\documentstyle[twoside,epsf]{article}

\input{ibvs2.sty}

\begin{document}

\IBVShead{4882}{20 April 2000}

\IBVStitletl{Outburst Activity of BF Eridani in 1999}

\IBVSauth{Kato, T.; Uemura, M.}

\IBVSinsto{Dept.\ of Astronomy, Kyoto University, Kyoto 606-8502,
Japan,\\ \indent e-mail: tkato@kusastro.kyoto-u.ac.jp, uemura@kusastro.kyoto-u.ac.jp}

\SIMBADobjAlias{BF Eri}{SV* HV 10410}
\IBVStyp{ UG }
\IBVSkey{dwarf novae -- photometry}

\begintext

BF Eri was originally classified as a slowly varying variable star.
The fourth edition of General Catalogue of Variable Stars listed it as
a semiregular variable star with a range of 13.5--15.5 $pg$.  More
recent identification with the Einstein X-ray source led to the correct
classification as a cataclysmic variable, which has been suggested to
be a low-amplitude dwarf nova based on photometry (Kato 1999 and
references therein).  We report on the 1999 outburst activity of BF Eri.

The observations were done using an unfiltered ST-7 camera attached to
the Meade 25-cm Schmidt-Cassegrain telescope.  The exposure time was
30~s.  The images were dark-subtracted, flat-fielded, and analyzed
using the Java$^{\rm TM}$-based aperture photometry package developed
by one of the authors (TK).  The differential magnitudes of the
variable were measured against GSC 4743.801 (USNO $r$-magnitude 11.7),
whose constancy was confirmed by comparison with GSC 4743.797 (USNO
$r$-magnitude 12.3).

\IBVSfig{7.85cm}{4882-f1.ps}{Light curve of BF Eri in 1999}

The resultant light curve of BF Eri in 1999 is shown in Figure 1.  Each
point represents a nightly averaged magnitude of 3 to 10 frames, with
an error bar indicating the standard error.  The light curve clearly
indicates the presence of two distinct outbursts, reaching maxima
around JD 2451469 and 2451533.  The interval between these two
outbursts was 64~d, which is close to the one-third of the GCVS period
(198~d), and it can be considered as a typical recurrence time of this
dwarf nova.  When compared to earlier observations (Kato 1999), the
amplitude (1.6 mag) of outbursts is remarkably larger in this season
than in the previous season, more clearly confirming the dwarf
nova-type classification.  The difference in the outburst activity
between seasons may indicate the presence of alternating stages of low
and high outburst amplitudes, as are most clearly demonstrated in Z
Cam-type dwarf novae (e.g.\ Warner 1995).

The rise to the second outburst (JD 2451533) was well covered by
observations.  The slow rise took seven days, while the fade (though
not completely covered by observations) was much faster.  This is
clearly a signature of ``inside-out'' type outburst (Smak 1984).  The
overall outburst behavior in 1999 resembles that of a low-amplitude
dwarf nova, RU~Peg.

\references

Kato, T. 1999, {\it IBVS}, No.\ 4745

Smak, J. 1984, {\it Acta Astron.}, {\bf 34}, 161

Warner, B. 1995, ``Cataclysmic Variable Stars" (Cambridge Univ.\ Press,
Cambridge)

\end{document}


