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Astron. Astrophys. 363, 29-40 (2000)


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Variable stars in nearby galaxies *

III. White light observations of Field B of IC 1613

E. Antonello, D. Fugazza, L. Mantegazza, M. Bossi and S. Covino

Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, Italy (elio,fugazza,luciano,bossi,covino@merate.mi.astro.it)

Received 13 June 2000 / Accepted 22 August 2000

Abstract

Two nearby galaxies, IC 1613 and NGC 6822, were observed over four years to detect short period Cepheids and to obtain good light curves for Fourier decomposition. Since the program was carried out with a relatively small telescope, the Dutch 0.9 m at ESO-La Silla, the observations were performed without filter (white light), or Wh-band; the advantage of this technique is that the photon statistics correspond to those of V-band observations of similar exposure time obtained with a 2-m class telescope. In this paper we discuss some properties of Wh photometry and present the results of the observations of Field B in IC 1613 ([FORMULA]x[FORMULA]). A total of 65 images were obtained and the reduction was performed with DAOPHOT. The light curves of 4037 stars were measured, and the analysis using various techniques allowed the detection of 121 variable stars. We detected 51 population I Cepheids, while previously only 12 Cepheids were known in the same field. Most of these have short periods and some are first overtone mode pulsators. The other variable stars include one eclipsing binary, two suspected W Vir stars, 57 irregular and semi-regular red variables, 3 periodic red variables and 6 irregular blue variables.

Key words: stars: oscillations – stars: variables: Cepheids – stars: variables: general – galaxies: individual: IC 1613 – galaxies: Local Group – galaxies: stellar content

* Based on observations collected at ESO-La Silla

Send offprint requests to: E. Antonello

© European Southern Observatory (ESO) 2000

Online publication: December 5, 2000

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