ap-6-11.dvi Acta Polytechnica Vol. 51 No. 6/2011 Czech Participation in INTEGRAL: 1996–2011 R. Hudec, M. Blažek, V. Hudcová Abstract The European Space Agency ESA INTEGRAL satellite launched in October 2002 is the first astrophysical satellite of the European Space Agency (ESA) with Czech participation. The results of the first 8 years of investigations of various scientific targets are briefly presented and discussed here, with emphasis on cataclysmic variables and blazars with the ESA INTEGRAL satellite with Czech participation. 1 Introduction There is a long tradition of involvement of Czech sci- entists in high-energy space projects, starting nearly 40 years agowithCzech involvement in various satel- lite experiments within the INTERKOSMOS pro- gramme. Collaboration with the European Space Agency(ESA)startedsoonafter thepolitical changes in Czechoslovakia in 1989. The ESA INTEGRAL projectwas the first ESAproject in space astronomy withofficialCzechparticipationbasedonacollabora- tion agreement between ESA and the Czech Repub- lic, i.e. prior to fullmembership of theCzechRepub- lic in ESA. The INTEGRAL (International Gamma- RayAstrophysics Laboratory) satellite has nowbeen in orbit formore than 8 years, and some general con- clusions may be drawn at this point. Fig. 1: OMCTestDevice (providing real test images) op- erated atAIOndrejovprior to the launchof INTEGRAL. BART Wide Field CCD camera, FOV 6×7 degrees, lim mag 15.5, identical with INTEGRAL OMC Test Device (18 arcsec/pixel) There are four co-aligned instruments on board INTEGRAL: (1) an IBIS gamma-ray imager (15 keV to 10 MeV, full coded field of view (FOV) 8.3 × 8 deg, 12 arc min FWHM), (2) an SPI gamma- ray spectrometer (12 keV–8 MeV, full coded FOV 16×16deg), (3) a JEM-XX-raymonitor (3–35 keV, fully illuminated FOV diameter 4.8 deg), and (4) an OMC optical monitoring camera (Johnson V filter, FOV 5×5 deg) (Winkler et al. 2003). These exper- iments enable simultaneous observation in the opti- cal, medium X-ray, hard X-ray, and gamma spec- tral region (or at least a suitable upper limit) for each object, assuming that it is inside the field of view. The basic observation codes are as follows: (a) Regular (weekly) Galactic Plane Scans (GPS) (−14 deg < bII < +14 deg), (b) Pointed observa- tions (AO), (c) Targets of opportunity (ToO). In this paper, we deal with examples of observa- tions and analyses of INTEGRAL data with Czech participation, focusing on two categories of objects, namely cataclysmic variables (CVs) and blazars. 2 Czech involvement in the INTEGRAL Project Czech involvement in the ESA INTEGRAL project started in 1996,whenReneHudecwas invited to join the OMC and ISDC consortia, on the basis of a col- laboration agreement between ESA and the Czech Republic. At that time, our participation focused on ISDC and OMC. In OMC (Optical Monitoring Camera), our par- ticipation focused on various software packages, such as OMC PS (OMC Pointing Software) for Integral ISOC, and also on the design, development and op- eration of OMC TD (Test Device), a ground-based camera with output analogous (pixel size 18 arcsec) with the real OMC. For ISDC (Integral Science andData Center), lo- cated in Versoix, Switzerland, the main part of our contribution involved providing manpower, i.e. one 20 Acta Polytechnica Vol. 51 No. 6/2011 personworkingwithin the team,withvarious respon- sibilities and involvements in the ISDC operations. As for the scientific responsibilities, Rene Hudec was delegated to lead the study of cataclysmic variables, andhewas later also amember of theworkinggroups on gamma-raybursts (GRBs) andAGNs. In this pa- per, we very briefly summarize the scientific achieve- ments in these fields. In addition, we have partici- pated in the development and operation of dedicated robotic telescopes, considered as the ground-based segment of the project, and in delivering supplemen- tary optical data for satellite triggers. This work has been done mainly by young research fellows and by students. TheCzech scientific participation focused on top- ics allocated by INTEGRAL bodies, mostly cata- clysmic variables but also blazars and some other objects, such as Gamma-Ray Bursts (GRBs). Fig. 2: Test image provided by the OMC Test Device operated at the Ondrejov Observatory (FOV 6 × 7 deg, lim mag 15.5, pixel size 18 arcsec identical with the real OMC camera) Fig. 3: Example of an OMC image from space 3 Cataclysmic variables Responsibility for the category of cataclysmic vari- ables (CVs) and related objects was delegated to Rene Hudec. The results of hard X-ray detections of these binary galactic objects were surprising. The soft X-ray emission of the group was already known in advance, but the hard X-ray extension to (in some cases) more than 80 keV was a new discov- ery. These findings have even led to the idea that CVs may make a contribution to the galactic X-ray background. In total, 32cataclysmicvariables (CVs)havebeen detected by the INTEGRAL IBIS gamma-ray tele- scope (this is more than had been expected before launch, and represents almost 10 percent of INTE- GRAL detections). 22 CVs have been seen by IBIS and found by the IBIS survey team (Barlow et al. 2006, Bird et al. 2007, Galis 2008), based on a cor- relation of the IBIS data and the Downes CV cat- alogue (Downes et al. 2001). Four sources are CV candidates revealed by optical spectroscopy of IGR sources (Masetti et al. 2006), i.e. new CVs, not in the Downes catalogue. They are mainly magnetic systems: 22 were confirmed or probable IPs, 4 prob- able magnetic CVs, 3 polars, 2 dwarf novae, 1 un- known. The vast majority have an orbital period Porb > 3 hr, i.e. above the period gap (only one has Porb < 3 hr), but 5 objects are long-period systems with Porb > 7 hr. The long lifetime of the INTEGRAL satellite (> 10 years) has enabled long-term variability stud- ies, albeit limited by observation sampling. At least in some cases, the hard X-ray fluxes of CVs seen by INTEGRAL exhibit time variations, very prob- ably related to the activity/inactivity states of the objects. The spectra of the CVs observed by IBIS are in most cases similar. A power law or thermal bremsstrahlungmodel compares well with the previ- ous high-energy spectral fits (de Martino et al. 2004, Suleimanov et al. 2005, Barlow et al. 2006). Another surprise is that while the group of IPs represents only ∼2 percent of the cataloguedCVs, it dominates the group of CVs detected by IBIS. More such detections and new identifications can therefore be expected, as confirmedbyour search for IPs in the IBIS data, which provided 6 newdetections (Galis et al. 2008). Many CVs covered by the Core Program (CP) remain unobservable by IBIS because of short exposure time, but new CVs have been discovered. IBIS tends to detect IPs and asynchronous polars: in hardX-rays, these objects seem to bemore luminous (uptoa factorof10) thansynchronouspolars. Detec- tion of CVs by IBIS typically requires 150–250 ksec of exposure timeormore, but someof themremained invisible even after 500 ksec., at least in some cases. However, this can be related to the activity state of 21 Acta Polytechnica Vol. 51 No. 6/2011 Fig. 4: Preview of 32 CVs observed by INTEGRAL– INTEGRAL IBIS sky coverage (up to March 2009) Fig. 5: Symbiotic starRTCru observed as an IBIS source up to energy 60 keV. The detection of symbiotic stars in hard X-rays by INTEGRAL was a surprise the sources — the hard X-ray activity is temporary or variable. Detecting hard X-ray flaring activity is another important issue. There is an indication for a hard X-ray flare in a CV system, namely V1223 Sgr, seen by IBIS (a flare lasting for > 3.5 hr during revolu- tion 61 (MJD 52743), with the peak flux > 3 times above the average (Barlowet al. 2006)). These flares had already been seen in the optical in the past by a ground-based instrument (duration of several hours) (vanAmerongen&vanParadijs 1989). This confirms the importance of the OMC-like instrument (prefer- ably with the same FOV as a gamma-ray telescope) on board gamma-ray satellites: evenwith the V lim- itingmag 15, this can provide valuable optical simul- taneousdata forgamma-rayobservations. Analogous flares are also known for other IPs in the optical, but not in hard X-rays. TV Col (Hudec et al. 2005) can serve as an example: in this system, 12 optical flares have been observed so far, five of them on archival plates from the Bamberg Observatory, and the re- maining flares by others observers. TV Col is an IP, and the optical counterpart of the X-ray source 2A0526–328 (Cooke et al. 1978). This system is the firstCVdiscoveredthrough itsX-rayemission, newly confirmedas an INTEGRAL source. The physics be- hind the outbursts in IPs is either the instability of the disk or an increase in the mass transfer from the secondary. 4 Blazars Another category of INTEGRAL targets that we have investigated is a special class of AGN (Active GalacticNuclei), knownasblazars. Theseobjectsbe- long to the most important and also optically most violently variable extragalactic high-energy objects. We focus on objects found by data mining in the IN- TEGRAL archive for faint and hidden objects. For moredetails onblazaranalyseswith INTEGRAL, see Hudec et al. (2007). In addition, successful blazar observations have been performedmostly in theToO regime. The extensive collaboration led by E. Pian serves as an example (Pian et al. 2007). We have de- veloped procedures for accessing faint blazars in the IBIS database. Blazar 1ES 1959+650 can serve as an example. This blazar is a gamma-ray loud vari- able object visible by IBIS in 2006 only, invisible in totalmosaics and/or other periods. The optical light curve available for this blazar confirms the relation of active gamma-ray and the active optical state. Fig. 6: The most significant result of the IBIS data min- ing procedure for faint sources. The flux corresponding to the excess in the lower spectral band for Mrk 501 is (1.57 ± 0.24) 10–11 erg/cm2/s. The coordinates of the images are given in pixels, one pixel being 4.9 arcmin; the mosaics are centered on the catalogue position of the source 5 OMC The small optical camera on board the INTEGRAL OMC satellite delivered a great amount of valuable simultaneousopticaldata for observationsof gamma- rayandhardX-ray sources. However, for gamma-ray 22 Acta Polytechnica Vol. 51 No. 6/2011 bursts (GRBs) this is the case only for a few triggers, as the field of view (FOV) of OMC is much smaller than theFOVof themostwidely-used instrument on INTEGRAL, namely IBIS (5 vs. 8 degrees). How- ever, OMC proved to be an efficient tool for opti- cal objects without gamma–ray counterparts, such as eclipsing binaries. For these objects, the uninter- rupted nature (no day/night cycles) of space-based observations was found to be positive for studying the light curves and for determining the times of the minima. 6 ISDC The Czech involvement focused on direct participa- tion in the operation and activities of the Integral Science and Data Center (ISDC), including provid- ing one person continuously working directly within the ISDC team (aswell as other persons occasionally visiting ISDC). The person at ISDC participated in the service work of Center (especially by contribut- ing to ISDC operations), and also in scientific anal- yses. Participation in the scientific programme has involved observations, data analyses, data archiving, data interpretation, and scientific evaluations. In addition, wehaveworkedon transferring ISDC s/w packages, further development of tools for effec- tive and interactive scientific analyses and the use of INTEGRAL data, further improving the quality of astrometry and photometry, and on operating the second (local) ISDC center/office (Ondrejov Integral Data Center, OIDC) at the Ondrejov Astronomical Institute, enabling the astronomical community in the Czech Republic and in Central and East Europe to participate in scientific activities related to IN- TEGRAL, data evaluation, data archiving, and in- terpretation. The scientific activities have focused on allocated scientific tasks, especially Cataclysmic Variables and white dwarfs, Gamma ray Bursts, and Blazars-AGNs. Czech participation in ISDC (INTEGRAL Sci- ence and Data Centre) in Versoix has included the following tasks, which are listed below as examples. idx merge tool. Idx merge is a tool program developed at ISDC, which was used in archive pro- cessing for merging two FITS indices. Petr Kubanek carried out benchmark tests to provide information about possible speed-up in this program. The tests identified the fast-merge patch as the best possible solution. A fast-merge patch was developed by Petr Kubanek, tests for this patch were made, and the patchwas delivered to ISDC. The patch significantly speeded up archive processing. ISR – Integral Source Results web pages. Based on discussions with Mathias Beck, Mohamed Meherga and Roland Walter, Petr Kubanek created the IntegralSourceResultswebpages. Theseenabled users not familiar with OSA (Offline Scientific Anal- ysis, a software package used for analysing INTE- GRAL data) to access data products from standard OSA runs, which are executed at ISDC (Kubanek and Hudec, 2007). The web pages were later further developed by the ISDC staff. The web pages enabled access to light-curves, spectra and IBIS andJEM-Xprocessed images of ob- jects. They contained processed data for all public observations of sources that were flagged as detected in the INTEGRALSourceResults catalogue, version 15. ISDC repeatably reprocessed this data with new OSA releases, which provided better results on this quick-look page. A user guide for ISR was written, and also a description of ISR for the ISDC Newslet- ter. The ISR Perl source code was fully documented and delivered as the ISDC SW package. lc extract tools. Based on discussions with FilipMunz,PetrKubanekdeveloped lc extract tools, which were tested for extracting the countrates of weak sources from the INTEGRAL IBIS detector. lc extract uses a variant of the pure open/closemask element method to detect weak sources inside the IBIS field of view. VO – Virtual Observatory at ISDC Almost all facilities dealing with astronomical data archiving contribute to the development of Virtual Observatory. Virtual Observatory can be used for quick multispectral analysis of various sources, and for computer-driven data mining and processing. It can help researchers to gain quick access to informa- tion that they need in a format that they can use, so that they can focus onvalidating their theories rather than on learning variousmethods for processing data from various Earth and space based observatories. We contributed significantly to the development of Virtual Observatory by conforming access to IN- TEGRAL data. Petr Kubanek prepared the envi- ronment for enablingVirtual Observatory to provide access to INTEGRAL data. This work included in- stalling andconfiguring theApacheTomcat server on the ISDC Solaris computers. He decided to imple- ment VO services at ISDC as a set of Java Servlets. Themain reason for thiswashis experiencewithJava Servlets,whichhe foundsuperior to thePerl::CGIap- proach. Object-orientedprogramming (OOP),which forms the basis of Java language, allowsbetter design of complex programs. At the cost of a longer design phase, it enables better growth of initial small code subsets to full feature services and then procedural programming. It also promotes separation of code to small subsets with clearly defined interfaces. Thanks to this approach, the code can be reused. It should be noted thatOOPwas also introduced to Perl, but since Perl was not invented for OOP, 23 Acta Polytechnica Vol. 51 No. 6/2011 OOP implementation in it is introduced at the cost of variousdesign requirements,which layerOOPover the original Perl procedural language. Java also introduced JavaDoc for writing docu- mentation directly in code. This enables better and more up-to-date documentation than writing sepa- rate programming documentation. After deciding on the target enviroment (Java ServletContainer -Tomcat fromtheApacheFounda- tion), Petr Kubanek implemented VO access to the INTEGRAL catalogue. This first servlet was used as the prototype for developing of another servlet, which handles FITS images search and extraction. We developed a prototype for VO access to IN- TEGRAL IBIS mosaics. The advanced VO access was later offered by the ISDC staff to the world as- tronomical community, after further development of VO access, taking it from a prototype to production status, and including other high-level products in the VO database for all INTEGRAL instruments. As various VO developers have pointed out, the only currently available pure Java library to access FITS files, nom.tam.fits library, has significant draw- backs. These include bugs in reading big gzipped files, resulting in inability to read most of the IN- TEGRALdata, and lack of support forWCS (World Coordinate Systems) extensions (which are used for storing information about the part of the sky that the image contains). Petr Kubanek patched the nom.tam.fits library so the he can use it in his VO servlets. However, on the basis of discussions with other VO developers, he decided to recode the Java FITS access library, so that it will not suffer from thedrawbacksnotedduring itsuse. Hehas alsomade changes to theUKStarlink Starjavapackage, so that he can use it to quickly generate pages used for VO access. These efforts have been further developed by the ISDC staff. 7 Ground based segment Theoptical camera (OMC)onboard INTEGRALhas delivered valuable data, but there are some limits on magnitude, on accuracy, and on available FOV. There is an obvious need to provide additional op- tical data for simultaneous analyses of astrophysical objects detected by the onboard hard-energy experi- ments, above all IBIS. A similar procedure is consid- ered for theESAGaia satellite, since thephotometric sampling of the Gaia photometrywill not be optimal in many cases. For this reason we have from the beginning laid emphasis not only on space experiments but also on the related ground based segment, namely optical ground-based experiments, with emphasis on robotic telescopes. TheRTS2 dedicated control programhas been designed and developed. RTS2 was installed and runs on (nowaday) nu- merous robotics telescopes, which are spread around the globe. RTS2 was originally developed for conducting observations of gamma-ray burst error boxes in an optical window, but it has evolved to a full-featured package for any robotic telescope (http://rts2.org). On the basis of experience gained from develop- ing RTS1, RTS2 is layered to an abstract, device- independent communication layer, and drivers for various devices. Thanks to this layering, new de- vices can be integrated smoothly and very rapidly into RTS2. Members of the Czech Integral group have con- tinued to develop RTS2 (Remote Telescope System, 2nd version). A major change involved separat- ing the execution and selection logic, which had previously been handled by a single RTS2 compo- nent (planc), into two independent componets (rts2- executor, and rts2-selector). This separation enabled us to better fulfil the different requirements for dif- ferent scheduling algorithms for different telescopes (http://rts2.org). RTS2was installed e.g. in the 60 cmBIR (Bootes Infra-Rocho) telescope. BIR is located at the Insti- tuto de Astrofisica de Andalucia (IAA) Observato- rio de Sierra Nevada (OSN). RTS2 has also been in- stalled in the FRAM telescope at the Pierre-Auger Observatory in Argentina. It is used for monitoring the atmospheric conditions above the Pierre-Auger optical detectors. RTS2 has also been installed in the Watcher 1 telescope, located at the Boyden Ob- servatory in SouthAfrica. AsRTS2 is releasedunder GNU licence, the University College of Dublin mem- berswho builtWatcher downloaded it, customized it to fit their purpose and installed it in their telescope. Members of our grouphelped themwith the installa- tionprocess, andprovidedhelp in customizingRTS2. RTS2 was also customized for use in the MARK telescope, which is located in the Prague Stefanik Observatory, and we are running prelimary tests on RTS2 at this site. Thanks to the MARK tests, RTS2 acquired the ability to control observations se- tups with a copula. This ability will be very im- portant for the use of RTS2 in larger telescopes. It is currently under negotiation for various telescopes (more than 1m in diameter). RTS2 uses the lib- nova library to carry various astronomical calcula- tions. Petr Kubanek, who co-maintains libnova, has futher patched and developed libnova. 8 Other works The secondary science centre in Ondrejov has been put into operation. Various versions of OSA data analysis software have been transferred and successfully installed. Data for the most promising 24 Acta Polytechnica Vol. 51 No. 6/2011 sources has been reprocessedwith the OSA software packages and organized into a local archive in a way that enables any combination of SCWs to be con- structed on demand. Source database. Considerable time has been spent on developing a web interface for INTE- GRAL working groups, devoted to studies of blazars (http://altamira.asu.cas.cz/iblwg) and cataclysmicva- riable (CV) stars (http://altamira.asu.cas.cz/icvwg). Most of the features of these pages were supplied by a common code written in PHP with the underlying MySQL database. This database is filled with infor- mation from the ISDC archive (position and quality of individual pointings), and also with available HE data on the sources topredict their possible detection using INTEGRAL instruments. We still lack infor- mation on the X-ray spectra of CVs (only a small collection of about 20 spectra from ASCA observa- tions is available above 1 keV). More recently, a large new set of possible blazar positions (about 700, half of them corresponding to Veron-Cetty AGN locations) from astro-ph/0506720 has been included. We are currently checking the candidates with highest exposures. An important feature of these web pages is a scheduler thatusesdata fromthe ISOCpages (a com- plex script for retrieval of scheduled pointings and for importing them into the database was written by Jiri Polcar). This allows us to plan simultaneous observations with optical telescopes in advance, not just to react to GCN alerts about new INTEGRAL pointings (more suitable for robotic telescopes). In some cases, a given source is below the horizon at the time of INTEGRAL observation, so optical monitor- ing should be performed before the alert is issued. Weak source analysis. Our basic tool for ex- tracting physical data from reconstructed images is mosaic spec, a small program in C intended origi- nally as an alternative to standard spectral analy- sis (started at ISDC with Roland Walter in 2004). While the old version is currently employed by the INTEGRAL Source Result web interface to ISDC archive, the Czech team members have added some new features that allow us to obtain more informa- tion about the shape of the analysed peak in an IBIS image, the properties of the background (to sort out most of the false detections), and finally to retrieve a cutout from a large mosaic. This latter feature allows us significantly to reduce (by several orders of magnitude) the amount of data that needs to be transferred from ISDC when analyzing largemosaics (either available directly for pre-defined observation groups—OGs—or constructed fromselectedSCWs using the ii skyimage mosaicking capability). Since the energy binning of reconstructed IBIS images in the ISDC archive (revision 2) is too fine for a search of weak sources,mosaic spec can also sum-up several energy bins together to improve the statistics. The cut-outs should soon be available (once the bitmap conversion has been mastered). The analysis of short-timepre-definedOGs (up to 3 days in length) is well suited for studies of blazars (whose flares can appear at these time scales) but not so well suited for a search of cataclysmic vari- ables (whose variability has a more periodic nature). Where their basic periods (orbital, rotation or beat of these two) are known, we could employ phase re- solved analysis. A new tool called lc extract has been developed for this purpose by Petr Kubanek. It uses a pixel illumination factor (PIF) method similar to the standard IBIS light curve extraction process, but it should be less sensitive to variations of fluxes of strong sources in the field of view (which is the case for CVs close to the Galactic bulge). The produc- tionversionof this tool script includesGTI andnoisy pixel treatment. More recently, we have participated in the efforts at ISDC to further develop ISDC into amore general scientific and data centre for space astronomy. Inaddition, data fromastronomicalplatearchives has also been analysed for some of the targets, adding additional time dimensions to the investiga- tions, identification and classification of INTEGRAL sources. Not only the long-term evolution of optical light curves of objects (in some cases for up to 100 years) can be studied this way. Low-dispersion spectra (for various time epochs) can also be extracted and anal- ysed. 9 Conclusions TheCzech INTEGRAL teamhas contributed to var- ious fields of INTEGRAL science. Only a few exam- ples have been given in this paper. In general, the INTEGRAL satellite opens a new 10–100 keV X-ray observational window to which there had previously been only very limited access. The X-ray emisssion of some CVs and SSs extends to 80 keV. Our results confirm that the INTEGRAL satellite is an effective tool for finding new CVs, mainly IPs. The contribution of the Czech participants in the ESAINTEGRALprojecthas focused on the onboard OMCcamera, onwork at ISDC, and on INTEGRAL science, with emphasis on cataclysmic variables and blazars. The INTEGRAL satellite is clearly an effec- tive tool for analyzing both CVs and blazars. So far, 21 blazars, 32 CVs and 3 symbiotics have been de- tected, and the number is increasing with time. The successful observations of CVs using INTEGRAL provide proof that CVs can be successfully detected and observed in hard X-rays with INTEGRAL (for most CVs, these are considerably harder passbands than had been possible previously). These results 25 Acta Polytechnica Vol. 51 No. 6/2011 show that more CVs (in harder passbands) will be detectable with increasing integration time. There is also an increasing probability of detecting objects in outbursts, high and low states, etc. Simultane- ous hard X-ray and optical monitoring of CVs and blazars (or at least suitable upper limits) can pro- vide valuable inputs for better understanding of the physical processes that are involved. Acknowledgement The International Gamma-Ray Astrophysics Labo- ratory (INTEGRAL) is an European Space Agency mission with the instruments and the scientific data center funded by the ESA member states (espe- cially the PI countries: Denmark, France, Germany, Italy, Spain, Switzerland), the Czech Republic and Poland, and with the participation of Russia and the USA. This study was supported by the ESA PECSINTEGRAL98023projectandpartlybygrant 205/08/1207. The plate analyses have recently been supported by MSMT ME09027. The work described in this paper has been supported by current andpast members of the Czech INTEGRAL team and con- tributors, mainly P. Kubánek, J. Štrobl, V. Hud- cová, M. Kocka, M. Blažek, R. Gális, M. Nekola, C. Polášek, J. Polcar, F. Munz, V. Šimon, I. Sujová, F. Hroch, M. Topinka, and others. References [1] Barlow, E. J., Knigge, C., Bird, A. J., et al.: MNRAS, 372, 224, 2006. [2] Bianchini, A., Sabbadin, F.: IBVS, 2751, 1, 1985. [3] Bird,A. 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Lee, Enrico Ramírez-Ruiz)RevistaMexicanadeAstronomia y Astrofisica (Serie de Conferencias), Vol. 27, 2007, Contents of Supplementary CD, p. 204. 26 Acta Polytechnica Vol. 51 No. 6/2011 [28] Kubanek, P., Hudec, R.: Proceedings of 6th IN- TEGRAL Workshop, 2007. http://hea.iki.rssi.ru/integral06/papers/ René Hudec E-mail: rene.hudec@gmail.com Astronomical Institute Academy of Sciences of the Czech Republic CZ-25165 Ondřejov, Czech Republic Czech Technical University in Prague Faculty of Electrical Engineering Technicka 2, CZ-16627 Prague, Czech Republic Martin Blažek Astronomical Institute Academy of Sciences of the Czech Republic CZ-25165Ondřejov, Czech Republic Czech Technical University in Prague Faculty of Electrical Engineering Technicka 2, CZ-16627 Prague, Czech Republic Věra Hudcová Astronomical Institute Academy of Sciences of the Czech Republic CZ-25165Ondřejov, Czech Republic 27