Nancy S. Brickhouse

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New X-ray observatories (Chandra and XMM-Newton) are providing a wealth of high-resolution X-ray spectra in which hydrogenand helium-like ions are usually strong features. We present results from a new collisional-radiative plasma code, the Astrophysical Plasma Emission Code (apec), which uses atomic data in the companion Astrophysical Plasma Emission(More)
We obtain contemporaneous observations of the surface and corona of AB Dor, a young single cool star, using ground-based circularly polarised spectra from the AngloAustralian Telescope and X-ray lightcurves and spectra from the Chandra satellite. The ground-based data are used to construct surface magnetic field maps, which are extrapolated to produce(More)
The Chandra X-ray observatory monitored the single cool star, AB Doradus, continuously for a period lasting 88 ksec (1.98Prot) in 2002 December with the LETG/HRC-S. The X-ray lightcurve shows rotational modulation, with three peaks that repeat in two consecutive rotation cycles. These peaks may indicate the presence of compact emitting regions in the(More)
A survey of 28 stars (22 active binary systems, plus 6 single stars or wide binaries for comparison) using extreme ultraviolet spectra has been conducted to establish the structure of stellar coronae in active binary systems from the emission measure distribution (EMD), electron densities, and scale sizes. Observations obtained by the Extreme Ultraviolet(More)
We present the first detection of orbital motion in the cataclysmic variable EX Hydrae based on X-ray data from the Chandra X-ray Observatory. The large collecting area of the telescope and the high resolution of the HETG spectrometers allow for an unprecedented velocity accuracy of ∼15 km s in the X-ray wavelength regime. We find an emission line velocity(More)
Four of the most active RS CVn stars (V711 Tau, II Peg, Gem, and UX Ari) have been observed for a total of 3Ms with the Extreme Ultraviolet Explorer satellite (EUVE) between 1992 and 2000 January. Flaring and quiescent states of extreme ultraviolet spectra ( 70–740) and light curves ( 75–175) have been analyzed to provide emission measure distributions(More)
We show that the Fe (vii-xii) M-shell unresolved transition array (UTA) in the NGC 3783 900 ks Chandra HETGS observation clearly changes in opacity in a timescale of 31 days responding to a factor of ∼ 2 change in the ionizing continuum. The opacity variation is observed at a level > 10σ. There is also evidence for variability in the O vi K edge (at ∼ 3σ).(More)
Spectra of highly charged Kr ions, produced in an electron-beam ion trap (EBIT), have been recorded in a broad x-ray energy band (0.3 keV to 4 keV) with a microcalorimeter detector. Most of the spectral lines have been identified as transitions of B- to Al-like Kr. The transition energies have been determined with 0.2% uncertainty. A semi-empirical EBIT(More)
We have analyzed Chandra High-Energy Transmission Grating spectra of the active RS CVn–type binary V711 Tauri (HR 1099; HD 22468) in order to examine the chemical composition of its coronae. Observed fluxes and flux upper limits for spectral lines from a range of charge states of iron, covering species Fe xvi–Fe xxv, have been used to determine the emission(More)