T Andromedae
T Andromedae (T And) is a variable star of the Mira type in the constellation Andromeda. Like all the stars of this kind, T And is a cool asymptotic giant branch star of spectral type M4e-M7.5e. Its brightness varies periodically, completing a cycle in 281 days. The peak luminosity, however, is different every variability cycle, but can reach a peak magnitude mv=7.70.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 00h 22m 23.14956s |
| Declination | +26° 59′ 45.73676″ |
| Apparent magnitude (V) | 7.70 – 14.30 variable |
| Characteristics | |
| Spectral type | M4e-M7.5e |
| B−V color index | 2.63 |
| Variable type | Mira |
| Astrometry | |
| Radial velocity (Rv) | −90±10 km/s |
| Proper motion (μ) | RA: −7.108 mas/yr Dec.: −3.352 mas/yr |
| Parallax (π) | 0.5913 ± 0.0815 mas |
| Distance | approx. 5,500 ly (approx. 1,700 pc) |
| Details | |
| Mass | 4.9 M☉ |
| Luminosity | 8.928 L☉ |
| Surface gravity (log g) | −0.51 cgs |
| Temperature | 3,235 K |
| Metallicity [Fe/H] | −0.39 dex |
| Other designations | |
| Database references | |
| SIMBAD | data |
Thomas David Anderson discovered that T Andromedae is a variable star, in 1894. The next year, Edward Charles Pickering examined archival photographic plates to derive a light curve for the star, and calculated a period of 281 days.
Measurements of the angular size variations of T And made with the Palomar Testbed Interferometer show no clear correlation with the star's brightness variations.