Search

The models and results of the experimental studies of the characteristics of objects that are new for domestic instrumentation are presented: an X-ray mirror system and a CdTe strip semiconductor detector that are used in the first Russian ART-XC reflecting X-ray telescope. This telescope is a part of the Spektr-RG international space observatory, which started to the L2 libration point in July 2019.

Full list of authors: Krawczynski, Henric; Muleri, Fabio; Dovciak, Michal; Veledina, Alexandra; Cavero, Nicole Rodriguez; Svoboda, Jiri; Ingram, Adam; Matt, Giorgio; Garcia, Javier A.; Loktev, Vladislav; Negro, Michela; Poutanen, Juri; Kitaguchi, Takao; Podgorny, Jakub; Rankin, John; Zhang, Wenda; Berdyugin, Andrei; Berdyugina, Svetlana, V; Bianchi, Stefano; Blinov, Dmitry; Capitanio, Fiamma; Di Lalla, Niccolo; Draghis, Paul; Fabiani, Sergio; Kagitani, Masato; Kravtsov, Vadim; Kiehlmann, Sebastian; Latronico, Luca; Lutovinov, Alexander A.; Mandarakas, Nikos; Marin, Frederic; Marinucci, Andrea; Miller, Jon; Mizuno, Tsunefumi; Molkov, Sergey, V; Omodei, Nicola; Petrucci, Pierre-Olivier; Ratheesh, Ajay; Sakanoi, Takeshi; Semena, Andrei N.; Skalidis, Raphael; Soffitta, Paolo; Tennant, Allyn F.; Thalhammer, Phillipp; Tombesi, Francesco; Weisskopf, Martin C.; Wilms, Joern; Zhang, Sixuan; Agudo, Ivan; Antonelli, Lucio A.; Bachetti, Matteo; Baldini, Luca; Baumgartner, Wayne H.; Bellazzini, Ronaldo; Bongiorno, Stephen D.; Bonino, Raffaella; Brez, Alessandro; Bucciantini, Niccolo; Castellano, Simone; Cavazzuti, Elisabetta; Ciprini, Stefano; Costa, Enrico; De Rosa, Alessandra; Del Monte, Ettore; Di Gesu, Laura; Di Marco, Alessandro; Donnarumma, Immacolata; Doroshenko, Victor; Ehlert, Steven R.; Enoto, Teruaki; Evangelista, Yuri; Ferrazzoli, Riccardo; Gunji, Shuichi; Hayashida, Kiyoshi; Heyl, Jeremy; Iwakiri, Wataru; Jorstad, Svetlana G.; Karas, Vladimir; Kolodziejczak, Jeffery J.; La Monaca, Fabio; Liodakis, Ioannis; Maldera, Simone; Manfreda, Alberto; Marscher, Alan P.; Marshall, Herman L.; Massaro, Francesco; Mitsuishi, Ikuyuki; Ng, Chi-Yung; O'Dell, Stephen L.; Oppedisano, Chiara; Papitto, Alessandro; Pavlov, George G.; Peirson, Abel L.; Perri, Matteo; Pesce-Rollins, Melissa; Pilia, Maura; Possenti, Andrea; Puccetti, Simonetta; Ramsey, Brian D.; Romani, Roger W.; Sgro, Carmelo; Slane, Patrick; Spandre, Gloria; Tamagawa, Toru; Tavecchio, Fabrizio; Taverna, Roberto; Tawara, Yuzuru; Thomas, Nicholas E.; Trois, Alessio; Tsygankov, Sergey; Turolla, Roberto; Vink, Jacco; Wu, Kinwah; Xie, Fei; Zane, Silvia., A black hole x-ray binary (XRB) system forms when gas is stripped from a normal star and accretes onto a black hole, which heats the gas sufficiently to emit x-rays. We report a polarimetric observation of the XRB Cygnus X-1 using the Imaging X-ray Polarimetry Explorer. The electric field position angle aligns with the outflowing jet, indicating that the jet is launched from the inner x-ray–emitting region. The polarization degree is 4.01 ± 0.20% at 2 to 8 kiloelectronvolts, implying that the accretion disk is viewed closer to edge-on than the binary orbit. These observations reveal that hot x-ray–emitting plasma is spatially extended in a plane perpendicular to, not parallel to, the jet axis. © 2022 The Authors., H.K. acknowledges NASA support under grants 80NSSC18K0264, 80NSSC22K1291, 80NSSC21K1817, and NNX16AC42G. F.Mu., J.R., S.B., S.F., A.R., P.So., E.D.M., E.Co., A.D.M., G.M., Y.E., R.F., F.L.M., M.Pe., and A.T. were funded through contract ASI-INAF-2017-12-H0. L.B., R.Bo., R.Be., A.Br., L.L., S.Ca., S.M., A.Man., C.O., M.P.-R., C.S., and G.S. were funded by the ASI through contracts ASI-INFN-2017.13-H0 and ASI-INFN 2021-43-HH.0. M.Pi. was funded through contract ASI-INAF-2022-14-HH.0. I.A. acknowledges support from MICINN (Ministerio de Ciencia e Innovación) Severo Ochoa award for the IAA-CSIC (SEV-2017-0709) and through grants AYA2016-80889-P and PID2019-107847RB-C44. M.D., J.S., and V.Ka. acknowledge support from GACR (Grantová agentura České republiky) project 21-06825X and institutional support from the Astronomical Institute of the Czech Academy of Sciences (RVO:67985815). J.A.G. acknowledges support from NASA grant 80NSSC20K0540. J.Pod. acknowledges support from Charles University project GA UK No. 174121 and from the Barrande Fellowship Programme of the Czech and French governments. A.V., J.Pou., and S.S.T. acknowledge support from Russian Science Foundation grant 20-12-00364 and the Academy of Finland grants 333112, 347003, 349144, and 349906. M.N. acknowledges support from NASA under award number 80GSFC21M0002. T.K. is supported by JSPS KAKENHI Grant Number JP19K03902. P.-O.P. acknowledges support from the High Energy National Programme (PNHE) of Centre national de la recherche scientifique (CNRS) and from the French space agency (CNES) as well as from the Barrande Fellowship Programme of the Czech and French governments. D.B., S.K., N.M., and R.S. acknowledge support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program under grant agreement no. 771282. V.Kr. thanks Vilho, Yrjö and Kalle Väisälä Foundation. P.T. and J.W. acknowledge funding from Bundesministerium für Wirtschaft and Klimaschutz under Deutsches Zentrum für Luft- und Raumfahrt grant 50 OR 1909. A.I. acknowledges support from the Royal Society. J.H. acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), funding reference number 5007110, and the Canadian Space Agency. S.G.J. and A.P.M. are supported in part by National Science Foundation grant AST-2108622, by NASA Fermi Guest Investigator grant 80NSSC21K1917, and by NASA Swift Guest Investigator grant 80NSSC22K0537. C.-Y.N. is supported by a General Research Fund of the Hong Kong Government under grant number HKU 17305419. P.Sl. acknowledges support from NASA Contract NAS8-03060.

SXP 1323 is a peculiar high-mass X-ray binary located in the Small Magellanic Cloud, renowned for its rapid spin-up. We investigate for the first time broadband X-ray properties of SXP1323, as observed by the Mikhail Pavlinsky ART-XC and eRosita telescopes on board the SRG observatory. Using ART-XC and eRosita, data we produced first broadband 1-20 keV X-ray spectrum and estimated pulsed fraction above 8 keV. With the addition of archival XMM-Newton observations we traced evolution of the SXP 1323 spin period over the last five years and found that after 2016 the source switched to a linear spin-up with rate of -29.9 s yr$^{-1}$. Broadband X-ray spectrum is typical for accreting X-ray pulsars, with steep powerlaw index ($\Gamma$=-0.15) and exponential cutoff energy of 5.1 keV. No significant difference between spectra obtained in states with and without pulsations were found., Comment: Submitted to A&A for the Special Issue: The Early Data Release of eROSITA and Mikhail Pavlinsky ART-XC on the SRG Mission. 5 pages, 3 figures

We have investigated the X-ray spectral properties of the ten heavily obscured nearby (z < 0.1) active galactic nuclei (AGNs) IGR J00256+6821, NGC 1194, CGCG 420−015, IGR J09253+6929, NGC 3281, NGC 4939, IGR J14175−4641, NGC 5643, NGC 5728, and ESO 137−G034 from the catalogue of hard X-ray sources detected during the INTEGRAL seven-year all-sky survey. Based on data from the NuSTAR space telescope supplemented with XMM-Newton and Chandra data at low energies, we have estimated the intrinsic absorption column densities, photon indices, and intrinsic luminosities of these AGNs. In three objects (NGC 5643, NGC 3281, and ESO 137−G034) the absorption column density (NH) exceeds 2 × 1024 cm−2, while the observed spectrum is dominated by the emission from the central source scattered in the surrounding gas-dust torus. In five objects (IGR J00256+6821, IGR J14175−4641, CGCG 420−015, NGC 1194, and NGC 5728) NH = 1−2 × 1024 cm−2, while the emissions transmitted through the torus and reflected from it make comparable contributions to the recorded X-ray flux. Two more sources (IGR J09253+6929 and NGC 4939) manifested themselves as Compton-thin (NH < 5 × 1023 cm−2) AGNs during the NuSTAR observations. The intrinsic luminosities of the investigated AGNs exceed the observed ones by up to a factor of 7. Given the results obtained now for almost the entire sample of AGNs from the catalogue of the INTEGRAL seven-year all-sky survey, there are reliable absorption column density and intrinsic luminosity estimates, which make it one of the best samples for investigating the population of AGNs in the local Universe.

We present a first catalog of sources detected by the Mikhail Pavlinsky ART-XC telescope on board the SRG observatory in the 4-12 keV energy band during its ongoing all-sky survey. The catalog comprises 867 sources detected on the combined map of the first two 6-month scans of the sky (December 2019 - December 2020). The achieved sensitivity to point sources varies between ~4x10^-12 erg/s/cm2 near the ecliptic plane and ~8x10^-13 erg/s/cm2 (4-12 keV) near the ecliptic poles, and the typical localization accuracy is ~15 arcsec. Of the 750 sources of known or suspected origin in the catalog, 56% are extragalactic (mostly active galactic nuclei, AGN; and clusters of galaxies) and the rest are Galactic (mostly cataclysmic variables, CVs; and low- and high-mass X-ray binaries). For 114 sources, ART-XC has detected X-rays for the first time. Although the majority of these (~80) are expected to be spurious (given the adopted detection threshold), there can be a significant number of newly discovered astrophysical objects. We have started a program of optical follow-up observations of the new and previously unidentified X-ray sources, which has already led to the identification of several AGN and CVs. With the SRG all-sky survey planned to continue for a total of four years, we can expect the ART-XC survey in the 4-12 keV band to significantly surpass previous surveys that were carried out in similar (medium X-ray) energy bands in terms of the combination of angular resolution, sensitivity, and sky coverage., To appear on A&A, Special Issue: The Early Data Release of eROSITA and Mikhail Pavlinsky ART-XC on the SRG Mission; 40 pages, 10 figures, the catalog of sources is included

ART-XC (Astronomical Roentgen Telescope - X-ray Concentrator) is the hard X-ray instrument with grazing incidence imaging optics on board the Spektr-Roentgen-Gamma (SRG) observatory. The SRG observatory is the flagship astrophysical mission of the Russian Federal Space Program, which was successively launched into orbit around the second Lagrangian point (L2) of the Earth-Sun system with a Proton rocket from the Baikonur cosmodrome on 13 July 2019. The ART-XC telescope will provide the first ever true imaging all-sky survey performed with grazing incidence optics in the 4-30 keV energy band and will obtain the deepest and sharpest map of the sky in the energy range of 4-12 keV. Observations performed during the early calibration and performance verification phase as well as during the on-going all-sky survey that started on 12 Dec. 2019 have demonstrated that the in-flight characteristics of the ART-XC telescope are very close to expectations based on the results of ground calibrations. Upon completion of its 4-year all-sky survey, ART-XC is expected to detect ~5000 sources (~3000 active galactic nuclei, including heavily obscured ones, several hundred clusters of galaxies, ~1000 cataclysmic variables and other Galactic sources), and to provide a high-quality map of the Galactic background emission in the 4-12 keV energy band. ART-XC is also well suited for discovering transient X-ray sources. In this paper, we describe the telescope, results of its ground calibrations, major aspects of the mission, the in-flight performance of ART-XC and first scientific results., 19 pages, 30 figures, accepted for publication in Astronomy and Astrophysics

From October 2016 to September 2017, we performed tests of the ART-XC /SRG spare mirror system and detector unit at the 60-m-long IKI X-ray test facility. We describe some technical features of this test facility. We also present a brief description of the ART-XC mirror system and focal detectors. The nominal focal length of the ART-XC optics is 2700 mm. The field of view is determined by the combination of the mirror system and the detector unit and is equal to ∼0.31 square degrees. The declared operating energy range is 5–30 keV. During the tests, we illuminated the detector with a 55Fe+241 Am calibration source and also with a quasi-parallel X-ray beam. The calibration source is integrated into the detector’s collimator. The X-ray beam was generated by a set of Oxford Instruments X-ray tubes with Cr, Cu and Mo targets and an Amptek miniature X-ray tube (Mini-X) with Ag transmission target. The detector was exposed to the X-ray beam either directly or through the mirror system. We present the obtained results on the detector’s energy resolution, the muon on-ground background level and the energy dependence of the W90 value. The accuracy of a mathematical model of the ART-XC mirror system, based on ray-tracing simulations, proves to be within 3.5% in the main energy range of 4–20 keV and 5.4% in the “hard” energy range of 20–40 keV.

This article presents the findings of experimental research on the thermal conditions of the grazing-incidence mirrors used in the first Russian X-ray mirror telescope and theoretical studies of the influence of the temperature gradients on the characteristics of the X-ray mirrors.

An all-sky monitor (MVN) is an instrument intended for a long-term experiment for measurement of cosmic x-ray background (CXB). It will be installed on the international space station (ISS) surface in 2018. In this instrument four CdTe detectors are used to measure CXB energy spectrum. To obtain accurate spectral measurements with planned accuracy, detectors’ temperature should not deviate by more than two degrees from minus 30◦C during the experiment. Thermal stabilization of the detectors is complicated because of strongly variable external thermal conditions on the ISS surface. Influence of variable heat fluxes can be compensated for by using oppositely oriented radiators. In this article we describe the method application in the case of MVN.

We present phase-resolved spectroscopy, photometry and circular spectropolarimetry of the eclipsing polar UZ Fornacis. Doppler tomography of the strongest emission lines using the inside-out projection revealed the presence of three emission regions: from the irradiated face of the secondary star, the ballistic stream and the threading region, and the magnetically confined accretion stream. The total intensity spectrum shows broad emission features and a continuum that rises in the blue. The circularly polarized spectrum shows the presence of three cyclotron emission harmonics at $\sim$4500 \AA{}, 6000 \AA{} and 7700 \AA{}, corresponding to harmonic numbers 4, 3, and 2, respectively. These features are dominant before the eclipse and disappear after the eclipse. The harmonics are consistent with a magnetic field strength of $\sim$57 MG. We also present phase-resolved circular and linear photopolarimetry to complement the spectropolarimetry around the times of eclipse. MeerKAT radio observations show a faint source which has a peak flux density of 30.7 $\pm$ 5.4 $\mu$Jy/beam at 1.28 GHz at the position of UZ For., Comment: Accepted on MNRAS

A two dimensional numerical model in the axisymmetric approximation that describes the flow structure in the magnetosphere of the white dwarf in the EX Hya system has been developed. Results of simulations show that the accretion in EX Hya proceeds via accretion columns, that are not closed and have curtain-like shapes. The thickness of the accretion curtains depends only weakly on the thickness of the accretion disk. This thickness developed in the simulations does not agree with observations. It is concluded that the main reason for the formation of thick accretion curtains in the used model is the assumption that the magnetic field penetrates fully into the plasma of the disk. An analysis based on simple estimates shows that a diamagnetic disk that fully or partially shields the magnetic field of the star may be a more attractive explanation for the observed features of the accretion in EX Hya., 21 pages, 11 figures

ART-XC is an X-ray grazing incidence mirror telescopes array onboard the Spectrum-Roentgen-Gamma (SRG) mission, that is currently scheduled for launch in March 2019. This instrument was developed by the Space Research Institute (IKI) and the All-Russian Scientific Research Institute for Experimental Physics (VNIIEF). The NASA Marshall Space Flight Center (MSFC) has developed and fabricated flight X-ray mirror modules. Each mirror module is aligned with a focal plane CdTe double-sided strip detector which will operate over the energy range of 4−30 keV, with an angular resolution of

The properties of the aperiodic variability in X-ray binaries with black holes are considered. The power spectra of the luminosity variability for a flat accretion disk that is an emission source with a power-law energy spectrum have been modeled. At low frequencies the derived power spectrum has the form of a power law with a slope $\rho\approx-1$ and a cutoff at a frequency approximately equal to the fluctuations characteristic frequency at the disk inner edge; at higher frequencies the power spectrum has a complex form. The high-frequency variability is suppressed due to the arrival time delays of the photons emerging in the different parts of the disk. The presence of azimuthal accretion rate fluctuations in the disk and the azimuthal non-uniformity of the disk surface brightness in the observer's imaginary plane caused by the relativistic effects give rise to an additional variability at frequencies $\sim$200 Hz., Comment: 13 pages, 6 figures, published in the Astronomy Letters

ART-XC – a medium-x-ray-energy survey instrument for SRG project is being developed in Russia. Space Research institute (IKI) and Federal Nuclear Center (VNIIEF) has developed and tested the STM (Structural and Thermal Model) of ART-XC/SRG Instrument. The STM was tested in a 40 m 3 vacuum chamber, equipped with black cryogenic screens, cooled by liquid nitrogen. During the tests various thermal telescope modes were simulated. In particular we have simulated emergency mode, when mirrors heaters were switched-off. During the tests temperature of instrument’s structure was controlled by 64 independent sensors. Stability of optical axis of mirror systems was also measured. STM test has shown that temperature of mirror system was lower than required, temperature of detectors met the requirements. The test also confirmed geometrical stability of the carbon fiber housing despite of significant temperature gradients. Additional experiments with two mirror systems, each containing a full set of simple nickel shells, were performed. In these experiments we have measured longitudinal and transverse temperature gradients of mirror systems. Next thermovacuum tests of the qualification model of the ART-XC instrument are being prepared. Results of STM tests are presented in this paper.

Spectrum Roentgen Gamma (SRG) is an X-ray astrophysical observatory, developed by Russia in collaboration with Germany. The mission will be launched in beginning 2017 from Baikonur and placed in a 6-month-period halo orbit around L2. The scientific payload consists of two independent telescopes – a soft-x-ray survey instrument, eROSITA, being provided by Germany and a medium-x-ray-energy survey instrument ART-XC being developed by Russia. ART-XC will consist of seven independent, but co-aligned, telescope modules. The ART-XC flight mirror modules has been developed and fabricated at the NASA Marshall Space Flight Center (MSFC). Each mirror module will be aligned with a focal plane CdTe double-sided strip detector which will operate over the energy range of 6−30 keV, with an angular resolution of

We present current results on the theoretical and experimental studies of optimal cryogenic cooling of gamma-ray spectrometers based on high-purity germanium (HPGe) detectors. We show that the technology of cryogenic heat pipe diodes (HPDs) usually allows one to meet cooling requirements with minimal weight, power consumption and cost. Results of computer modeling and laboratory tests of HPDs, Stirling cooler and complete cooling solutions are presented.

Spectrum Roentgen Gamma (SRG) is an X-ray astrophysical observatory, developed by Russia in collaboration with Germany. The mission will be launched in 2014 from Baikonur, by a Zenit rocket with a Fregat booster and placed in a 6-month-period halo orbit around L2. The scientific payload consists of two independent telescopes . a soft-x-ray survey instrument, eROSITA, being provided by Germany and a medium-x-ray-energy survey instrument ART-XC being developed by Russia. ART-XC will consist of seven independent, but co-aligned, telescope modules with seven corresponding cadmium-telluride focal plane detectors. Each will operate over the approximate energy range of 6- 30 keV, with an angular resolution of

MVN (Monitor Vsego Neba) - new small X-ray astronomical experiment, which will be mounted on Russian segment of International Space Station. The main scientific goal for the instrument is the precise measurement of cosmic X-ray background in energy range 6-70 keV, which is important for theories of black hole evolution in the Universe. The ultimate aim of the experiment is to reach the accuracy of the CXB measurements, which will allow us to measure the large scale anisotropy of the Cosmic X-ray Background caused by inhomogeneities of the matter distribution in the local Universe. The MVN instrument is a simple collimated spectrometer, equipped with 4 CdTe pixellated detectors. The field of view of the instrument will be scanning the zenith of the ISS. The accuracy of the instrumental background subtraction, which is the main obstacle for the proposed task, will be provided by a cover, which will periodically block the aperture of detectors. According to our estimates, with not unfavourable radiation environment on orbit of ISS during period of operation of MVN we will be able to measure the CXB surface brightness at different sky directions with accuracy better than 1% after 2 years of the experiment. The planned dates of the experiment is 2013-2016.

International audience; Probing of Hermean exosphere by ultraviolet spectroscopy (PHEBUS) is a double spectrometer for the Extreme Ultraviolet range (55-155 nm) and the Far Ultraviolet range (145-315 nm) devoted to the characterization of Mercury's exosphere composition and dynamics, and surface-exosphere connections. This French-led instrument is implemented in a cooperative scheme involving Japan (detectors), Russia (scanner) and Italy (ground calibration). PHEBUS will address the following main scientific objectives relative to Mercury's exosphere: determination of the composition and the vertical structure of the exosphere; characterization of the exospheric dynamics: day to night circulation, transport between active and inactive regions; study of surface release processes; identification and characterization of the sources of exospheric constituents; detection and characterization of ionized species and their relation with the neutral atmosphere; space and time monitoring of exosphere/magnetosphere exchange and transport processes; study and quantification of escape, global scale source/sink balance and geochemical cycles synergistically with other experiments of BepiColombo (Mercury Sodium Atmospheric Spectral Imager (MSASI), Mercury Plasma Particle Experiment (MPPE) on Mercury Magnetospheric Orbiter (MMO); Mercury imaging X-ray spectrometer (MIXS), Search for exosphere refilling and emitted neutral abundance (SERENA) on Mercury Planetary Orbiter (MPO)). Two gratings and two detectors are used according to a specific, compact design. The spectrum detection is based on the photon counting method and is realized using micro-channel plate (MCP) detectors with Resistive Anode Encoder (RAE). Typical photocathodes are CsI or KBr for the extreme ultra-violet (EUV) range, CsTe for the far ultra-violet (FUV) range. Extra visible lines are monitored using a photo-multiplier (PM) that is also used in photon counting mode. In order to prevent sensitivity losses which are critical in UV ranges, a minimum of reflections is achieved inside the instrument using only an off-axis parabola and a set of holographic gratings. A one degree-of-freedom scanning system allows to probe, at the highest possible signal-to-noise ratio, selected regions and altitude ranges of interest. Different modes of observation will be used sequentially (vertical scans, along-orbit scans, grazing observations at twilight, etc.). During the mission, the instrument will be regularly calibrated on well chosen stars, in such a way to quantitatively estimate the overall degradation of the sensitivity of the instrument.

The Spectrum-Roentgen-Gamma mission will be launched in the 2012 year into a L2 orbit with Soyuz launcher and Fregat buster from Baikonur. The mission will conduct all-sky survey with X-ray mirror telescopes eROSITA and ART-XC up to 11 keV. It will allow detection of about 100 thousand clusters of galaxies and discovery large scale Universe structure. It will also discover all obscured accreting Black Holes in nearby galaxies and many (about 3 millions) new distant AGN. Then it is planned to observe dedicated sky regions with high sensitivity and thereafter to perform follow-up pointed observations of selected sources.

The ART-XC instrument is an X-ray grazing-incidence telescope system in an ABRIXAS-type optical configuration optimized for the survey observational mode of the Spectrum-RG astrophysical mission which is scheduled to be launched in 2011. ART-XC has two units, each equipped with four identical X-ray multi-shell mirror modules. The optical axes of the individual mirror modules are not parallel but are separated by several degrees to permit the four modules to share a single CCD focal plane detector, 1/4 of the area each. The 450-micron-thick pnCCD (similar to the adjacent eROSITA telescope detector) will allow the detection of X-ray photons up to 15 keV. The field of view of the individual mirror module is about 18×18 arcminutes2 and the sensitivity of the ART-XC system for 4 years of survey will be better than 10-12 erg s-1 cm-2 over the 4-12 keV energy band. This will allow the ART-XC instrument to discover several thousands new AGNs.

Spatially resolved X-ray spectroscopy with high spectral resolution allows the study of astrophysical processes in extended sources with unprecedented sensitivity. This includes the measurement of abundances, temperatures, densities, ionisation stages as well as turbulence and velocity structures in these sources. An X-ray calorimeter is planned for the Russian mission Spektr Rontgen-Gamma (SRG), to be launched in 2011. During the first half year (pointed phase) it will study the dynamics and composition of of the hot gas in massive clusters of galaxies and in supernova remnants (SNR). During the survey phase it will produce the first all sky maps of line-rich spectra of the interstellar medium (ISM). Spectral analysis will be feasible for typically every 5° x 5° region on the sky. Considering the very short time-scale for the development of this instrument it consists of a combination of well developed systems. For the optics an extra eROSITA mirror, also part of the Spektr-RG payload, will be used. The detector will be based on spare parts of the detector flown on Suzaku combined with a rebuild of the electronics and the cooler will be based on the design for the Japanese mission NeXT. In this paper we will present the science and give an overview of the instrument.

The hard X-ray telescope-concentrator ART-XC on board the Spectrum-X-Gamma X-ray astrophysical observatory (launching in 2011) is one of the main instruments of the mission. The instrument will be used for an all-sky survey and then for pointed observations which are planned for the first four and the next three years of the Mission, respectively. ART-XC will be sensitive in the 4-30 keV energy range and will have an effective area of several hundred square centimeters at 10 keV. It will have a field of view of about ~28 arcmin, angular resolution better than 1 arcmin and will be an order of magnitude more sensitive than the current generation of collimated instruments and coded mask telescopes in the survey mode and a two or three orders of magnitude more sensitive in the pointing mode. With its high sensitivity in the hard X-ray band and good imaging capabilities, ART-XC will extend the operating energy range of the observatory (complementing the capabilities of the primary science instrument eROSITA), thus significantly enhancing the mission both in the all-sky survey over the energy band 4-10 keV and, especially, in pointed observations over the energy band 4-30 keV. During the 4-year survey, this ART-XC would detect more than ~10 4 sources over 4-10 keV. For a 10 5 second pointed observation, the telescope will provide better than 10 microCrab sensitivity in the 4-20 keV energy range.