Epsilon Trianguli Australis

Epsilon Trianguli Australis, Latinized from ε Trianguli Australis, is a star in the southern circumpolar constellation of Triangulum Australe. It is visible to the naked eye with an apparent visual magnitude of +4.11.^[2] Based upon an annual parallax shift of 16.17 mas as seen from the Earth,^[1] the star is located about 340 light years from the Sun. The star is moving closer to the Sun with a radial velocity of around −15.5 km/s.^[4]

Epsilon Trianguli Australis

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Triangulum Australe
Right ascension	15h 36m 43.22223s[1]
Declination	−66° 19′ 01.3334″[1]
Apparent magnitude (V)	+4.11[2]
Characteristics
Spectral type	K0 III[3]
U−B color index	+1.16[2]
B−V color index	+1.17[2]
Astrometry
Radial velocity (Rv)	−15.5±2.7[4] km/s
Proper motion (μ)	RA: +24.35[1] mas/yr Dec.: −54.47[1] mas/yr
Parallax (π)	16.17 ± 0.18 mas[1]
Distance	202 ± 2 ly (61.8 ± 0.7 pc)
Absolute bolometric magnitude (Mbol)	−0.16±0.10[5]
Details[5]
Mass	1-2 M☉
Radius	16.2±0.2 R☉
Luminosity	91 L☉
Surface gravity (log g)	2.20+0.14 −0.19 cgs
Temperature	4,436 K
Other designations
ε TrA, CPD−65° 3102, FK5 574, HD 138538, HIP 76440, HR 5771, SAO 253226, WDS J15367-6619[6]
Database references
SIMBAD	data

This is an evolved K-type giant star with a stellar classification of K0 III.^[3] It has around 1−2 times the mass of the Sun and has expanded to 16.2 times the Sun's radius. The star is radiating 91 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,039 K.^[5] It has an A5 type^[7] magnitude 9.36 companion at an angular separation of 81.9 arc seconds along a position angle of 220°, as of 2010.^[8] The pair may form a wide binary system.^[7]

References

1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
3. Buscombe, W. (1962), "Spectral classification of Southern fundamental stars", Mount Stromlo Observatory Mimeogram, 4: 1, Bibcode:1962MtSOM...4....1B.
4. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
5. Cruzalèbes, P.; et al. (September 2013), "Fundamental parameters of 16 late-type stars derived from their angular diameter measured with VLTI/AMBER", Monthly Notices of the Royal Astronomical Society, 434 (1): 437–450, arXiv:1306.3288, Bibcode:2013MNRAS.434..437C, doi:10.1093/mnras/stt1037.
6. "eps TrA". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-06-30.{{cite web}}: CS1 maint: postscript (link)
7. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
8. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2015-07-22 "Optical pair, based on study of relative motion of the components using the method of apparent motion parameters. —DUN 188"