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\IBVShead{4890}{26 April 2000}

\IBVStitletl{Photometry of Stars in the Field of}{ AF Cygni and AW 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

At the request of AAVSO chartmaker Charles Scovil, I observed a number of
comparison stars in the field of the carbon star variable AW Cygni and the
brighter star AF Cygni.  The preliminary AAVSO sequence had both a zero-point
and scale error at the faint end, evident even from visual observations.  The
present 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 14 and 25 August, 1 September 1992, 4 October 1995, and
9 October 1996 using either 19\arcs\ or 29\arcs\ diaphragms and Str\"omgren $b$
and $y$ filters.  The number of standard stars ranged from a handful to a
couple dozen on each night.  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\fmm004 and 0\fmm008 in both $V$ and $b-y$.  Data on the first night were
taken only in the Str\"omgren $y$ filter.  These were re-reduced to add in the
color term to correct them to standard $V$ using colors from later observations.
I have left the 14 August 1992 magnitude of AF Cygni without adjustment, since
the color at that time could have been somewhat different than what was
observed later.

Table 1 shows the results for the stars in order of decreasing brightness;
observations of the variables are given in the first two entries.  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) except for the last four stars,
which are from the GSC-ACT (Gray 1999).  Where two observations have been made,
the {\it rms} scatter of these are given in the second line of the relevant
entries.

     BD+45\deg2901 is a little-reddened early-M giant, and my two observations
are sufficiently different to suggest it is perhaps slightly variable, but not
at a level to make it unsuitable as a comparison star for visual observers.  It
is worth noting that the colors of the two named variables lie well beyond the
range of the standard stars, and so are subject to both `reduction' and
`conformity' errors of the type described by Manfroid \& Sterken (1992).  Based
on my experience with this particular instrumental set-up, the errors in color
and magnitude for AF Cyg will not be substantial, but those for the very red
carbon star AW Cyg could amount to several percent.

\newpage

\begin{center}
\normalsize
{Table 1:  Photometry of stars in the field of AF and AW 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
AF Cygni*      & 19\hr30\mm12\fsec86 & +46\deg08\arcm52\farcs1 & 7.65~\,&   ---  &    & M4III & HD 184008  \\
               &             &             & 7.49~\,& 1.50~\,&    &       &  \\
AW Cygni*      & 19 28 47.57 & +46 02 38.2 & 8.86~\,& 3.21~\,&    & C5,4  & BD+45\deg2906  \\
HD 184147*     & 19 31 01.09 & +46 19 54.5 &  7.166 &--0.016 & 2,1& A0    &  \\
               &             &             &   .007 &        &    &       &  \\
HD 183299*     & 19 26 52.82 & +45 50 09.8 &  8.022 &  0.694 & 2,1& G5    &  \\
               &             &             &   .006 &        &    &       &  \\
BD+45\deg2898  & 19 26 40.94 & +46 10 15.1 &  9.293 &  0.577 & 2  & G5    &  \\
               &             &             &   .004 &   .003 &    &       &  \\
HD 183829      & 19 29 17.81 & +46 21 26.1 &  9.338 &  0.076 & 2,1& A0    &  \\
               &             &             &   .006 &        &    &       &  \\
BD+45\deg2901* & 19 27 25.86 & +46 08 06.9 &  9.665 &  1.016 & 2  & M1    & DO 37291  \\
               &             &             &   .034 &   .016 &    &       &  \\
GSC 3543-2174  & 19 27 58.03 & +45 54 46.8 & 10.174 &  0.224 & 2  &       &  \\
               &             &             &   .014 &   .001 &    &       &  \\
GSC 3543-2617  & 19 28 18.15 & +45 59 59.8 & 11.008 &  0.111 & 2  &       &  \\
               &             &             &   .002 &   .008 &    &       &  \\
GSC 3543-2408  & 19 28 00.17 & +45 52 37.5 & 11.180 &  0.669 & 2  &       &  \\
               &             &             &   .003 &   .010 &    &       &  \\
GSC 3543-0802  & 19 29 16.07 & +46 01 50.0 & 11.848 &  0.263 & 2  &       &  \\
               &             &             &   .001 &   .003 &    &       &  \\
GSC 3543-0998  & 19 28 50.40 & +46 00 10.6 & 12.570 &  0.360 & 2  &       &  \\
               &             &             &   .020 &   .024 &    &       &  \\
GSC 3543-1411  & 19 28 40.69 & +46 01 44.0 &13.19~\,& 0.45~\,& 2  &       &  \\
               &             &             &  .02~\,&  .05~\,&    &       &  \\
GSC 3543-2413  & 19 28 51.16 & +46 01 44.9 &13.84~\,& 0.84~\,& 2  &       &  \\
               &             &             &  .02~\,&  .04~\,&    &       &  \\
\hline
\end{tabular}

\begin{tabular}{ll}
Notes \\
AF Cyg & observations on 14 Aug 1992 UT (JD 2448848.7)   \\
& and 4 Oct 1995 UT (JD 2449994.7). \\
AW Cyg & GSC 3543-2275; observation on 4 Oct 1995 UT (JD 2449994.7).   \\
HD 184147 & $V = 7.160$ (Kornilov {\it et al}.\ 1991).  \\
HD 183299 & $V = 8.026$, $b-y = 0.693$ (Olsen 1993).  \\
BD+45\deg2901 & slightly variable?  \\
\end{tabular}
\end{center}

\references

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   

Kornilov, V. G., Volkov, I. M., Zakharov, A. I., Kozyreva, L. N., 
Kornilova, L. N., Krutjakov, A. N., Krylov, A. V., Kusakin, A. V.,
Leontiev, S. E., Mironov, A. V., Moshkaliov, V. G., Pogrosheva, T. M.,
Sementsov, V. N., and Khaliullin, K. F., 1991, {\it Trudy Gosud.\ Astron.\ Inst.\
Sternberg}, {\bf 63}, 4   \BIBCODE {1991TrSht..63....4K}

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

Manfroid, J., and Sterken, C., 1992, {\it Astron.\ Astrophys.}, {\bf 258}, 600

Olsen, E. H., 1993, {\it Astron.\ Astrophys., Suppl.\ Ser.}, {\bf 102}, 89

Skiff, B. A., 1996, \\
{\tt http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet/msg00841.html}

\endreferences

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