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\IBVShead{4857}{2 March 2000}

\IBVStitletl{V1162 O\lowercase{ri}: a Mono- or a Multiperiodic}{ High-amplitude {\boldmath $\delta$} Scuti Star? }

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

\IBVSinst{Koninklijke Sterrenwacht van Belgi\"e, B-1180 Brussel, Belgium, email: patricia.lampens@oma.be}

\IBVSinst{Beersel Hills Observatory, Belgium, email: Paul.VanCauteren@advalvas.be}

\SIMBADobjAlias{V1162 Ori}{BD -07 1108}
\IBVSkey{photometry}
\IBVSabs{The second periodicity detected by Hintz et al. (1998) in the light variations}
\IBVSabs{of V1162 Ori can most probably be ascribed to variability of one of the comparison} 
\IBVSabs{stars, GSC 4778 324, recently shown to be a new multiperiodic small-amplitude}
\IBVSabs{short-period variable star.}

\begintext

The detection of the short-period variability of V1162 Ori was reported
by Lampens (1985). The light curve of this high-amplitude $\delta$
Scuti variable star was first shown to be asymmetric (due to the
presence of the first harmonic term) with a single periodicity of
0.078684 days and a half-amplitude of 0.09 mag in V\@.  Poretti et al.\
(1990) re-observed V1162 Ori in order to investigate the possible
presence of a second periodicity but concluded that they had no
evidence for a second periodicity and that the star was pulsating
monoperiodically. They refined the period to the value of $0.07868616
\pm 0.00000006$ days and also found a slightly larger half-amplitude
of 0.098 mag in V.

New data have been obtained by Hintz et al.\ (1998). Apart from
announcing a period break and a 50\% decrease in the amplitudes 
of both terms related to the principal frequency the authors 
also suggested the appearance of a second frequency (corresponding
to a periodicity of about 0.06 days) with a much smaller amplitude, 
i.e.\ comparable to the amplitude of the first harmonic term. This additional frequency was detected in their CCD data only (dataset 2) and not in the Str\"omgren magnitudes (dataset 1). From this, they inferred that V1162 Ori  had changed from the single-mode to the double-mode regime.

Very recently Van Cauteren \& Lampens (2000) reported the presence of a
new $\delta$ Scuti star in the field of view of V1162 Ori, measured in
the course of an intensive multisite campaign. This star, GSC 4778 324,
appears to be a multiperiodic pulsator with a small amplitude (full
amplitude of 0.014 mag at most) and a mean periodicity of about 0.07
days.  Since it was also one of the brighter comparison stars (star no.~5) used in the reduction of the CCD differential data on V1162 Ori by
Hintz et al.\ (1998), we conclude that the additional frequency found
in the Fourier decomposition of the CCD data of V1162 Ori is
entirely attributed to the variability of this comparison star.
Both the period and the amplitude estimates are compatible with the
the ones derived for the new variable star.
Furthermore, also Arentoft \& Sterken (2000) cannot support the 
finding of a second periodicity in their very recent paper on V1162 Ori.

Therefore, notwithstanding the other changes that may happen 
in this interesting $\delta$ Scuti star, our conclusion is that
V1162 Ori was and still should be considered as a monoperiodic 
$\delta$ Scuti pulsator.  

\newpage

\references

Arentoft, T. and Sterken, C., 2000, {\it A\&A}, {\bf 354}, 589

Hintz, E., Joner, M. and C. Kim, 1998, {\it PASP}, {\bf 110}, 689 

Lampens, P., 1985, {\it IBVS}, No.\ 2794

Poretti E., Antonello, A. and Le Borgne, J.F., 1990, {\it A\&A}, {\bf 228}, 350.

Van Cauteren, P. and Lampens, P., 2000, {\it IBVS}, No.\ 4849

\endreferences

\end{document}
