| No. 15 - June 18, 2004 | Edited by Marc Türler & Pierre-Olivier Petrucci |
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This 15th issue of the Newsletter corresponds to an important step for the INTEGRAL mission with the first data in the INTEGRAL Archive becoming public this Summer. The huge amount of data that will be accessible through the archive by the entire astrophysical community, will give to the INTEGRAL mission a new scientific dimension. The ISDC took this opportunity to change the archive structure and to reprocess the data (see below). Details on how to get public data are also presented here.
The ISDC staff and the Instrument Teams also worked hard to enable the new release of the 4th version of the Off-line Scientific Analysis (OSA 4.0) software in parallel to the archive data access opening. Improvement in the data analysis software of the future OSA 4.0 are described here in general and more specifically for the PICsIT detector of IBIS and for the two JEM-X instruments.
This Newsletter is also announcing the first INTEGRAL Data Analysis Workshop organized at the ISDC on 5-8 October 2004 to help and assist the astrophysical community. Finally, the Science News section is presenting a few highlights among the growing number of scientific results obtained with INTEGRAL.
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| Public INTEGRAL data release | ||
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Roland Walter (ISDC, Geneva) |
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On July 19th, 2004, all science window datasets distributed before July 19th, 2003 will be made publicly accessible in the archive. From then every month about 10 revolutions worth of data will become public in addition following the one year proprietary period.
The standard analysis products that were generated with early versions of the
scientific analysis software (OSA 1.0 to 3.0) are now completely obsolete. They
will not be made public. However the scientific analysis products can be
generated using the OSA 4.0 software. A reprocessing of all the data is now comming on. Those data
including science products will progressively become publicly available in a
second version of the archive. Note that the quality of the science window data
in the first version of the archive is almost as good as the reprocessed data.
| How to get public data ? | ||
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P. Binko (SynSpace SA), M. Meharga and K. Pottschmidt (ISDC, Geneva) |
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Public data are made available on the Internet. To select and retrieve them, you shall use the ISDC Browse WWW tool (see picture on the left), which is based upon the W3Browse by the High Energy Astrophysics Science Archive Research Center (HEASARC).
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At the end of the selection chain, you are offered the possibility to request the distribution of your final selection. For this purpose, you only need to enter your e-mail address (see picture on the right).
Almost in real time, you will receive an e-mail containing:
Running the script on your own computer will copy all the data needed from the ISDC INTEGRAL Archive. Please note that if you selected large datasets several GBytes will be copied which will take several hours.
| Data reprocessing and the evolution of the INTEGRAL archive | ||
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Roland Walter (ISDC, Geneva) |
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A first reprocessing of the INTEGRAL data is starting at the ISDC leading to the creation of a second version of the INTEGRAL archive. This reprocessing will be performed in two steps:
The first step of the reprocessing is starting now. The second step will start in September. It is expected that the reprocessing will catch up the public release of the data such that later this year (November) all science window datasets to become public will be available in the second version of the archive. The first version of the archive will then be discontinued.
The OSA4 software is capable to process both versions of the archive.
Previous OSA versions will only process the first version of the archive.
Data coming from the various archive versions should however not be
mixed together in a single analysis.
| Overview of changes in the forthcoming OSA 4.0 release | ||
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P. Kretschmar, P. Dubath and N. Produit (ISDC, Geneva) |
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The 4th version of the Off-line Scientific Analysis (OSA) software will become available together with the opening of the first data in the INTEGRAL Archive on July 19th, 2004. One of the main changes, but largely transparent for the user in the OSA 4.0 release, is the capability to handle data both from the first revision of the archive, i.e. as distributed up to now and in the new "reprocessed" format which is described in the "Data reprocessing" article above.
For reprocessed data, the analysis software will by default use the corrected data, Good-Time Intervals (GTIs), etc. as produced by the Science Window Pipeline. But if the user choses to do so, it is also able to regenerate new instances of these data as in previous versions of the analysis software, e.g., to refine the default corrections or to select personal GTIs.
Changes to the analysis software capabilities and instrument description are listed below by instrument:
| OSA 4.0 Improvements for PICsIT | ||
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Luigi Foschini (IASF/CNR, Bologna, Italy) |
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PICsIT is the high energy detector of the IBIS telescope and operates in the energy range 0.175-10 MeV. Instruments in this energy range work at a very low signal to noise level. For example, the Crab is detected by PICsIT over the entire energy range with about 10 count/s, while the background level is about 2500 count/s (single events only). It is evident that a correct background modelling is of fundamental importance in the data processing.
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OSA 4.0 for PICsIT presents important improvements compared to OSA 3.0:
| Jem-X Source Spectra in OSA 4.0 | ||
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Stefan Larsson (Stockholm Observatory) & Niels Jørgen Westergaard (DSRI, Copenhagen) |
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The software to extract source lightcurves and spectra from Jem-X has been
largely rewritten over the past year. The present design does a better job in
handling the energy and directional dependences of the detector response. A
basic property of the Jem-X detectors is an energy dependent detector
resolution. Since harder X-rays penetrate deeper into the detector the
resolution is asymmetric and depends on the direction of the incoming
radiation. These effects mean that the contrast of the coded mask shadow
pattern also varies with photon energy. To extract reliable spectra it is
necessary to model these effects accurately. The performance of the OSA 4.0
version of the spectral extraction is exemplified in the figures shown here,
which are results from XSPEC fits to Crab observations made in revolution 170.
Both Jem-X instruments were taking data, allowing us also to compare the
results from Jem-X 1 and Jem-X 2.
The resulting fit for a single science window, in this case 3.3 degrees off
axis is shown in the figure on the
right.
The extracted Crab spectrum for each science window was fitted in XSPEC with a power law and photoelectric absorption. nH was held fixed at 2.65 x 1021. The resulting spectral slope and normalization for the individual science windows are plotted in the figures below. The XSPEC-fits were made for the range from 3.4 - 34.4 keV. The spectral slopes (upper figures) cluster around 2.1 with a slight systematic difference between the two instruments. More importantly, there are no strong dependences on off-axis angle. Further details will be given in the OSA 4.0 Science Validation Report.
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The behavior of the spectral normalization in the lower panels is similar but with two differences. The present normalization give fluxes that are 20-30 % higher than canonical values for the Crab nebula/pulsar (for more details we again refer to the Science Validation Report). Secondly, there are systematic variations in extracted flux which depend on position in the field of view. There is now a major effort in the instrument team to improve the instrument model so that these remaining effects can be corrected in the analysis.
In summary, the Jem-X science software in OSA 4.0 produces source spectra with
shapes close to expectations over the range 3 - 35 keV. Within 3.5 degrees
from the center of the field of view there are systematic point-to-point
variations of extracted flux which has an amplitude of up to ? 10%. On the
other hand time variability of a source at a fixed position in the field of
view is limited essentially by photon statistics.
| INTEGRAL Data Analysis Workshop | ||
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Thierry Courvoisier (ISDC Geneva) |
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The ISDC is organising a data analysis workshop from October 5 to 8, 2004. We will address the INTEGRAL data, the instrument calibrations and the process to extract quantitative results from the complex coded-mask observations. The workshop is aimed at astrophysicists not yet familiar with coded mask and INTEGRAL data and intending to use INTEGRAL data in their research. We will offer both lectures from ISDC and instrument team specialists and hands-on sessions. More information is available on the workshop WWW page and a detailed programme will be available in a few weeks. The number of participants will be limited, so please register as soon as possible by using the registration form. Propositions for contributed talks with special emphasis on INTEGRAL data analysis methods can be send to Andrii Neronov.
The Organising Committee: Thierry Courvoisier, Andrii Neronov,
Jérôme Rodriguez, Marc Türler, Roland Walter and Juan Zurita
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| A supernova association for the INTEGRAL GRB 031203 | ||
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S. Mereghetti (IASF/CNR, Milano) and D. Malesani (INAF/OAB, Merate) |
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The INTEGRAL gamma-ray burst localized by IBAS on December 3 of last year and
showing the spectacular dust rings imaged with XMM-Newton (see previous newsletter) is again at the center of the
interest of astronomers. Several groups, monitoring the GRB host galaxy (see
figure on the right) noticed the possible appearance of a supernova, based on
photometric observations. This has been now confirmed by spectroscopic
observations obtained at European Southern Observatory Very Large Telescope and
recently reported in Malesani
et al. (2004, ApJ 609, L5).
Three color image (right) of a field of about 1.5x1.5 arcmin around the position of GRB 031203. The galaxy at redshift z=0.1 hosting the GRB is indicated by the arrow.
Until this discovery, the only other GRB with a firm supernova association
secured by spectroscopic data was GRB 030329 (SN2003dh), although also the
association between GRB 980425 and SN1998bw appears now very likely on the
basis of these recent results. The supernova associated to GRB 031203 has been
designated SN2003lw. The spectra of SN2003lw are shown in the figure on the
left, where they are compared to those of SN1998bw.
Spectra (left) of SN2003lw/GRB031203 (solid lines) compared to those of SN 1998bw (see Malesani et al. 2004 for details).
After GRB 031203, five more bursts have been detected by INTEGRAL in 2004: on
January 6, February 23, March 23, April 3 and 22. Accurate positions (about 3
arcmin radius) were derived for all of them and distributed by IBAS within a
few tens of seconds, as shown in the figure on the right.
Accuracy versus time delay for the 12 GRBs localized by IBAS (from Mereghetti
et al. 2004). The figure (right)
refers to the external distribution of GRB coordinates with IBAS Alert Packets
and GCN circulars. All the GRBs detected after April 2003 had very good
localizations in terms of accuracy and speed.
| INTEGRAL observes GRS 1915+105 | ||
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D. Hannikainen (Univ. of Helsinki), J. Rodriguez, O. Vilhu, S. Brandt, N. Lund, P. Kretschmar, T. Belloni, N. J. Westergaard, on behalf of a larger collaboration |
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GRS 1915+105 was the first Galactic source to exhibit apparent superluminal jets, earning it the nickname "microquasar". The system is composed of a 14 solar mass black hole, which makes it the heaviest stellar black hole in the Galaxy, and a K-M III giant. GRS 1915+105 has been observed extensively at all wavelengths ever since its discovery. Belloni et al. (2000), using RXTE data, showed that the source can exist in three distinct spectral states, exhibiting twelve different classes of variability (labelled with Greek letters).
During the AO-1 of INTEGRAL, we conducted a monitoring campaign on
GRS 1915+105. We had six separate observations of 100 ksec each. During
the first of these observations GRS 1915+105 displayed a form of
variability that had never been observed before. Preliminary results were
published in the special issue of A&A dedicated to INTEGRAL. The last
observation, conducted in May 2004, occurred as the source was
emerging from one of its famous "plateau" states. We had nearly 60
hours of uninterrupted observing time for this last
observation (as we had lost some time due to
solar flaring we were awarded extra time to make up for that).
Simultaneous RXTE observations confirmed that GRS 1915+105 was
displaying the "theta" class of variability at the start of the
observation.
The figure shows the JEM-X1 3-35 keV lightcurve from
the whole observation with a resolution of 8 seconds (the gap is due to a
crash of the IREM). The flares exceeding 3.5 Crab are among the brightest
ever observed from GRS 1915+105. The second part of the observation
shows more erratic behavior.
| INTEGRAL observation of the solar flare of 28 October 2003 | ||
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M. Gros (CEA-Saclay), J. Kiener and V. Tatischeff (CSNSM Orsay) |
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The very powerful
solar flare of 2003 Oct. 28th was detected by several instruments on
board INTEGRAL as an intense flash of about 15 minutes in the hard-X and
γ-ray bands. Despite the non-standard incidence of the solar γ-rays,
time-resolved spectra including several nuclear γ-ray lines and a
continuum at high energy were obtained with SPI, before the arrival of solar
particles.
Thefigure on the right shows the 2003-OCT-28 γ- ray flash as seen by the SPI ACS (125 ms) and by IREM (1 min time resolution).
For the first time, in addition to the 2.2 MeV 1H neutron capture line, the 4.4 MeV 12C* and 6.1 MeV 16O* nuclear interaction lines, the 6.9 and 7.1 MeV lines from 16O* are clearly resolved. The exceptional intensity of the flare and the good efficiency of SPI for high-energy γ-rays, combined with the excellent energy resolution inherent to Ge detectors give precise line profiles for the 4.4 MeV and 6.1 MeV γ-ray lines on low background. Taking into account the real profile and redshift of the 6.1 MeV line, we deduce the expected profile of the 6.9 – 7.1 MeV complex. Fitting this profile give a total number of counts detected in the 6.9 and 7.1 MeV lines of 137 ± 50 and 81 ± 49 respectively. Therefore, we could obtain the proton source spectrum index value without considering the chemical composition of the solar atmosphere.
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| The high energy X-ray tail of eta Car revealed by BeppoSAX | |
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R.F. Viotti, L.A. Antonelli, C. Rossi, S. Rebecchi 1. Istituto di Astrofisica Spaziale e Fisica Cosmica, CNR, Via Fosso del Cavaliere 100, 00133 Roma, Italy 2. INAF-Osservatorio Astronomico di Roma, 00040 Monte Porzio Catone, Roma, Italy | |
| Accepted for publication in A&A on February 12, 2004 | |
| Abstract. We report on the June 2000 long (100 ks) BeppoSAX exposure that has unveiled above 10 keV a new very high energy component of the X-ray spectrum of eta Car extending to at least 50 keV. We find that the 2-150 keV spectrum is best reproduced by a thermal plus non-thermal model. The thermal component dominates the 2-10 keV spectral range with kT=5.5+/-0.3 keV and log NH=22.68+/-0.01. The spectrum displays a prominent iron emission line centred at 6.70 keV. Its equivalent width of 0.94 keV, if produced by the thermal source, gives a slightly sub-solar iron abundance ([Fe/H]=-0.15+/-0.02). The high energy tail above 10 keV is best fitted by a power law with a photon index of 2.42+/-0.04. The integrated 13-150 keV luminosity of ~12 L_Sun is comparable to that of the 2-10 keV thermal component (19 L_Sun). The present result can be explained, in the eta Car binary star scenario, by Comptonisation of low frequency radiation by high energy electrons, probably generated in the colliding wind shock front, or in instabilities in the wind of the S Dor primary star. It is possible that the high energy tail had largely weakened near the minimum of the 5.53 yr cycle. With respect to the thermal component, it probably has a longer recovering time like that of the highest excitation optical emission lines. Both features can be associated with the large absorption measured by BeppoSAX at phase 0.05. | |
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| The Gamma-Ray Bright BL Lac Object RX J1211+2242 | |
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V. Beckmann1, P. Favre2, F. Tavecchio3, T. Bussien, J. Fliri, et al. 1. NASA Goddard Space Flight Center, Code 661, Greenbelt, MD 20771, USA 2. INTEGRAL Science Data Centre, ch. d' Ecogia 16, CH-1290 Versoix, Switzerland 3. Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate, Italy | |
| Accepted for publication in ApJ on March 3, 2004 | |
| Abstract. RX J1211+2242 is an optically faint (B = 19.2 mag) but X-ray bright (f2 - 10 keV = 5 x 10-12 erg cm-2 s-1) AGN, which has been shown to be a BL Lac object at redshift z = 0.455. The ROSAT X-ray, Calar Alto optical, and NVSS radio data suggest that the peak of the synchrotron emission of this object is at energies as high as several keV. BeppoSAX observations have been carried out simultaneously with optical observations in order to extend the coverage to higher energies. The new data indeed indicate a turn-over in the 2 - 10 keV energy region. We propose that RX J1211+2242 is the counterpart of the unidentified EGRET source 3EG J1212+2304, making it a gamma-ray emitter with properties similar to, for example, Markarian 501 in its bright state, though being at a much larger distance. | |
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| An X-ray Timing Study of XTE J1550-564: Evolution of the Low Frequency QPO for the Complete 2000 Outburst | |
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J. Rodriguez1, S. Corbel2, E. Kalemci,3 et al. 1. CEA Saclay, DSM/DAPNIA/SAp, F-91191 Gif Sur Yvette, France & ISDC ch. d' Ecogia 16, CH-1290 Versoix, Switzerland 2. Université Paris 7 Denis Diderot, 2 place Jussieu, 75005 Paris France & CEA Saclay 3. Space Science Laborator, University of California, Berkeley USA | |
| Accepted for publication in ApJ on May, 19, 2004 | |
| Abstract. We report on RXTE observations of the microquasar XTE J1550 during a ~70 day outburst in April-June 2000. We focus here on the temporal properties of the source and study the behavior of low frequency (0.1-10 Hz) quasi periodic oscillations (LFQPO), which seem to be of different types. We focus on the so-called type C (according to the classification of Remillard and collaborators), which corresponds to a strong 0.1-6 Hz LFQPO, found to be present during at least 17 observations. We find that the frequency of the QPO is better correlated with the soft X-ray (< 7 keV) flux than with the hard flux (> 7 keV). If soft X-rays represent the behavior of an accretion disk, the relation shows that the disk may set the LFQPO frequency. In two cases, the identification of the type of QPO is not straightforward. If the QPOs in those two cases are type A (or B), then we may be seeing the QPO type alternate between type C and type A (or B), and this may represent some rapid changes in the physical properties of the accretion flow, before the system stabilizes and slowly decays toward the end of the outburst. On the other hand, if all the QPOs are of type C, we may be observing an inversion in the frequency vs. flux relation, similar to that seen in GRO J1655-40. We discuss the QPO behavior in the framework of theoretical models. | |
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| Serpens X-1 observed by INTEGRAL | |
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N. Masetti, L. Foschini, E. Palazzi, et al. Instituto di Astrofisica Spaziale e Fisica Cosmica - Sezione di Bologna, CNR, via Gobetti 101, I-40129, Bologna, Italy | |
| Accepted for publication in A&A on May 11, 2004 | |
| Abstract. Here we report results of an INTEGRAL-AO1 observation of the X-ray burst and atoll source Ser X-1 performed in May 2003. The object was observed for a total on-source time of 400 ks but nearly 8 degrees off-axis due to its amalgamation with an observation of SS 433, the pointing target source. Ser X-1 has been clearly detected up to 30 keV with unprecedented positional accuracy for high-energy emission. The 20-30 keV light curve showed substantial variability during the observation. Comparison with previous observations indicates that the source was in its high (`banana') state and displayed a soft spectrum during the INTEGRAL pointing. A (non simultaneous) radio-to-γ-rays broad-band spectral energy distribution is also presented for the first time and discussed. | |
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E-mail contact | Preprint access |
| Discovery of hard non-thermal pulsed X-ray emission from the anomalous X-ray pulsar 1E 1841-045 | |
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L.Kuiper1,W. Hermsen1,2&M.Mendez1,2 1. SRON-National Institute for Space Research, Sorbonnelaan 2, 3584 CA, Utrecht, The Netherlands 2. Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Kruislaan 403, 1098 SJ, Amsterdam, The Netherlands | |
| Accepted for publication in ApJ on June 4,2004 | |
| Abstract. We report the discovery of non-thermal pulsed X-ray/soft γ-ray emission up to ~150 keV from the anomalous 11.8 s X-ray pulsar AXP 1E 1841-045 located near the centre of supernova remnant Kes 73 using RXTE PCA and HEXTE data. The morphology of the double-peaked pulse profile changes rapidly with energy from 2 keV up to ~8 keV, above which the pulse shape remains more or less stable. The pulsed spectrum is very hard, its shape above 10 keV can be described well by a power law with a photon index of 0.94 ± 0.16. 1E 1841-045 is the first AXP for which such very-hard pulsed emission has been detected, which points to an origin in the magnetosphere of a magnetar. We have also derived the total emission spectrum from the Kes 73/1 E1841-045 complex for the ~1-270 keV energy range using RXTE HEXTE and XMM-Newton PN data. A comparison of the total emission from the complex with the pulsed+DC emission from 1 E1841-045 as derived from Chandra ACIS CC-mode data (Morii et al. 2003) leaves little room for emission from Kes 73 at energies near 7 keV or above. This suggests that the HEXTE spectrum above ~15 keV, satisfactorily described by a power law with index 1.47 ± 0.05, is dominated by emission from 1E 1841-045. In that case the pulsed fraction for energies above 10 keV would increase from about 25% near 10 keV to 100% near 100 keV. The origin of the DC-component extending up to ~ 100 keV is probably magnetospheric and could be a manifestation of pulsed emission which is ``on" for all phases. | |
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| INTEGRAL and XMM-Newton Spectral Studies of NGC 4388 | |
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V. Beckmann1,2, N. Gehrels1, P. Favre3, R. Walter3, T. J.-L. Courvoisier3 et al. 1. NASA Goddard Space Flight Center, 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 24, 2004 | |
| Abstract. We present first INTEGRAL and XMM-Newton observations of a Seyfert galaxy, the type 2 AGN NGC 4388. Several INTEGRAL observations performed in 2003 allow us to study the spectrum in the 20 - 300 keV range. In addition two XMM-Newton observations give detailed insight into the 0.2 - 10 keV emission. The measurements presented here and comparison with previous observations by BeppoSAX, SIGMA and CGRO/OSSE show that the overall spectrum from soft X-rays up to the gamma-rays can be described by a highly absorbed (NH = 2.7x1023 cm-2) and variable non-thermal component in addition to constant non-absorbed thermal emission (T = 0.8 keV) of low abundance (Z = 7% Z⊙), plus a constant Fe Kα and Kβ line. The hard X-ray component is well described by a simple power law with a mean photon index of Γ = 1.7. During the INTEGRAL observations the 20 - 100 keV flux increased by a factor of 1.4. The analysis of XMM-Newton data implies that the emission below 3 keV is decoupled from the AGN and probably due to extended emission as seen in Chandra observations. The constant iron line emission is apparently also decoupled from the direct emission of the central engine and likely to be generated in the obscuring material, e.g. in the molecular torus. | |
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