Search results for "X-rays."
showing 10 items of 443 documents
Baseline design of the filters for the LAD detector on board LOFT
2014
The Large Observatory for X-ray Timing (LOFT) was one of the M3 missions selected for the phase A study in the ESA's Cosmic Vision program. LOFT is designed to perform high-time-resolution X-ray observations of black holes and neutron stars. The main instrument on the LOFT payload is the Large Area Detector (LAD), a collimated experiment with a nominal effective area of ~10 m 2 @ 8 keV, and a spectral resolution of ~240 eV in the energy band 2-30 keV. These performances are achieved covering a large collecting area with more than 2000 large-area Silicon Drift Detectors (SDDs) each one coupled to a collimator based on lead-glass micro-channel plates. In order to reduce the thermal load onto …
The Cryogenic AntiCoincidence detector for ATHENA: the progress towards the final pixel design
2014
“The Hot and Energetic Universe” is the scientific theme approved by the ESA SPC for a Large mission to be flown in the next ESA slot (2028th) timeframe. ATHENA is a space mission proposal tailored on this scientific theme. It will be the first X-ray mission able to perform the so-called “Integral field spectroscopy”, by coupling a high-resolution spectrometer, the X-ray Integral Field Unit (X-IFU), to a high performance optics so providing detailed images of its field of view (5’ in diameter) with an angular resolution of 5” and fine energy-spectra (2.5eV@E<7keV). The X-IFU is a kilo-pixel array based on TES (Transition Edge Sensor) microcalorimeters providing high resolution spectroscopy …
Attosecond soft-X-ray spectroscopy of a transition metal dichalcogenide material
2019
We use attosecond soft X-ray pulses between 284 eV to 543 eV for orbital-selective and real-time probing of the opto-electronic response of semi metallic TiS2.
Nanoflare Evidence from Analysis of the X-Ray Variability of an Active Region Observed with Hinode/XRT
2012
The heating of the solar corona is one of the big questions in astrophysics. Rapid pulses called nanoflares are among the best candidate mechanisms. The analysis of the time variability of coronal X-ray emission is potentially a very useful tool to detect impulsive events. We analyze the small-scale variability of a solar active region in a high cadence Hinode/XRT observation. The dataset allows us to detect very small deviations of emission fluctuations from the distribution expected for a constant rate. We discuss the deviations in the light of the pulsed-heating scenario.
Temperature Diagnostics of a Solar Active Region Using a Single-Filter Observation of Hinode/XRT
2012
Broad-band X-ray observations can provide limited temperature diagnostics through filter ratios. A high cadence observation of an active region made with a single Hinode/XRT filter allows us to use an alternative approach in which we measure the time fluctuations of the pixel count rate and use the variance as temperature proxy. We show the results and discuss limitations of method.
Sphinx measurements of the 2009 solar minimum x-ray emission
2012
The SphinX X-ray spectrophotometer on the CORONAS-PHOTON spacecraft measured soft X-ray emission in the 1-15 keV energy range during the deep solar minimum of 2009 with a sensitivity much greater than GOES. Several intervals are identified when the X-ray flux was exceptionally low, and the flux and solar X-ray luminosity are estimated. Spectral fits to the emission at these times give temperatures of 1.7-1.9 MK and emission measures between 4 x 10^47 cm^-3 and 1.1 x 10^48 cm^-3. Comparing SphinX emission with that from the Hinode X-ray Telescope, we deduce that most of the emission is from general coronal structures rather than confined features like bright points. For one of 27 intervals o…
INTEGRAL and RXTE observations of accreting millisecond pulsar IGR J00291+5934 in outburst
2005
Simultaneous observations of the accretion-powered millisecond pulsar IGR J00291+5934 by International Gamma-Ray Astrophysics Laboratory and Rossi X-ray Timing Explorer during the 2004 December outburst are analysed. The average spectrum is well described by thermal Comptonization with an electron temperature of 50 keV and Thomson optical depth tau_T ~ 1 in a slab geometry. The spectral shape is almost constant during the outburst. We detect a spin-up of the pulsar with nudot=8.4x10E-13 Hz/s. The ISGRI data reveal the pulsation of X-rays at a period of 1.67 milliseconds up to ~150 keV. The pulsed fraction is shown to increase from 6 per cent at 6 keV to 12--20 per cent at 100 keV. This is n…
Green direct determination of mineral elements in artichokes by infrared spectroscopy and X-ray fluorescence.
2015
Near infrared (NIR) and X-ray fluorescence (XRF) spectroscopy were investigated to predict the concentration of calcium, potassium, iron, magnesium, manganese and zinc in artichoke samples. Sixty artichokes were purchased from different Spanish areas (Benicarlo, Valencia and Murcia). NIR and XRF spectra, combined with partial least squares (PLS) data treatment, were used to develop chemometric models for the prediction of mineral concentration. To obtain reference data, samples were mineralised and analysed by inductively coupled plasma optical emission spectrometry (ICP-OES). Coefficients of determination obtained for the regression between predicted values and reference ones for calcium, …
A possible solution of the puzzling variation of the orbital period of MXB 1659-298
2017
MXB 1659-298 is a transient neutron star Low-Mass X-ray binary system that shows eclipses with a periodicity of 7.1 hr. The source went to outburst in August 2015 after 14 years of quiescence. We investigate the orbital properties of this source with a baseline of 40 years obtained combining the eight eclipse arrival times present in literature with 51 eclipse arrival times collected during the last two outbursts. A quadratic ephemeris does not fit the delays associated with the eclipse arrival times and the addition of a sinusoidal term with a period of $2.31 \pm 0.02$ yr is required. We infer a binary orbital period of $P=7.1161099(3)$ hr and an orbital period derivative of $\dot{P}=-8.5(…
Supersaturation and activity-rotation relation in PMS stars: the young Cluster h Per
2016
The magnetic activity of late-type MS stars is characterized by different regimes, and their activity levels are well described by Ro, the ratio between P_rot and the convective turnover time. Very young PMS stars show, similarly to MS stars, intense magnetic activity. However they do not show clear activity-rotation trends, and it still debated which stellar parameters determine their magnetic activity levels. To bridge the gap between MS and PMS stars, we studied the activity-rotation relation in the young cluster h Per, a ~13 Myr old cluster, that contains both fast and slow rotators, whose members have ended their accretion phase and have already developed a radiative core. It offers us…