The CoRoT target HD 175726: an active star with weak solar-like oscillations^*

¹ LESIA, CNRS, Université Pierre et Marie Curie, Université Denis Diderot, Observatoire de Paris, 92195 Meudon Cedex, France e-mail: benoit.mosser@obspm.fr
² Institut d'Astrophysique Spatiale, UMR8617, Université Paris XI, Bâtiment 121, 91405 Orsay Cedex, France
³ Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia
⁴ Laboratoire AIM, CEA/DSM-CNRS – Univ. Paris 7 Diderot – IRFU/SAp, 91191 Gif-sur-Yvette Cedex, France
⁵ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
⁶ Universidad de la Laguna, 38206 La Laguna, Tenerife, Spain
⁷ Astronomy Unit, Queen Mary, University of London Mile End Road, London E1 4NS, UK
⁸ Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 av. Edouard Belin, 31400 Toulouse, France
⁹ Indian Institute of Astrophysics, Bangalore, India

Received: 20 February 2009
Accepted: 5 July 2009

Abstract

Context. The CoRoT short runs give us the opportunity to observe a large variety of late-type stars through their solar-like oscillations. We report observations of the star HD 175726 that lasted for 27 days during the first short run of the mission. The time series reveals a high-activity signal and the power spectrum presents an excess due to solar-like oscillations with a low signal-to-noise ratio.

Aims. Our aim is to identify the most efficient tools to extract as much information as possible from the power density spectrum.

Methods. The most productive method appears to be the autocorrelation of the time series, calculated as the spectrum of the filtered spectrum. This method is efficient, very rapid computationally, and will be useful for the analysis of other targets, observed with CoRoT or with forthcoming missions such as Kepler and Plato.

Results. The mean large separation has been measured to be   μHz, slightly below the expected value determined from solar scaling laws. We also show strong evidence for variation of the large separation with frequency. The bolometric mode amplitude is only  ppm for radial modes, which is 1.7 times less than expected. Due to the low signal-to-noise ratio, mode identification is not possible for the available data set of HD 175726.