New Homogeneous v sin i Determinations for B Stars in Galactic Open Clusters

Abstract

We present new observations of projected rotational velocities of main sequence B stars in the galactic clusters NGC 2439, NGC 3293, NGC 3766, NGC 4755, NGC 7160 and h & χ Persei. 257 stars have been observed with three instruments, 207 of which are presented here. Projected rotational velocities have been determined by least-squares fit to synthetic spectra. Our v sin i scale is compared with that of Slettebak et al. (1975).

Does Rotation of B Stars Depend on Metallicity? Preliminary Results from GIRAFFE Spectra

“…The resulting v sin i values were then transformed to the scale of [7]. For the Galaxy, we defined the v sin i distribution using 1) the measurements made in the h & χ Per clusters by [6] and 2) the large sample of [1] of bright field B stars, Geneva photometry being used to determine MV through the calibration of [2]. The SB2 systems were eliminated from this sample, which, although magnitude-limited, does not significantly differ from a volume limited one.…”

“…

We show the v sin i distribution of main sequence B stars in sites of various metallicities, in the absolute magnitude range −3.34 < MV < −2.17. These include Galactic stars in the field measured by [1], members of the h & χ Per open clusters measured by [6], and five fields in the SMC and LMC measured at ESO Paranal with the FLAMES-GIRAFFE spectrograph, within the Geneva-Lausanne guaranteed time. Following the suggestion by [5], we do find a higher rate of rapid rotators in the Magellanic Clouds than in the Galaxy, but the v sin i distribution is the same in the LMC and in the SMC in spite of their very different metallicities.

…”