Related papers: Chandra/HETG Doppler velocity measurements in stel…
Using the Chandra/High Energy Transmission Grating Spectrometer (hereafter HETGS) we have detected Doppler motion of Capella's X-ray emission lines in the 6 -- 25AA wave-band. The observed motion follows the expected orbital motion of…
We probe the relationship between surface magnetic fields and the X-ray emitting corona in the rapidly rotating star AB Dor. Circularly polarised spectra have been inverted to produce a surface (photospheric) magnetic field map. This…
The Chandra X-ray observatory monitored the single cool star, AB Doradus, continuously for a period lasting 88 ksec (1.98 Prot) in 2002 December with the LETG/HRC-S. The X-ray lightcurve shows rotational modulation, with three peaks that…
Capella is the brightest chromospherically active binary in the sky, hosting a cooler G8III giant (Aa) and an hotter G1III companion (Ab). The source has been extensively observed in the X-rays in the past decades not only for its…
The high-resolution X-ray spectroscopy made possible by the 1999 deployment of the Chandra X-ray Observatory has revolutionized our understanding of stellar X-ray emission. Many puzzles remain, though, particularly regarding the mechanisms…
The Chandra Multiwavength Plane (ChaMPlane) Survey of the galactic plane incorporates serendipitous sources from selected Chandra pointings in or near the galactic plane (b < 12deg; >20 ksec; lack of bright diffuse or point sources) to…
Coronal astronomy is by now a fairly mature discipline, with a quarter century having gone by since the detection of the first stellar X-ray coronal source (Capella), and having benefitted from a series of major orbiting observing…
Spectroscopy with the Chandra High Energy Transmission Grating Spectrometer provides details on X-ray emission and activity from young and cool stars through resolution of emission lines from a variety of ions. We are beginning to see…
High resolution spectra of the active binary Capella (G8 III + G1 III) covering the energy range 0.4-8.0 keV (1.5-30 Angstroms) show a large number of emission lines, demonstrating the performance of the HETGS. A preliminary application of…
Chandra High-Energy Transmission Grating observations of the bright eclipsing contact binary 44i Boo show X-ray line profiles which are Doppler-shifted by orbital motions. The X-ray emission spectrum contains a multitude of lines…
The Chandra X-ray Observatory grating spectrometers allow study of stellar spectra at resolutions on the order of 1000. Prior x-ray observatories' low resolution data have shown that nearly all classes of stars emit x-rays. Chandra reveals…
We have carried out optical and X-ray spectral analyses on a sample of 136 candidate optical counterparts of X-ray sources found in five Galactic-bulge fields included in our Chandra Multi-wavelength Plane Survey. We use a combination of…
We analyze the X-ray spectra of 19 main sequence stars observed by Chandra using its LETGS configuration. Emission measure (EM) distributions are computed based on emission line measurements, an analysis that also yields evaluations of…
Chandra High-Energy Transmission Grating (HETG) X-ray spectra are extracted from 17 bright, narrow regions of Cas A and provide unique measurements of their kinematic and plasma states. From the dominant emission lines, e.g. He-like Si, we…
The grating instruments on board Chandra and XMM-Newton now allow measurements of electron densities. These rely on the ratios of fluxes in emission lines, where one line depends on both collisional and radiative decay rates. The electron…
The X-ray luminous RS CVn binary system HR 1099 has been observed on several occasions in the early phases of \textit{Chandra} and \textit{XMM-Newton}. A very hot (up to 40 MK) dominant coronal plasma has been identified from the…
A fine analysis of spectral line widths and Doppler shifts employing Fourier transform and cross-correlation techniques has been applied to Chandra HETG spectra obtained in 1999 October of the rapidly rotating young star AB Doradus in order…
We present the first X-ray spectrum obtained by the Low Energy Transmission Grating Spectrometer (LETGS) aboard the Chandra X-ray Observatory. The spectrum is of Capella and covers a wavelength range of 5-175 A (2.5-0.07 keV). The measured…
We report the discovery of eight X-ray sources with periodic variability in 487 ks of observations of the Galactic center with Chandra. The sources are identified from a sample of 285 objects detected with 100-4200 net counts. Their periods…
Identifying trends between observational data and the range of physical parameters of massive stars is a critical step to the still-elusive full understanding of the source, structure, and evolution of X-ray emission from the stellar winds,…