Rotational velocities of A-type stars II. Measurement of vsini in the northern hemisphere

TL;DR

This study provides new measurements of projected rotational velocities (vsini) for 249 A-type stars in the northern hemisphere, confirming previous systematic biases and combining data into a large, homogenized catalog of over 2150 stars.

Contribution

It introduces a refined method using Fourier transforms for measuring vsini and updates the standard scale, improving the accuracy of stellar rotational velocity data.

Findings

Measurement error is about 5% on average.

Confirmed systematic underestimation in previous standard values.

Established a linear relation between new and old vsini scales.

Abstract

This work is the second part of the set of measurements of vsini for A-type stars, begun by Royer et al. (2002). Spectra of 249 B8 to F2-type stars brighter than V=7 have been collected at Observatoire de Haute-Provence (OHP). Fourier transforms of several line profiles in the range 4200--4600 A are used to derive vsini from the frequency of the first zero. Statistical analysis of the sample indicates that measurement error mainly depends on vsini and this relative error of the rotational velocity is found to be about 5% on average. The systematic shift with respect to standard values from Slettebak et al. (1975), previously found in the first paper, is here confirmed. Comparisons with data from the literature agree with our findings: vsini values from Slettebak et al. are underestimated and the relation between both scales follows a linear law: vsini(new) = 1.03 vsini(old) + 7.7. Finally, these data are combined with those from the previous paper (Royer et al. 2002), together with the catalogue of Abt & Morrell (1995). The resulting sample includes some 2150 stars with homogenized rotational velocities.