Simultaneous Extreme Ultraviolet Explorer and Rossi X-Ray Timing Explorer Observations of AM Herculis

Details Simultaneous Extreme Ultraviolet Explorer and Rossi X-Ray Timing Explorer Observations of AM Herculis Simultaneous Extreme Ultraviolet Explorer and Rossi X-Ray Timing Explorer Observations of AM Herculis

Apr 2000

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000aj....119.1930c&link_type=abstract

The Astronomical Journal, Volume 119, Issue 4, pp. 1930-1941.

Astronomy and Astrophysics

Astronomy

6

Stars: Binaries: Close, Stars: Novae, Cataclysmic Variables, Stars: Individual (Am Herculis), X-Rays

Scientific paper

We present coordinated Extreme Ultraviolet Explorer (EUVE) and Rossi X-Ray Timing Explorer (RXTE) target of opportunity observations of the 1998 August high state of AM Herculis. The EUVE light curve sampled phases ~0.0-0.3 and ~0.5-0.8 and showed AM Her to be uncharacteristically bright during these phases but lacking the expected counts at phase ~0.5, possibly because of absorption. The RXTE proportional counter array (PCA) 2-20 keV and HEXTE 15-60 keV light curves clearly show the 3.09 hr orbital modulation. No correlations between the soft and hard bands predicted in the simple one-pole accretion model were detected in the ~1600 s of true, simultaneous EUVE and RXTE data. Quasi-periodic oscillations (QPOs) of 1-3 s found in optical data for several magnetic cataclysmic variables were not detected in PCA high time resolution data of AM Her with a 90% confidence upper limit for the rms amplitude of 3%. No significant QPOs were detected in the 10s-100s of seconds range with EUVE or RXTE. The EUVE spectrum was well fitted with a 19 eV blackbody. The phase-averaged PCA spectrum was well fitted with a 17.6+0.2-0.4 keV thermal bremsstrahlung (TB) continuum plus a broad iron line centered at 6.5 keV and absorption edge at 9.2 keV. HEXTE detections extended to 100 keV and preferred a highly absorbed TB continuum with temperature of 37+9-8 keV. The thermal bremsstrahlung plus emission-line (Eline=6.7 keV) and edge model fit to PCA spectra as a function of phase could be described as a single TB temperature of 18.9+/-0.2 keV with a variable column density of 7.1-53.5x1021 cm-2 and did not require more complex continuum models. The ratio of EUV to X-ray luminosity showed no soft excess and was more in accord with the simple one-pole model than previous observations.

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