Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Andromeda |
Right ascension | 23h 11m 32.08609s[2] |
Declination | +36° 53′ 35.10721″[2] |
Apparent magnitude (V) | 9.49 ( – 10.32) – 10.46[3] |
Characteristics | |
Spectral type | G5+G5V[3] |
Apparent magnitude (B) | 10.62[4] |
Apparent magnitude (V) | 9.675[4] |
Apparent magnitude (G) | 9.6953[2] |
Apparent magnitude (J) | 8.172[5] |
Apparent magnitude (H) | 7.805[5] |
Apparent magnitude (K) | 7.665[5] |
B−V color index | 0.9163[4] |
Variable type | EW |
Astrometry | |
Radial velocity (Rv) | −27.53±0.67[6] km/s |
Proper motion (μ) | RA: 107.923±0.046 [2] mas/yr Dec.: −53.357±0.036[2] mas/yr |
Parallax (π) | 11.7027 ± 0.0367 mas[2] |
Distance | 278.7 ± 0.9 ly (85.5 ± 0.3 pc) |
Orbit[7] | |
Period (P) | 0.3319 days |
Semi-major axis (a) | 2.308 R☉[8] |
Eccentricity (e) | 0.002±0.001 |
Argument of periastron (ω) (secondary) | 40±5° |
Argument of periastron (ω) (primary) | 220±5° |
Semi-amplitude (K1) (primary) | 233±1 km/s |
Semi-amplitude (K2) (secondary) | 133±1 km/s |
Details[9] | |
Primary | |
Mass | 1.04 M☉ |
Radius | 1.03 R☉ |
Surface gravity (log g) | 4.392[10] cgs |
Temperature | 5,798 K |
Age | 5.53±2.00[8] Gyr |
Secondary | |
Mass | 0.60 M☉ |
Radius | 0.78 R☉ |
Surface gravity (log g) | 4.347[10] cgs |
Temperature | 5,450 K |
Age | 5.53±2.00[8] Gyr |
Other designations | |
Database references | |
SIMBAD | data |
AB Andromedae (AB And) is a binary star in the constellation Andromeda. Paul Guthnick and Richard Prager discovered that the star is an eclipsing binary in 1927.[11][12] Its maximum apparent visual magnitude is 9.49 but shows a variation in brightness down to a magnitude of 10.46 in a periodic cycle of roughly 8 hours. The observed variability is typical of W Ursae Majoris variable stars,[3] so the two stars in this system form a contact binary.
The observed spectral type of both stars in this system is G5, and one of them is a main sequence star very similar to the sun.[3] They are orbiting so close that their envelopes touch each other. This is a dynamically stable phase that should last until one of the two stars leaves the main sequence.
The system could also host a third body with an orbital period of 19,046 days, with a minimum mass of 0.007 M☉ and an eccentricity of 0.22, but not all data collected in time are consistent with this hypothesis.[7]
The two stars eclipse each other during their orbit, but they have an elongated shape so they show a constant variation instead of discrete eclipses. Anyway, a periodicity can be seen clearly, but it changes with time; the period shows a long-term trend and a periodic modulation of 7,000 days. The effects responsible for this behaviour could be a third body in the system, magnetic interaction between two stars,[9] mass transfer from one star to the other, mass loss of the system, and recently even an internal mechanism in the touching envelopes have been proposed.[10]