Eta Trianguli Australis

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Eta Trianguli Australis
Observation data
Epoch J2000.0        Equinox J2000.0 (ICRS)
Constellation Triangulum Australe
Right ascension 16h 41m 23.10722s [1]
Declination −68° 17′ 46.0412″ [1]
Apparent magnitude  (V)+5.91 [2]
Characteristics
Spectral type B7 V [3] or B7 IVe [4]
U−B color index −0.42 [2]
B−V color index −0.08 [2]
Astrometry
Radial velocity (Rv)−10.0±7.6 [5]  km/s
Proper motion (μ)RA: −14.067 [1]   mas/yr
Dec.: −11.535 [1]   mas/yr
Parallax (π)4.2679 ± 0.0842 [1]   mas
Distance 760 ± 20  ly
(234 ± 5  pc)
Absolute magnitude  (MV)−0.36 [6]
Details [7]
Mass 3.76±0.12  M☉
Luminosity 318  L☉
Temperature 12,162  K
Rotational velocity (v sin i)234 km/s
Age 199 [6]   Myr
Other designations
η TrA, CPD−68° 2789, GC  22379, HD  149671, HIP  81710, HR  6172, SAO  253649 [8]
Database references
SIMBAD data

Eta Trianguli Australis (η Trianguli Australis) is a solitary, [9] blue-white hued star in the southern constellation Triangulum Australe. It is sometimes given a superscript: η1 Trianguli Australis, though it is the only star that is commonly referred to by this Bayer designation. Lacaille named a close by star as Eta as well, which was inconsistently followed by Francis Baily, who used the name for the brighter or both stars in two different publications. Despite their faintness, Gould upheld their Bayer designation as they were closer than 25 degrees to the south celestial pole. The second Eta is now designated as HD 150550. [10]

This star is faintly visible to the naked eye with an apparent visual magnitude of +5.91. [2] Based upon an annual parallax shift of just 4.93  mas as seen from the Earth, it is located roughly 760  light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction of 0.28 due to interstellar dust. [6] The system appears to be moving closer to the Sun with a radial velocity of around −10 km/s. [5]

Eta Trianguli Australis is a B-type main-sequence star with a stellar classification of B7 V. [3] Although it has been classified as a B7 IVe Be subgiant star in the past, [4] Jaschek and Jaschek (1992) found no trace of emission in the spectrum. [11] Grady et al. (1989) reported only "weak or narrow double-peaked Hα emission, but no emission at Hβ". [12] The star shows a relatively high peculiar velocity of 40±20 km/s. [4] It is spinning rapidly with a projected rotational velocity of 234 km/s. [7]

Related Research Articles

Epsilon Trianguli Binary star in the constellation Triangulum

Epsilon Trianguli, Latinized from ε Trianguli, is a binary star system in the northern constellation of Triangulum. Based upon measurement of its trigonometric parallax, it is approximately 390 light years from Earth.

Gamma Trianguli Australis Star in the constellation Triangulum Australe

Gamma Trianguli Australis is a single, white-hued star in the southern constellation of Triangulum Australe. Along with Alpha and Beta Trianguli Australis it forms a prominent triangular asterism that gives the constellation its name. It is the third-brightest member of this constellation with an apparent visual magnitude of +2.87. based upon parallax measurements, Gamma Trianguli Australis is located at a distance of about 184 light-years from Earth.

Eta Tucanae Star in the constellation Tucana

Eta Tucanae, Latinized from η Tucanae, is a probable binary star system in the southern constellation of Tucana, a few degrees to the north of Epsilon Tucanae. It is visible to the naked eye as a dim, white-hued point of light with an apparent visual magnitude of +5.00. parallax measurements provide a distance estimate of about 154 light years from the Sun, and it is drifting further away with a mean radial velocity of +32.5 km/s. It is a member of the 30 million year old Tucana-Horologium association of co-moving stars.

18 Andromedae, abbreviated 18 And, is a single star in the northern constellation of Andromeda. 18 Andromedae is the Flamsteed designation. It is visible to the naked eye with an apparent visual magnitude of 5.350. The annual parallax shift of 7.9 mas can be used to estimate a distance of 413 light years. It is moving further from the Earth with a heliocentric radial velocity of +10 km/s.

18 Aurigae is a star located 233 light years away from the Sun in the northern constellation of Auriga. The brightness of this object is near the limit of visibility to the naked eye under good viewing conditions, appearing as a dim, white-hued star with an apparent visual magnitude of 6.49. The star is moving away from the Sun with a heliocentric radial velocity of 7 km/s.

Nu<sup>2</sup> Boötis Star in the constellation Boötes

Nu2 Boötis is a white-hued binary star system in the northern constellation of Boötes. It is faintly visible to the naked eye with a combined apparent visual magnitude of 5.02. Based upon an annual parallax shift of 7.86 mas as seen from the Earth, it is located roughly 415 light years from the Sun. The system is moving closer to the Sun with a radial velocity of −16.6 km/s.

Eta Canis Minoris Star in the constellation Canis Minor

Eta Canis Minoris is a binary star system in the equatorial constellation of Canis Minor. It is approximately 318 light-years from Earth.

HD 102776, also known by its Bayer designation j Centauri, is a suspected astrometric binary star system in the southern constellation of Centaurus. It has a blue-white hue and is faintly visible to the naked eye with a typical apparent visual magnitude of 4.30. The distance to this star is approximately 600 light years based on parallax, and it is drifting further away with a radial velocity of ~29 km/s. It is a member of the Lower Centaurus Crux subgroup of the Sco OB2 association. HD 102776 has a relatively large peculiar velocity of 31.1 km/s and is a candidate runaway star that was ejected from its association, most likely by a supernova explosion.

3 Centauri is a triple star system in the southern constellation of Centaurus, located approximately 300 light years from the Sun. It is visible to the naked eye as a faint, blue-white hued star with a combined apparent visual magnitude of 4.32. As of 2017, the two visible components had an angular separation of 7.851″ along a position angle of 106°. The system has the Bayer designation k Centauri; 3 Centauri is the Flamsteed designation. It is a suspected eclipsing binary with a variable star designation V983 Centauri.

HD 16004 is blue-white hued star in the northern constellation of Andromeda. It is a challenge to see with the naked eye even under good viewing conditions, having an apparent visual magnitude of 6.26. Located approximately 660 light-years away from the Sun based on parallax, it is drifting closer with a heliocentric radial velocity of −7 km/s.

VZ Arietis is single, white-hued star in the northern zodiac constellation of Aries. Varying between magnitudes 5.82 and 5.89, the star can be seen with the naked eye in dark, unpolluted areas. Based upon an annual parallax shift of 5.8 mas, it is located 560 light years from the Sun. It is moving further away with a heliocentric radial velocity of +14 km/s. The star was formerly known as 16 Trianguli, but as the star is no longer in the constellation Triangulum, this designation has fallen out of use.

HD 32188 Star in the constellation Auriga

HD 32188 is suspected variable star in the northern constellation of Auriga, and is positioned roughly in between Eta and Zeta Aurigae. It has a white hue and is just barely visible to the naked eye with an apparent visual magnitude that fluctuates around 6.08. The distance to this star is approximately 3,000 light years, based on parallax. It has an absolute magnitude of −2.87.

21 Vulpeculae is a single, white-hued star in the northern constellation of Vulpecula. Its distance can be estimated from the annual parallax shift of 10.4302±0.0696 mas, yielding a separation of 313 light years. The star is faintly visible to the naked eye at night, having an apparent visual magnitude of 5.19. It is moving further away with a heliocentric radial velocity of about +7 km/s, having come within 243 ly (74.53 pc) around 4.2 million years ago.

Eta1 Coronae Australis, Latinized from η1 CrA, is a suspected astrometric binary star system in the constellation of Corona Australis. It is visible to the naked eye as a dim, white-hued point of light with an apparent visual magnitude of 5.456. Parallax measurements put it at a distance of 317 light-years away from the Sun.

Iota1 Cygni, Latinized from ι1 Cygni, is a probable binary star system in the northern constellation Cygnus, and is separated by less than a degree from its brighter visual neighbor, Iota2 Cygni. It is near the lower limit of visibility to the naked eye with an apparent visual magnitude of 5.75. The system is located approximately 387 light years away based on parallax, and it is drifting further away with a radial velocity of +2 km/s.

HD 16754 is a binary or triple-star system in the constellation Eridanus. It has the Bayer designation s Eridani; HD 16754 is the designation from the Henry Draper catalogue. The system is visible to the naked eye as a faint point of light with an apparent visual magnitude of +4.74. It is located at a distance of approximately 132 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +18 km/s. The system is a member of the Columba association of co-moving stars.

74 Cygni is a visual binary star system in the northern constellation Cygnus, located around 249 light years distant from the Sun. It is visible to the naked eye as a faint, white-hued star with a combined apparent visual magnitude of 5.04. The pair orbit each other with a period of 1.57 years and an eccentricity of 0.5. The system is a source of X-ray emission, which is most likely coming from the secondary component.

Sigma1 Gruis, a Latinization of σ1 Gruis, is a star in the constellation Grus. It is a dim, white-hued star near the lower limit for visibility to the naked eye with an apparent visual magnitude of 6.26. This object is located 229 light-years (70.1 pc) distant from the Sun based on parallax. The radial velocity of this star is poorly constrained, but it appears to be drifting further away at the rate of +7 km/s.

HR 4339 is a single star in the equatorial constellation of Hydra. It was designated as Beta Antliae by Lacaille, and Gould intended to keep it in that constellation. However, the delineating of constellation boundaries by the IAU in 1930 saw it transferred to Hydra. It has a white hue and is just visible to the naked eye with an apparent visual magnitude of 5.79. The distance to this star, as determined from parallax measurements, is approximately 366 light years. It is drifting further away with a radial velocity of +1.3 km/s.

V4024 Sagittarii is a single variable star in the southern constellation of Sagittarius. It has a blue-white hue and is dimly visible to the naked eye with an apparent visual magnitude that fluctuates around 5.49. The star is located at a distance of approximately 1,700 light years based on stellar parallax, but is drifting closer with a radial velocity of −20 km/s. The position of this star near the ecliptic means it is subject to lunar occultations.

References

  1. 1 2 3 4 5 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics . 616. A1. arXiv: 1804.09365 . Bibcode: 2018A&A...616A...1G . doi: 10.1051/0004-6361/201833051 . Gaia DR2 record for this source at VizieR.
  2. 1 2 3 4 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. 1 2 Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, 1, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  4. 1 2 3 Berger, D. H.; Gies, D. R. (July 2001), "A Search for High-Velocity Be Stars", The Astrophysical Journal, 555 (1): 364–367, Bibcode:2001ApJ...555..364B, doi: 10.1086/321461 .
  5. 1 2 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.
  6. 1 2 3 Gontcharov, G. A. (November 2012), "Spatial distribution and kinematics of OB stars", Astronomy Letters, 38 (11): 694–706, arXiv: 1606.09028 , Bibcode:2012AstL...38..694G, doi:10.1134/S1063773712110035, S2CID   119108982.
  7. 1 2 Zorec, J.; Royer, F. (January 2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv: 1201.2052 , Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID   55586789.
  8. ↑ "eta01 TrA". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2017-09-14.CS1 maint: postscript (link)
  9. ↑ 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.
  10. ↑ Wagman, Morton (2003), Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others, Blacksburg, VA: The McDonald & Woodward Publishing Company, pp. 303–04, Bibcode:2003lslm.book.....W, ISBN   978-0-939923-78-6
  11. ↑ Jaschek, C.; Jaschek, M. (November 1992), "A southern Be star survey - Spectra and envelope radii", Astronomy and Astrophysics Supplement Series, 95 (3): 535–540, Bibcode:1992A&AS...95..535J.
  12. ↑ Grady, C. A.; et al. (April 1, 1989), "Highly ionized stellar winds in Be stars. II - Winds in B6-B9.5e stars", Astrophysical Journal, Part 1, 339: 403–419, Bibcode:1989ApJ...339..403G, doi:10.1086/167306.
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