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\IBVShead{}{}
\IBVStitletl{Photometry of stars in the field of T Cassiopeiae}
\IBVSauth{Brian A. Skiff}
\IBVSinsto{Lowell Observatory, 1400 West Mars Hill Road, Flagstaff\enskip
           AZ\quad 86001-4499, USA}
\vskip -1mm
\IBVSinsto{e-mail:  bas@lowell.edu}

\IBVSobj{T Cas, NSV 148}
\IBVSkey{Str\"{o}mgren photometry, photometric sequences}
\IBVSabs{Str\"{o}mgren $b,y$ photometry is given for stars in the field of T Cas in the range 7.1 < V < 12.2.}

\begintext

     T Cassiopeiae is a bright, well-observed Mira that varies from 7\mm\/ to
as faint as 13\mm\/ with periods near 445 days.  As a check on existing
sequences, I obtained photometry of comparison stars in the field covering
nearly the full range of the variable.  The stars were selected from the AAVSO
(d)-scale chart whose magnitudes were last revised in 1952.  Most of the chart
magnitudes are found to be fairly close to the V scale, although some minor
errors exist.  The AAVSO `standard' charts for the star are available via the
Web starting from:  {\tt http://www.aavso.org}.  The present (Jan. 1994)
versions {\sl do not} include the results from the present work.

     I measured the stars on four nights in September and October 1995 using
the Lowell 53cm photometric telescope.  Str\"{o}mgren $y$ and $b$ filters were
used through a 29\arcs\/ diaphragm.  Each observation consisted of at
least three 10\sec\, integrations on `star' and two 10\sec\, integrations on
`sky', with more integrations for stars fainter than V $\sim$9\mm.  Between
16 and 24 primary and secondary standards were observed each night for
calibration to Johnson V and Str\"{o}mgren {\it b--y}.  Seasonal mean
extinction values (Lockwood \& Thompson 1986) were adopted for the reductions.
Per-star residuals from the linear fits to the standards averaged 0\fmm009 in V
and 0\fmm007 in {\it b--y}.

     Results for the stars near T Cas are shown in Table 1, sorted in order
of decreasing brightness.  An observation of T Cas itself is shown as the first
entry.  The stars are identified by HD, BD, or GSC number; positions come from
the Hipparcos catalogue, ACT (Urban {\it et al}. 1998), or the GSC version 1.2
(STScI 1996) for progressively fainter stars.  An asterisk by the star name
indicates that a note is given at the bottom of the table.  The standard
deviations of the mean values in V and {\it b--y} are given on the second line
of each entry.  Column `n' shows the number of observations.

     The bright, blue companion to T Cas, HD 1873 = NSV 148, has been suspected
of variability of up to 0\fmm4\, since Ta\ss's (1905) early report.  However,
there has been no suspicion of this in modern observations, including those in
the Hipparcos dataset (mean V = 8.12, 5th/95th percentile range 8.12--8.17) and
in the present series.

\vfil
\eject

     For the convenience of observers, a chart derived from the GSC is shown in
Figure 1.  The comparison stars are idicated by their V magnitudes rounded to
the nearest tenth (decimal point omitted) in the style of visual variable-star
charts.

     Preparation of this report was facilitated by the use of SIMBAD and
VizieR, maintained by the Centre de Donn\'{e}es astronomiques, Strasbourg,
and the GSC v1.2 look-up utility at Space Telescope Science Institute.

\bigskip

\normalsize
\begin{center}
{Table 1.  Photometry of Stars in the Field of T Cassiopeiae\phantom{(}}\\
\begin{tabular}{lccrrcll}
\hline
Name & \multicolumn{2}{c}{RA  (2000)  Dec}& \multicolumn{1}{c}{V}& \multicolumn{1}{c}{\it b--y}& n & spec & Remarks \\
\hline
\\[-3mm]
HD 1845*       & 0 23 14.3 & +55 47 33 &  9.171 & 2.221 & 1 & M7e & T Cas \\
               &	   &	       &        &       &   &     &  \\
HD 2152*       & 0 26 06.4 & +55 29 27 &  7.110 & 0.779 & 2 & K0  &  \\
               &           &           &   .008 &  .005 &   &	  &  \\
HD 1873*       & 0 23 24.1 & +55 48 08 &  8.106 & 0.097 & 3 & B9  &  NSV 148 \\
               &           &           &   .005 &  .003 &   &	  &  \\
HD 1902*       & 0 23 39.2 & +55 23 23 &  8.344 & 0.081 & 2 & A2  &  \\
               &           &           &   .006 &  .004 &   &	  &  \\
HD 1733        & 0 21 55.0 & +56 00 46 &  8.588 & 0.233 & 2 & F0  &  \\
               &           &           &   .003 &  .006 &   &	  &  \\
HD 232179      & 0 24 22.3 & +55 34 50 &  8.674 & 0.649 & 2 & G5  &  \\
               &           &           &   .003 &  .000 &   &	  &  \\
HD 232186      & 0 26 00.9 & +55 42 44 &  9.151 & 0.350 & 2 & G0  &  \\
               &           &           &   .001 &  .007 &   &	  &  \\
BD+54\deg53    & 0 24 58.5 & +55 43 00 & 10.353 & 0.341 & 2 &     & GSC 3657-0550 \\
               &           &           &   .007 &  .001 &   &	  &  \\
BD+55\deg63    & 0 23 21.6 & +55 56 43 & 10.402 & 0.382 & 2 &     & GSC 3657-0705 \\
               &           &           &   .005 &  .008 &   &	  &  \\
GSC 3657-0468  & 0 23 47.1 & +55 55 20 & 10.687 & 0.736 & 2 &	  &  \\
               &           &           &   .004 &  .006 &   &	  &  \\
GSC 3657-0704  & 0 23 05.9 & +55 44 46 & 10.987 & 0.728 & 2 &	  &  \\
               &           &           &   .013 &  .006 &   &	  &  \\
LS\, I\, +55\deg09*& 0 24 44.5 & +55 47 04 & 11.646 & 0.180 & 2 &     & GSC 3657-0075 \\
               &           &           &   .014 &  .001 &   &	  &  \\
GSC 3657-1139  & 0 23 35.8 & +55 49 13 & 12.232 & 0.281 & 2 &	  &  \\
               &           &           &   .010 &  .003 &   &	  &  \\
\hline
\end{tabular}
\end{center}
\medskip

Notes:

HD 1845\hspace{1.25cm} observation on 13 Sep 1995 UT.

HD 2152\hspace{1.25cm} V = 7.138 (Kornilov {\it et al.} 1991); V = 7.130,
{\it b--y} = 0.789 (Olsen 1993).

HD 1873\hspace{1.25cm} V = 8.13 (Oja 1985); V = 8.118 (Kornilov {\it et al.}
1991); Hipparcos V = 8.12$\pm$0.01.

HD 1902\hspace{1.25cm} V = 8.37, {\it b--y} = 0.066 (Perry \& Johnston 1982)

LS\, I\, +55\deg09\quad\quad V = 11.67 (Haug 1970).



\normalsize
\references

Haug, U., 1970, {\it Astron. Astrophys., Suppl. Ser.}, {\bf 1}, 35

Kornilov, V. G., {\it et al.}, 1991, {\it Trudy Gosud. Astron. Inst.
Sternberg}\, {\bf 63}, 4

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

Oja, T., 1985, {\it Astron. Astrophys., Suppl. Ser.}, {\bf 59}, 461

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

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

Space Telescope Science Institute, 1996, {\tt http://www-gsss.stsci.edu/gsc/gsc12/description.html}

Ta\ss, A., 1905, {\it Astron. Nach.}, {\bf 167}, 109

Urban, S. E., Corbin, T. E., and Wycoff, G. L., 1998, {\it Astron. J.},
{\bf 115}, 2161

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