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\IBVShead{5475}{11 November 2003}

\IBVStitle{NSV 25610: A High-Amplitude {\boldmath $\delta$} Scuti Star}

\IBVSauth{Wils, P.$^1$; Van Cauteren, P.$^{1,2}$; Lampens, P.$^3$}

\IBVSinst{Vereniging Voor Sterrenkunde, Belgium; email: patrick.wils@cronos.be}
\IBVSinst{Beersel Hills Observatory, Laarheidestraat 166, B-1650 Beersel, Belgium; email: paulvancauteren@skynet.be}
\IBVSinst{Koninklijke Sterrenwacht van Belgi\"e, B--1180 Brussel, Belgium;
email: patricia.lampens@oma.be}

\SIMBADobjAlias{NSV 25610}{HD 204615}
\IBVSkey{Delta Scuti stars - photometry}
\IBVSabs{CCD-B and V photometric data reveal that NSV 25610 = HD 204615 is a}
\IBVSabs{high-amplitude Delta Scuti variable with a fundamental period of 0.0942064 days.}

\begintext

NSV 25610 (= HD 204615 = BD+46\deg 3325; $\alpha_{2000}= 21\hr28\mm24\fsec56$;
$\delta_{2000}= +46\deg40\arcm30\farcs8$) was suspected of variability by Yoss et al. (1991).  
They derived a distance of 215 parsec, an absolute magnitude $M_v = 2.2$, 
and a total space velocity $S = 32$ with components $U = 5$, $V = 31$ and 
$W = -2$ (in $km/s$). They also determined $V = 8.86$ and $(B-V) = +0.27$ mag, which 
classifies this star as of spectral type F2. Piquard (2001) analysed the available 
Tycho data (H{\o}g et al., 2000), and suggested it is a SX~Phe variable star with a 
period of 0.094206 days.

This variable star was monitored on five nights in September and October 2003 
at Beersel Hills Observatory (BHO) with a 40-cm telescope equipped with an ST10 XME camera 
(during three nights) and a 13-cm refractor with an ST7E camera (during two nights), using 
$B$ and $V$ filters.
The total observation time was 28 hours, resulting in 622 $V$ and 151 $B$ data points.
The frames were reduced with the aperture photometry procedure of the Mira AP software package.\IBVSfm\ The brightness of the variable was measured with respect to 10 stars in the immediate 
vicinity (with $V$ and $B-V$ ranging from 8.2 to 10.6 mag and from 0.0 to 1.4 mag 
respectively ). The magnitudes were then transformed to standard Johnson $B \& V$ magnitudes 
using the $V$ and $B-V$ values from the Tycho catalogue (ESA, 1997).
Standard deviations on the comparison stars data ranged between 0\fmm005 and 0\fmm016 mag. 

\IBVSfoot{The Mira AP software is produced by Axiom Research Inc.} 

Our data confirm that NSV 25610 is a high amplitude $\delta$ Scuti star (HADS), 
with the period given by Piquard (2001). The $V$ magnitude varied between 8.53 and 8.97 
mag, while the $B$ magnitude varied between 8.82 and 9.38 mag. Due to its location near
the galactic plane ($b = -3\fdeg13$) and its low space velocity, the star is most likely 
a Population I star, and not a SX Phe variable star. The following improved ephemeris 
could be derived:
$$\begin{array}{r@{}r@{}l}
{\rm Max. = HJD}~2452885.3992 & {} + 0\fday0942075 & {} \times E. \\
{} \pm 0.0001 & {} \pm 0.0000003 \\
\end{array}$$

The list of observed maxima, is given in Table~1.  $O-C$ values are given with respect 
to the above ephemeris. A phase plot is shown in Fig.~1.
Using Period98 (Sperl, 1998), the Fourier parameters presented in Table~2 were derived.
These can be directly compared to those of other $\delta$ Scuti stars (Morgan, 2003). 
However, Fourier terms cannot aid
to discriminate between these two stellar populations (Poretti, 2002).

\begin{center}
{\normalsize Table 1. Observed times of maximum.} \vskip2mm 
\begin{tabular}{crrc}
\hline
HJD & \multicolumn{1}{c}{E} & \multicolumn{1}{c}{$O-C$} & Filter \\
\hline
2452885.3991 & 0 & $-$0.0001 & V \\
2452885.3993 & 0 & 0.0001 & B \\
2452887.3777 & 21 & 0.0001 & B \\
2452887.3778 & 21 & 0.0002 & V \\
2452887.4720 & 22 & 0.0002 & V \\
2452887.4720 & 22 & 0.0002 & B \\
2452887.5656 & 23 & $-$0.0003 & V \\
2452887.5658 & 23 & $-$0.0002 & B \\
2452887.6599 & 24 & $-$0.0002 & V \\
2452928.2634 & 455 & $-$0.0002 & V \\
2452928.3582 & 456 & 0.0004 & V \\
2452928.4520 & 457 & $-$0.0001 & V \\
2452928.5465 & 458 & 0.0003 & V \\
2452929.2996 & 466 & $-$0.0002 & V \\
2452929.3940 & 467 & $-$0.0001 & V \\
2452929.4885 & 468 & 0.0002 & V \\
2452929.5823 & 469 & $-$0.0002 & V \\
2452931.4667 & 489 & 0.0000 & V \\
\hline
\end{tabular}
\end{center}

\IBVSfig{10cm}{5475-f1.eps}{Phased B and V light curves of NSV 25610.}
%%\IBVSfigKey{5475-f1.eps}{NSV 25610}{light curve}

\vfill
\eject
\begin{center}
{\normalsize Table 2. Fourier parameters for the $B$ and $V$ data.} \vskip2mm 
\begin{tabular}{ccc}
\hline
Parameter & $B$ & $V$ \\
\hline
$A_0$ & 9.15 & 8.80 \\
$R_{21}$ & 0.269 & 0.276 \\
$R_{31}$ & 0.095 & 0.099 \\
$R_{41}$ & 0.039 & 0.043 \\
$\Phi_{21}$ & 4.17 & 4.20 \\
$\Phi_{31}$ & 1.48 & 1.51 \\
$\Phi_{41}$ & 5.30 & 5.37 \\
\hline
\end{tabular}
\end{center}


{\bf Acknowledgements:} 
P. Lampens acknowledges support from the Fund for Scientific Research (FWO) - Flanders (Belgium) 
through project G.0178.02. P. Van Cauteren is grateful to the Royal Observatory of Belgium for 
putting at his disposal material acquired by the same FWO project. Part of the data were acquired 
with equipment purchased thanks to a research fund financed by the Belgian National Lottery (1999).
This research has made use of the Simbad and VizieR databases operated at the {\it Centre de 
Donn\'ees Astronomiques} (Strasbourg) in France.

\references

ESA, 1997, {\it The Hipparcos and Tycho Catalogues}, ESA SP--1200

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

Morgan, S. M., 2003, {\it PASP}, {\bf 115}, 1250 ({\tt http://nitro9.earth.uni.edu/fourier/})

Piquard, S., 2001, {\it PhD Dissertation, Strasbourg} \\({\tt http://vizier.u-strasbg.fr/viz-bin/Cat?II/233}) 
%%\BIBCODE{2001yCat.2233....0P}

Poretti, E., 2002, {\it ASP Conf. Ser.}, {\bf 256}, 269, in {\it 'Observational aspects of pulsating B and A stars'}, ed. C. Sterken \& D. Kurtz
% Original : Poretti, E., 2002, {\it ASP Conf. Ser.}, {\bf 256}, 277, in {\it 'Observational aspects of pulsating B and A stars'}, ed. C. Sterken \& D. Kurtz
% Corrected: Fri May 27 10:09:22 MEST 2005

Sperl, M., 1998, Manual for {\tt Period98 (V1.0.4)}. A period search-program for Windows and Unix, ({\tt http://dsn.astro.univie.ac.at/\~{}period98})

Yoss, K. M., Bell, D. J., Detweiler, H. L., 1991, {\it AJ}, {\bf 102}, 975

\endreferences

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