Flare star

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An M-type flare star stripping away the atmosphere of its planet Red Dwarf Flare Star (Artist's Illustration) (2018-46-4241).tif
An M-type flare star stripping away the atmosphere of its planet

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 the magnetic energy stored in the stars' atmospheres. The brightness increase is across the spectrum, from X-rays to radio waves. Flare activity among late-type stars was first reported by A. van Maanen in 1945, for WX Ursae Majoris and YZ Canis Minoris. [1] However, the best-known flare star is UV Ceti, first observed to flare 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.

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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 had also been seen to undergo flare events [2] prior to the flood of superflare data from the Kepler observatory. 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

A flare star with orbiting planet (artist's impression) Stellar flare hits HD 189733 b (artist's impression).jpg
A flare star with orbiting planet (artist's impression)

Flare stars are intrinsically faint, but have been found to distances of 1,000 light years from Earth. [4] On April 23, 2014, NASA's Swift satellite detected the strongest, hottest, and longest-lasting sequence of stellar flares ever seen from a nearby red dwarf, DG Canum Venaticorum. The initial blast from this record-setting series of explosions was as much as 10,000 times more powerful than the largest solar flare ever recorded. [5]

Proxima Centauri

Proxima Centauri, with planet c in the foreground and the Alpha Centauri binary in the background Proxima Centauri c.png
Proxima Centauri, with planet c in the foreground and the Alpha Centauri binary in the background

The Sun's nearest stellar neighbor Proxima Centauri is a flare star that undergoes occasional increases in brightness because of magnetic activity. [6] 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. [7]

Wolf 359

The flare star Wolf 359 is another near neighbor (2.39 ± 0.01 parsecs). This star, also known as Gliese 406 and CN Leo, is a red dwarf of spectral class M6.5 that emits X-rays. [8] It is a UV Ceti flare star, [9] and has a relatively high flare rate.

Artist's interpretation of Wolf 359 Wolf359incelestia.jpg
Artist's interpretation of Wolf 359

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. [10] 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. [11]

Barnard's Star

Size comparison between Jupiter, Barnard's star and the Sun Barnard'sStarSize en.jpg
Size comparison between Jupiter, Barnard's star and the Sun

Barnard's Star is the fourth nearest star to the Sun. Given its age, at 7–12 billion years of age, Barnard's Star is considerably older than the Sun. It was long assumed to be quiescent in terms of stellar activity. However, in 1998, astronomers observed an intense stellar flare, showing that Barnard's Star is a flare star. [12] [13]

EV Lacertae

Artist's conception of a flare explosion on EV Lacertae Nasa EV Lacertae 250408.jpg
Artist's conception of a flare explosion on EV Lacertae

EV Lacertae is located 16.5 light-years away, and is the nearest star in its constellation. It is a young star, about 300 million years old, and has a strong magnetic field. In 2008, it produced a record-setting flare that was thousands of times more powerful than the largest observed solar flare. [14]

TVLM513-46546

TVLM 513-46546 is a very low mass M9 flare star, at the boundary between red dwarfs and brown dwarfs. Data from Arecibo Observatory at radio wavelengths determined that the star flares every 7054 s with a precision of one one-hundredth of a second. [15]

2MASS J18352154-3123385 A

The more massive member of the binary star 2MASS J1835, an M6.5 star, has strong X-ray activity indicative of a flare star, although it has never been directly observed to flare.

Record-setting flares

The most powerful stellar flare detected, as of December 2005, may have come from the active binary II Peg. [16] Its observation by Swift suggested the presence of hard X-rays in the well-established Neupert effect as seen in solar flares.

See also

Related Research Articles

<span class="mw-page-title-main">Barnard's Star</span> Red dwarf star about six light-years from Earth in the constellation Ophiuchus

Barnard's Star is a small red dwarf star in the constellation of Ophiuchus. At a distance of 5.96 light-years (1.83 pc) from Earth, it is the fourth-nearest-known individual star to the Sun after the three components of the Alpha Centauri system, and the closest star in the northern celestial hemisphere. Its stellar mass is about 16% of the Sun's, and it has 19% of the Sun's diameter. Despite its proximity, the star has a dim apparent visual magnitude of +9.5 and is invisible to the unaided eye; it is much brighter in the infrared than in visible light.

<span class="mw-page-title-main">Proxima Centauri</span> Star in the constellation Centaurus

Proxima Centauri is a small, low-mass star located 4.2465 light-years (1.3020 pc) away from the Sun in the southern constellation of Centaurus. Its Latin name means the 'nearest [star] of Centaurus'. It was discovered in 1915 by Robert Innes and is the nearest-known star to the Sun. With a quiescent apparent magnitude of 11.13, it is too faint to be seen with the unaided eye. Proxima Centauri is a member of the Alpha Centauri star system, being identified as component Alpha Centauri C, and is 2.18° to the southwest of the Alpha Centauri AB pair. It is currently 12,950 AU (0.2 ly) from AB, which it orbits with a period of about 550,000 years.

<span class="mw-page-title-main">Wolf 359</span> Red dwarf in the constellation Leo

Wolf 359 is a red dwarf star located in the constellation Leo, near the ecliptic. At a distance of 7.86 light-years from Earth, it has an apparent magnitude of 13.54 and can only be seen with a large telescope. Wolf 359 is one of the nearest stars to the Sun; only the Alpha Centauri system, Barnard's Star, and the brown dwarfs Luhman 16 and WISE 0855−0714 are known to be closer. Its proximity to Earth has led to its mention in several works of fiction.

Ross 154 is a star in the southern zodiac constellation of Sagittarius. It has an apparent visual magnitude of 10.44, making it much too faint to be seen with the naked eye. At a minimum, viewing Ross 154 requires a telescope with an aperture of 6.5 cm (3 in) under ideal conditions. The distance to this star can be estimated from parallax measurements, which places it at 9.71 light-years away from Earth. It is the nearest star in the southern constellation Sagittarius, and one of the nearest stars to the Sun.

<span class="mw-page-title-main">Ross 128</span> Small star in constellation of Virgo

Ross 128 is a red dwarf in the equatorial zodiac constellation of Virgo, near β Virginis. The apparent magnitude of Ross 128 is 11.13, which is too faint to be seen with the unaided eye. Based upon parallax measurements, the distance of this star from Earth is 11.007 light-years, making it the twelfth closest stellar system to the Solar System. It was first cataloged in 1926 by American astronomer Frank Elmore Ross.

<span class="mw-page-title-main">Groombridge 1830</span> Star in the constellation Ursa Major

Groombridge 1830 is a star in the constellation Ursa Major.

Gliese 65, also known as Luyten 726-8, is a binary star system that is one of Earth's nearest neighbors, at about 8.7 light years from Earth in the constellation Cetus. The two component stars are both flare stars with the variable star designations BL Ceti and UV Ceti.

<span class="mw-page-title-main">K-type main-sequence star</span> Stellar classification

A K-type main-sequence star, also referred to as a K-type dwarf, or orange dwarf, is a main-sequence (hydrogen-burning) star of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars and yellow/white G-type main-sequence stars. They have masses between 0.6 and 0.9 times the mass of the Sun and surface temperatures between 3,900 and 5,300 K. These stars are of particular interest in the search for extraterrestrial life due to their stability and long lifespan. Well-known examples include Alpha Centauri B and Epsilon Indi.

<span class="mw-page-title-main">YZ Ceti</span> Star in the constellation Cetus

YZ Ceti is a red dwarf star in the constellation Cetus. Although it is relatively close to the Sun at just 12 light years, this star cannot be seen with the naked eye. It is classified as a flare star that undergoes intermittent fluctuations in luminosity. YZ Ceti is about 13 percent the mass of the Sun and 17% of its radius.

TZ Arietis is a red dwarf in the northern constellation of Aries. With a normal apparent visual magnitude of 12.3, it is too faint to be seen by the naked eye, although it lies relatively close to the Sun at a distance of 14.6 light-years. It is a flare star, which means it can suddenly increase in brightness for short periods of time.

<span class="mw-page-title-main">Omicron Aquilae</span> Star in the constellation Aquila

Omicron Aquilae is the Bayer designation for a double star in the equatorial constellation of Aquila. The brighter component has an apparent visual magnitude of +5.11, which means it is faintly visible to the naked eye in dark suburban skies. The annual parallax shift of this star is 52.11 mas, which is equivalent to a physical distance of 62.6 light-years from Earth.

<span class="mw-page-title-main">AD Leonis</span> M-type star in the constellation Leo

AD Leonis (Gliese 388) is a red dwarf star. It is located relatively near the Sun, at a distance of 16.2 light-years, in the constellation Leo. AD Leonis is a main sequence star with a spectral classification of M3.5V. It is a flare star that undergoes random increases in luminosity.

Kappa<sup>1</sup> Ceti Variable yellow dwarf star in the constellation Cetus

Kappa1 Ceti, Latinized from κ1 Ceti, is a variable yellow dwarf star approximately 30 light-years away in the equatorial constellation of Cetus.

<span class="mw-page-title-main">II Pegasi</span> Star in the constellation Pegasus

II Pegasi is a binary star system in the constellation of Pegasus with an apparent magnitude of 7.4 and a distance of 130 light-years. It is a very active RS Canum Venaticorum variable, a close binary system with active starspots.

<span class="mw-page-title-main">EQ Virginis</span> Star in the constellation Virgo

EQ Virginis is a single variable star in the equatorial constellation of Virgo. It has a baseline visual apparent magnitude of 9.36, but is a flare star that undergoes sporadic bursts of brightening. The star is located at a distance of 67 light-years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −23 km/s. It is a member of the IC 2391 moving group of stars, which is between 30 and 50 million years old.

<span class="mw-page-title-main">EV Lacertae</span> Star in the constellation Lacerta

EV Lacertae is a faint red dwarf star 16.5 light years away in the constellation Lacerta. It is the nearest star to the Sun in that region of the sky, although with an apparent magnitude of 10, it is only barely visible with binoculars. EV Lacertae is spectral type M3.5 flare star that emits X-rays.

<span class="mw-page-title-main">Gliese 752</span> Binary star system in the constellation Aquila

Gliese 752 is a binary star system in the Aquila constellation. This system is relatively nearby, at a distance of 19.3 light-years.

Superflares are very strong explosions observed on stars with energies up to ten thousand times that of typical solar flares. The stars in this class satisfy conditions which should make them solar analogues, and would be expected to be stable over very long time scales. The original nine candidates were detected by a variety of methods. No systematic study was possible until the launch of the Kepler space telescope, which monitored a very large number of solar-type stars with very high accuracy for an extended period. This showed that a small proportion of stars had violent outbursts, up to 10,000 times as powerful as the strongest flares known on the Sun. In many cases there were multiple events on the same star. Younger stars were more likely to flare than old ones, but strong events were seen on stars as old as the Sun.

<span class="mw-page-title-main">DG Canum Venaticorum</span> Binary star in constellation Canes Venatici

DG Canum Venaticorum is a variable binary star system in the northern constellation of Canes Venatici. As of 2009, the pair have an angular separation of 0.20″ along a position angle of 285°, which corresponds to a physical separation of around 3.6 AU. With an apparent visual magnitude of 12.02, the pair are much too faint to be seen with the naked eye. Parallax measurements place the system at a distance of roughly 59 light years from the Earth.

<span class="mw-page-title-main">V1005 Orionis</span> Young flame star in the constellation of Orion

V1005 Orionis is a young flare star in the equatorial constellation of Orion. It has the identifier GJ 182 in the Gliese–Jahreiß catalogue; V1005 Ori is its variable star designation. This star is too faint to be visible to the naked eye, having a mean apparent visual magnitude of 10.1. It is located at a distance of 79.6 light years from the Sun and is drifting further away with a radial velocity of 19.2 km/s. The star is a possible member of the IC 2391 supercluster.

References

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