Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum
Abstract
Aims: We propose a method for measuring the projected rotational velocity vsini with high precision even in spectra with blended lines. Though not automatic, our method is designed to be applied systematically to large numbers of objects without excessive computational requirement.
Methods: We calculated the cross correlation function (CCF) of the object spectrum against a zerorotation template and used the Fourier transform (FT) of the CCF central maximum to measure the parameter vsini taking the limb darkening effect and its wavelength dependence into account. The procedure also improves the definition of the CCF base line, resulting in errors related to the continuum position under 1% even for vsini = 280 km s^{1}. Tests with highresolution spectra of Ftype stars indicate that an accuracy well below 1% can be attained even for spectra where most lines are blended.
Results: We have applied the method to measuring vsini in 251 Atype stars. For stars with vsini over 30 km s^{1} (23 times our spectra resolution), our measurement errors are below 2.5% with a typical value of 1%. We compare our results with Royer et al. (2002a) using 155 stars in common, finding systematic differences of about 5% for rapidly rotating stars.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 July 2011
 DOI:
 10.1051/00046361/201016386
 arXiv:
 arXiv:1012.4858
 Bibcode:
 2011A&A...531A.143D
 Keywords:

 stars: fundamental parameters;
 stars: rotation;
 methods: data analysis;
 Astrophysics  Solar and Stellar Astrophysics;
 Astrophysics  Instrumentation and Methods for Astrophysics
 EPrint:
 Replaced by the version accepted in Astronomy and Astrophysics. 14 pages, 11 figures (5 new figures), new section 3.1, Table 1 added to the printer version