Chromospheric Variability in Early F-type Stars
| Autor: | Rachford, Brian L., Foight, Dillon R. |
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| Rok vydání: | 2009 |
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| Zdroj: | Astrophys.J.698:786-802,2009 |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1088/0004-637X/698/1/786 |
| Popis: | Using precise measurements of the helium D3 line, we have searched for statistically significant variations in the strength of chromospheric activity in 13 early F-type stars and two late F-type stars. In two early F-type stars, we find short-term (hours to days) variability based on ~25 observations over the course of a week. In an additional two cases we find significant differences between observations taken years apart, but we can most likely explain this apparent long-term variation as an artifact of probable short-term variations. The evidence suggests that pure rotational modulation of discrete active regions is not responsible for the short-term variations in the early F-type stars and that either a more global process is at work, or we are seeing large number of small active regions spread across the star. In contrast, the two late F-type stars in the sample show strength and/or wavelength variations that are consistent with "solar-type" activity typified by the rotational modulation of active regions. Our results suggest that variability does not cause the wide range in activity levels observed within the early F-type stars. Comment: 36 pages, 9 figures, accepted for publication in ApJ |
| Databáze: | arXiv |
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