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Article: Radio constraints on coronal models for dMe stars

TitleRadio constraints on coronal models for dMe stars
Authors
KeywordsRadio Continuum: Stars
Stars: Coronae
Stars: Late-Type
Stars: Magnetic Fields
Issue Date1994
PublisherInstitute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/2041-8205
Citation
Astrophysical Journal Letters, 1994, v. 422 n. 1, p. 293-303 How to Cite?
AbstractRadio data are used to test coronal models for dMe stars. Specifically, we show that pnotospheric magnetic field observations imply that the low corona of a dMe star should be saturated by magnetic fields with an average strength in excess of 1 kG. In such fields the hot component of the corona detected in X-ray observations (temperature of order 2 × 10 7 K) would be optically thick at least up to 15 GHz due to thermal gyroresonance opacity. The resulting emission would easily be detectable by radio observations and should have a radio spectrum rising in the microwave range. We have carried out observations to test this prediction, and in the majority of cases find that the observed fluxes at 15 GHz are too low to be consistent with the assumptions. In the few cases where the stars were detected at 15 GHz, the evidence indicates that the observed emission is nonthermal. These results imply that the hot component of the X-ray-emitting plasma in the corona is not coincident with the strong magnetic fields in the lower corona. Because the hot plasma must still be confined by closed magnetic field lines, it is likely to be restricted to heights of the order of a stellar radius above the photosphere. The results seem to imply a different genesis for the two components of the X-ray-emitting corona of flare stars: the hot component may be cooling flare plasma, while the cooler component (temperature of order 3 × 10 6 K) is associated with a more conventional coronal heating mechanism.
Persistent Identifierhttp://hdl.handle.net/10722/174910
ISSN
2015 Impact Factor: 5.487
2015 SCImago Journal Rankings: 3.369

 

DC FieldValueLanguage
dc.contributor.authorWhite, SMen_US
dc.contributor.authorLim, Jen_US
dc.contributor.authorKundu, MRen_US
dc.date.accessioned2012-11-26T08:48:05Z-
dc.date.available2012-11-26T08:48:05Z-
dc.date.issued1994en_US
dc.identifier.citationAstrophysical Journal Letters, 1994, v. 422 n. 1, p. 293-303en_US
dc.identifier.issn2041-8205en_US
dc.identifier.urihttp://hdl.handle.net/10722/174910-
dc.description.abstractRadio data are used to test coronal models for dMe stars. Specifically, we show that pnotospheric magnetic field observations imply that the low corona of a dMe star should be saturated by magnetic fields with an average strength in excess of 1 kG. In such fields the hot component of the corona detected in X-ray observations (temperature of order 2 × 10 7 K) would be optically thick at least up to 15 GHz due to thermal gyroresonance opacity. The resulting emission would easily be detectable by radio observations and should have a radio spectrum rising in the microwave range. We have carried out observations to test this prediction, and in the majority of cases find that the observed fluxes at 15 GHz are too low to be consistent with the assumptions. In the few cases where the stars were detected at 15 GHz, the evidence indicates that the observed emission is nonthermal. These results imply that the hot component of the X-ray-emitting plasma in the corona is not coincident with the strong magnetic fields in the lower corona. Because the hot plasma must still be confined by closed magnetic field lines, it is likely to be restricted to heights of the order of a stellar radius above the photosphere. The results seem to imply a different genesis for the two components of the X-ray-emitting corona of flare stars: the hot component may be cooling flare plasma, while the cooler component (temperature of order 3 × 10 6 K) is associated with a more conventional coronal heating mechanism.en_US
dc.languageengen_US
dc.publisherInstitute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/2041-8205en_US
dc.relation.ispartofAstrophysical Journal Lettersen_US
dc.subjectRadio Continuum: Starsen_US
dc.subjectStars: Coronaeen_US
dc.subjectStars: Late-Typeen_US
dc.subjectStars: Magnetic Fieldsen_US
dc.titleRadio constraints on coronal models for dMe starsen_US
dc.typeArticleen_US
dc.identifier.emailLim, J: jjlim@hku.hken_US
dc.identifier.authorityLim, J=rp00745en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.scopuseid_2-s2.0-12044253084en_US
dc.identifier.volume422en_US
dc.identifier.issue1en_US
dc.identifier.spage293en_US
dc.identifier.epage303en_US
dc.publisher.placeUnited Kingdomen_US
dc.identifier.scopusauthoridWhite, SM=7404079906en_US
dc.identifier.scopusauthoridLim, J=7403453870en_US
dc.identifier.scopusauthoridKundu, MR=7102095820en_US

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