File Download
There are no files associated with this item.
Supplementary
-
Citations:
- Scopus: 0
- Appears in Collections:
Article: Radio constraints on coronal models for dMe stars
Title | Radio constraints on coronal models for dMe stars |
---|---|
Authors | |
Keywords | Radio Continuum: Stars Stars: Coronae Stars: Late-Type Stars: Magnetic Fields |
Issue Date | 1994 |
Publisher | Institute 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? |
Abstract | Radio 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 Identifier | http://hdl.handle.net/10722/174910 |
ISSN | 2023 Impact Factor: 8.8 2023 SCImago Journal Rankings: 2.766 |
DC Field | Value | Language |
---|---|---|
dc.contributor.author | White, SM | en_US |
dc.contributor.author | Lim, J | en_US |
dc.contributor.author | Kundu, MR | en_US |
dc.date.accessioned | 2012-11-26T08:48:05Z | - |
dc.date.available | 2012-11-26T08:48:05Z | - |
dc.date.issued | 1994 | en_US |
dc.identifier.citation | Astrophysical Journal Letters, 1994, v. 422 n. 1, p. 293-303 | en_US |
dc.identifier.issn | 2041-8205 | en_US |
dc.identifier.uri | http://hdl.handle.net/10722/174910 | - |
dc.description.abstract | Radio 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.language | eng | en_US |
dc.publisher | Institute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/2041-8205 | en_US |
dc.relation.ispartof | Astrophysical Journal Letters | en_US |
dc.subject | Radio Continuum: Stars | en_US |
dc.subject | Stars: Coronae | en_US |
dc.subject | Stars: Late-Type | en_US |
dc.subject | Stars: Magnetic Fields | en_US |
dc.title | Radio constraints on coronal models for dMe stars | en_US |
dc.type | Article | en_US |
dc.identifier.email | Lim, J: jjlim@hku.hk | en_US |
dc.identifier.authority | Lim, J=rp00745 | en_US |
dc.description.nature | link_to_subscribed_fulltext | en_US |
dc.identifier.scopus | eid_2-s2.0-12044253084 | en_US |
dc.identifier.volume | 422 | en_US |
dc.identifier.issue | 1 | en_US |
dc.identifier.spage | 293 | en_US |
dc.identifier.epage | 303 | en_US |
dc.publisher.place | United Kingdom | en_US |
dc.identifier.scopusauthorid | White, SM=7404079906 | en_US |
dc.identifier.scopusauthorid | Lim, J=7403453870 | en_US |
dc.identifier.scopusauthorid | Kundu, MR=7102095820 | en_US |
dc.identifier.issnl | 2041-8205 | - |