-1 (Z), Sco X-1 (Z) and GX 13+1 (Atoll). This is the first detection of a hard tail in the X-ray spectrum of the peculiar GX 13+1. Using radio data from the literature we find, in all Z sources and bright "GX" Atolls, a systematic positive correlation between the X-ray hard tail (40-100 keV) and the radio luminosity. This suggests that hard tails and energetic electrons causing the radio emission may have the same origin, most likely the Compton cloud located inside the NS magnetosphere. | |
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E-mail contact | |
| IGR J08408-4503: a new recurrent Supergiant Fast X-ray Transient | |
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D. Götz1, M. Falanga1, F. Senziani2,3, et al. 1. CEA-Saclay, Service d'Astrophysique, F-91191, Gif-sur-Yvette, France 2. INAF - IASF Milano, Via Bassini, 15 - 20133 Milano, Italy 3. Université Paul Sabatier, Toulouse, France | |
| Accepted for publication in ApJ Letters on Dec 15, 2006 | |
| Abstract. The supergiant fast X-ray transient IGR J08408-4503 was discovered by INTEGRAL on May 15, 2006, during a bright flare. The source shows sporadic recurrent short bright flares, reaching a peak luminosity of 1036 erg s-1 within less than one hour. The companion star is HD 74194, an Ob5Ib(f) supergiant star located at 3 kpc in the Vela region. We report the light curves and broad-band spectra (0.1-200 keV) of all the three flares of IGR J08408-4503 detected up to now based on INTEGRAL and Swift data. The flare spectra are well described by a power-law model with a high energy cut-off at ~15 keV. The absorption column density during the flares was found to be ~1021 cm-2, indicating a very low matter density around the compact object. Using the supergiant donor star parameters, the wind accretion conditions imply an orbital period of the order of one year, a spin period of the order of hours and a magnetic field of the order of 1013 G. | |
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E-mail contact | Preprint access |
| The discovery outburst of the X-ray transient IGR J17497-2821 observed with RXTE and ATCA | |
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J. Rodriguez1, M. Cadolle-Bel2, 1, J. A. Tomsick3, S. Corbel1 et al. 1. CEA Saclay, UMR AIM, DSM/DAPNIA/Sap, Bat 709, F-91191 Gif sur Yvette France 2. {European Space Astronomy Centre, Villafranca del Castillo, 28629 Madrid, Spain 3. Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720 & Center for Astrophysics and Space Sciences, 9500 Gilman Drive, Code 0424, University of California at San Diego, La Jolla, CA 92093, USA | |
| Accepted for publication in ApJ on December, 14, 2006 | |
| Abstract. We report the results of a series of RXTE and ATCA observations of the recently-discovered X-ray transient IGR J17497-2821. Our 3-200 keV PCA+HEXTE spectral analysis shows very little variations over a period of ~10 days around the maximum of the outburst. IGR J17497-2821 is found in a typical Low Hard State (LHS) of X-ray binaries (XRB), well represented by an absorbed Comptonized spectrum with an iron edge at about 7 keV. The high value of the absorption (~4 x 1022 cm-2) suggests that the source is located at a large distance, either close to the Galactic center or beyond. The timing analysis shows no particular features, while the shape of the power density spectra is also typical of LHS of XRBs, with ~36 % RMS variability. No radio counterpart is found down to a limit of 0.21 mJy at 4.80 GHz and 8.64 GHz. Although the position of IGR J17497-2821 in the radio to X-ray flux diagram is well below the correlation usually observed in the LHS of black holes, the comparison of its X-ray properties with those of other sources leads us to suggest that it is a black hole candidate. | |
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E-mail contact | Preprint access |
| Simultaneous multiwavelength observations of the Low/Hard State of the X-ray transient source SWIFT J1753.5-0127 | |
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M. Cadolle Bel, M. Ribo, J. Rodriguez, S. Chaty, S. Corbel, et al. 1. SAp CEA-Saclay & APC, Gif-sur-Yvette, FRANCE 2. ESAC, Madrid, SPAIN | |
| Accepted for publication in ApJ on December 20, 2006 | |
| Abstract. We report the results of simultaneous multiwavelength observations of the X-ray transient source SWIFT J1753.5-0127 performed with INTEGRAL, RXTE, NTT, REM and VLA on 2005 August 10-12. The source, which underwent an X-ray outburst since 2005 May 30, was observed during the INTEGRAL Target of Opportunity program dedicated to new X-ray novae located in the Galactic Halo. Broad-band spectra and fast timing variability properties of SWIFT J1753.5-0127 are analyzed together with the optical, near infra-red and radio data. We show that the source was significantly detected up to 600 keV with Comptonization parameters and timing properties typical of the so-called Low/Hard State of black hole candidates. We build a spectral energy distribution and we show that SWIFT J1753.5-0127 does not follow the usual radio/X-ray correlation of X-ray binaries in the Low/Hard State. We give estimates of distance and mass. We conclude that SWIFT J1753.5-0127 belongs to the X-ray nova class and that it is likely a black hole candidate transient source of the Galactic Halo which remained in the Low/Hard State during its main outburst. We discuss our results within the context of Comptonization and jet models. | |
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E-mail contact | Preprint access |
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With the recent results obtained with the actual running observatories, INTEGRAL, SWIFT, HESS, AUGER, AMANDA, and those expected to come with the forthcoming GLAST, ANTARES and the first gravitational waves observatories, we are at a time were high energy phenomena in the Universe can be precisely studied. Therefore it is timely to contribute to the education of young and senior scientists that are facing the instruments, the data analysis or the out coming questions. The physics involved is extremely vast, including in particular hydrodynamics, general relativity, particle physics, nuclear physics and astrophysics. There is no scientific course allowing tackling all these topics. The observation means are in space, ground based or even deep in the sea and involve interactions and detection techniques specific to each domain. Having the chance to see them presented side by side is a rare opportunity.
The violent events in the universe exhibit very different behaviour and the scientist studying those phenomena come from different communities and thus have different "cultures". Helping students to step into these diversities and be reinforced with it is one of the aims of this school. Another one is to favor encounters between young scientists from different fields.
The goal of the school is to present a review of the high energy non- thermal phenomena in the Universe both from the theoretical and observational points of view. Reviews of all the vectors of information (photons, neutrinos, gravitational waves, cosmic rays) will be given.
The school is targeted to all researchers, PhD, postdocs, young and senior scientists with an interest in the school's topics. The number of participants is however limited to ~60. Graduate students may be considered if possible.
For further details and registration visit the school website.
In the frame of the European Astronomical Society (EAS) annual meeting in Yerevan August 20-25 2007 (JENAM 2007) we are organising a 2.5 days EAS symposium on high energy astrophysics.
The main goal of this meeting is to bring together the high energy astrophysics community working not only on the space based X-ray and gamma ray energy domains (keV-GeV), but also the ground based GeV-TeV community. We have indeed seen a number of breakthroughs in the Cerenkov detection technology that have brought many very new results. These results are important for the understanding of the physics of many high energy astrophysical sources. It is therefore particularly timely to bring closer the communities working on all aspects of observations and modelling of these sources to cross fertilise.
The meeting will also discuss a number of space borne and ground based projects that are being discussed now with a view to harmonise the developments. This latter element will be of particular importance in Europe in the next years with the implementation of ESA s Cosmic Vision programme and the progress of some European Union initiatives in ground based high energy astrophysics.
The meeting will be organised in 5 sessions on:
For further details and registration see the PDF meeting announcement and visit the Symposium website.
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