HD 28254

HD 28254 is an 8th magnitude G-type main sequence star located approximately 178 light years[1] away in the constellation Dorado. This star is larger, cooler, brighter, and more massive than our Sun. Also its metal content is 2.3 times as much as the Sun. In 2009, a gas giant planet was found in orbit around the star.

HD 28254
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Dorado
Right ascension 04h 24m 50.70s[1]
Declination –50° 37′ 19.9″[1]
Apparent magnitude (V) 7.69[2]
Characteristics
Spectral type G1IV/V[2]
Apparent magnitude (B) 8.41
Apparent magnitude (R) 7.7
Apparent magnitude (J) 6.395
Apparent magnitude (H) 6.13
Apparent magnitude (K) 6.006
B−V color index 0.722[2]
V−R color index 0.01
Astrometry
Radial velocity (Rv)−9.315±0.002[2] km/s
Proper motion (μ) RA: −67.15±0.59[1] mas/yr
Dec.: −144.50±0.53[1] mas/yr
Parallax (π)18.29 ± 0.53[1] mas
Distance178 ± 5 ly
(55 ± 2 pc)
Absolute magnitude (MV)4.001[2]
Details
Mass1.11 ± 0.01[3] M☉
Radius1.57 ± 0.02[3] R☉
Luminosity2.19 ± 0.01[3] L☉
Surface gravity (log g)4.08 ± 0.02[3] cgs
Temperature5607 ± 37[3] K
Metallicity [Fe/H]0.36 ± 0.03[2] dex
Rotation2.50 ± 1.0[2]
Age7.8 ± 0.4[3] Gyr
Other designations
CD–50°1385, GC 5376, HIP 20606, PPM 333464, SAO 233508 [4]
Database references
SIMBADdata
Exoplanet Archivedata
Extrasolar Planets
Encyclopaedia		data

Properties

HD 28254 is a G-type star with a spectral type G1IV/V,[2] indicating that it has begun its evolution off the main sequence. It is estimated to have a mass 11% larger than the Sun's, a radius 57% larger, and an age around 7.8 billion years. It has a luminosity of 1.57 times the solar luminosity and an effective temperature of about 5,600 K.[3] HD 28254 has a low activity level and a larger metallicity than the Sun, with 2.3 times the solar iron abundance.[2]

HD 28254 is the brighter component of a visual binary. Its companion, HD 28254 B, has a visual apparent magnitude of 13.8 and is located at a separation of 4.3 arcseconds. The two stars have maintained the same separation through time, indicating that they form a physical binary system.[5] Furthermore, the radial velocity of the primary shows signs of orbital motion. From its brightness, the companion star is probably a red dwarf with spectral type between M0V and M2V, with about 48% the solar mass. The projected separation between the stars is 235 AU, corresponding to an orbital period of more than 1,000 years.[2]

Planetary system

In 2010, the discovery of an exoplanet orbiting HD 28254 was published. It was detected by Doppler spectroscopy from observations with the HARPS spectrograph between October 2003 and April 2009. The best fit model for the 32 radial velocity data obtained consists of a planet in an eccentric 1116 days orbit, plus a quadratic trend that is probably caused by the star HD 28254 B.[2]

The planet is a gas giant with a minimum mass of 1.16 times the mass of Jupiter. It is at a mean distance of 2.15 AU from the star, and takes 1116 days to complete an orbit. Its orbit has a very high eccentricity of 0.81, carrying the planet between 0.41 and 3.90 AU from the star. This can be the result of gravitational interactions with the secondary star via the Kozai mechanism.[2]

The HD 28254 planetary system[2]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b ≥ 1.16+0.10
−0.06 MJ		 2.15+0.04
−0.05		 1116±26 0.81+0.05
−0.02		 — —

See also
  • List of extrasolar planets

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. Vizier catalog entry
  2. Naef, D.; et al. (2010). "The HARPS search for southern extrasolar planets XXIII. 8 planetary companions to low-activity solar-type stars". Astronomy and Astrophysics. 523. A15. arXiv:1008.4600. Bibcode:2010A&A...523A..15N. doi:10.1051/0004-6361/200913616. S2CID 118845989.
  3. Bonfanti, A.; Ortolani, S.; Nascimbeni, V. (2016). "Age consistency between exoplanet hosts and field stars". Astronomy & Astrophysics. 585: A5, 14 pp. arXiv:1511.01744. Bibcode:2016A&A...585A...5B. doi:10.1051/0004-6361/201527297. S2CID 53971692.
  4. "HD 28254 -- Double or multiple star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2018-01-01.
  5. Tokovinin, Andrei (2014). "From Binaries to Multiples. I. Data on F and G Dwarfs within 67 pc of the Sun". The Astronomical Journal. 147 (4): article 86, 14 pp. arXiv:1401.6825. Bibcode:2014AJ....147...86T. doi:10.1088/0004-6256/147/4/86. S2CID 53965918.

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