Murat Hudaverdi

Characterization of the supermirror hard-x-ray telescope for the InFOCμS balloon experiment

A hard-x-ray telescope is successfully produced for balloon observations by making use of depth-graded multilayers, or so-called supermirrors, with platinum-carbon (Pt/C) layer pairs. It consists of four quadrant units assembled in an optical configuration with a diameter of 40 cm and a focal length of 8 m. Each quadrant is made of 510 pieces of coaxially and confocally aligned supermirrors that significantly enhance the sensitivity in an energy range of 20-40 keV. The configuration of the telescope is similar to the x-ray telescope onboard Astro-E, but with a longer focal length. The reflectivity of supermirrors is of the order of 40% in the energy range concerned at a grazing angle of 0.2 deg. The effective area of a fully assembled telescope is 50 cm2 at 30 keV. The angular resolution is 2.37 arc min at half-power diameter 8.0 keV. The field of view is 12.6 arc min in the hard-x-ray region, depending somewhat on x-ray energies. We discuss these characteristics, taking into account the figure errors of reflectors and their optical alignment in the telescope assembly. This hard-x-ray telescope is unanimously afforded in the International Focusing Optics Collaboration for muCrab Sensitivity balloon experiment.

Suzaku observation of the Galactic supernova remnant CTB 37A (G348.5+0.1)

In this paper, we present the results of the observations of CTB 37A obtained with the X-ray imaging spectrometer onboard the Suzaku satellite. The X-ray spectrum of CTB 37A is fitted well by two components: a single-temperature ionization equilibrium component (VMEKAL), with solar abundances, an electron temperature of kTe∼ 0.6 keV and an absorbing column density of NH∼ 3 × 1022 cm−2, and a power-law component with a photon index of Γ∼ 1.6. The X-ray spectrum of CTB 37A is characterized by clearly detected K-shell emission lines of Mg, Si, S and Ar. The plasma with solar abundances supports the idea that the X-ray emission originates from the shocked interstellar material. The ambient gas density and the age of the remnant are estimated to be ∼ 1f−1/2 cm−3 and ∼ 3 × 104f1/2 yr, respectively. The centre-filling X-ray emission, surrounded by a shell-like radio structure, and other X-ray properties indicate that this remnant could be a new member of the class of mixed-morphology supernova remnants.

Suzaku observations of ejecta-dominated Galactic supernova remnant G346.6−0.2

We present here the results of the X-ray analysis of Galactic supernova remnant G346.6-0.2 observed with Suzaku. K-shell emission lines of Mg, Si, S, Ca and Fe are detected clearly for the first time. Strong emission lines of Si and S imply that X-ray emission nature of G346.6-0.2 is ejecta-dominated. The ejecta-dominated emission is well fitted with a combined model consisting of thermal plasma in non-equilibrium ionization and a non-thermal component, which can be regarded as synchrotron emission with a photon index of Γ ∼ 0.6. Absorbing column density of NH ∼ 2.1 × 10 22 cm is obtained from the best-fitting implying a high-density medium, high electron temperature of kTe ∼ 1.2 keV, and ionization timescale of net ∼ 2.9 × 10 11 cms indicating that this remnant may be far from full ionization equilibrium. The relative abundances from the ejecta show that the remnant originates from a Type Ia supernova explosion.

ASCA and XMM-Newton observations of A2029

Abstract The X-ray data of A2029 obtained with XMM-Newton show no evidence of an embedded AGN in the central region of this cluster, which was suggested from the analysis of restored ASCA image data, although some hot spots are seen within or around the central cD galaxy. The absence of AGN at the cluster center is consistent with the result of Chandra observations. Radial profiles of the iron abundance and the 2D (surface) temperature obtained from the XMM-Newton data are in good agreement with the Chandra data as a whole.

The correlations of space weather and satellite anomalies: RASAT

The main focus of this work is to review documented operational anomalies for Turkish Remote Sensing Satellite of RASAT, by assessing the identification and estimation of potential source of space weather agents. A statistical evaluation and correlation analysis were made using the log files from the launching up to date for RASAT. A number of severe solar flares have been reported during these operational periods by NAOO. The proton and electron fluxes are obtained from GOES-13 satellite archival data. The values are also simulated by Spenvis algorithm for comparison. RASAT was monitored regularly and all key parameters are logged in order to track operational values and alert if anything goes beyond the thresholds. Both tables are compared by superposed epoch analysis technique. Possible similarities or dissimilarities in fluctuations are interpreted for better understanding of space environment and its effects on electronics. We have detected four dates (29.11.2011, 04.02.2012, 12.07.2012 and 16.12.2012) in which RASAT performed severe corrections. Space weather conditions for the dates are checked by mainly focusing on the solar energetic particle flux variations. We try to understand underlying mechanisms of failure and anomalies. The results hopefully enable Turkish engineers, designers and scientists to efficiently eliminate the risk, minimize the cost, and optimize the design for future national space missions.

Space environment and evaluation for RASAT

The space environment is a set of surrounding composed of energetic particle radiation, micrometeoroids and space debris. The quantity of each element is defined by external physical world for a given launch time, altitude and duration of a specific mission. Proper evaluation is the key to verify best performance, problem avoidance and survivability of a system in space environment. In this work, the space environment analysis and evaluation for RASAT is reported with an emphasis on radiation analysis as being the most significant source of space product failures. For 2 mm aluminium shielding thickness, the forecasted value of total ionizing dose (TID) is 1.89 × 104 rads (Si) and non-ionizing displacement damage dose (DDD) is 5.42 × 107 MeV/g(Si) for 5-year mission lifetime of RASAT. We estimate 0.0005 m−2 flux of 1 mgr space debris for 5-year. Based on the analysis and evaluation results it is determined that RASAT components should not be less than ∼20 krad.

1E 1207.4–5209-LIKE RADIO-QUIET NEUTRON STARS

In this work, the results of X-ray spectral analysis of radio-quiet X-ray pulsar 1E 1207.4–5209 and RX J0002+6246, RX J0822–4300, CXOU J185238.6+00402, which have the same observational characteristics as 1E 1207.4–5209, are represented based on XMM-Newton satellite observations. These four neutron stars with common physical properties may have similar physical evolution. It is shown that all of them have Pure blackbody spectra (two-blackbody fits in three cases) without a power law component. No pulsar wind nebula has been observed around any one of them, which strongly shows that they have low rotational energy loss despite their small ages. All of these neutron stars are physically connected to shell-type supernova remnants which are younger than (1–2) × 104yr. None of these sources has been detected to emit at radiofrequencies. These common spectral properties (and possibly common timing characteristics) of these neutron stars are examined. Their possible evolution is discussed based on a model represented in Ref. 1. As a result, it is quite possible that these objects form a new class of neutron stars quite different than the other types.

Characterizing decaying dark matter: X-ray emission from sterile neutrinos

Recently, an unknown emission line at E

Spectral analysis of metal ejection from NGC3311

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Structural formation of the universe: As observed by X-ray satellites

3.5 keV from several astrophysical objects has been detected. The line is suggested to be originating from decaying dark matter particles. The results have drawn great attention from the astrophysics and particle physics community. Since the detected line is significantly weak there has also been a long debate over the origin of this mysterious signal. The most accepted scenario is a radiatively decaying sterile neutrino of 7.1 keV in mass producing a monochromatic 3.5 keV line, which is observable in X-ray energy ranges. The problem has not been settled and further observations from more objects are needed to verify the detection in order to constrain the physical properties and the nature of the signal. In this paper, we present the current situation and provide further insights into the subject.