Taking the Pulse of DQ Herculis

Details Taking the Pulse of DQ Herculis Taking the Pulse of DQ Herculis

Jul 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...448..380m&link_type=abstract

Astrophysical Journal v.448, p.380

Astronomy and Astrophysics

Astronomy

16

Stars: Binaries: Close, Stars: Binaries: Eclipsing, Stars: Novae, Cataclysmic Variables, Stars: Individual Constellation Name: Dq Herculis

Scientific paper

We discuss high-speed spectrophotometric observations of DQ Herculis acquired with the Double Spectrograph and "2D-FRUTTI" detector on the Hale 5 m telescope. Trailed spectrograms and Doppler tomograms of the steady (unpulsed) light of Balmer, He I and He II lines reveals disk emission, while disk absorption components appear in He I and Ca II lines. Balmer and Ca II emission also originate in the Roche lobe of the secondary star; in neither case can we be certain whether the emission is intrinsic or is due to irradiation of the secondary star.
We detect 71 s pulsations in both the continuum and in the He II λ4686 emission line. Our pulse-phased trailed spectrograms exhibit He II λ4686 emission moving from red to blue across the line profile but not from blue to red, verifying with improved sensitivity and wavelength resolution the basic results of Chanan, Nelson, & Margon (1978). We also find some evidence for pulsation on the red side of the Balmer lines. For pulses arising from reprocessing of rotating X-ray beams irradiating an accretion disk, we are evidently seeing the reprocessing sites on the far side but not on the near side, owing to a less favorable viewing angle. In the context of this model, our data are largely consistent with a single beam sweeping the disk with period 71 s, although we cannot rule out the possibility that two beams (originating at the two poles of a magnetic dipole) excite the pulsed optical emission. The latter circumstance would imply a white dwarf spin period of 142 s.
The pulsed component of the He II λ4686 light is totally eclipsed, and the center of the source of pulsed He II λ4686 light is likely to be displaced or extended from the white dwarf. The He II λ4686 pulsation amplitude is strongest at +500 km s-1, implying that the reprocessed emission is anisotropic, enhanced in the inward (toward the white dwarf) and backward (opposite to the local Keplerian flow) directions. This anisotropy could arise through enhanced emissivity of the saturated He II line in the direction of acceleration, inward and backward in the corotating frame, as disk gas becomes threaded onto field lines of the more slowly rotating magnetosphere inside the corotation radius. Subject headings: binaries: close binaries: eclipsing novae, cataclysmic variables stars: individual (DQ Herculis)

Affiliated with

Also associated with

No associations

Rating

Taking the Pulse of DQ Herculis does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Taking the Pulse of DQ Herculis, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Taking the Pulse of DQ Herculis will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1170569