Chandra High Energy Transmission Grating Spectrum of AE Aquarii

(Abridged) The results of a Chandra X-ray Observatory High-Energy Transmission Grating (HETG) observation of the nova-like cataclysmic binary AE Aqr are described. First, the X-ray spectrum is that of an optically thin multi-temperature thermal plasma; the X-ray emission lines are broad, with widths that increase with the line energy, from sigma~1 eV for O VIII to sigma~5.5 eV for Si XIV; the X-ray spectrum is reasonably well fit by a plasma model with a Gaussian emission measure distribution that peaks at log T(K)=7.16, has a width sigma=0.48, an Fe abundance equal to 0.44 times solar, and other metal (primarily Ne, Mg, and Si) abundances equal to 0.76 times solar; and for a distance d=100 pc, the total emission measure EM=8.0E53 cm^-3 and the 0.5-10 keV luminosity L_X=1.1E31 erg/s. Second, based on the f/(i+r) flux ratios of the forbidden (f), intercombination (i), and recombination (r) lines of the He alpha triplets of N VI, O VII, and Ne IX measured by Itoh et al. in the XMM-Newton Reflection Grating Spectrometer spectrum and those of O VII, Ne IX, Mg XI, and Si XIII in the Chandra HETG spectrum, either the electron density of the plasma increases with temperature by over three orders of magnitude, from n_e~6E10 cm^-3 for N VI to n_e~1E14 cm^-3 for SI XIII, and/or the plasma is significantly affected by photoexcitation. Third, the radial velocity of the X-ray emission lines varies on the white dwarf spin phase, with two oscillations per spin cycle and an amplitude K~160 km/s. These results appear to be inconsistent with the recent models of Itoh et al., Ikhsanov, and Venter & Meintjes of an extended, low-density source of X-rays in AE Aqr, but instead support earlier models in which the dominant source of X-rays is of high density and/or in close proximity to the white dwarf.Comment: 13 pages including 1 table and 11 encapsulated postscript figure (3 in color); uses emulateapj.cls and apjfonts.sty; accepted on 2009 October 1 for publication in The Astrophysical Journa

EUVE Spectroscopy of Polars

An admittedly pedantic but hopefully useful and informative analysis is presented of the EUVE 70--180 Angstrom spectra of nine polars. These spectra are fit with three different models---a blackbody, a pure-H stellar atmosphere, and a solar abundance stellar atmosphere---to reveal the presence of spectral features such as absorption lines and edges, and to investigate the sensitivity of the derived (kT, N_H, solid angle) and inferred (fractional emitting area, bolometric luminosity) parameters to the model assumptions. Among the models tested, the blackbody model best describes the observed spectra, although the untested irradiated solar abundance stellar atmosphere model is likely a better overall description of the EUV/soft X-ray spectra of polars.Comment: 12 pages, 6 Postscript figures; LaTeX format, uses paspconf.sty, epsf.sty, and psfig.sty. To appear in the Proceedings of the Annapolis Workshop on Magnetic Cataclysmic Variables, ed. C. Hellier and K. Mukai (San Francisco: ASP

EUVE Observations of VW Hydri in Superoutburst

EUVE observed the SU UMa-type dwarf nova VW Hydri in superoutburst for an interval of nearly 2 days in 1994 June and produced EUV light curves and the first EUV spectrum of this important CV.Comment: 4 pages including 2 encapsulated postscript figures; LaTeX format, uses kluwer.cls; another old paper, brought kicking and screaming into the digital ag

The Quasi-Coherent Oscillations of SS Cygni

Properties of the quasi-coherent oscillations in the extreme ultraviolet (EUV) flux of the dwarf nova SS Cygni are described, with emphasis on (1) the scaling between the period of the oscillation and the EUV flux and (2) the mean power spectra and waveforms. In addition, a quasi-coherent oscillation at \nu = 0.012 +/- 0.002 Hz (FWZI) is discovered and proposed to be the spin frequency of the white dwarf.Comment: LaTeX format, uses paspconf.sty, 4 pages, 2 Postscript figures, Submitted for inclusion in Proceedings of IAU Colloquium No. 163 --- Accretion Phenomena & Related Outflows, ed. D. Wickramasinghe, L. Ferrario, & G. Bicknell (San Francisco: ASP