Search results for "X-Ray"
showing 10 items of 4234 documents
Hot Plasma Detected in Active Regions by HINODE/XRT and SDO/AIA
2012
Multiple ratios of Hinode/XRT filters showed evidence of a minor very hot emission measure component in active regions. Recently also SDO/AIA detected hot plasma in the core of an active region. Here we provide estimates showing that the amount of emission measure of the hot component detected with SDO is consistent with that detected with Hinode/XRT.
Rotationally modulated X-ray emission from the accretion shock in CTTS
2011
To study the accretion shocks of classical T Tauri stars (CTTS) we obtained high-resolution X-ray spectra of two CTTS, V2129 Oph and V4046 Sgr, to look for phase-resolved X-ray signatures of shock-heated plasma. The 200 ks Chandra/HETGS observation of V2129 Oph (a 1.35 M sun star, rotating in 6.5 d) covered 0.5 stellar rotation. The 360 ks XMM/RGS observation of V4046 Sgr (a binary system, with two 0.9 M sun components, synchronously rotating in 2.42 d) monitored 2.2 system rotations. The stellar photosphere, magnetic field, and accretion geometry of both stars were constrained by quasi-simultaneous optical monitoring (photometry, spectroscopy, and spectropolarimetry). The cool plasma compo…
Coordinated Optical/X-ray observations of the CTTS V2129 Oph The Chandra View
2011
Young low-mass accreting stars (classical T Tauri stars; CTTSs) possess strong magnetic fields that are responsible for the regulation of the accretion and outflow processes, and the confinement and heating of coronal plasma. Understanding the physics of CTTS magnetospheres and of their interaction with circumstellar disks can elucidate the history and evolution of our own Sun and Solar System, at the stage when planets were being formed. In June 2009 we have conducted an extensive multi-wavelength observing campaign of V2129 Oph, a K5 CTTS in the ρ Ophiuchi molecular cloud, with the goal of obtaining a synoptic view of its photosphere, magnetic field, coronal plasma, and of its accretion s…
Evolution in Recycling Scenario
2011
The recycling model argues the existence of an evolutionary connection between low mass X-ray binaries and radio millisecond pulsars. The main difficulties which this model finds in predict the parameters of the fully recycled millisecond pulsars, as mass and spin period, can be overcome by the onset of the so-called radio-ejection mechanism. This work is to provide observational support to the radio-ejection mechanism by inspecting the orbital and spin parameters of the known population of fully recycled radio pulsars and compare these with the expectation for the occurrence of this mechanism.
The EM(T) of stellar coronae
2010
Studying the solar corona, due to its vicinity, is the starting point to understand stellar activity. The emission measure distribution vs temperature, EM(T), is a useful tool to study coronal plasmas, in fact it allows: to investigate the energy balance of coronal plasmas, to easily compare different stars, and also to compare the solar corona to that of other active stars irrespective of the very different observing techniques. The EM(T) of the solar corona differs significantly, in terms of average plasma temperatures, peak temperatures, and total emission measure, with respect to that of active stars. In this work it is discussed how the evaluation of the EM(T) of the solar corona, and …
Synthesis, X-ray Structure, Antimicrobial and Anticancer Activity of a Novel [Ag(ethyl-3-quinolate)2(citrate)] Complex
2022
A novel Ag(I) citrate complex with ethyl-3-quinolate (Et3qu) was synthesized. Its structure was confirmed using X-ray single crystal to be [Ag(Et3qu)2(citrate)]. It crystallized in the Triclinic crystal system and P-1 space group with unit cell parameters of a = 8.6475(2) Å, b = 11.4426(3) Å, c = 15.2256(3) Å, α = 73.636(2)°, β = 79.692(2)° and γ = 86.832(2)°, while the unit cell volume was 1422.19(6) Å3. In the unit cell, there are two [Ag(Et3qu)2(citrate)] molecules and one unit as the asymmetric formula. The molecular structure comprised one Ag(I) coordinated with two Et3qu molecules via two almost equidistant Ag-N bonds and one citrate ion acting as a mono-negative monodentate ligand vi…
Science case study and scientific simulations for the enhanced X-ray Timing Polarimetry mission, eXTP
2022
The X-ray astronomy mission eXTP (enhanced X-ray Timing Polarimetry) is designed to study matter under extreme conditions of density, gravity and magnetism. Primary goals are the determination of the equation of state (EoS) of matter at supranuclear density, the physics in extremely strong magnetic fields, the study of accretion in strong-field gravity (SFG) regime. Primary targets include isolated and binary neutron stars, strong magneticfield systems like magnetars, and stellar-mass and supermassive black holes. In this paper we report about key observations and simulations with eXTP on the primary objectives involving accretion under SFG regimes and determination of NS-EoS.
Improving methods in X-ray nanotomography of fibre bonds
2017
X-ray nanotomography has proven to be a useful yet challenging method in the study of cellulose fibre bonds. The challenges encountered in previous researches are related to lengthy imaging times and low success rate per sample. To counter these obstacles, fibre staining in order to enhance contrast in radiographic images and an alternative method for marker particle placement were examined in this study. Cesium iodide proved to be a suitable staining material, and the alternative method for particle placement may increase success rate by reducing microfibril structure fracturing during the marker placement process.
Observational diagnostics of accretion on young stars and brown dwarfs
2010
I present a summary of recent observational constraints on the accretion properties of young stars and brown dwarfs with focus on the high-energy emission. In their T Tauri phase young stars assemble a few percent of their mass by accretion from a disk. Various observational signatures of disks around pre-main sequence stars and the ensuing accretion process are found in the IR and optical regime: e.g. excess emission above the stellar photosphere, strong and broad emission lines, optical veiling. At high energies evidence for accretion is less obvious, and the X-ray emission from stars has historically been ascribed to magnetically confined coronal plasmas. While being true for the bulk of…
Time-resolved Spectroscopy of DROXO X-ray Sources: Flares and Fe Kα emission
2011
We present a systematic search for Fe Kα emission from young stellar objects of the ρ Ophiuchi star forming region observed in the Deep Rho Ophiuchi XMM-Newton Observation.