R Trianguli
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Triangulum |
| Right ascension | 02h 37m 02.340s |
| Declination | +34° 15′ 51.34″ |
| Apparent magnitude (V) | 5.4–12.6 |
| Characteristics | |
| Spectral type | M3.5-8IIIe |
| Apparent magnitude (B) | 8.524±0.018 |
| Apparent magnitude (G) | 6.699±0.055 |
| Apparent magnitude (R) | 8.24 |
| Apparent magnitude (J) | 2.23±0.27 |
| Apparent magnitude (H) | 1.36±0.22 |
| Apparent magnitude (K) | 1.05±0.21 |
| Variable type | Mira |
| Astrometry | |
| Radial velocity (Rv) | 67.52±0.88 km/s |
| Proper motion (μ) | RA: +34.272 mas/yr Dec.: −10.683 mas/yr |
| Parallax (π) | 2.4334±0.2487 mas |
| Distance | approx. 1,300 ly (approx. 410 pc) |
| Details | |
| Mass | 1.71 M☉ |
| Radius | 196±41 R☉ |
| Luminosity | 1,784 L☉ |
| Surface gravity (log g) | −0.09 cgs |
| Temperature | 3184±120 K |
| Other designations | |
| R Tri, HR 758, HD 16210, HIP 12193, 2MASS J02370234+3415513, Gaia DR2 134874621777526400, Gaia DR3 134874621778128896 | |
| Database references | |
| SIMBAD | data |
R Trianguli (abbreviated as R Tri) is a short-period oxygen-rich Mira variable in Triangulum with a period of 266.9 days, discovered by T. H. E. C. Espin in 1890. When it is near its maximum brightness, it is faintly visible to the naked eye under excellent observing conditions.
The star is losing about 1.1×10−7 M☉/yr, close to average for a short-period Mira variable. While most short-period Mira variables reside in the Galactic halo, R Trianguli is a member of the thick disk, and its proper motion is fairly high for its distance. Its angular diameter in the K band was measured in 2002 to be, on average, 5.22±0.30 mas, with a shape suggesting that there is an optically thin disk structure surrounding the star.