Chandra HETG X-ray Spectra and Variability of $π$ Aqr, a $γ$ Cas-type Be star

Kavli Affiliate: Norbert S. Schulz

| First 5 Authors: David P. Huenemoerder, Pragati Pradhan, Claude R. Canizares, Sean Gunderson, Richard Ignace

| Summary:

High-resolution X-ray spectra of $pi,$Aqr, a $gamma,$Cas-type star,
obtained with the Chandra/HETG grating spectrometer, revealed emission lines of
H-like ions of Mg, Si, S, and Fe, a strong, hard continuum, and a lack of
He-like ions, indicating the presence of very hot thermal plasma. The X-ray
light curve showed significant fluctuations, with coherent variability at
period of about 3400 seconds in one observation. The hardness ratio was
relatively constant except for one observation in which the spectrum was much
harder and more absorbed. We interpret the X-ray emission as arising from
accretion onto the secondary, which is likely a magnetic white dwarf, an
intermediate polar system.

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