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Paper: The ESO WFI Slitless Spectroscopic Survey of Hα Emission-Line Stars in the MW, LMC, and SMC
Volume: 491, Fifty Years of Wide Field Studies in the Southern Hemisphere: Resolved Stellar Populations in the Galactic Bulge and the Magellanic Clouds
Page: 351
Authors: Martayan, C.; Aguayo, G.; Baade, D.; Fabregat, J.; Garrido, H.; Rivinius, T.; Stefl, S
Abstract: The ESO Wide Field Imager (WFI) at the 2.2m on La Silla was used with its slitless facility to do a survey of the H-alpha emission-line stars (ELS) in the Magellanic Clouds and in two Galactic open clusters. About 8 million spectra were obtained in the LMC and SMC in less than 2 nights, highlighting that the WFI in slitless mode is an efficient instrument for such a spectroscopic survey. In the coming sections, we briefly describe the observations, the data reduction, and the analysis processes of this specific mode of WFI imagers, with examples from the obtained Galactic and Magellanic observations. The results with the WFI-slitless survey in about 80 SMC open clusters of the ELS search, with a special emphasis on Be stars are then presented. The comparison of the frequency of Be stars among early B stars populations shows that they are 3 to 5 times more abundant in the SMC than in the Galaxy. This result is consistent with the metallicity gradient between those two galaxies, leading to lower angular momentum loss, then to faster rotational velocities, and therefore to more Be stars in the SMC. Finally, the first results of the ongoing studies in the LMC are briefly mentioned.
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