Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996apj...456..777w&link_type=abstract
Astrophysical Journal v.456, p.777
Astronomy and Astrophysics
Astronomy
6
Stars: Novae, Cataclysmic Variables, Stars: Individual Constellation Name: Bt Monocerotis
Scientific paper
We present time-resolved spectrophotometry of the old nova BT Monocerotis (Nova Monocerotis 1939). While BT Mon's light curve possibly suggests the presence of an accretion disk, trailed spectrograms and Doppler tomograms of the data provide no such evidence. The spectra do reveal, however, high-velocity gas motions near eclipse that are of a character unique among other cataclysmic variables studied similarly to date. On the basis of the available data, we cannot describe the precise nature of BT Mon, but we suggest and discuss four possible interpretations of this extraordinary nova.
Accretion by the system's white dwarf via the standard stream-disk mechanism is roughly supported by the appearance of BT Mon's light curve, yet our spectroscopy does not indicate the presence of an accretion disk. And while accretion by the white dwarf of a wind from the secondary star might explain the high-velocity gas motions we observe surrounding eclipse, our spectroscopy provides no evidence for a wind. A third possible interpretation of our and other's data for BT Mon involves two mass-transfer streams that emanate from the secondary star. One stream is the classical mass transfer stream; the other is a supersonic stream driven from the secondary star by a de Laval nozzle. This two-stream model explains the appearance of BT Mon's unusual, high-velocity gas motions visible during eclipse, but we find no additional evidence to support it. Finally, we consider the possibility that the system's white dwarf is highly magnetized, accretion occurring via an accretion column onto the primary star's surface. Our observations mildly support such an interpretation, and recent results from other magnetic cataclysmic variables strengthen this last interpretation.
Honeycutt Kent R.
Schlegel Eric M.
White James C. II
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