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\IBVShead{4889}{26 April 2000}

\IBVStitle{Photometry of Stars in the Field of BI Andromedae}

\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

BI Andromedae (2\hr25\mm54\fsec34; +38\deg07\arcm22\farcs2 [2000]) is a
chemically-peculiar AGB variable of type S7.5 Zr6Ti4 ({\AA}ke 1979).  The star
is an interesting one, and although fairly well-studied in the infrared, has
not been followed in the visible.  The period of variation (if any) is not well
determined.  The most recent work in this regard appears to be by G\"otz
(1956), who found a period of 159\fday5 with a photographic-blue range from
11\fmm0 to 13\fmm3.  

As a check on the AAVSO standard chart comparison sequence, I made
$V/(b-y)$ measurements of stars in the field.  I worked from the AAVSO
`special' (e)-scale chart issued March 1958 but redrafted more recently (AAVSO
2000).  The stars were observed on a single night (21 January 1996 UT) using
the Lowell 53-cm photometric telescope, Str\"omgren $b$ and $y$ filters, and a
29\arcs\ diaphragm.  I also measured fifteen primary and secondary standards
whose {\it rms} residuals from linear fits were 0.009 and 0.005 mag. in $V$ and
$b-y$, respectively.  Since the field was observed at low airmass, mean
extinction values (Lockwood \& Thompson 1986) were applied in the reductions.
The match with HD\,15025 in common with Perry \& Johnston (1982) and Olsen
(1983) is satisfactory, so the results for the other stars should be adequate
for most purposes.

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).  The sequence covers the
known range of the variable in roughly half-magnitude increments.  The spectral
types in lower-case and parentheses are {\it estimates} based on the $b-y$
colors along with the assumption of near-zero reddening.

The magnitudes on the 1958 AAVSO chart have a lot of scatter:  some are
accurate, others off by 0.5 mag.

\newpage

\begin{center}
{\normalsize Table 1:  Photometry of stars in the field of BI Andromedae}
\vskip 1mm
\begin{tabular}{lllrrl}
\hline
Name & \multicolumn{2}{c}{RA\quad (2000)\quad Dec}& \multicolumn{1}{c}{$V$} & \multicolumn{1}{c}{$b-y$} & spec  \\
\hline
\\[-3mm]
HD 15025*      & 2\hr26\mm24\fsec17 &+38\deg13\arcm51\farcs1 &  8.065 & 0.132 & F0      \\
BD+37\deg550   & 2 25 29.92 &+37 50 35.2 &  9.453 & 0.619 & K0      \\
BD+37\deg553*  & 2 26 05.90 &+38 25 30.3 &  9.932 & 0.345 & (f8v)   \\
GSC 2831-0144  & 2 24 30.53 &+38 15 01.8 & 10.332 & 0.244 & (f2v)   \\
BD+37\deg551*  & 2 25 38.29 &+38 18 40.6 & 10.667 & 0.587 & (g8iii) \\
GSC 2831-1586  & 2 26 13.72 &+38 20 32.8 & 10.995 & 0.331 & (f8v)   \\
GSC 2831-0298  & 2 25 46.06 &+38 15 31.8 & 11.393 & 0.351 & (f8v)   \\
GSC 2831-0702  & 2 25 49.20 &+38 07 15.5 & 12.201 & 0.355 & (f8v)   \\
\hline
\end{tabular}

\begin{tabular}{ll}
Notes \\
HD 15025     & $V = 8.08$, $ b-y = 0.132$ (Perry \& Johnston 1982);
$V = 8.075$, \\
             & $b-y = 0.142$ (Olsen 1983).  \\
BD+37\deg553 & GSC 2831-2395.  \\
BD+37\deg551 & GSC 2831-0278.  \\
\end{tabular}
\end{center}

\references

AAVSO, 2000, {\tt http://charts.aavso.org/STANDARD/AND/BI\_AND}

{\AA}ke, T. B., 1979, {\it Astrophys.\ J.}, {\bf 234}, 538   

G\"otz, W., 1956, {\it Astron.\ Nach.}, {\bf 283}, 6   
%\BIBCODE {1956AN....283....6A}

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   

Olsen, E. H., 1983, {\it Astron.\ Astrophys., Suppl.\ Ser.}, {\bf 54}, 55  

Perry, C. L., and Johnston, L., 1982, {\it Astrophys.\ J., Suppl.\ Ser.}, {\bf 50}, 451   

\endreferences

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