Related papers: X-ray Fluorescent Fe Kalpha Lines from Stellar Pho…
X-ray observations are a direct diagnostic of fast electrons produced in solar flares, energized during the energy release process and directed towards the Sun. Since the properties of accelerated electrons can be substantially changed…
We present results from monitoring observations of the gravitationally lensed quasar RX J1131-1231 performed with the Chandra X-ray Observatory. The X-ray observations were planned with relatively long exposures that allowed a search for…
In the classical flare picture, hard X-ray emission from the chromosphere is succeeded by soft-X-ray emission from hot plasma in the flare loop, the soft X-ray emission being a direct consequence of the impact of the non-thermal particle…
Extremely strong ionized Fe emission lines, with the equivalent width reaching about 4000 eV, were discovered with ASCA from a few Galactic compact objects, including AX J2315-0592, RX J1802.1+1804 and AX J1842.8-0423. These objects are…
The masses of compact objects in X-ray binaries are best constrained through dynamical measurements, relying on radial velocity curves of the companion star. In anticipation of upcoming high X-ray spectral resolution telescopes, we explore…
The X-ray spectra of accreting compact objects often exhibit discrete emission features associated with fluorescent emission in the accretion disk, the strongest of which is the Fe Kalpha fluorescence line at 6.4--6.97keV. These reflection…
Strong wind-wind collisions in massive binaries generate a very hot plasma that frequently produces a moderately strong iron line. The morphology of this line depends upon the properties of the wind interaction zone and its orientation with…
Fluorescent excitation of spectral lines is demonstrated as a function of temperature-luminosity and the distance of the emitting region from the central stars of planetary nebulae. The electron densities and temperatures are determined,…
We report on an X-ray flare detected on the active binary system II~Pegasi with the Swift telescope. The trigger had a 10-200 keV luminosity of 2.2$\times10^{32}$ erg s$^{-1}$-- a superflare, by comparison with energies of typical stellar…
The heating mechanisms of solar white-light flares remain unclear. We present an X1.0 white-light flare on 2022 October 2 (SOL2022-10-02T20:25) observed by the Chinese \ha\ Solar Explorer (CHASE) that provides two-dimensional spectra in the…
We report on X-ray flares that were observed from the active galactic nucleus I Zwicky 1 (I Zw 1) in 2020 January by the NuSTAR and XMM-Newton observatories. The X-ray spectrum is well-described by a model comprised of the continuum…
The source of fluorine is not well understood, although core-collapse supernovae, Wolf-Rayet stars, and asymptotic giant branch stars have been suggested. A search for evidence of the nu process during Type II supernovae is presented.…
Long-lasting, intense, stellar X-ray flares may approach conditions of breaking magnetic confinement and evolving in open space. We explore this hypothesis with hydrodynamic simulations of flares occurring in a non-confined corona: model…
The simultaneous presence of a strong quasi periodic oscillation of period of about 10 seconds in the optical and X-ray lightcurves of the X-ray transient XTE J1118+480 suggests that a significant fraction of the optical flux originates…
Iron emission lines at 6.4-6.97 keV, identified with fluorescent Kalpha transitions, are among the strongest discrete features in the X-ray band. These are therefore one of the most powerful probes to infer the properties of the plasma in…
We present the results of an archival 54 ks long Chandra observation of the peculiar source Cir X--1 during the phase passage 0.223-0.261. A comparative analysis of X-ray spectra, selected at different flux levels of the source, allows us…
For the first time, we have used RHESSI's spatial and energy resolution to determine the combined chromospheric and coronal density profile of the flaring solar atmosphere in a statistical manner, using a dataset of 838 flares observable in…
Most theoretical descriptions of the production of solar flare bremsstrahlung radiation assume the collision of dilute accelerated particles with a cold, dense target plasma, neglecting interactions of the fast particles with each other.…
We study the spatial distribution of the Fe 6.4 and 6.7 keV lines in the nuclear region of M82 using the Chandra archival data with a total exposure time of 500 ks. The deep exposure provides a significant detection of the Fe 6.4 keV line.…
We analyse the spatial distribution and vertical stratification of the physical parameters of the solar atmosphere when an X-class flare occurs. We made use of observations acquired by the Interferometric Bidimensional Spectropolarimeter…