UV Ceti

Catalog numbers:
     Luyten (L) 726-8, Luyten Double Star (LDS) 838, Gliese (Gl) 65, Giclas (G) 272-61
Arity: binary
Points of interest:
     Properly, only the less bright star in this system (Luyten 726-8 B) bears the name UV Ceti, since it is a variable star — the UV indicates that this was the 35th variable star discovered in the constellation Cetus. It is an extreme flare star; in less than a minute, it can quintuple its total brightness, afterwhich it will fall back down to normal brightness levels within two or three minutes; and then flare suddenly again after several hours. In 1952, UV Ceti was observed flaring to 75 times its normal brightness in only 20 seconds!
     If van de Kamp's orbital data are to be believed, these two stars would have to be exceedingly small and light -- their masses would be only 0.044 x Sol for the "A" star and 0.035 x Sol for UV Ceti. This would mean that, although each of these stars is brighter than Wolf 359, Wolf 359 would have a higher mass than both of these stars combined. However, if we assume that Worley & Behall's orbital data are the more accurate, the two stars' total mass would be 0.23 x Sol, which is more in keeping with the measurements of both their luminosities and their diameters.

Right Ascension and Declination: 1h36m25s, -18°12'42" (epoch 1950.0)
Distance from Sol: 8.554 light-years (2.623 parsecs)
Standard error in distance: 0.113%
Source for distance: Gliese
Celestial (X,Y,Z) coordinates in ly: 7.417, 3.318, -2.673
Galactic (X,Y,Z) coordinates in ly: -2.102, 0.169, -8.290
Proper motion: 3.368 arcsec/yr (80.4° from north)
Source for proper motion: Gliese

What do all these fields mean?

Data for A and B's orbit around one other:
Combined absolute visual magnitude: +14.79
Combined visual luminosity: 0.000106 x Sol
Period: 200 years
Semimajor Axis: 14.61 A.U.s
Eccentricity: 0.718
Periastron distance: 4.119 A.U.s
Apastron distance: 25.10 A.U.s
Year in which periastron occurs: 1949
Source for orbit data: P. van de Kamp
As seen from A:
     At periastron, B would appear as magnitude -12.89
     At apastron, B would appear as magnitude -8.97
As seen from B:
     At periastron, A would appear as magnitude -13.02
     At apastron, A would appear as magnitude -9.10

Data for A and B's orbit, take 2:
Period: 26.52 years
Semimajor Axis: 5.455 A.U.s
Eccentricity: 0.615
Periastron distance: 2.100 A.U.s
Apastron distance: 8.810 A.U.s
Year in which periastron occurs: 1971.88
Source for orbit data: Worley & Behall
As seen from A:
     At periastron, B would appear as magnitude -14.35
     At apastron, B would appear as magnitude -11.24
As seen from B:
     At periastron, A would appear as magnitude -14.48
     At apastron, A would appear as magnitude -11.37

Component A:
Proper names: BL Ceti
Catalog numbers:
Luyten Half-Second (LHS) 9
Proper motion: 3.368 arcsec/yr (80.4° from north)
Radial Velocity: 29 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -43.00, -19.19, -19.42
Spectral class: M5.5e
Luminosity Class: V
Apparent visual magnitude: +12.57
Absolute visual magnitude: +15.48
Visual luminosity: 0.0000561 x Sol
Variable type: UV Ceti flare star (eruptive variable)
Mass: 0.12 x Sol
Diameter: 0.15 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 0.00749 A.U.s
Orbital period in CZ: 16.4112 hours
Tidal index in CZ: 285314
Angular size of star in sky in CZ: 10.673077 degrees

Component B:
Proper names: UV Ceti, Luyten's Flare Star
Catalog numbers:
Luyten Half-Second (LHS) 10
Proper motion: 3.368 arcsec/yr (80.4° from north)
Radial Velocity: 32 km/sec
Source for proper motion and radial velocity: Gliese
Galactic (U,V,W) velocity components in km/s: -43.74, -19.13, -22.33
Spectral class: M6e
Luminosity Class: V
Apparent visual magnitude: +12.70 (increasing to +8.00)
Absolute visual magnitude: +15.61 (increasing to +10.91)
Visual luminosity: 0.0000498 x Sol (increasing to 0.00378 x Sol)
Variable type: UV Ceti flare star (eruptive variable)
Mass: 0.1 x Sol
Diameter: 0.14 x Sol
Source for diameter: Apparent Diameters and Absolute Radii of Stars (Fracassini+ 1988)
Comfort Zone (visual): 0.00706 A.U.s
Orbital period in CZ: 16.4334 hours
Tidal index in CZ: 284542
Angular size of star in sky in CZ: 10.576152 degrees

Data for this star system were most recently updated on 4-April-2001.