V 1162 Ori: A multiperiodic δ Scuti star with variable period and amplitude ^*,**

¹ University of Brussels (VUB), Pleinlaan 2, 1050 Brussels, Belgium
² South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa
³ Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium
⁴ Laboratório Nacional de Astrofísica, CP 21, 37500-000 Itajubá -MG, Brazil
⁵ Department of Astrophysics, Astronomy and Mechanics, University of Athens, 157 84 Zografos, Athens, Greece
⁶ Beersel Hills Observatory, Belgium
⁷ Osservatorio Astronomico di Brera, Via E. Bianchi 46, 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 Astronomical Observatory, Chinese Academy of Sciences, Beijing 100012, PR China
¹¹ Research School of Astronomy and Astrophysics, Australian National University, Weston Creek PO, ACT 2611, Australia
¹² Instituto de Astrofisica de Andalucia, CSIC, Apdo. 3004, 18080 Granada, Spain
¹³ Braeside Observatory, Flagstaff, Arizona, USA
¹⁴ Ege University Observatory, Bornova 35100, Izmir, Turkey
¹⁵ Astrophysical Sciences Department, Princeton University, Princeton, New Jersey 08544, USA
¹⁶ Centre for Astrophysics, University of Central Lancashire, Preston PR1 2HE, UK
¹⁷ Department of Astronomy, University of Cape Town, Rondebosch 7701, South Africa
¹⁸ Laboratoire d'Astrophysique, Observatoire Midi-Pyrénées, 31400 Toulouse, France

Corresponding author: T. Arentoft, tarentof@vub.ac.be

Received: 26 April 2001
Accepted: 31 May 2001

Abstract

We present the results of multisite observations of the δ Scuti star V 1162 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 previously observed in this star, and to search for low-amplitude frequencies. We detect, apart from the main frequency and its two first 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 V 1162 Ori has variable amplitude and period/phase, the latter is also displayed in the O-C diagram from light extrema. The amplitude variability in our data is cyclic with a period of 282 d and a range of nearly 20 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 V 1162 Ori displays a linear period change as well as sudden or cyclic variations on a time scale similar to that of the amplitude variations. ]