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\IBVShead{4817}{9 December 1999}

\IBVStitletl{New \lowercase{uvby}$\beta$ photometry}{ of stars of ``astrophysical interest'' }

\IBVSauth{Handler, G.$^{1, 2, 3}$}
\IBVSinst{South African Astronomical Observatory, P. O. Box 9, Observatory 7935, South Africa\\ \indent e-mail: gerald@saao.ac.za}
\IBVSinst{Institut f\"ur Astronomie, Universit\"at Wien, 
T\"urkenschanzstra\ss e 17, A-1180 Wien, Austria}
\IBVSinst{Guest observer, McDonald Observatory, The University of Texas at Austin}

\IBVStyp{ DSCT }

\begintext

This note reports the continuation of a project designed to acquire
Str\"omgren--Crawford indices for stars of ``astrophysical interest'',
mostly variable or candidate variable stars in the lower instability
strip, for which this information was missing so far. The first part of
the measurements was published by Handler (1995).

Since this program is being carried out during ``leftover'' observing
time, progress is rather slow. Consequently, we consider it most useful to
release the data for use of the community as soon as a reasonable amount
has been collected, as opposed to waiting for the completion of the whole
project (which could never happen). 

The bulk of our observations (including {\it all} $uvby$ measurements) was
acquired with the 50-cm telescope at the South African Astronomical
Observatory (SAAO) in July and November, 1999. A few additional
H$\beta$ measurements were taken with the McDonald Observatory 91-cm
telescope in March 1996 and with the SAAO 75-cm telescope in October,
1999. We took care that also for fainter stars a sufficient number of
counts ($\geq 100\,000$) was collected in each filter.

Transformations were calculated for each observing run separately by using
a sufficient number of standard stars (10--30, depending on the observing run). A colour term was included in the equations. Care was taken that the standard stars spanned a larger range in color indices than the program stars did. Average zeropoints were applied for each observing run as well, with the exception of the November 1999 run which was spread out over several nights so that nightly zeropoint corrections for the $V$ magnitude were found necessary; the transformation equation was recalculated thereafter. The rms residuals of a single standard star measurement were typically around 6~mmag for $V$ and $\beta$, 3~mmag for $(b-y)$ and 12~mmag for $m_1$ and $c_1$, respectively. We are careful to note that these values may not always apply to the program stars, which are often fainter than the standards and which are mostly variable stars. 

Our results are summarized in Table~1, where the program stars are ordered
by increasing HD number. Objects without a HD identification can be found 
at the end of Table 1 in alphabetical order. We would now like to describe 
a few interesting findings from our results:

\newpage

\begin{center}
{\normalsize Table 1: $uvby\beta$ photometry of program stars}
\vskip2mm
\begin{tabular}{lcrccc}
\hline
Star & $V$ & $b-y$ & $m_1$ & $c_1$ & $\beta$\\
\hline
HD 984 & & & & & 2.636 \\
HD 4494 & 9.45 & 0.177 & 0.171 & 0.779 & 2.762 \\
HD 12389 & & & & & 2.861 \\
HD 12901 & & & & & 2.719 \\
HD 13755 & & & & & 2.723 \\
HD 14147 & & & & & 2.747 \\
HD 14940 & & & & & 2.737 \\
HD 16723 & & & & & 2.769 \\
HD 17978 & 9.60 & 0.177 & 0.163 & 0.838 & 2.745 \\
HD 21438 & & & & & 2.805 \\
HD 22625 & 9.27 & 0.224 & 0.175 & 0.664 & \\
HD 27093 & 7.45 & 0.126 & 0.164 & 1.021 & 2.801 \\
HD 29870 & & & & & 2.712 \\
HD 32195 & & & & & 2.625 \\
HD 33957 & & & & & 2.879 \\
HD 34025 & 7.85 & 0.261 & 0.155 & 0.608 & 2.688 \\
HD 34409 & & & & & 2.727 \\
HD 38643 & & & & & 2.768 \\
HD 41448 & 7.62 & 0.189 & 0.184 & 0.693 & 2.747 \\
HD 42304 & & & & & 2.749 \\
HD 42503 & 7.46 & 0.130 & 0.139 & 1.057 & 2.779 \\
HD 58453 & & & & & 2.742 \\
HD 59594 & 7.33 & 0.126 & 0.167 & 0.832 & 2.803 \\
HD 63176 & & & & & 2.727 \\
HD 65526 & 6.98 & 0.188 & 0.151 & 0.662 & 2.734 \\
HD 66829 & 9.22 & 0.242 & 0.152 & 0.559 & 2.713 \\
HD 77347 & & & & & 2.766 \\
HD 79766 & 8.87 & 0.148 & 0.172 & 0.814 & 2.800 \\
HD 81421 & 6.97 & 0.173 & 0.169 & 0.754 & 2.751 \\
HD 87271 & 7.10 & 0.151 & 0.094 & 0.939 & 2.775 \\
HD 99267  & & & & & 2.724 \\
HD 108100 & & & & & 2.705 \\
HD 173173 & & & & & 2.673 \\
HD 177120 & 6.74 & 0.157 & 0.118 & 1.091 & 2.813 \\
HD 184190 & 9.76 & 0.232 & 0.113 & 0.693 & \\
HD 187615 & 7.98 & 0.207 & 0.153 & 0.692 & \\
HD 192871 & & & & & 2.741 \\
HD 193084 & 7.61 & $-0.029$ & 0.121 & 0.561 & 2.764 \\
HD 199434 & 8.71 & 0.271 & 0.205 & 0.690 & \\
HD 207651 & & & & & 2.834 \\
HD 209295 & 7.29 & 0.139 & 0.185 & 0.840 & 2.821 \\
HD 213669 & 7.40 & 0.155 & 0.113 & 0.835 & 2.758 \\
HD 214291 & & & & & 2.627 \\
HD 218225 & 8.71 & 0.235 & 0.182 & 0.649 & 2.705 \\
HD 221866 & 7.44 & 0.151 & 0.207 & 0.766 & 2.791 \\
HD 230990 & & & & & 2.781 \\
HD 261331 & 9.73 & 0.136 & 0.187 & 0.992 & 2.784 \\
\hline
\end{tabular}
\end{center}

\newpage

\begin{center}
{\normalsize Table 1 (continued)}
\vskip2mm
\begin{tabular}{lccccc}
\hline
Star & $V$ & $b-y$ & $m_1$ & $c_1$ & $\beta$\\
\hline
HD 261446 & 10.32 & 0.243 & 0.225 & 0.719 & 2.706 \\
HD 290764 & 9.92 & 0.208 & 0.170 & 0.859 & 2.720 \\
AI Hya & & & & & 2.764 \\
BD\,+21\deg1613 & 9.34 & 0.309 & 0.125 & 0.358 & 2.639 \\
BD\,+21\deg1616 & 9.28 & 0.222 & 0.150 & 0.586 & 2.694 \\
CD\,$-$41\deg15264 & 10.31 & 0.378 & 0.170 & 0.344 & \\
GSC 4778-00324 & 10.26 & 0.202 & 0.168 & 0.894 & 2.797 \\
V829 Aql & 10.28 & 0.390 & 0.135 & 0.748 & 2.675 \\
\hline
\end{tabular}
\end{center}

\bigskip
\noindent
{\it HD\,42503, HD\,87271, HD\,213669:} These are all suspected
$\delta$~Scuti stars from HIPPARCOS photometry, but they also turned out
to be quite metal-poor. It is suspected that they could be
$\lambda$~Bootis stars or even Pop.\,II objects. 

\vspace{2mm}
\noindent
{\it HD\,193084:} This star was found to be a short-period variable by
Paunzen (1997), who noted that its spectral classification (B8\,V) makes
it a very interesting object if it turned out not to be a binary. Our
photometry corroborates this spectral classification. A detailed study of
HD 193084 is recommended.

\vspace{2mm}
\noindent   
{\it HD\,209295:} This is the hottest $\gamma$~Doradus star known to date. 
Handler (1999a) did not consider it for his outline of the
$\gamma$~Doradus star domain in the HR diagram, since he was suspicious of
the published $(b-y)$ (Twarog 1980). Our new measurement confirms this
value, however. On the other hand, evidence for binarity of HD 209295 has
recently been discovered (Balona 1999). 

\vspace{2mm}
\noindent
{\it BD\,+21\deg1613, BD\,+21\deg1616:} Handler (1999b) suspected that one of these stars is variable, but he was unable to determine which one. The
Str\"omgren--Crawford indices of BD\,+21\deg1616 are typical for a $\gamma$~Doradus star (Handler 1999a). We also note that BD\,+21\deg1613 seems quite metal-poor.

\vspace{2mm}
\noindent
{\it HD 261446:} This is a pre-main sequence $\delta$~Scuti star (Breger
1972) in the open cluster NGC~2264. It has a rather high $m_1$ compared to
the second $\delta$~Scuti star (HD 261331) in this cluster. Since the
astrophysical interpretation of this result is not straightforward, we
solicit an investigation of this star's spectrum. 

\vspace{2mm}
\noindent
{\it V\,829 Aql:} This is one of only three radial triple-mode pulsators
among $\delta$~Scuti stars (Handler, Pikall \& Diethelm 1998). Our
photometry puts the star somewhat outside the cool luminous border of the
$\delta$~Scuti instability strip (Breger 1979); requiring $Q = 0.033$ for
the longest period mode moves it even further out.

\bigskip

{\it Acknowledgements:}
This work was partially supported by the Austrian Fonds zur F\"orderung
der wissenschaftlichen Forschung under grant No.\ S7304-AST. The author
thanks Michel Breger and Don Kurtz for helpful discussions about the
nature of HD 261446.

\references

Balona, L. A., 1999, private communication

Breger, M., 1972, {\it ApJ}, {\bf 171}, 539

Breger, M., 1979, {\it PASP}, {\bf 91}, 5

Handler, G., 1995, {\it IBVS}, No.\ 4216

Handler, G., 1999a, {\it MNRAS}, {\bf 309}, L19

Handler, G., 1999b, PhD thesis, University of Vienna

Handler, G., Pikall, H., Diethelm, R., 1998, {\it IBVS}, No.\ 4549

Paunzen, E., 1997, {\it IBVS}, No.\ 4443

Twarog, B. A., 1980, {\it ApJS}, {\bf 44}, 1

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