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\IBVShead{4891}{26 April 2000}

\IBVStitle{Photometry of Stars in the Field of BF Cygni}

\IBVSauth{Skiff, Brian A.}
\IBVSinsto{Lowell Observatory, 1400 West Mars Hill Road, Flagstaff\enskip AZ\enskip 86001-4499, USA\enskip (bas@lowell.edu)} %email


\begintext

The symbiotic variable BF Cygni (19\hr23\mm53\fsec51;
+29\deg40\arcm29\farcs2 [2000]) lies a few arcminutes from the
fifth-magnitude star 2~Cygni in a crowded region of the southern Cygnus
starcloud with numerous other variables.  Monitoring of the star by
visual observers has been hampered by poor comparison sequences.  The
original BAA sequence simply did not reach faint enough to cover the
minimum observed in 1995, when the star faded to $m_v\sim12.5$,
and fainter still in more recent years.  The AAVSO chart goes fainter,
but is based on photographic photometry that clearly has a zero-point
error.  At the request of Gary Poyner (British Astronomical Association
Variable Star Section) I verified and extended the comparisons to reach
past the level of the 1995 faint episode.  I worked from the AAVSO
preliminary (d)-scale chart last revised in September 1988 (AAVSO
2000).  For stars fainter than AAVSO `125' (which has $V=12.2$), I chose
stars closer to the variable than the ones labelled on the chart. The
results were originally distributed via the `vsnet' list-server (Skiff
1996).

The observations were made with the Lowell 53-cm photometric telescope
on the UT dates 26 October and 13 November 1995, and 5 August 1996 using a
29\arcs\ diaphragm and Str\"omgren $b$ and $y$ filters.  About ten primary and
secondary standards were observed each night for adjustment to the standard
system.  The field was observed at low airmass, so mean extinction values
(Lockwood \& Thompson 1986) were applied in the reductions.  The per-star
residuals in the linear fits to the standards averaged between 0\fmm006 and 0\fmm010
in both $V$ and $b-y$.

Table 1 shows the results for the stars in order of decreasing brightness.
An asterisk by the star name indicates a note following the table.  The
positions are from Tycho-2 (H{\o}g {\it et al}.\ 2000) or the GSC-ACT (Gray
1999).  The {\it rms} scatter of the magnitudes and colors are given in the
second line of each entry.  These new data have been incorporated onto the
revised BAA chart (Poyner 1995).  Benson \& Salter (1999) provide BVRI
photometry for two additional stars in this field that complement the present
set.

\newpage

\begin{center}
\normalsize
{Table 1:  Photometry of stars in the field of BF Cygni \phantom{(}} \\
\vskip 1mm
\begin{tabular}{lllrrcll}
\hline
Name & \multicolumn{2}{c}{RA\quad (2000)\quad Dec}& \multicolumn{1}{c}{$V$} & \multicolumn{1}{c}{$b-y$} & $n$ & spec & Remarks \\
\hline
BD+29\deg3579  & 19\hr23\mm11\fsec33 & +29\deg30\arcm09\farcs6 &  9.742 & 1.202 &3& K2 &  \\
               &             &             &   .033 &  .016 & &    &  \\
BD+29\deg3586* & 19 24 37.35 & +29 34 17.1 & 10.522 & 0.259 &3&    & GSC 2137-0298  \\
               &             &             &   .014 &  .004 & &    &  \\
GSC 2137-1762  & 19 24 12.68 & +29 35 04.3 & 10.987 & 0.783 &2&    &  \\
               &             &             &   .025 &  .018 & &    &  \\
GSC 2136-0649  & 19 23 35.51 & +29 39 18.8 & 11.312 & 0.822 &3&    &  \\
               &             &             &   .019 &  .017 & &    &  \\
GSC 2136-0027* & 19 23 27.69 & +29 41 27.7 & 12.208 & 0.680 &3&    &  \\
               &             &             &   .013 &  .017 & &    &  \\
GSC 2136-0778  & 19 23 41.06 & +29 37 04.7 & 12.888 & 0.760 &2&    &  \\
               &             &             &   .023 &  .023 & &    &  \\
GSC 2137-1408* & 19 23 52.35 & +29 43 57.5 &13.40~\,&0.49~\,&2&    &  \\
               &             &             &  .05~\,& .01~\,& &    &  \\
\hline
\end{tabular}

\begin{tabular}{ll}
Notes \\
GSC 2136-0027 &  star $\sim$20\arcs\ north excluded, but two very faint companions included.  \\
GSC 2137-1408 &  very faint close companion on northeast.  \\
\end{tabular}
\end{center}

\references

AAVSO, 2000, {\tt http://charts.aavso.org/PRELIM/CYG/BF\_CYG}

Benson, P. J., and Salter, D. M., 1999, {\it IBVS}, No.\,4728  

Gray, W., 1999, {\tt http://www.projectpluto.com/gsc\_act.htm}

H{\o}g, E., Fabricius, C., Makarov, V. V., Urban, S. E., Corbin, T.,
Wycoff, G., Bastian, U., Schwekendiek, P., and Wicenec, A., 2000, {\it Astron.\ 
Astrophys.}, {\bf 355}, L27  

Lockwood, G. W., and Thompson, D. T., 1986, {\it Astron.\ J.}, {\bf 92}, 976   

Poyner, G., 1995, {\tt http://www.telf-ast.demon.co.uk/charts/\_08802.gif}

Skiff, B. A., 1996, \\
{\tt http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet/msg00720.html}

\endreferences

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