Projected rotational velocities of some δ Scuti and γ Doradus stars

Abstract

We present the projected rotational velocities of some Scuti or Doradus stars as derived from high-resolution spectrograms. For 6 stars the values are the rst determinations. In the past years during our campaigns of monitoring of some selected Scuti stars (see for example Mantegazza & Poretti 2002 and references therein) we obtained spectra of a few Scuti or Doradus stars in order to estimate their projected rotational velocities. Most of the spectra were taken with the Coud e Echelle Spectrograph attached at the Coud e Auxiliary Telescope at La Silla Observatory (ESO) in the 90’s. These spectra have a resolution of 60000 and cover the spectral range between 4490 and 4525 A; their typical S/N in the center is usually better than 200 at the continuum level. Few more spectrograms were taken with the FEROS spectrograph, then attached at the ESO 1.5 m telescope of La Silla Observatory in the years 2001-2002. These spectrograms have a resolution of 48000 and cover the spectral range 3600-9300A. For the present work the useful lines between 4400-4600A were considered. All the spectrograms were normalized to the continuum, dened by selecting a set of continuum windows star by star and tting them with a low-degree polynomial. The unblended lines were then tted by means of a non-linear least-squares routine with a rotational prole convolved with a Gaussian intrinsic one taking also into account the limb darkening. Limb darkening coecients were derived from the paper by Diaz-Cordoves et al. (1995). The number of useful lines varies from 2 to 7, depending upon rotational velocity, spectral type and spectrograph. The typical rms uncertainties, resulting by averaging the values obtained form dierent lines and/or spectrograms, are between 1-2 km/s. The