X Trianguli Australis is a star in the southern constellation Triangulum Australe. It is a red-hued carbon star approximately 920 light years (280 parsecs) from Earth, though this could vary by up to 200 light years.[10] It is a semi-regular variable star with two periods of around 385 and 455 days, and is of spectral type C5.5(Nb).[1] It ranges from magnitudes 5.03 to 6.05.[11] Its designation is from the variable star designation developed by German astronomer Friedrich Wilhelm Argelander.

X Trianguli Australis

A visual band light curve for X Trianguli Australis, plotted from data published by Tabur et al. (2009)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Triangulum Australe
Right ascension	15h 14m 19.17448s[2]
Declination	−70° 04′ 46.1266″[2]
Apparent magnitude (V)	+5.75[3]
Characteristics
Spectral type	C5.5[4]
B−V color index	3.271±0.019[3]
Variable type	Lb[5]
Astrometry
Radial velocity (Rv)	−3.2±1.5[6] km/s
Proper motion (μ)	RA: +4.276[2] mas/yr Dec.: −7.566[2] mas/yr
Parallax (π)	3.5388 ± 0.1944 mas[2]
Distance	920 ± 50 ly (280 ± 20 pc)
Absolute magnitude (MV)	−1.97[3]
Details
Mass	4.1[7] M☉
Radius	257[7] R☉
Luminosity (bolometric)	8,599[8] L☉
Temperature	2,860±350[8] K
Other designations
X TrA, CPD−69°2267, HD 134453, HIP 74582, HR 5644, SAO 253062[9]
Database references
SIMBAD	data

It is a cool star, with estimates of its surface temperature ranging from 2,200 to 2,700 Kelvin.[10] A giant star, its diameter is 400 times that of the sun, and if placed at the center of the Solar System would stretch out to 30% further than Mars' orbit. Its absolute magnitude is −2.0.[10]

References