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\IBVShead{4694}{8 April 1999}

\IBVStitle{HD~129231: A New Short-Period $\delta$ S\lowercase{ct} Variable}

\IBVSauth{E. RODRIGUEZ$^1$, S.F. GONZALEZ-BEDOLLA$^{2,}$\IBVSfm, M.J. LOPEZ-GONZALEZ$^1$, A. ROLLAND$^1$, V. COSTA$^1$}

\IBVSinst{Instituto de Astrof\'{\i}sica de Andaluc\'{\i}a, CSIC, P.O. Box 3004, 
E-18080 Granada, Spain}
\IBVSinst{Instituto de Astronom\'{\i}a, UNAM, P.O. Box 70-264, CP-4510 
M\'{e}xico D.F., Mexico}

\IBVSfoot{Deceased}

\SIMBADobj{HD 129231}

\begintext

During an observational program on $\delta$~Sct variables, HD~129727
(SAO~140102, V = 9\fmm5, F0) was used as comparison star and HD~129231
(SAO~140074, V = 7\fmm8, A2) as check star. The observing run was
carried out through the years 1995 and 1996 at the observatories of San
Pedro M\'{a}rtir, M\'{e}xico (1.5-m telescope) and Sierra Nevada, Spain
(0.9-m telescope) by using similar simultaneous {\em uvby$\beta$}
Str\"omgren photometers attached to each telescope. The observations
showed that while HD~129727 kept a constant brightness, HD~129231
presented a slight photometric variability. This latter star has not been
reported as variable before in any catalogue, hence it has to be
considered as a new variable star. This star was observed by the
Hipparcos satellite (ESA, 1997) but it was considered as a constant
star in the final results.

Figure~1 shows the light curves obtained for this star in the {\em v}
filter during three nights 17, 22 and 27 of February, 1996. In this
figure magnitude differences HD~129231\,$-$ HD~129727 versus
Heliocentric Julian Day have been plotted. From this it can be seen
that the period is about 0.032~days and the amplitude of luminosity
variation is of about 0\fmm01 (from peak to peak).  Multiperiodicity is
also suggested from the light curves shown in the figure. We tried to
make use of the data collected by the Hipparcos satellite (HIP 71820,
ESA, 1997) in order to gain some insight on the frequency content of
this new variable. Unfortunately, this data set contains very few
points (70 points) on this star, randomly distributed in time with a
time span of 3.1 years. Moreover, the error of each measurement is too
large (about 0\fmm011). Therefore, it is not possible to reveal any
reliable variability in the data. On the other hand, the geometric
distance of HD~129231, as measured by the Hipparcos satellite, is of
only 123($\pm$15)~pc.  Since the star is far from the Galactic plane
and lies within close proximity to the Sun, the interstellar reddening
can be neglected. This way, a visual absolute magnitude of M$_v$ =
2\fmm38($\pm$0.26) is obtained (assuming V = 7\fmm83 from the same
catalogue). Hence, due to the characteristics shown, we can conclude
that this star is a new $\delta$~Sct-type variable located near to the
main sequence and blue edge of the instability strip.

\smallskip

{\it Acknowledgements.} This research was supported by the Junta de 
Andaluc\'{\i}a and the Direcci\'{o}n General de Ense\~{n}anza Superior (DGES) 
under project PB96-0840 and CONACYT. 

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\IBVSfig{14cm}{4694-f1.ps}{Differential light curves HD~129231\,$-$\,HD~129727 in the {\it v} filter versus Heliocentric Julian
Day}


\reference

ESA 1997, The Hipparcos and Tycho Catalogues, ESA SP-1200

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