Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004aas...205.1202a&link_type=abstract
American Astronomical Society Meeting 205, #12.02; Bulletin of the American Astronomical Society, Vol. 36, p.1356
Astronomy and Astrophysics
Astronomy
1
Scientific paper
Fast-rotating early-G giants often display ultraviolet profiles of ``hot lines,'' like O VI (3×105 K), up to twice as broad as anticipated from the photospheric υsin {i}. This peculiar behavior has been attributed to highly extended coronal outer atmospheres.
FUSE recently has contributed fundamentally to the exploration of these ``super-rotational'' effects by observing the fascinating object FK Comae Berenices (G5 III). It is prototype of a class of rapidly rotating single giants which display spectacular emission activity from X-rays to radio. FK Com has a spin period of only 2.4 d, and a remarkable υsin {i} of 160 km s-1. The origins of such ultra-fast--rotating stars are controversial. They might result from a coalesced contact binary, cannibalism of a ``hot Jupiter,'' or simply represent the top of the natural spin distribution of moderate-mass Hertzsprung gap giants.
In February 2004, FUSE obtained a 13 ks exposure of FK Com in the 920--1180 Å range, the first UV observation of this unusual object since the IUE era a decade ago, and by far the best quality spectrum to date. The FUV emissions of O VI λ 1031 and C III λ 977 are enormously broad, asymmetric, but nearly identical in shape, aside from a blue-shifted absorption component in the latter. The FHWM's are a remarkable 600 km s-1, about twice the broadest FUV profile of any late-type star observed up to that point.
The blueshifted C III feature might represent a wind at ˜ 3×104 K, or alternatively a scattering structure in the highly extended coronal envelope, something like the ``prominences'' seen already in Hα . The asymmetric O VI profile might indicate an outflow at higher ˜ 3× 105 K temperatures; or simply reflects a skewed distribution of high-altitude activity in the equatorial zones of FK Com. The relationship between the hot lines and photospheric active regions---deduced from contemporaneous optical Doppler mapping---also will be discussed.
This work was supported by FUSE Guest Investigator grant NNG04GH25G.
Ayres Thomas R.
Brown Adrian
Harper Graham M.
Korhonen Heidi
Redfield Seth
No associations
LandOfFree
FK Comae: King of Spin 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 FK Comae: King of Spin, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and FK Comae: King of Spin will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1635954