R Trianguli Australis
Variable star in the constellation Triangulum Australe
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R Trianguli Australis is a yellow-white hued variable star in the southern constellation Triangulum Australe. It is near the limit of visibility to the naked eye, having a typical apparent visual magnitude of about six. Based upon an annual parallax shift of 1.48 mas,[3] it is located 2,210 light years away. R TrA is moving closer with a heliocentric radial velocity of −13 km/s.[7]
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Triangulum Australe[2] |
| Right ascension | 15h 19m 45.71231s[3] |
| Declination | −66° 29′ 45.7417″[3] |
| Apparent magnitude (V) | 6.33 - 6.90[4] |
| Characteristics | |
| Spectral type | F7 Ib/II[5] |
| Variable type | δ Cep[6] |
| Astrometry | |
| Radial velocity (Rv) | −13.2±1.6[7] km/s |
| Proper motion (μ) | RA: −5.113[3] mas/yr Dec.: −8.317[3] mas/yr |
| Parallax (π) | 1.4754±0.0371 mas[3] |
| Distance | 2,210 ± 60 ly (680 ± 20 pc) |
| Absolute magnitude (MV) | 2.69[8] |
| Details | |
| Mass | 5.42 or 5.66[9] M☉ |
| Radius | 24.7±1.9[10] or 35.8±0.8[9] R☉ |
| Surface gravity (log g) | 2.10[9] cgs |
| Temperature | 5,852±21[9] K |
| Metallicity [Fe/H] | +0.06±0.08[8] dex |
| Rotational velocity (v sin i) | 16 km/s |
| Other designations | |
| R TrA, CD−66° 1728, HD 135592, HIP 75018, SAO 253107[11] | |
| Database references | |
| SIMBAD | data |
Benjamin Apthorp Gould discovered that the star's brightness varies, in 1871.[12] This is a Classical Cepheid variable with an apparent magnitude that ranges from 6.33 to 6.90 over 3.38926 days.[4] It is a bright giant/supergiant with a nominal stellar classification of F7 Ib/II,[5] but pulsates between spectral types F5Ib/II-G5.[4] Depending on the method employed, the estimated mass is 5.42 or 5.66 times the mass of the Sun and it has 24.7 or 35.8 times the Sun's radius.[9] R TrA has an infrared excess that is being emitted by circumstellar silicate dust heated to 150–200 K. It is losing mass at the rate of 4×10−9 M☉·y−1.[9]