Astronomy and Astrophysics – Astronomy
Scientific paper
Feb 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...440..853s&link_type=abstract
Astrophysical Journal v.440, p.853
Astronomy and Astrophysics
Astronomy
3
Stars: Binaries: Spectroscopic, Stars: Individual Constellation Name: Ar Andromedae, Stars: Novae, Cataclysmic Variables
Scientific paper
Radial velocity studies of the dwarf nova AR And during quiescence and eruption are presented and compared. These data strongly suggest the orbital period is 0.1640 + 0.0005 days, although 1 cycle day-1 aliases of this period cannot be ruled out unequivocally. Despite being formed in dissimilar disk environments, the quiescent emission and outburst absorption lines yield similar radial velocity amplitudes. The quiescent emission-line amplitude obtained from measurements of Hα is Kem = 83±7 km s-1. The amplitude during outburst, as determined from analysis of the Hβ and Hγ absorption lines is slightly lower, but consistent with the quiescent value. Observations obtained on 1991 December 10, ˜1 week after outburst maximum, yielded Kabs = 74±10 km s-1 for both Hβ and Hγ. The following night the lines were weaker, the data noisier, and the spectra fewer, resulting in less reliable velocity amplitudes. Nevertheless, the average amplitude of 73±16 km s-1 is consistent with the amplitudes determined on the previous night.
The similarity between the emission- and absorption-line amplitudes in AR And is a robust result. The derived velocity amplitudes are insensitive to the portion of the line profiles used in the velocity measurements, suggesting that the disk radiation is nearly axisymmetric. This result is corroborated by a Doppler tomogram of the quiescent Hα data, which shows that the emission is distributed fairly evenly over the surface of the disk. The results presented here add confidence that velocity variations of spectral features from the accretion disk in AR And may provide a reliable tracer of the orbital motion of the white dwarf in this system.
Robinson Emma L.
Shafter Allen W.
Veal Jeffrey Matthew
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