The stellar composition of the star formation region CMa R1 – II. Spectroscopic and photometric observations of nine young stars |
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Authors: | HRE Tjin A Djie ME van den Ancker PFC Blondel VS Shevchenko OV Ezhkova D de Winter KN Grankin |
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Institution: | 1Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, the Netherlands;2Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 42, Cambridge MA 02138, USA;3Astronomical Institute of the Academy of Sciences of Uzbekistan, Astronomicheskaya 33, Tashkent 700052, Uzbekistan;4TNO-TPD, Stieltjesweg 1, PO Box 155, 2600 AD Delft, the Netherlands |
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Abstract: | We present new high- and low-resolution spectroscopic and photometric data of nine members of the young association CMa R1. All the stars have circumstellar dust at some distance, as could be expected from their association with reflection nebulosity. Four stars (HD 52721, HD 53367, LkH α 220 and LkH α 218) show H α emission and we argue that they are Herbig Be stars with discs. Our photometric and spectroscopic observations of these stars reveal new characteristics of their variability. We present first interpretations of the variability of HD 52721, HD 53367 and the two LkH α stars in terms of a partially eclipsing binary, a magnetic activity cycle and circumstellar dust variations, respectively. The remaining five stars show no clear indications of H α emission in their spectra, although their spectral types and ages are comparable with those of HD 52721 and HD 53367. This indicates that the presence of a disc around a star in CMa R1 may depend on the environment of the star. In particular we find that all H α emission stars are located at or outside the arc-shaped border of the H ii region, which suggests that the stars inside the arc have lost their discs through evaporation by UV photons from nearby O stars, or from the nearby (<25 pc) supernova, about 1 Myr ago. |
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Keywords: | circumstellar matter stars: early-type stars: evolution stars: pre-main-sequence stars: variables: other open clusters and associations: individual: CMa R1 |
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