HD 205739 / Sāmaya
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Piscis Austrinus
Right ascension 21h 38m 08.40391s[1]
Declination −31° 44′ 14.9407″[1]
Apparent magnitude (V) 8.56[2]
Characteristics
Spectral type F7 V[3]
B−V color index 0.546±0.015[2]
Astrometry
Radial velocity (Rv)+9.30±0.30[2] km/s
Proper motion (μ) RA: +21.914[1] mas/yr
Dec.: −82.166[1] mas/yr
Parallax (π)10.7826 ± 0.1029 mas[1]
Distance302 ± 3 ly
(92.7 ± 0.9 pc)
Absolute magnitude (MV)3.42[2]
Details[4]
Mass1.329±0.003 M☉
Radius1.59±0.04 R☉
Luminosity3.52±0.01 L☉
Surface gravity (log g)4.15±0.02 cgs
Temperature6,276±41 K
Metallicity [Fe/H]0.21[5] dex
Rotational velocity (v sin i)4.06[5] km/s
Age2.8±0.2 Gyr
Other designations
Samaya, CD−32° 16667, HD 205739, HIP 106824, SAO 213152, PPM 301636[6]
Database references
SIMBADdata

HD 205739 is a yellow-white hued star in the southern constellation of Piscis Austrinus, positioned near the western constellation boundary with Microscopium. It has the proper name Sāmaya, which was selected in the NameExoWorlds campaign by Sri Lanka, during the 100th anniversary of the IAU. Sāmaya means peace in the Sinhalese language.[7][8]

With an apparent visual magnitude of 8.56,[2] this star requires a small telescope to view. It is located at a distance of approximately 302 light years from the Sun based on stellar parallax, and is drifting further away with a radial velocity of +9 km/s[2] This star has an absolute magnitude of 3.42.[2]

HD 205739 is an ordinary F-type main-sequence star with a stellar classification of F7 V.[3] This indicates that, like the Sun, it is generating energy through core hydrogen fusion. The star is 2.8[4] billion years old with an inactive chromosphere[9] and is spinning with a projected rotational velocity of 4 km/s.[5] It has 1.3 times the mass of the Sun and 1.6 times the Sun's radius.[4] The abundance of iron is 60% greater than in the Sun, suggesting a higher metallicity.[5] The star is radiating 3.5 times the luminosity of the Sun from its photosphere at an effective temperature of 6,276 K.[4]

A Jupiter-like planet has been detected in an eccentric orbit around this star via Doppler spectroscopy. The eccentricity of 0.27 indicates that the orbit carries the body from 0.65 AU out to 1.14 AU between periastron and apastron. The maximum surface temperature of the planet is ~400 K, varying by 100 K over the course of an orbit. There is a data trend in the results which may point to an additional companion further from its star, but this will require a longer observation period to validate.[9]

The HD 205739 planetary system[9]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b / Samagiya ≥1.37 MJ 0.896 279.8±0.1 0.27±0.07 — —

See also

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 5 6 7 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
  3. 1 2 Houk, Nancy (1979). Michigan catalogue of two-dimensional spectral types for the HD stars. Vol. 3. Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan. Bibcode:1982mcts.book.....H.
  4. 1 2 3 4 Bonfanti, A.; et al. (2015). "Revising the ages of planet-hosting stars". Astronomy and Astrophysics. 575: A18. arXiv:1411.4302. Bibcode:2015A&A...575A..18B. doi:10.1051/0004-6361/201424951. S2CID 54555839.
  5. 1 2 3 4 Delgado Mena, E.; et al. (April 2015). "Li abundances in F stars: planets, rotation, and Galactic evolution". Astronomy & Astrophysics. 576: A69. arXiv:1412.4618. Bibcode:2015A&A...576A..69D. doi:10.1051/0004-6361/201425433. S2CID 56051637. A69.
  6. ↑ "9 Cet". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-11-27.
  7. ↑ "Approved names". NameExoworlds. Retrieved 2020-01-02.
  8. ↑ "International Astronomical Union | IAU". www.iau.org. Retrieved 2020-01-02.
  9. 1 2 3 López-Morales, Mercedes; et al. (2008). "Two Jupiter-Mass Planets Orbiting HD 154672 and HD 205739". The Astronomical Journal. 136 (5): 1901–1905. arXiv:0809.1037. Bibcode:2008AJ....136.1901L. doi:10.1088/0004-6256/136/5/1901. S2CID 119242543.
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