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\input ibvs2.sty

\begin{document}

\IBVShead{5552}{3 August 2004}

\IBVStitle{B\lowercase{rh}~V128 is a Double-Mode High-Amplitude {\large \boldmath $\delta$} Scuti Star}

\IBVSauth{Bernhard, K.$^{1,2}$; Pejcha, O.$^3$; Proksch, W.$^{2,4}$; Quester, W.$^{2,5}$; Van Cauteren, P.$^{6,7}$; Wils, P.$^7$}

\IBVSinst{A--4030 Linz, Austria; e-mail: {\tt kl.bernhard@aon.at}}
\IBVSinst{Bundesdeutsche Arbeitsge\-mein\-schaft f\"{u}r Ver\"{a}nderliche Sterne e.V. (BAV), Munsterdamm 90, D--12169~Berlin, Germany}
\IBVSinst{Nicolas Copernicus Observatory and Planetarium, Krav\'{\i} Hora 2, 616~00~Brno, Czech Republic; e-mail: {\tt pejcha@astro.sci.muni.cz}}
\IBVSinst{D--84543 Winhoering, Germany; e-mail: {\tt willi.proksch@t-online.de}}
\IBVSinst{D--73730 Esslingen, Germany; e-mail: {\tt wquester@aol.com}}
\IBVSinst{Beersel Hills Observatory, Laarheidestraat 166, B--1650 Beersel, Belgium; email: {\tt paulvancauteren@skynet.be}}
\IBVSinst{Vereniging Voor Sterrenkunde, Belgium; email: {\tt patrick.wils@cronos.be}}

\SIMBADobjAlias{GSC 01893-00089}{Brh V128}
\IBVStyp{ DSCT(B) }
\IBVSkey{Delta Scuti stars - Double mode variability - photometry}
\IBVSabs{CCD-V and unfiltered photometric data show that Brh V128 = GSC 1893-89}
\IBVSabs{is a new high-amplitude double-mode Delta Scuti variable}
\IBVSabs{ with a fundamental period of 0.1534 days and a period ratio of 0.767.}
\IBVSabs{The amplitude of the first overtone pulsation is slightly larger}
\IBVSabs{than that of the fundamental mode.}

\begintext

\vspace*{-0.8cm}

The star Brh~V128 (= GSC~1893-89; $\alpha_{2000}= 06\hr44\mm01\fsec06$;
$\delta_{2000}= +22\deg44\arcm31\farcs7$) was detected as a short period variable by Bernhard (2003).  

The star was subsequently monitored by the authors from observatories across Europe.
The instruments used were 20-cm Cassegrain telescopes equipped with a Startlight Xpress SX CCD-camera (KB),
an SBIG ST-7 (WQ) and an ST-6 (WP), and 40-cm Newtonian telescopes with an SBIG ST-7 (OP) 
and an ST10 XME camera (PVC).  
KB and WP observed unfiltered, all other observers used a $V$ filter.  OP additionally observed two nights in $R_c$ and $I_c$.
Comparison star magnitudes were derived from the ASAS3 database (Pojmanski, 2002).  
The data are available electronically through the IBVS website as {\tt 5552-t2.txt}. 

\IBVSedata{5552-t2.txt}
\IBVSdataKey{5552-t2.txt}{Brh V128}{photometry}

The observations showed that Brh~V128 is a pulsating variable with a total amplitude of about 0.4 mag and
two peaks in the periodogram, at 0.1177 and 0.1534 days.  
Folded light curves for these periods, after prewhitening for the other, are given in Figs.~1 and~2.
$V$ data are represented with filled circles, unfiltered data with open squares.
The ratio between these periods is $0.7673 \pm 0.0002$, which makes 
this star a member of the rare group of radially pulsating double-mode HADS (Petersen and Christensen-Dalsgaard, 1996; McNamara, 2000).  
Recently found examples include V575~Lyr (Van Cauteren and Wils, 2001), 
BQ~Ind (Sterken et al., 2002) and GSC~2583-504 (Wils et al., 2003).

Using the Fourier analysis program {\tt Period98} (Sperl, 1998), other peaks at linear combinations of the main
frequencies were found as well, see Table~1 for an overview.  
Note that the amplitude of the first overtone frequency
$f_1$ is slightly larger than that of the fundamental mode $f_0$, unlike in most other double-mode HADS.


The proper motion of Brh~V128 is small, $0.2\ mas/y$ in RA and $-1.6\ mas/y$ in declination, according to UCAC2 (Zacharias et al., 2004).
Together with the rather long period, this makes it an unlikely candidate to be an SX~Phe star,
but rather a Population~I object.

Fig.~3 gives the Petersen diagram for the known double-mode HADS in the Milky Way, with data from the literature.  
The open square indicates the position of Brh~V128.

\IBVSfig{8cm}{5552-f1.eps}{Phase plot for the first overtone period of 0.1177 days, after prewhitening for the fundamental period.}
\IBVSfigKey{5552-f1.eps}{Brh V128}{light curve}

\IBVSfig{8cm}{5552-f2.eps}{Phase plot for the fundamental period of 0.1534 days, after prewhitening for the first overtone.}
\IBVSfigKey{5552-f2.eps}{Brh V128}{light curve}

\begin{table}
\begin{center}
{\normalsize Table 1. Frequencies detected in Brh~V128} \vskip2mm 
\begin{tabular}{crcc}
\hline
Mode & Frequency ($c/d$) & Semi-amplitude (mag) & Phase \\
\hline
$f_1$ & $8.497 \pm 0.001$ & 0.10 & 0.96 \\
$f_0$ & $6.519 \pm 0.001$ & 0.07 & 0.71 \\
$f_0 + f_1$ & $15.016 \pm 0.001$ & 0.03 & 0.14 \\
$2f_1$ & $16.993 \pm 0.001$ & 0.03 & 0.40 \\
\hline
\end{tabular}
\end{center}
\end{table}

\IBVSfig{6cm}{5552-f3.eps}{Petersen diagram for the Galactic double-mode HADS.}
\IBVSfigKey{5552-f3.eps}{Brh V128}{diagram}

{\bf Acknowledgements:}
The research of O. Pejcha was supported by the Grant Agency of the Czech Republic, grant No.~205/04/2063.
P. Van Cauteren is grateful to the Royal Observatory of Belgium for putting at his disposal material
acquired through project G.0178.02 from the Fund for Scientific Research - Flanders.  
This research has made use of the VizieR database operated at the {\it Centre de Donn\'ees Astronomiques} (Strasbourg) in France.


\references

Bernhard, K., 2003, {\it BAV Rundbrief}, {\bf 52}, 168 
%\BIBCODE{2003BAVSR..52..168B}

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

McNamara, D.H., 2000, {\it ASP Conf. Series}, {\bf 210}, 373, in `Delta Scuti and Related Stars: R{}eference Handbook', eds. Breger, M., \& Montgomery, M.H.
%Corrected : Fri May 27 09:38:45 MEST 2005

Petersen, J.O, and Christensen-Dalsgaard, J., 1996, {\it A\&A}, {\bf 312}, 463

Pojmanski, G., 2002, {\it Acta Astronomica}, {\bf 52}, 397

Sperl, M., 1998, Manual for Period98 (V1.0.4). A period search-program for Windows and Unix, (http://www.astro.univie.ac.at/\~{}dsn/dsn/Period98)

Sterken, C., Brogt, E., Fu, J.N., Zhou, A.Y., 2002, {\it JAD}, {\bf 8}, 3

Van Cauteren, P. and Wils, P., 2001, {\it IBVS}, No.\,5205

Wils, P., Lampens, P., Robertson, C.W., Van Cauteren, P., 2003, {\it IBVS}, No.\,5442

Zacharias, N., Urban, S.E., Zacharias, M.I., Wycoff, G.L., Hall, D.M., Monet, D.G., 
Rafferty, T.J., 2004, {\it AJ}, {\bf 127}, 3043


\endreferences

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