Villanueva de la Cañada, Spain
Villanueva de la Cañada, Spain
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Bohringer H.,Max Planck Institute for Extraterrestrial Physics | Chon G.,Max Planck Institute for Extraterrestrial Physics | Retzlaff J.,ESO | Trumper J.,Max Planck Institute for Extraterrestrial Physics | And 2 more authors.
Astronomical Journal | Year: 2017

As the largest, clearly defined building blocks of our universe, galaxy clusters are interesting astrophysical laboratories and important probes for cosmology. X-ray surveys for galaxy clusters provide one of the best ways to characterize the population of galaxy clusters. We provide a description of the construction of the NORAS II galaxy cluster survey based on X-ray data from the northern part of the ROSAT All-Sky Survey. NORAS II extends the NORAS survey down to a flux limit of 1.8 ×10-12 erg s-1 cm-2 (0.1-2.4 keV), increasing the sample size by about a factor of two. The NORAS II cluster survey now reaches the same quality and depth as its counterpart, the southern REFLEX II survey, allowing us to combine the two complementary surveys. The paper provides information on the determination of the cluster X-ray parameters, the identification process of the X-ray sources, the statistics of the survey, and the construction of the survey selection function, which we provide in numerical format. Currently NORAS II contains 860 clusters with a median redshift of z =0.102. We provide a number of statistical functions, including the log N-log S and the X-ray luminosity function and compare these to the results from the complementary REFLEX II survey. Using the NORAS II sample to constrain the cosmological parameters, σ 8 and Ωm, yields results perfectly consistent with those of REFLEX II. Overall, the results show that the two hemisphere samples, NORAS II and REFLEX II, can be combined without problems into an all-sky sample, just excluding the zone of avoidance. © 2017. The American Astronomical Society. All rights reserved..

Ng C.,ESAC | Diaz Trigo M.,Science Operations Center | Cadolle Bel M.,Integral Science Operations Center | Migliari S.,ESAC
Astronomy and Astrophysics | Year: 2010

We analysed the XMM-Newton archival observations of 16 neutron star (NS), low-mass X-ray binaries (LMXBs) to study the Fe K emission in these objects. The sample includes all the observations of NS LMXBs performed in EPIC pn timing mode with XMM-Newton publicly available until September 30, 2009. We performed a detailed data analysis considering pile-up and background effects. The properties of the Fe lines differed from previous published analyses because of either incorrect pile-up corrections or different continuum parameterisation. Eighty percent of the observations for which a spectrum can be extracted showed significant Fe line emission. We found an average line centroid of 6.67 ± 0.02 keV and a finite width, σ, of 0.33 ± 0.02 keV. The equivalent width of the lines varied between 17 and 189 eV, with an average weighted value of 42 ± 3 eV. For sources where several observations were available, the Fe line parameters changed between observations whenever the continuum changed significantly. The line parameters did not show any correlation with luminosity. Most important, we could fit the Fe line with a simple Gaussian component for all the sources. The lines did not show the asymmetric profiles that were interpreted as indicating relativistic effects in previous analyses of these LMXBs. © 2010 ESO.

Diaz Trigo M.,ESO | Sidoli L.,Istituto di Astrofisica Spaziale e Fisica Cosmica | Boirin L.,11 Rue Of Luniversite | Parmar A.N.,ESAC
Astronomy and Astrophysics | Year: 2012

We analysed data from five XMM-Newton observations of GX 13 + 1 to investigate the variability of the photo-ionised absorber in this source. We fitted EPIC and RGS spectra obtained from the "least-variable" intervals with a model consisting of disc-blackbody and blackbody components together with a Gaussian emission feature at ∼6.55-6.7 keV modified by absorption due to cold and photo-ionised material. We found a significant correlation between the hard, ∼6-10 keV, flux, the ionisation and column density of the absorber and the equivalent width of the broad iron line. We interpret the correlation in a scenario in which a disc wind is thermally driven at large, ∼1010 cm, radii and the broad line results from reprocessed emission in the wind and/or hot atmosphere. The breadth of the emission line is naturally explained by a combination of scattering, recombination and fluorescence processes. We attribute the variations in the absorption and emission along the orbital period to the view of different parts of the wind, possibly located at slightly different inclination angles. We constrain the inclination of GX 13 + 1 to be between 60 and 80° from the strong absorption in the line of sight, which obscures up to 80% of the total emission in one observation, and the absence of eclipses. We conclude that either a disc wind and/or a hot atmosphere can explain the current observations of narrow absorption and broad iron emission features in neutron star low-mass X-ray binaries as a class. © 2012 ESO.

Rahoui F.,Harvard University | Rahoui F.,Harvard Smithonian Center for Astrophysics | Coriat M.,University of Southampton | Corbel S.,University Paris Diderot | And 7 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

The microquasar GX 339-4, known to exhibit powerful compact jets that dominate its radio to near-infrared emission, entered an outburst in 2010 for the fifth time in about 15yr. An extensive radio to X-ray multiwavelength campaign was immediately triggered, and we report here on European Southern Observatory/FORS2+ISAAC optical and near-infrared spectroscopic observations, supported by Australia Telescope Compact Array radio and Rossi X-ray Timing Experiment/Swift X-ray quasi-simultaneous data. GX 339-4 was observed at three different epochs, once in the soft state and twice in the hard state. In the soft state, the optical and near-infrared continuum is largely consistent with the Raleigh-Jeans tail of a thermal process. As an explanation, we favour irradiation of the outer accretion disc by its inner regions, enhanced by disc warping. An excess is also present at low frequencies, likely due to an M subgiant companion star. During the first hard state, the optical/near-infrared continuum is well described by the optically thin synchrotron emission of the compact jet combined with disc irradiation and perhaps another component peaking in the ultraviolet. The spectral break where the jet transits from the optically thick to thin regimes, located below 1.20 × 10 14Hz, is not detected and the extension of the optically thin synchrotron is consistent with the 3-50keV spectrum. In contrast, the emission during the second hard state is more difficult to understand and points towards a more complex jet continuum. In both cases, the near-infrared continuum is found to be variable at time-scales at least as short as 20s, although these variabilities are smoothed out beyond a few hundred seconds. This implies rapid variations - in flux and frequency - of the location of the spectral break, i.e. dramatic short time-scale changes of the physical conditions at the base of the jet, such as the magnetic field and/or the base radius. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Clerc N.,SAP | Sadibekova T.,SAP | Pierre M.,SAP | Pacaud F.,University of Bonn | And 4 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

We have processed 2774 high galactic observations from the XMM archive (as of 2010 May) and extracted a serendipitous catalogue of some 850 clusters of galaxies based on purely X-ray criteria, following the methodology developed for the XMM-Large-Scale Survey. Restricting the sample to the highest signal-to-noise ratio objects (347 clusters), we perform a cosmological analysis using only the X-ray information. The analysis consists in the modelling of the observed colour-magnitude [count rate and hardness ratio (CR-HR)] diagram constructed from cluster instrumental count rates measured in the [0.5-2], [1-2] and [0.5-1] keV bands. A Monte Carlo Markov chain procedure simultaneously fits the cosmological parameters, the evolution of the cluster scaling laws and the selection effects. Our results are consistent with the σ 8 and Ω m values obtained by the 5-year Wilkinson Microwave Anisotropy Probe (WMAP5) and point towards a negative evolution of the cluster scaling relations with respect to the self-similar expectation. We are further able to constrain the cluster fractional radius x c,0=r c/R 500c to x c, 0= 0.24 ± 0.04. This study stresses again the critical role of selection effects in deriving cluster scaling relations, even in the local universe. Finally, we show that the CR-HR method applied to the eRosita all-sky survey - provided that cluster photometric redshifts are available - will enable the determination of the equation of state of the dark energy at the level of the Dark Energy Task Force (DETF) stage IV predictions; simultaneously, the evolution of the cluster scaling relations will be unambiguously determined. The XMM CLuster Archive Super Survey (X-CLASS) serendipitous cluster catalogue is available online at © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Weisskopf M.C.,NASA | Guainazzi M.,ESAC | Jahoda K.,NASA | Shaposhnikov N.,College Park | And 4 more authors.
Astrophysical Journal | Year: 2010

Motivated by a paper of Kirsch et al. on possible use of the Crab Nebula as a standard candle for calibrating X-ray response functions, we examine consequences of intrinsic departures from a single (absorbed) power law upon such calibrations. We limit our analyses to three more modern X-ray instruments - the ROSAT/PSPC, the RXTE/Proportional Counter Array, and the XMM-Newton/EPIC-pn (burst mode). The results indicate a need to refine two of the three response functions studied. We are also able to distinguish between two current theoretical models for the system spectrum. © 2010 The American Astronomical Society.

Rodriguez J.,University Paris Diderot | Corbel S.,University Paris Diderot | Caballero I.,University Paris Diderot | Tomsick J.A.,University of California at Berkeley | And 4 more authors.
Astronomy and Astrophysics | Year: 2011

We present the results of the first four (quasi-)simultaneous radio (ATCA), X-ray (Swift, RXTE), and γ-ray (INTEGRAL) observations of the black hole candidate IGR J17091-3624, performed in February and March 2011. The X-ray analysis shows that the source was in the hard state, and then it transited to a soft intermediate state. We study the correlated radio/X-ray behaviour of this source for the first time. The radio counterpart to IGR J17091-3624 was detected during all four observations with the ATCA. In the hard state, the radio spectrum is typical of optically thick synchrotron emission from a self-absorbed compact jet. In the soft intermediate state, the detection of optically thin synchrotron emission is probably due to a discrete ejection event associated with the state transition. The position of IGR J17091-3624 in the radio versus X-ray luminosity diagram (aka fundamental plane) is compatible with that of the other black hole sources for distances greater than 11 kpc. IGR J17091-3624 also appears as a new member of the few sources that show a strong quenching of radio emission after the state transition. Using the estimated luminosity at the spectral transition from the hard state, and for a typical mass of 10 M, we estimate a distance to the source between ∼11 and ∼17 kpc, compatible with the radio behaviour of the source. © 2011 ESO.

Balog Z.,Max Planck Institute for Astronomy | Muller T.,Max Planck Institute for Extraterrestrial Physics | Nielbock M.,Max Planck Institute for Astronomy | Altieri B.,ESAC | And 8 more authors.
Experimental Astronomy | Year: 2014

This paper provides an overview of the PACS photometer flux calibration concept, in particular for the principal observation mode, the scan map. The absolute flux calibration is tied to the photospheric models of five fiducial stellar standards (α Boo, α Cet, α Tau, β And, γ Dra). The data processing steps to arrive at a consistent and homogeneous calibration are outlined. In the current state the relative photometric accuracy is ~2 % in all bands. Starting from the present calibration status, the characterization and correction for instrumental effects affecting the relative calibration accuracy is described and an outlook for the final achievable calibration numbers is given. After including all the correction for the instrumental effects, the relative photometric calibration accuracy (repeatability) will be as good as 0.5 % in the blue and green band and 2 % in the red band. This excellent calibration starts to reveal possible inconsistencies between the models of the K-type and the M-type stellar calibrators. The absolute calibration accuracy is therefore mainly limited by the 5 % uncertainty of the celestial standard models in all three bands. The PACS bolometer response was extremely stable over the entire Herschel mission and a single, time-independent response calibration file is sufficient for the processing and calibration of the science observations. The dedicated measurements of the internal calibration sources were needed only to characterize secondary effects. No aging effects of the bolometer or the filters have been found. Also, we found no signs of filter leaks. The PACS photometric system is very well characterized with a constant energy spectrum νF ν = λF λ = const as a reference. Colour corrections for a wide range of sources SEDs are determined and tabulated. © 2013 Springer Science+Business Media Dordrecht.

Benkhoff J.,European Space Agency | van Casteren J.,European Space Agency | Hayakawa H.,Japan Aerospace Exploration Agency | Fujimoto M.,Japan Aerospace Exploration Agency | And 5 more authors.
Planetary and Space Science | Year: 2010

BepiColombo is an interdisciplinary mission to explore Mercury, the planet closest to the sun, carried out jointly between the European Space Agency and the Japanese Aerospace Exploration Agency. From dedicated orbits two spacecraft will be studying the planet and its environment. The scientific payload of both spacecraft will provide the detailed information necessary to understand the origin and evolution of the planet itself and its surrounding environment. The scientific objectives focus on a global characterization of Mercury through the investigation of its interior, surface, exosphere and magnetosphere. In addition, instrumentation onboard BepiColombo will be used to test Einstein's theory of general relativity. Major effort was put into optimizing the scientific return of the mission by defining a payload complement such that individual measurements can be interrelated and complement each other. This paper gives an in-depth overview of BepiColombo spacecraft composite and the mission profile. It describes the suite of scientific instruments on board of the two BepiColombo spacecraft and the science goals of the mission. © 2009 Elsevier Ltd. All rights reserved.

Rawle T.D.,ESAC | Lucey J.R.,Durham University | Smith R.J.,Durham University | Head J.T.C.G.,Durham University
Monthly Notices of the Royal Astronomical Society | Year: 2013

We present deep Gemini Multi-Object Spectrograph long-slit spectroscopy of 15 Coma cluster SO galaxies, and extract kinematic properties along the major axis to several times the disc scalelength. Supplementing our data set with previously published data, we create a combined sample of 29 Coma SOs, as well as a comparison sample of 38 Coma spirals. Using photometry from the Sloan Digital Sky Survey and Two Micron All Sky Survey, we construct the Tully-Fisher relation (TFR; luminosity versus maximum rotational velocity) for SO galaxies. At fixed rotational velocity, the Coma SO galaxies are on average fainter than Coma spirals by 1.10 ± 0.18, 0.86 ±0.19 and 0.83 ± 0.19 mag in the g, i and KS bands, respectively. The typical SO offsets remain unchanged when calculated relative to large field-galaxy spiral samples. The observed offsets are consistent with a simple star formation model in which S0s are identical to spirals until abrupt quenching occurs at some intermediate redshift. The offsets form a continuous distribution tracing the time since the cessation of star formation, and exhibit a strong correlation (>6σ) with residuals from the optical colour-magnitude relation. Typically. SOs which are fainter than average for their rotational velocity are also redder than average for their luminosity. The SO TFR offset is also correlated with both the projected cluster-centric radius and the Σ (projected) local density parameter. Since current local environment is correlated with time of accretion into the cluster, our results support a scenario in which transformation of spirals to SOs is triggered by cluster infall.© 2013 The Authors.

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