Flare star
A flare star is a variable star that can undergo unpredictable dramatic increases in brightness for a few minutes. It is believed that the flares on flare stars are analogous to solar flares in that they are due to magnetic reconnection in the atmospheres of the stars. The brightness increase is across the spectrum, from X rays to radio waves. The first known flare stars (V1396 Cygni and AT Microscopii) were discovered in 1924. However, the best-known flare star is UV Ceti, discovered in 1948. Today similar flare stars are classified as UV Ceti type variable stars (using the abbreviation UV) in variable star catalogs such as the General Catalogue of Variable Stars. Flares can happen once every few days, [1] [dubious – discuss] or, as in the case of Barnard's Star, much less frequently.
Most flare stars are dim red dwarfs, although recent research indicates that less massive brown dwarfs might also be capable of flaring.[citation needed] The more massive RS Canum Venaticorum variables (RS CVn) are also known to flare, but it is understood that these flares are induced by a companion star in a binary system which causes the magnetic field to become tangled. Additionally, nine stars similar to the Sun have also been seen to undergo flare events.[2] It has been proposed that the mechanism for this is similar to that of the RS CVn variables in that the flares are being induced by a companion, namely an unseen Jupiter-like planet in a close orbit.[3]
Nearby flare stars
Flare stars are intrinsically faint, but have been found to distances of 1,000 light years from Earth.[4]
Proxima Centauri
The Sun's nearest stellar neighbor Proxima Centauri is a flare star that undergoes random increases in brightness because of magnetic activity.[5] The star's magnetic field is created by convection throughout the stellar body, and the resulting flare activity generates a total X-ray emission similar to that produced by the Sun.[6]
Wolf 359
The flare star Wolf 359 is another near neighbor (2.39 ± 0.01 parsecs). Wolf 359, also known as Gliese 406 and CN Leo, is a red dwarf of spectral class M6.5 that emits X-rays.[7] It is a UV Ceti flare star,[8] and has a relatively high flare rate.
The mean magnetic field has a strength of about 2.2 kG (0.2 T), but this varies significantly on time scales as short as six hours.[9] By comparison, the magnetic field of the Sun averages 1 G (100 μT), although it can rise as high as 3 kG (0.3 T) in active sunspot regions.[10]
Barnard's Star
Barnard's Star, the second nearest star system, is also suspected of being a flare star.[citation needed]
TVLM513-46546
A very low mass flare star is TVLM513-46546, slightly heavier than the lower limit for red dwarfs.
See also
References
- ^ http://www.solstation.com/stars/alp-cent3.htm
- ^ Schaefer, Bradley; King, Jeremy R.; Deliyannis, Constantine P. (2000-02). "Superflares on Ordinary Solar-Type Stars". The Astrophysical Journal. 529 (2). Astrophysical Journal: 1026. arXiv:astro-ph/9909188. Bibcode:2000ApJ...529.1026S. doi:10.1086/308325.
{{cite journal}}: Check date values in:|date=(help) - ^ Rubenstein, Eric; Schaefer, Bradley E. (2000-02). "Are Superflares on Solar Analogues Caused by Extrasolar Planets?". The Astrophysical Journal. 529 (2). Astrophysical Journal: 1031. arXiv:astro-ph/9909187. Bibcode:2000ApJ...529.1031R. doi:10.1086/308326.
{{cite journal}}: Check date values in:|date=(help) - ^ Kulkarni SR, Rau A (2006). "The Nature of the Deep Lens Survey Fast Transients". Ap J. 644 (1): L63. arXiv:astro-ph/0604343. Bibcode:2006ApJ...644L..63K. doi:10.1086/505423.
- ^ Christian DJ, Mathioudakis M, Bloomfield DS, Dupuis J, Keenan FP (2004). "A Detailed Study of Opacity in the Upper Atmosphere of Proxima Centauri". Ap J. 612 (2): 1140–6. Bibcode:2004ApJ...612.1140C. doi:10.1086/422803.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Wood BE, Linsky JL, Müller HR, Zank GP (2001). "Observational Estimates for the Mass-Loss Rates of α Centauri and Proxima Centauri Using Hubble Space Telescope Lyα Spectra". Ap J. 547 (1): L49–L52. arXiv:astro-ph/0011153. Bibcode:2001ApJ...547L..49W. doi:10.1086/318888.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Schmitt JHMM, Fleming TA, Giampapa MS (1995). "The X-Ray View of the Low-Mass Stars in the Solar Neighborhood". Ap J. 450 (9): 392–400. Bibcode:1995ApJ...450..392S. doi:10.1086/176149.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Gershberg RE, Shakhovskaia NI (1983). "Characteristics of activity energetics of he UV Cet-type flare stars". Astrophys Space Sci. 95 (2): 235–53. Bibcode:1983Ap&SS..95..235G. doi:10.1007/BF00653631.
- ^ Reiners A, Schmitt JHMM, Liefke C (2007). "Rapid magnetic flux variability on the flare star CN Leonis". Astronomy and Astrophysics. 466 (2): L13–6. arXiv:astro-ph/0703172. Bibcode:2007A&A...466L..13R. doi:10.1051/0004-6361:20077095.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Staff (January 7, 2007). "Calling Dr. Frankenstein! : Interactive Binaries Show Signs of Induced Hyperactivity". National Optical Astronomy Observatory. Retrieved 2006-05-24.
External links
- UV Ceti and the flare stars, Autumn 2003 Variable Star Of The Season prepared by Dr. Matthew Templeton, AAVSO(www.aavso.org)
- Stellar Flares - D. Montes, UCM.
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