CoRoT 102749568: mode identification in a δ Scuti star based on regular spacings

Abstract

Context. The high accuracy of space data increased the number of the periodicities determined for pulsating variable stars, but the mode identification is still a critical point in the non-asymptotic regime.
Aims: We use regularities in frequency spacings for identifying the pulsation modes of the recently discovered δ Sct star ID 102749568.
Methods: In addition to analysing CoRoT light curves (15 252 datapoints spanning 131 days), we obtained and analysed both spectroscopic and extended multi-colour photometric data. We applied standard tools (MUFRAN, Period04, SigSpec, and FAMIAS) for time-series analysis.
Results: A satisfactory light-curve fit was obtaining by means of 52 independent modes and 15 combination terms. The frequency spacing revealed distinct peaks around large (25.55-31.43 μHz), intermediate (9.80, 7.66 μHz), and low (2.35 μHz) separations. We directly identified 9 modes, and the l and n values of other three modes were extrapolated. The combined application of spectroscopy, multi-colour photometry, and modelling yielded the precise physical parameters and confirmed the observational mode identification. The large separation constrained the log g and related quantities. The dominant mode is the radial first overtone.

The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain. Discovery and multi-colour follow-up observations were obtained at Piszkéstető, the mountain station of Konkoly Observatory. Spectra were acquired using the AAOmega multi-object spectrograph mounted at the 3.9-m telescope of the Australian Astronomical Observatory in programme 07B/040 and 08B/003 and the HERMES spectrograph, installed at the 1.2-m Mercator Telescope, operated on the island of La Palma by the Flemish Community.Table 9 is available in electronic form at http://www.aanda.org