[vsnet-chat 5482] Re: (fwd) Assistance Needed with Light Curve of V1432 Aql

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

Re: (fwd) Assistance Needed with Light Curve of V1432 Aql

    V1432 Aql is an eclipsing polar (AM Her star).  In contrast to other
CVs (dwarf novae, novalike stars etc.), the emission source (and the eclipsed
body) is an accretion stream and accretion column on a white dwarf
(not an accretion disk).  The temporal structure of the accretion stream
and accretion column strongly vary, and have own irregularities (blobs,
QPOs originating near the accretion shock region etc.).  They may have
affected Donn's observation.

    By the way, the source of emission from a polar is a combination of
synchrotron emission and thermal emission in the optical range.  The
frequency dependency of the former emission is strikingly different from
usual CVs (with thermal emissions).  There even exist outstanding differences
between V-band and "white light" (unfiltered) light curves.  Due to this
complexity, "white light" light curves in polars convey less information
than in other CVs.  So we don't usually recommend unfiltered photometry
(as in other CVs) of polars except on rare occasions (simultaneous observation
with an X-ray sattelite or when knowledge of one-pole or two-pole accretion
is important).  Filtered photometry is more recommended in these sources,
but they are usually too faint to get sufficient S/N and time-resolution
with small telescopes.  A minimum requirement would be 0.5-1.0 m telescope
with a high Q.E. CCD except on a few bright sources.

Regards,
Taichi Kato

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