Astronomy and Astrophysics – Astrophysics
Scientific paper
2002-11-15
Astrophys.J. 585 (2003) 993-1006
Astronomy and Astrophysics
Astrophysics
29 pages, 7 figures, AASTEX v5.0, accepted by ApJ
Scientific paper
10.1086/346129
We present a survey of coronal forbidden lines detected in Far Ultraviolet Spectroscopic Explorer (FUSE) spectra of nearby stars. Two strong coronal features, Fe XVIII 974 A and Fe XIX 1118 A, are observed in 10 of the 26 stars in our sample. Various other coronal forbidden lines, observed in solar flares, also were sought but not detected. The Fe XVIII feature, formed at log T (K) = 6.8, appears to be free of blends, whereas the Fe XIX line can be corrupted by a C I multiplet. FUSE observations of these forbidden iron lines at spectral resolution R ~ 15,000 provides the opportunity to study dynamics of hot coronal plasmas. We find that the velocity centroid of the Fe XVIII feature deviates little from the stellar rest frame, confirming that the hot coronal plasma is confined. The observed line widths generally are consistent with thermal broadening at the high temperatures of formation and show little indication of additional turbulent broadening. The fastest rotating stars, 31 Com, alpha Aur Ab, and AB Dor, show evidence for excess broadening beyond the thermal component and the photospheric v sin i. The anomalously large widths in these fast rotating targets may be evidence for enhanced rotational broadening consistent with emission from coronal regions extending an additional delta R ~ 0.4-1.3 R_star above the stellar photosphere or represent the turbulent broadening caused by flows along magnetic loop structures. For the stars in which Fe XVIII is detected, there is an excellent correlation between the observed Rontgensatellit} (ROSAT) 0.2-2.0 keV soft X-ray flux and the coronal forbidden line flux. As a result, Fe XVIII is a powerful new diagnostic of coronal thermal conditions and dynamics that can be utilized to study high temperature plasma processes in late-type stars.
Ake Thomas B.
Ayres Thomas R.
Dupree Andrea K.
Linsky Jeffrey L.
Redfield Seth
No associations
LandOfFree
A Far Ultraviolet Spectroscopic Explorer Survey of Coronal Forbidden Lines in Late-Type Stars does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A Far Ultraviolet Spectroscopic Explorer Survey of Coronal Forbidden Lines in Late-Type Stars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A Far Ultraviolet Spectroscopic Explorer Survey of Coronal Forbidden Lines in Late-Type Stars will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-629331