V1162 Ori: a multiperiodic delta Scuti star with variable period and amplitude

T. Arentoft (1) - C. Sterken (1) - G. Handler (2) - L.M. Freyhammer (1,3) - A. Bruch (4) - P. Niarchos (5) - K. Gazeas (5) - V. Manimanis (5) - P. Van Cauteren (6) - E. Poretti (7) - D.W. Dawson (8,9) - A.L. Liu (10) - A.Y. Zhou (10) - B.T Du (10) - R.R. Shobbrook (11) - R. Garrido (12) - R. Fried (13) - M.C. Akan (14) - C. Ibanoglu (14) - S. Evren (14) - G. Tas (14) - D. Johnson (8) - C. Blake (15) - D.W. Kurtz (16,17,18)

(1) University of Brussels (VUB), Pleinlaan 2, B-1050 Brussles, Belgium
(2) South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa
(3) Royal Observatory of Belgium, Ringlaan 3, B-1180 Brussels, Belgium
(4) Laboratório Nacional de Astrofísica, CP 21, BR-37500-000 Itajubá - MG, Brazil
(5) Department of Astrophysics, Astronomy and Mechanics, University of Athens, GR-157 84 Zografaos, Athens, Greece
(6) Beersel Hills Observatory, Belgium
(7) Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate, Italy
(8) Department of Astronomy, San Diego State University, San Diego, California, USA
(9) Department of Physics and Astronomy, Western Connecticut State University, Danbury, Connecticut 06810, USA
(10) Beijing Astronomincal Observatory, Chinese Academy of Sciences, Beijing 100012, P.R. China
(11) Reseach School of Astronomy and Astrophysics, Australian National University, Weston Creek P.O., ACT 2611, Australia
(12) Instituto de Astrofisica de Andalucia, CSIC, Apdo. 3004, E-18080 Granada, Spain
(13) Braeside Observatory, Flagstaff, Arizona, USA
(14) Ege University Observatory, Bornova 35100, Izmir, Turkey
(15) Astrophysical Science Department, Princeton Universtiy, Princeton, New Jersey 08544, USA
(16) Center for Astrophysics, University of Central Lancashire, Preston PR1 2HE, England
(17) Departmenot of Astronomy, University of Cape Town, Rondebosch 7701, South Africa
(18) Laboratoire d'Astrophysique, Observatoire Midi Pyrénée, Toulouse 31400, France

Abstract:

We present the results of multiside observations of the delta Scuti star V1162 Ori. The observations were done in the period October 1999 - May 2000, when 18 telescopes at 15 observatories were used to collect 253 light extrema during a total of 290 hours of time-series observations. The purpose of the observations was to investigate amplitude and period variability oberved in this star, and to search for low-amplitude frequencies. We detect, apart from the main frequency and its first two harmonics, four additional frequencies in the light curves, all with low amplitudes (1 - 3 mmag). Combining the present data set with data obtained in 1998-99 at ESO confirms the new frequencies and reveals the probable presence of yet another pulsational frequency. All five low-amplitude frequencies are statistically significant in the data, but at least one of them (f₅) suffers from uncertainty due to aliasing. Using colour photometry we find evidence for a radial main frequency (f₁), while most or all low-amplitude frequencies are likely non-radial. We show that the main frequency of V1162 Ori has variable amplitude and period/phase, the latter also dispayed in the O - C diagram from light extrema. The amplitude variability in out data is cyclic with a period of 285 days and a range of nearly 10 mmag, but earlier amplitude values quoted in the literature cannot be explained by this cyclic variation. O - C analysis including data from the literature show that the period of V1162 Ori displays a linear period change as well as sudden or cyclic variations on a time scale of that of the amplitude variations.

Keywords: stars: variables: delta Scuti - stars: individual: V1162 Ori - techniques: photometric - methods: data analysis