Iota Trianguli Australis

Iota Trianguli Australis (ι Trianguli Australis) is a binary star[10] system in the constellation Triangulum Australe. It is visible to the naked eye with a combined apparent visual magnitude of +5.27.[2] Based upon an annual parallax shift of 25.77 mas as seen from the Earth, it is located around 127 light years from the Sun. The system appears to be moving closer to the Sun with a radial velocity of around −6 km/s.[5] It shows itself to be composed of a yellow and a white star when seen though a 7.5 cm telescope.[11]

Iota Trianguli Australis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Triangulum Australe
Right ascension  16h 27m 57.34498s[1]
Declination −64° 03′ 28.5964″[1]
Apparent magnitude (V) +5.27[2]
Characteristics
Spectral type F4 IV[3]
U−B color index −0.02[2]
B−V color index +0.36[2]
Variable type γ Dor[4]
Astrometry
Radial velocity (Rv)−5.6±4.2[5] km/s
Proper motion (μ) RA: +53.12[1] mas/yr
Dec.: +25.45[1] mas/yr
Parallax (π)25.77 ± 0.51[1] mas
Distance127 ± 3 ly
(38.8 ± 0.8 pc)
Absolute magnitude (MV)+2.34[6]
Orbit[4]
Period (P)39.880±0.002 d
Eccentricity (e)0.253±0.004
Periastron epoch (T)54661.65 ± 0.11 HJD
Argument of periastron (ω)
(secondary)		93.1±1.1°
Semi-amplitude (K1)
(primary)		38.4±0.3 km/s
Semi-amplitude (K2)
(secondary)		43.9±0.3 km/s
Details
ι TrA A
Mass1.42[7] M☉
Surface gravity (log g)4.28±0.14[7] cgs
Temperature7,045±240[7] K
Metallicity [Fe/H]−0.16[8] dex
Rotational velocity (v sin i)13.0±0.9[6] km/s
Age735[7] Myr
ι TrA B
Rotational velocity (v sin i)10.0±1.7[6] km/s
Other designations
ι TrA, CPD−63° 3923, GC 22100, HD 147787, HIP 80645, HR 6109, SAO 253555, CCDM 16280-6403, WDS J16280-6403A[9]
Database references
SIMBADdata

This is a double-lined spectroscopic binary system with an orbital period of 39.88 days and an eccentricity of 0.25. The brighter member, component A, is yellow-white hued F-type subgiant star and a Gamma Doradus type variable, pulsating by 0.12 magnitudes with a dominant period of 1.45 days.[4] There a magnitude 9.42 visual companion, located 16.2 arcseconds away.[12]

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.
  2. Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
  3. Malaroda, S. (August 1975), "Study of the F-type stars. I. MK spectral types", Astronomical Journal, 80: 637–641, Bibcode:1975AJ.....80..637M, doi:10.1086/111786.
  4. De Cat, P.; et al. (2009), "Is HD147787 a double-lined binary with two pulsating components? Preliminary results from a spectroscopic multi-site campaign", AIP Conference Proceedings, 1170: 483–85, Bibcode:2009AIPC.1170..483D, doi:10.1063/1.3246549.
  5. 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, A61.
  6. Ammler-von Eiff, M.; Reiners, A. (2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: 31, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724, A116.
  7. David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146.
  8. Casagrande, L.; et al. (June 2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy and Astrophysics, 530: A138, arXiv:1103.4651, Bibcode:2011A&A...530A.138C, doi:10.1051/0004-6361/201016276.
  9. "iot TrA". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-09-17.
  10. 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.
  11. Hartung, Ernst Johannes (1984), Astronomical Objects for Southern Telescopes, with an Addendum for Northern Observatories: A Handbook for Amateur Observers, CUP Archive, p. 214, ISBN 0521318874.
  12. Mason, B. D.; et al. (2014), The Washington Visual Double Star Catalog, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
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