
\documentstyle[epsf]{article}

\input ibvs.sty

\begin{document}

% Call for macro \IBVShead{Number}{Date} - To be filled by the editors!
\IBVShead{4120}{5 December 1994}                      % Use it with dummy or empty arguments

% Call for macro \title {Title of the paper}
\title{A flare event on HR\,2517}\footnotemark
\footnotetext{Based
on observations carried out at the ESO La Silla Observatory}

% Call for macro \begintext
\begintext

HR\,2517 = SAO\,114465 (spectral type B II-III, $V=6.15$)
was not known
as a variable. It is even listed as ``a photoelectric
standard with
confirmed long-term stability'' in the Hipparcos Input
Catalogue (Turon
et al. 1992).  The star was used for more than  ten years
as
comparison star to the Be star V~505~Mon (Vogt \& Sterken
1993) in  the
framework of the ``Long-term Photometry of Variables''
(LTPV) project
(Sterken 1983). HR\,2517 also figured as a standard star for
the LTPV
project, until 1992, when it suddenly brightened by about
0\fm10 in the
$y$, $b$ and $v$ bands, and by 0\fm15  in $u$.  As shown in
Fig.~1,
this flash-like activity is modulated with a period slightly
longer
than one month, suggesting rotation of a hot spot.
\vskip 5mm
\epsfysize=10cm
\centerline{\epsffile{4120-f1.ps}}
\centerline{Figure 1}

\vfill \eject
\centerline{2}
 
Unfortunately, this increased activity approximately
coincided with the
end of the observations of the star, so that only two cycles
have been
monitored.  Only a few points have been obtained in 1993,
but they show
that the star was still active.
 
Detailed analysis of this  flare and of the previous
microvariability
of HR\,2517 is being carried out.  We plan to secure more
photometric
and spectroscopic observations of this object in the
following months.
Photometric monitoring of HR\,2517 by other observers, with
special
emphasis towards the determination of  the duration of the
active
state,   is strongly encouraged.
 
All data used here will become  available in the course of
1995 through
the CDS Data Center in Strasbourg.

\vskip 10mm


% Call for macros \authors - \authorsrightcol - \endauthors
\beginauthors
C. STERKEN$^1$
University of Brussels (VUB)
Pleinlaan 2
B-1050 Brussels, Belgium
\authorsrightcol
J. MANFROID$^2$
Institut d'Astrophysique
Avenue de Cointe 5
B-4000 Li\`ege, Belgium
\vskip 1.5mm
\endauthors
\vskip 2mm
$^1$ Belgian Fund for  Scientific Research (NFWO)

$^2$ Belgian Fund for Scientific Research (FNRS)
\vskip 5mm
% Call for macro \references
\references

Sterken, C., 1983, The Messenger 33, 10.
 
 
Turon, C., Cr\'ez\'e, M., Egret, D. et al., 1992, {\it The
Hipparcos
Input Catalogue}, ESA SP-1136
 
Vogt N., Sterken C. 1993, Inf. Bull. Var. Stars, 3958

\end{document}



