HD 170714
This star is found periodic. The possible period is 0.359 days. Wepresent the phase curve with this period.
HD 171219
This star is not variable at our detection level. In Gutierrez-Soto et al(2003) we also found this star constant.
HD 173637
Short term variability is found. The periodogram analysis shows asignificant peak in 3.01 c/d and in its aliases caused by the spectralwindow. The frequency too close to an entire fraction of a day makesdifficult to distinguish the actual frequency from the aliases. Wepresent the phase curve with the 0.33 days period, which we considerthe most likely one. The determination of the actual period would needmore observational work.
HD 181231
This star is not variable at our detection level. The same conclusionshas been reached from the observations by Poretti et al (2003),presented at this meeting.
HD 181367
That star is not variable at our detection level.
PHOTOMETRY OF BRIGHT Be STARS IN THE CONESOF COROT
J. Gutiérrez-Soto1, J. Fabregat1, J. Suso2, A.M. Hubert3, M. Floquet3, C. Neiner3,
E. Janot-Pacheco4 and R. Garrido5
1Observatori Astronòmic, Universitat de València, 2Instituto Ciencia de los Materiales, Universitat de València,3GEPI, Observatoire de Paris-Meudon, 4IAG, Universidade de São Paulo, 5Instituto de Astrofísica de Andalucía
Abstract: We present differential photometry of bright Be stars in the cones of COROT. Several stars are found to beshort period variables and two of them multiperiodic variables with high amplitude.
Introduction
The observation of classical Be stars by COROT will provide importantkeys to understand the physics of these objects and the nature of theBe phenomenon. In particular, the detection of photosphericmultiperiodicity will confirm the presence of non radial pulsations (nrp)as the origin of the short term variability. COROT observations willallow the study of the beat phenomenon of nrp modes and its relationwith the recurrent outburst and the building of the circumstellar disc.
Our group is proposing the observation of Be stars as secondarytargets in the asteroseismology fields. The first results of our searchwere presented at CW4 (Gutierrez-Soto et al 2003). Now we areextending our photometric search to bright Be stars, in order to findlikely candidates to be proposed as primary targets in theasteroseismolgy fields for the short runs. In this paper we present theresults of our first observing campaigns.
Observations and data analysis
Observations were done at the 0.9 m telescope of the Observatorio deSierra Nevada (Granada, Spain). The instrument used was theautomatic six-channel spectrophotometer which allows simultaneousobservations through the four uvby filters of the Strömgren system.Differential photometry of eight Be stars in the galactic center directionwas obtained in the period 1 to 12 of July 2003.
The observing strategy was to observe all eight stars every night. Wechose a comparison and a check star which were constant for eachtarget and observed these set of stars every night. Fortunately, wehave 9 consecutive photometric days, from 1 to 9 of July.
The period analysis was performed by means of standard Fourier-analysis with subsequent prewhitening steps. For this we have usedScargle (1982) and PDM (Stellingwerf 1978) techniques andmultifrequency least squares to fit the parameters. Phase curves atthe detected frequencies were made.
Notes on individual stars
HD 168797
This star has been studied by Hubert et al (1998) using Hipparcosdata. A period of 0.488 days is proposed. Percy et al (1999) found twopossible periods: 0.46d and 5.5d from both the Hipparcos and ground-based data. Pavlovski et al (1997) noted that the amplitude variesfrom season to season.
Our 9-days light curve shows a variation in amplitude in a short lenghtof time which can be caused by the beat of two close frequencies. Theperiodogram analysis gives 4 short periods: 1.5835 d ,0.694 d, 0.4537d, 0.4427 d. Moreover there is a long term variation which iscompatible with the 5.5d period given by Percy.
HD 173817
This star is found variable with a 0.2849 d. period. We present thephase curve with this period.
HD 179405
This star presents short term variability. The variation of amplitudeimplies the existence of at least two frequencies. 2.024 d, 0.56 d,0.3879 d, 0.3634 d are the most likely periods we have found in ouranalysis. The two shorter periods are so close that their precisedetermination would need a longer photometric study.
Conclusions
Our observations confirm that stars HD 168797, HD 170714, HD173637, HD 173817 and HD 179405 are periodic variables, with theperiods given in Table 1. HD 171219, HD 181231 and 181367 appearas no variables in our data. All results are summarized in Table 1.
Among them, HD 168797 and HD 179405 are multiperiodic variables.We consider them as suitable candidates for the COROT short runs. Amore detailed description of the variablity of these stars is presentedat this meeting (Fabregat et al 2003).
References
•Fabregat et al. 2003, 5th COROT Week, Berlin.
•Gutierrez-Soto et al. 2003, 4th COROT Week, Marseille.
•Hubert, A.M. et al. 1998, A&A, 335, 565-572
•Pavlovski et al. 1997, A&AS, 125,75
•Percy J. R. et al. 1999, A&A, 348, 553-556
•Poretti et al. 2003, 5th COROT Week, Berlin.
•Scargle, J.D. 1982, ApJ, 263, 835
•Stellingwerf, R. F. 1978, ApJ, 224, 953S
5th COROT WEEK, BERLIN 10-12 DECEMBER 2003
TABLE 1
