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2002MNRAS.332..409G - Mon. Not. R. Astron. Soc., 332, 409-421 (2002/May-2)
On the source of the flaring activity in AB Doradus: the UV spectral signatures.
GOMEZ DE CASTRO A.I.
Abstract (from CDS):
The most frequently observed profiles are the narrow redshifted profiles; six out of the nine events display this type of profile. An analysis of the velocity field at the stellar surface shows up that they are most likely associated with matter infall. Henceforth, it is feasible that this type of flares are associated with downward flowing material in post-flare magnetic loops, as frequently observed in the Sun.
The broad profiles have a FWHM≃300km.s–1 and are very asymmetric with an extended blue wing reaching 400km.s–1. These profiles have been observed during the strongest flare in the monitoring when the line flux rose up to three times the quiescent value. The large width and asymmetry of the profiles are best explained if this type of flares are associated with gas flows in curved magnetic structures. Three possible mechanisms are analysed: (1) the development of thermal instabilities in large magnetic loops, (2) gas infall and (3) the interaction between the fast and slow components of the stellar wind. The last mechanism seems to be the most feasible given the short duration of the flares.
Finally, a possible absorption caused by the hot component of `sling-shot' prominences has been searched for in the Civ[uv1] and Siiv[uv1] profiles. Two of the three strongest Hα prominences (A and H) seem to have been detected. The most compelling evidence corresponds to A, when an absorption component is observed moving from blue to redshifted velocities from φ =10440.978 to φ =10441.010. The strength of the absorption at φ =10441.010 is 0.2x10–12erg.s–1.cm–2 and has a FWHM=86km.s–1
Abstract Copyright: 2002 Blackwell Science Ltd
Journal keyword(s): stars: individual: AB Dor - stars: pre-main-sequence - stars: variables: other
Simbad objects: 2
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