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Takey A.,Leibniz Institute for Astrophysics Potsdam | Takey A.,National Research Institute of Astronomy and Geophysics NRIAG | Schwope A.,Leibniz Institute for Astrophysics Potsdam | Lamer G.,Leibniz Institute for Astrophysics Potsdam
Astronomy and Astrophysics | Year: 2013

Aims. We compile a sample of X-ray-selected galaxy groups and clusters from the XMM-Newton serendipitous source catalogue (2XMMi-DR3) with optical confirmation and redshift measurement from the Sloan Digital Sky Survey (SDSS). We present an analysis of the X-ray properties of this new sample with particular emphasis on the X-ray luminosity-temperature (LX-T) relation. Methods. The X-ray cluster candidates were selected from the 2XMMi-DR3 catalogue in the footprint of the SDSS-DR7. We developed a finding algorithm to search for overdensities of galaxies at the positions of the X-ray cluster candidates in the photometric redshift space and to measure the redshifts of the clusters from the SDSS data. For optically confirmed clusters with good quality X-ray data we derived the X-ray flux, luminosity, and temperature from proper spectral fits, while the X-ray flux for clusters with low-quality X-ray data was obtained from the 2XMMi-DR3 catalogue. Results. The detection algorithm provides the photometric redshift of 530 galaxy clusters. Of these, 310 clusters have a spectroscopic redshift for at least one member galaxy. About 75 percent of the optically confirmed cluster sample are newly discovered X-ray clusters. Moreover, 301 systems are known as optically selected clusters in the literature while the remainder are new discoveries in X-ray and optical bands. The optically confirmed cluster sample spans a wide redshift range 0.03-0.70 (median z = 0.32). In this paper, we present the catalogue of X-ray-selected galaxy groups and clusters from the 2XMMi/SDSS galaxy cluster survey. The catalogue has two subsamples: (i) a cluster sample comprising 345 objects with their X-ray spectroscopic temperature and flux from the spectral fitting; and (ii) a cluster sample consisting of 185 systems with their X-ray flux from the 2XMMi-DR3 catalogue, because their X-ray data are insufficient for spectral fitting. For each cluster, the catalogue also provides the X-ray bolometric luminosity and the cluster mass at R500 based on scaling relations and the position of the likely brightest cluster galaxy (BCG). The updated LX-T relation of the current sample with X-ray spectroscopic parameters is presented. We found the slope of the LX-T relation to be consistent with published ones. We see no evidence for evolution in the slope and intrinsic scatter of the LX-T relation with redshift when excluding the low-luminosity groups. © 2013 ESO.

Hanna M.,National Research Institute of Astronomy and Geophysics NRIAG
Journal of the Korean Astronomical Society | Year: 2014

We present the first period variation study for the Algol eclipsing binary V346 Cyg by constructing the (O-C) residual diagram using all the available precise minima times. We conclude that the period variation can be explained by a sine-like variation due to the presence of a third body orbiting the binary in about 68:89 ± 4:69 years, together with a long-term orbital period decrease (dP/dt = -1:23 × 10-7day=yr) that can be interpreted to be due to slow mass loss from the δ-Scuti primary component. The sinusoidal variation may also be explained by using the the Applegate (1992) mechanism involving cyclic magnetic activity due to star{spots on the secondary component. The present preliminary solution needs more precise photometric observations to be confirmed. © 2014. The Korean Astronomical Society. All rights reserved.

Amin S.M.,National Research Institute of Astronomy and Geophysics NRIAG
Journal of the Korean Astronomical Society | Year: 2015

The orbital period changes of theWUMa eclipsing binary AU Ser are studied using the (O−C) method. We conclude that the period variation is due to mass transfer from the primary star to the secondary one at a very low and decreasing rate dP/dt = −8.872× 10−8, superimposed on the sinusoidal variation due to a third body orbiting the binary with period 42.87 ± 3.16 years, orbital eccentricity e = 0.52±0.12 and a longitude of periastron passage ω = 133◦.7±15. On studying the magnetic activity, we have concluded that the Applegate mechanism failed to describe the cycling variation of the (O − C) diagram of AU Ser. © 2015. The Korean Astronomical Society. All rights reserved.

Saleh S.,National Research Institute of Astronomy and Geophysics NRIAG
Pure and Applied Geophysics | Year: 2013

Crustal and lithospheric thicknesses of the southeastern Mediterranean Basin region were determined using 3D Bouguer and elevation data analysis. The model is based on the assumption of local isostatic equilibrium. The calculated regional and residual Bouguer anomaly maps were employed for highlighting both deep and shallow structures. Generally, the regional field in the area under study is considered to be mainly influenced by the density contrast between the crust and upper mantle. Use of the gravity and topographic data with earthquake focal depths has improved both the geometry and the density distribution in the 3-D calculated profiles. The oceanic-continental boundary, the basement relief, Moho depth and lithosphere-asthenosphere boundary maps were estimated. The results point to the occurrence of thick continental crust areas with a thickness of approximately 32 km in northern Egypt. Below the coastal regions, the thickness of crust decreases abruptly (transition zone). An inverse correlation between sediment and crustal thicknesses shows up from the study. Furthermore, our density model reveals the existence of a continental crustal zone below the Eratosthenes Seamount block. Nevertheless, the crustal type beneath the Levantine basin is typically oceanic; this is covered by sedimentary sequences more than 14 km thick. The modeled Moho map shows a depth of 28-30 km below Cyprus and a depth of 26-28 km beneath the south Florence Rise in the northern west. However, the Moho lies at a constant shallow depth of 22-24 km below the Levantine Basin, which indicates thinning of the crust beneath this region. The Moho map reveals also a maximum depth of about 33-35 km beneath both the northern Egypt and northern Sinai, both of which are of the continental crust. The resulting mantle density anomalies suggest important variations of the lithosphere-asthenosphere boundary (LAB) topography, indicating prominent lithospheric mantle thinning beneath south Cyprus (LAB ~90 km depth), followed by thickening beneath the Eratosthenes seamount, Florence Rise, Levantine Basin and reaching to maximum thickness below Cyprian Arc (LAB ~115-120 km depth), and further followed by thinning in the north African margin plate and north Sinai subplate (LAB ~90-95 km depth). According to our density model profiles, we find that almost all earthquakes in the study area occurred along the western and central segments of the Cyprian arc while they almost disappear along the eastern segment. The active subduction zone in the Cyprian Arc is associated with large negative anomalies due to its low velocity upper mantle zone, which might be an indication of a serpentinized mantle. This means that collision between Cyprus and the Eratosthenes Seamount block is marked by seismic activity. Additionally, this block is in the process of dynamically subsiding, breaking-up and being underthrusted beneath Cyprus to the north and thrusted onto the Levantine Basin to the south. © 2013 Springer Basel.

Abdelwahed M.F.,King Abdulaziz University | Abdelwahed M.F.,National Research Institute of Astronomy and Geophysics NRIAG
Computers and Geosciences | Year: 2012

Although numerous seismological programs are currently available, most of them suffer from the inability to manipulate different data formats and the lack of embedded seismological tools. SeismoGRAPHer, or simply SGRAPH, is a new system for maintaining and analyzing seismic waveform data in a stand-alone, Windows-based application that manipulates a wide range of data formats. SGRAPH was intended to be a tool sufficient for performing basic waveform analysis and solving advanced seismological problems. The graphical user interface (GUI) utilities and the Windows functionalities, such as dialog boxes, menus, and toolbars, simplify the user interaction with the data. SGRAPH supports common data formats, such as SAC, SEED, GSE, ASCII, and Nanometrics Y-format, and provides the ability to solve many seismological problems with built-in inversion tools. Loaded traces are maintained, processed, plotted, and saved as SAC, ASCII, or PS (post script) file formats. SGRAPH includes Generalized Ray Theory (GRT), genetic algorithm (GA), least-square fitting, auto-picking, fast Fourier transforms (FFT), and many additional tools. This program provides rapid estimation of earthquake source parameters, location, attenuation, and focal mechanisms. Advanced waveform modeling techniques are provided for crustal structure and focal mechanism estimation. SGRAPH has been employed in the Egyptian National Seismic Network (ENSN) as a tool assisting with routine work and data analysis. More than 30 users have been using previous versions of SGRAPH in their research for more than 3 years. The main features of this application are ease of use, speed, small disk space requirements, and the absence of third-party developed components. Because of its architectural structure, SGRAPH can be interfaced with newly developed methods or applications in seismology. A complete setup file, including the SGRAPH package with the online user guide, is available. © 2011 Elsevier Ltd.

Abd El-Aal A.E.-A.K.,National Research Institute of Astronomy and Geophysics NRIAG
Geophysical Prospecting | Year: 2011

In this paper, an improved method is presented to reduce vibrator harmonic distortion, one harmonic at a time and the method is illustrated with both simulated and field data. This method improves on the previous method that treated all the harmonics at once. The significant contribution in this procedure is a considerable reduction for the harmonics without any alteration for the weakest signals possibly present in positive and negative times. The core of the proposed technique depends on an accurate simulation for all the harmonics one by one existing in the positive and negative times of the data after cross-correlation with the fundamental sweep and then subtracting the simulated harmonics from the original data using an optimization procedure. The steps and mathematical equations of the procedure are explained in detail in the body of the article in the section titled 'harmonic by harmonic attenuation procedure'. Accordingly, a well-developed procedure for enhancing the vibroseis data quality in both down- and up-sweep data is illustrated. The procedure was tested on both synthetic and field data sets. © 2010 European Association of Geoscientists & Engineers.

Abdel Hafiez H.E.,National Research Institute of Astronomy and Geophysics NRIAG
Arabian Journal of Geosciences | Year: 2015

After Cairo Earthquake in 1992 (Ms 5.9), the government established the Egyptian National Seismological Network (ENSN) organized by the National Research Institute of Astronomy and Geophysics (NRIAG) start to work since 1997; NRIAG has a real monitoring of the seismological activity in and around different parts of Egypt. A selected 5000 events from the ENSN annual bulletin in the period 2004–2013 with calculated local magnitude (ML) based on Richter regular formula was used in this study; a duration magnitude was calculated for these events and regressed with ML. Another aim of this study is to develop a regression relation of the calculated body wave magnitude (Mb) to the unified moment magnitude (Mw) which is the base for homogenization of earthquake catalogue needed for seismic hazard studies. Standard least square regression usually fails to give reliable results when both regressed variables have measurement errors; orthogonal standard regression (OSR) is the most reliable tool used for conversion of observed Mb values with the moment magnitude Mw. The accuracy of the resulting relations from regression have been checked with another 20 events of the data and shows the advantage of using OSR method to get regressed relation to homogenize any catalogue containing various magnitudes with measurement errors, by their regression with a Mw. The proposed procedure also remains valid in case the magnitudes have measurement errors different from unity. © 2015, Saudi Society for Geosciences.

Hafiez H.E.A.,National Research Institute of Astronomy and Geophysics NRIAG
Arabian Journal of Geosciences | Year: 2015

After the Cairo Earthquake in 1992 with moderate magnitude (Ms 5.9), the government established the Egyptian National Seismological Network (ENSN) with 66 short-period and broadband stations, organized by National Research Institute of Astronomy and Geophysics (NRIAG). Around 55,000 local events were recorded from 1997 to 2014. The aim of this study is to assess the magnitude of completeness (Mc) of an instrumental earthquake catalogue. Three different methods named the maximum curvature (MAXC), b value stability (MBS), and entire magnitude range (EMR) were applied to calculate Mc and the results are compared together; all of these used methods are catalogue-based methods, in which Mc is estimated based on departure from the linear frequency-magnitude relation of the local earthquakes published in the ENSN catalogue. Accurate knowledge of the magnitude of completeness Mc is essential for many seismicity-based studies and particularly for mapping out seismicity parameters such as the b value of the Gutenberg-Richter relationship. The difference in Mc between the three used methods is 0.9. However, tests performed on the diverse data sets presented here had confirmed that the EMR method is the more accurate method to estimate Mc. Estimating Mc solely based on the frequency-magnitude distribution (FMD) has some obvious drawbacks like the difficulty of estimating Mc in areas of low seismicity. The final results showed that the MAXC technique (Mc = 1.6 ± 0.02) needs fewer events to reach a stable result. While the MBS results (Mc = 2.5 ± 0.04) gave always higher Mc values compared with the other two methods, comparing to the third method, the EMR results (Mc = 1.8 ± 0.03) maximize the amount of data available for the Mc determination, which should serve to stabilize the Mc estimates. This study will play an important role in the future reconfiguration of the ENSN stations. © 2015 Saudi Society for Geosciences

Hanna M.A.,National Research Institute of Astronomy and Geophysics NRIAG | Amin S.M.,National Research Institute of Astronomy and Geophysics NRIAG
Journal of the Korean Astronomical Society | Year: 2013

We discuss the orbital period changes of the Algol semi-detached eclipsing binary DI Peg by constructing the (O-C) residual diagram via using all the available precise minima times. We conclude that the period variation can be explained by a sine-like variation due to the presence of a third body orbiting the binary together with a long-term orbital period increase (dP/dt = 0.17 sec/century) that can be interpreted to be due to mass transfer from the evolved secondary component (of rate 1.52 x 10~8M⊙/yr) to the primary one. The detected low-mass third body (M3 min.. = 0.22 ±0.0006 M⊙) is responsible for a periodic variation of about 55 years light time effect. We have determined the orbital parameters of the third component which show a considerable eccentricity e3 = 0.77 ± 0.07 together with a longitude of periastron ω3 = 300° ± 10°. © 2013 The Korean Astronomical Society. All Rights Reserved.

Rabeh T.,National Research Institute of Astronomy and Geophysics NRIAG
Environmental Earth Sciences | Year: 2016

In this study, an ideal area known for manganese ore accumulations in Sinai Peninsula has been investigated in detail using geological, laboratory analyses and magnetic tools. The main target is to establish a relationship between the ore accumulations, geology and the subsurface faults (shear structures) which are extending to deeper depths in the basement rocks of the study area and then use it as key for the un-explored areas in the Sinai Peninsula. To achieve this target, a detailed land magnetic survey has conducted to the selected area and later extended to include the whole peninsula. The geological data have obtained from the drilled wells and Egyptian Geological Survey and Mining Authority of Egypt. The geological investigations are including studying the surface geology and interpretation the well logging data to trace the ore mineral distributions along the different depths in the peninsula. The magnetic data has processed using a series of techniques, namely, second vertical gradient, 3D analytical signal, trend analyses, Euler deconvolution, Werner deconvolution and 3D modeling techniques. Also, the Curie depth method has applied along more than 31 grids forming the magnetic map of Sinai Peninsula to study the behavior of geothermal solutions and their effects in the host country rocks and their relationship to the existing ore accumulations. Furthermore, more than 300 rock samples have collected from different sites covering Sinai Peninsula area. These samples were subjected to laboratory measurements of the magnetic susceptibility. The results show that the Curie magnetic depth confirms that these shear structures at the intersection points are extended to deep depths which make as a pass way for the hydrothermal solutions into the host rocks which are probably forming the ore accumulations. The ore mineral accumulations appear to be confined to the carbonate rocks and to the shear zones intersections of the structures which are trending NW–SE and NE–SW directions. The depth to these accumulations was found to be ranging between 300 m at the southern parts to more than 3 km at the northern parts of the Sinai Peninsula. The measured magnetic susceptibility values range between 0.4 SI and 1.8 SI. Five new areas namely; Sharm El Sheikh, Wadi Zaghrah, SW Taba, Libni and Maghara can be prospected in the Sinai Peninsula have the similar conditions which are existing at Abu Zneima known mine area. © 2015, Springer-Verlag Berlin Heidelberg.

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