Flare on UV Ceti, Jan 23, 1959

A flaring UV Ceti was resolved as at least two evolving spatial components that were separated by four to five stellar radii, in this VLBA/VLA radio image at 3.6 cm wavelength. The components changed in appearance over about six hours of observation but stayed aligned along the axis of the binary orbit, as shown by the arrow. . - best seen in the UV/ble part, quite faint in visible (especially shorter wavelengths)

UV Ceti (flare star, aka eruptive star)

- Constellation: Cetus
- fainter member of the star system
- Right ascension: 01 h, 39m, 1.3 sec
- Declination: -17h 57m
- Spectral type: M5.5e/M6eV
- Type of variable star
- Parallax: 373.7 +/- 2.7 mas (milliarcsecond)

System data

- Period: 26.5 years
- Semimajor axis: 1.95”
- Eccentricity: 0.62

Calculation data

- Mass: 0.1 solar masses
- Radius: 0.14 solar radiuses
- Luminosity: .00004/.00006 solar luminosities
- Temp: 2670 K
- Visual magnitude: 15.3/ 15.8
- Distance: 2.63 pc or 8.57 light-years

As a class, the known flare stars have spectral types of late M through late-K, corresponding
to temperatures between about 2500 to 4000 K. Often, they have detectable emission
lines of hydrogen and calcium in their spectra, indicating chromospheric activity.. They
have masses between 0.1 and 0.6 times that of the Sun; some brown dwarfs may
exhibit flaring activity, though the study of these stars is still very much in its infancy
Many of the known flare stars are members of young stellar associations (e.g. the
Orion and Taurus star-forming regions), though some older flare stars are known.
Many are also known to be binary stars, and this may correspond to an increased
likelihood of activity. Some of the UV Ceti flare stars are also members of the BY Draconis
class of spotted variables.

- Extreme flare star: can boost its brightness by five times in less than a minute,
then fall somewhat slower back down to normal luminosity within two or three
minutes before flaring suddenly again after several hours

- Flare star: variable star which can undergo unpredictable dramatic increases in
brightness for a few minutes or a few hours. The brightness increase is across the
spectrum, from X rays to radio waves – usually red dwarfs, may be brown dwarfs

- UV Ceti is the prototype for flare stars

- Discovered (star system) 1948 by Willem Jacob Luyten (2 low-mass red dwarfs)

- both members of the system are flare stars

- Flaring believed to be similar to solar flares: sudden release of energy via magnetic
reconnection: coupling of solar material and magnetic fields à prevents convection
(sunspot) à magnetic field rearranges self to a lower-energy configuration à rapidly
heated solar plasma à solar flare (light rays and particles go flying): but flares are much
bigger in proportion to the star

- 6th closest star system