SIMBAD references

1997A&A...326..741S - Astronomy and Astrophysics, volume 326, 741-750 (1997/10-2)

HeI D3 absorption and its relation to rotation and activity in G and K dwarfs.

SAAR S.H., HUOVELIN J., OSTEN R.A. and SHCHERBAKOV A.G.

Abstract (from CDS):

We have obtained high resolution, high S/N spectra of the He I D3 line (5876 Å) for 53 stars. Combining these data with previous measurements, we investigate correlations between the flux absorbed by D3, FD3, rotation and other stellar activity indicators for a set of 76 G and K dwarfs. We find that FD3∝Prot–1.2 for Prot≥4days. For Prot<4days, FD3 behaviour depends on spectral type, either remaining roughly constant (G stars), decreasing (K stars), or even going into emission (a few late K stars). We study correlations between D3 and chromospheric (Ca II HK), transition region (C IV 1550Å) and coronal emission, and find, for Prot>4days, FD3∝{DELTA}FHK1.5, FD3∝FCIV0.7, and FD3∝FX0.6, respectively. Thus, D3 has a response intermediate between Ca II HK and C IV in low to moderate activity stars, consistent with its formation in the upper chromosphere. Our data suggest that the maximum flux absorbed by D3 is FD3∝Teff9.3≃2x105erg/cm2/s in G stars (equivalent widths Wλ≤80mÅ), and about 40% of that value (or Wλ≤50mÅ) in K stars, less than predicted by current theoretical models. We discuss the implications of our results for stellar activity and He I line formation, and suggest future avenues of study.

Abstract Copyright:

Journal keyword(s): stars: activity - stars: chromospheres - stars: coronae - stars: late-type

Simbad objects: 78

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