PIXEL 2010 - a Resume

The Pixel 2010 conference focused on semiconductor pixel detectors for particle tracking/vertexing as well as for imaging, in particular for synchrotron light sources and XFELs. The big LHC hybrid pixel detectors have impressively started showing their capabilities. X-ray imaging detectors, also using the hybrid pixel technology, have greatly advanced the experimental possibilities for diiffraction experiments. Monolithic or semi-monolithic devices like CMOS active pixels and DEPFET pixels have now reached a state such that complete vertex detectors for RHIC and superKEKB are being built with these technologies. Finally, new advances towards fully monolithic active pixel detectors, featuring full CMOS electronics merged with efficient signal charge collection, exploiting standard CMOS technologies, SOI and/or 3D integration, show the path for the future. This r\'esum\'e attempts to extract the main statements of the results and developments presented at this conference.Comment: 8 pages, 19 figures, conference summar

Space Astronomy for the mid-21st Century: Robotically Maintained Space Telescopes

The historical development of ground based astronomical telescopes leads us to expect that space-based astronomical telescopes will need to be operational for many decades. The exchange of scientific instruments in space will be a prerequisite for the long lasting scientific success of such missions. Operationally, the possibility to repair or replace key spacecraft components in space will be mandatory. We argue that these requirements can be fulfilled with robotic missions and see the development of the required engineering as the main challenge. Ground based operations, scientifically and technically, will require a low operational budget of the running costs. These can be achieved through enhanced autonomy of the spacecraft and mission independent concepts for the support of the software. This concept can be applied to areas where the mirror capabilities do not constrain the lifetime of the mission.Comment: 4 pages, accepted in February 2012 for publication in A

Background study for the pn-CCD detector of CERN Axion Solar Telescope

The CERN Axion Solar Telescope (CAST) experiment searches for axions from the Sun converted into photons with energies up to around 10 keV via the inverse Primakoff effect in the high magnetic field of a superconducting Large Hadron Collider (LHC) prototype magnet. A backside illuminated pn-CCD detector in conjunction with an X-ray mirror optics is one of the three detectors used in CAST to register the expected photon signal. Since this signal is very rare and different background components (environmental gamma radiation, cosmic rays, intrinsic radioactive impurities in the set-up, ...) entangle it, a detailed study of the detector background has been undertaken with the aim to understand and further reduce the background level of the detector. The analysis is based on measured data taken during the Phase I of CAST and on Monte Carlo simulations of different background components. This study will show that the observed background level (at a rate of (8.00+-0.07)10^-5 counts/cm^2/s/keV between 1 and 7 keV) seems to be dominated by the external gamma background due to usual activities at the experimental site, while radioactive impurities in the detector itself and cosmic neutrons could make just smaller contribution.Comment: Comments: 10 pages, 9 figures and images, submitted to Astroparticle Physic

XMM observation of 1RXS J180431.1-273932: a new M-type X-ray binary with a 494 s-pulse period neutron star?

Low-mass X-ray binaries are binary systems composed of a compact object and a low-mass star. Recently, a new class of these systems, known as symbiotic $X$-ray binaries (with a neutron star with a M-type giant companion), has been discovered. Here, we present long-duration ${\it XMM}$ observations of the source 1RXS J180431.1-273932. Temporal and spectral analysis of the source was performed along with a search for an optical counterpart. We used a Lomb-Scargle periodogram analysis for the period search and evaluated the confidence level using Monte-Carlo simulations. The source is characterized by regular pulses so that it is most likely a neutron star. A modulation of $494.1\pm0.2$ s (3$\sigma$ error) was found with a confidence level of $>$99%. Evidence of variability is also present, since the data show a rate of change in the signal of $\sim -7.7\times 10^{-4}$ counts s$^{-1}$ hr$^{-1}$. A longer observation will be necessary in order to determine if the source shows any periodic behavior. The spectrum can be described by a power law with photon index $\Gamma\sim 1$ and a Gaussian line at 6.6 keV. The X-ray flux in the 0.2--10 keV energy band is $5.4\times 10^{-12}$ erg s$^{-1}$ cm$^{-2}$. The identification of an optical counterpart (possibly an M6III red-giant star with an apparent visual magnitude of $\simeq 17.6$) allows a conservative distance of $\sim 10$ kpc to be estimated. Other possibilities are also discussed. Once the distance was estimated, we got an $X$-ray luminosity of L_X\ut<6\times 10^{34} erg s$^{-1}$, which is consistent with the typical $X$-ray luminosity of a symbiotic LMXB system.Comment: in press on A&

The Supernova Remnant G296.7-0.9 in X-rays

Aims: We present a detailed study of the supernova remnant (SNR) G296.7-0.9 in the 0.2-12 keV X-ray band. Methods: Using data from XMM-Newton we performed a spectro-imaging analysis of G296.7-0.9 in order to deduce the basic parameters of the remnant and to search for evidence of a young neutron star associated with it. Results: In X-rays the remnant is characterized by a bright arc located in the south-west direction. Its X-ray spectrum can best be described by an absorbed non-equilibrium collisional plasma model with a hydrogen density of N_H=1.24_{-0.05}^{+0.07} x 10^{22} cm^{-2} and a plasma temperature of 6.2^{+0.9}_{-0.8} million Kelvin. The analysis revealed a remnant age of 5800 to 7600 years and a distance of 9.8_{-0.7}^{+1.1} kpc. The latter suggests a spatial connection with a close-by HII region. We did not find evidence for a young neutron star associated with the remnant.Comment: accepted by A&A, 5 pages, 2 figure

Science with the EXTraS Project: Exploring the X-ray Transient and variable Sky

The EXTraS project (Exploring the X-ray Transient and variable Sky) will characterise the temporal behaviour of the largest ever sample of objects in the soft X-ray range (0.1-12 keV) with a complex, systematic and consistent analysis of all data collected by the European Photon Imaging Camera (EPIC) instrument onboard the ESA XMM-Newton X-ray observatory since its launch. We will search for, and characterize variability (both periodic and aperiodic) in hundreds of thousands of sources spanning more than nine orders of magnitude in time scale and six orders of magnitude in flux. We will also search for fast transients, missed by standard image analysis. Our analysis will be completed by multiwavelength characterization of new discoveries and phenomenological classification of variable sources. All results and products will be made available to the community in a public archive, serving as a reference for a broad range of astrophysical investigations.Comment: 4 pages, 1 figure. Refereed Proceeding of "The Universe of Digital Sky Surveys" conference held at the INAF - Observatory of Capodimonte, Naples, on 25th-28th November 2014, to be published in the Astrophysics and Space Science Proceedings, edited by Longo, Napolitano, Marconi, Paolillo, Iodic

A prominent relativistic iron line in the Seyfert 1 MCG-02-14-009

I report the discovery of a prominent broad and asymmetrical feature near 6.4 keV in the Seyfert 1 MCG-02-14-009 (z=0.028) with XMM-Newton/EPIC. The present short X-ray observation (PN net exposure time ~5 ks) is the first one above 2 keV for MCG-02-14-009. The feature can be explained by either a relativistic iron line around either a Schwarzschild (non-rotating) or a Kerr (rotating) black hole. If the feature is a relativistic iron line around a Schwarzschild black hole, the line energy is 6.51 (+0.21,-0.12) keV with an equivalent width of 631 (+259,-243) eV and that the inclination angle of the accretion disc should be less than 43 degrees. A relativistically blurred photoionized disc model gives a very good spectral fit over the broad band 0.2-12keV energy range. The spectrum is reflection dominated and this would indicate that the primary source in MCG-02-14-009 is located very close to the black hole, where gravitational light bending effect is important (about 3-4 Rg), and that the black hole may rapidly rotate.Comment: Accepted for publication, A&A Letters, 5 pages, 3 figures, and 1 tabl

Constraining the thermal history of the Warm-Hot Intergalactic Medium

We have identified a large-scale structure traced by galaxies at z=0.8, within the Lockman Hole, by means of multi-object spectroscopic observations. By using deep XMM images we have investigated the soft X-ray emission from the Warm-Hot Intergalactic Medium (WHIM) expected to be associated with this large-scale structure and we set a tight upper limit to its flux in the very soft 0.2-0.4 keV band. The non-detection requires the WHIM at these redshifts to be cooler than 0.1 keV. Combined with the WHIM emission detections at lower redshift, our result indicates that the WHIM temperature is rapidly decreasing with redshift, as expected in popular cosmological models.Comment: 10 pages, 5 figures, 1 appendix. A&A accepte

A New Comprehensive 2-D Model of the Point Spread Functions of the XMM-Newton EPIC Telescopes : Spurious Source Suppression and Improved Positional Accuracy

We describe here a new full 2-D parameterization of the PSFs of the three XMM-Newton EPIC telescopes as a function of instrument, energy, off-axis angle and azimuthal angle, covering the whole field-of-view of the three EPIC detectors. It models the general PSF envelopes, the primary and secondary spokes, their radial dependencies, and the large-scale azimuthal variations. This PSF model has been constructed via the stacking and centering of a large number of bright, but not significantly piled-up point sources from the full field-of-view of each EPIC detector, and azimuthally filtering the resultant PSF envelopes to form the spoke structures and the gross azimuthal shapes observed. This PSF model is available for use within the XMM-Newton Science Analysis System via the usage of Current Calibration Files XRTi_XPSF_0011.CCF and later versions. Initial source-searching tests showed substantial reductions in the numbers of spurious sources being detected in the wings of bright point sources. Furthermore, we have uncovered a systematic error in the previous PSF system, affecting the entire mission to date, whereby returned source RA and Dec values are seen to vary sinusoidally about the true position (amplitude ~0.8") with source azimuthal position. The new PSF system is now available and is seen as a major improvement with regard to the detection of spurious sources. The new PSF also largely removes the discovered astrometry error and is seen to improve the positional accuracy of EPIC. The modular nature of the PSF system allows for further refinements in the future.Comment: Accepted for publication in A&A. 15 pages, 13 figures (some of reduced quality). A full-resolution version is available at http://www.star.le.ac.uk/~amr30/amr_PSFpaper.pd

Imaging Molecules from Within: Ultra-fast, {\AA}ngstr\"om Scale Structure Determination of Molecules via Photoelectron Holography using Free Electron Lasers

A new scheme based on (i) upcoming brilliant X-ray Free Electron Laser (FEL) sources, (ii) novel energy and angular dispersive, large-area electron imagers and (iii) the well-known photoelectron holography is elaborated that provides time-dependent three-dimensional structure determination of small to medium sized molecules with {\AA}ngstr\"om spatial and femtosecond time resolution. Inducing molecular dynamics, wave-packet motion, dissociation, passage through conical intersections or isomerization by a pump pulse this motion is visualized by the X-ray FEL probe pulse launching keV photoelectrons within few femtoseconds from specific and well-defined sites, deep core levels of individual atoms, inside the molecule. On their way out the photoelectrons are diffracted generating a hologram on the detector that encodes the molecular structure at the instant of photoionization, thus providing 'femtosecond snapshot images of the molecule from within'. Detailed calculations in various approximations of increasing sophistication are presented and three-dimensional retrieval of the spatial structure of the molecule with {\AA}ngstr\"om spatial resolution is demonstrated. Due to the large photo-absorption cross sections the method extends X-ray diffraction based, time-dependent structure investigations envisioned at FELs to new classes of samples that are not accessible by any other method. Among them are dilute samples in the gas phase such as aligned, oriented or conformer selected molecules, ultra-cold ensembles and/or molecular or cluster objects containing mainly light atoms that do not scatter X-rays efficiently.Comment: 18 pages, 11 figure