Capella: Structure and Abundances

The analysis of the Advanced Satellite for Cosmology and Astrophysics (ASCA) spectra of the cool star binary system Capella is reported. The results of EUVE analysis, ASCA analysis, application of EUVE model to ASCA analysis, and Uncertainty Analysis are discussed

Dissecting the EUV spectrum of Capella

Extreme ultraviolet spectra of Capella, obtained at various orbital phases over the past two years by the EUVE satellite, show strong emission lines from a continuous distribution of temperatures (approximately 10(exp 5 -10(exp 7.3) K). In addition to the strong He II lambda 303.8, the spectra are dominated by emission lines of highly ionized iron. Strong lines of Fe IX, XV, XVI, and XVIII-XXIV are used to construct emission measure distributions for the individual pointings, which show several striking features, including a minimum near 10(exp 6) K and a local maximum at 10(exp 6.8) K. Furthermore, intensities of the highest temperature lines (Te is greater than 10(exp 7) K) show variations (factors of 2-3) at different orbital phases, while the lower temperature Fe lines show variations of about 30% or less. The low variability of most of the strong low temperature features motivates a detailed analysis of the summed spectrum. With approximately 280 ksec of total exposure time, we have measured over 200 emission features with S/N greater than or equal to 3.0 in the summed spectrum. We report here initial results from the analysis of this spectrum. We can now identify lines of Fe VIII and X-XIV, as well as a number of electron density and abundance diagnostic lines. We also report here the first direct measurement of the continuum flux around approximately 100 A in a cool star atmosphere with EUVE. The continuum flux can be predicted from the emission measure model based on Fe line emission, and demonstrates that the Fe/H abundance ratio is dose to the solar photospheric value

Eleventh International Conference on Atomic and Molecular Data and Their Applications

The 11th International Conference on Atomic and Molecular Data and their Applications (ICAMDATA) was held on November 11–15, 2018, in Cambridge, Massachusetts, and was organized by the Center for Astrophysics | Harvard & Smithsonian. This meeting is a continuation of a series which began in 1997 that was chartered to promote the use of atomic and molecular (AM) data in various fields of science and technology, to provide a forum for the interaction of AM data producers and users, and to foster crossdisciplinary cooperation between AM data producers and users as the coordination of AM data activities and databases worldwide

New resonance scattering model in AtomDB: application to line suppression in galaxy clusters and elliptical galaxies

In this paper, we present a simple, one-step, self-consistent, and fast resonance scattering model rsapec based on the AtomDB database. This model can be used as an alternative to the commonly used APEC model for fitting such X-ray spectra with optically thick lines. The current model is intended, in general, for verifying the presence of the effect and for spectral modeling of galaxy clusters and elliptical galaxies under applicable assumptions. We test rsapec to derive the line suppression in the elliptical galaxy NGC 4636 and the Perseus cluster of galaxies and obtain resonance suppression of ~ 1.24 and ~ 1.30, respectively.Comment: Accepted for publication in Ap

Photoionized features in the X-ray spectrum of Ex Hydrae

We present the first results from a long (496 ks) Chandra High Energy Transmission Grating observation of the intermediate polar EX Hydrae ( EX Hya). In addition to the narrow emission lines from the cooling post-shock gas, for the first time we have detected a broad component in some of the X-ray emission lines, namely, O VIII lambda 18.97, Mg XII lambda 8.42, Si XIV lambda 6.18, and Fe XVII lambda 16.78. The broad and narrow components have widths of similar to 1600 km s(-1) and similar to 150 km s(-1), respectively. We propose a scenario where the broad component is formed in the pre-shock accretion flow, photoionized by radiation from the post-shock flow. Because the photoionized region has to be close to the radiation source in order to produce strong photoionized emission lines from ions such as O VIII, Fe XVII, Mg XII, and Si XIV, our photoionization model constrains the height of the standing shock above the white dwarf surface. Thus, the X-ray spectrum from EX Hya manifests features of both magnetic and non-magnetic cataclysmic variables

High temperature structure in cool binary stars

Strong high temperature emission lines in the EUVE spectra of binary stars containing cool components (Alpha Aur (Capella), 44 iota Boo, Lambda And, and VY Ari) provide the basis to define reliably the differential emission measure of hot plasma. The emission measure distributions for the short-period (P less than or equal to 13 d) binary systems show a high temperature enhancement over a relatively narrow temperature region similar to that originally found in Capella (Dupree et al. 1993). The emission measure distributions of rapidly rotating single stars 31 Com and AB Dor also contain a local enhancement of the emission measure although at different temperatures and width from Capella, suggesting that the enhancement in these objects may be characteristic of rapid rotation of a stellar corona. This feature might be identified with a (polar) active region, although its density and absolute size are unknown; in the binaries Capella and VY Ari, the feature is narrow and it may arise from an interaction region between the components

EUV spectroscopy of 3 RSCVn binaries

The extreme ultraviolet (EUV) spectroscopy of several binary stars containing cool components is used to define the high temperature plasma structure of these stars and their stellar atmospheres. Different line emission spectra are reported, along with a spectrum analysis of Capella, a nearby bright multiple star system, using data from the EUVE satellite