R Trianguli Australis

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 6.73.^[3] Based upon an annual parallax shift of 1.48 mas,^[2] it is located 2,210 light years away. R TrA is moving closer with a heliocentric radial velocity of −13 km/s.^[7]

R Trianguli Australis

A light curve for R Trianguli Astralis, plotted from TESS data[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Triangulum Australe
Right ascension	15h 19m 45.71231s[2]
Declination	−66° 29′ 45.7417″[2]
Apparent magnitude (V)	6.73[3] (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[2] mas/yr Dec.: −8.317[2] mas/yr
Parallax (π)	1.4754±0.0371 mas[2]
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

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]