Issue |
A&A
Volume 444, Number 1, December II 2005
|
|
---|---|---|
Page(s) | 213 - 220 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20053711 | |
Published online | 21 November 2005 |
Doppler tomography of the asynchronous polar BY Camelopardalis
1
Astrophysikalsches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany e-mail: rschwarz@aip.de
2
Center for Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Received:
28
June
2005
Accepted:
1
August
2005
We present phase-resolved, high-resolution (1.3 Å) spectroscopy
of the brightest near-synchronous polar BY Cam taken on two different
occasions in 1998 and 1999. The first tomographic study of such a system
reveals line emission spread out over a large velocity range forming a
crescent at negative vy velocities in the Doppler maps.
In contrast to the majority of synchronous AM Her systems there is only
weak indication for the presence of a focused accretion stream.
These two facts suggest that the majority of the matter is accreted
via an extended curtain. Location and extent of the structure in the
Doppler maps can be reproduced with a simple curtain model raised over
a wide (~180°) range in azimuth implying that the ballistic
stream stretches to a point far behind the white dwarf.
In order to reach such small magnetospheric radii mass accretion
rates a factor of 10 to 20 in excess of that normally seen
in polars would be required.
In addition to the curtain emission, the Balmer lines
show a narrow emission line component likely originating from the
heated side of the secondary star. Its velocity amplitude
of 190 together with an illumination model of the secondary star
suggests a rather heavy white dwarf of
and
an inclination larger than
°.
Timings of this feature in the present and historical
data unequivocally determine the orbital period and have been used
to establish a high-precision, long-term ephemeris.
Key words: accretion: accretion disks / stars: binaries: close / stars: novae, cataclysmic variables / stars: magnetic fields
© ESO, 2005
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