Astronomy:HD 27894

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Short description: Star in the constellation Reticulum
HD 27894
Observation data
Equinox J2000.0]] (ICRS)
Constellation Reticulum[1]
Right ascension  04h 20m 47.046s[2]
Declination −59° 24′ 39.02″[2]
Apparent magnitude (V) 9.36[1]
Characteristics
Spectral type K2 V[3]
U−B color index +0.90[4]
B−V color index +1.003±0.002[1]
Astrometry
Radial velocity (Rv)82.785±0.0008[5] km/s
Proper motion (μ) RA: 182.473±0.012[2] mas/yr
Dec.: 270.012±0.017[2] mas/yr
Parallax (π)22.8888 ± 0.0121[2] mas
Distance142.50 ± 0.08 ly
(43.69 ± 0.02 pc)
Absolute magnitude (MV)6.225[6]
Details
Mass0.83±0.03[7] M
Radius0.79±0.02[7] R
Luminosity0.33±0.01[7] L
Surface gravity (log g)4.56±0.03[7] cgs
Temperature4,923±32[7] K
Metallicity [Fe/H]+0.30±0.07[6] dex
Rotation44 days[6]
Rotational velocity (v sin i)≤ 1.5[6] km/s
Age7.7±2.3[8] Gyr
Other designations
CD−59° 829, HD 27894, HIP 20277, LTT 1953[4]
Database references
SIMBADdata

HD 27894 is a single star with a system of orbiting exoplanets, located in the southern constellation of Reticulum. It is too faint to be seen with the naked eye at an apparent visual magnitude of 9.36.[1] This system lies at a distance of 142.5 light years from the Sun, as determined via parallax measurements, and is drifting further away with a radial velocity of 83 km/s.[5]

The spectrum of HD 27894 presents as a K-type main-sequence star, an orange dwarf,[6] with a stellar classification of K2 V.[3] This is a quiescent solar-type star that displays no significant magnetic activity in its chromosphere[9] and is spinning slowly with a rotation period of roughly 44 days.[6] The abundance of iron in the star is much higher than in the Sun, an indicator that it is metal-rich.[6] It has 83% of the mass of the Sun and 79% of the Sun's radius. The star is radiating 33% of the luminosity of the Sun from its photosphere at an effective temperature of 4,923 K.[7]

Planetary system

In 2005, the Geneva Extrasolar Planet Search Team announced the discovery of an extrasolar planet orbiting the star.[6] In 2017, the discovery of two additional exoplanets was announced. One is very close to the star like the one discovered earlier, while the other one orbits the star at a much larger distance. It is the first system where such a large gap between orbital distances has been found.[9][10] In 2022, the inclination and true mass of HD 27894 d were measured via astrometry. The study only found strong evidence for planets b and d.[11]

The HD 27894 planetary system[9][11]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
Eccentricity Inclination Radius
b ≥0.665+0.009
−0.007
 MJ
0.125±0.0001 18.02+0.01
−0.02
0.047+0.012
−0.008
c ≥0.162+0.011
−0.040
 MJ
0.198±0.001 36.07+0.26
−0.09
0.015+0.020
−0.002
d 6.493+0.987
−0.353
 MJ
5.362+0.206
−0.223
5019.5+32.6
−31.1
0.343+0.031
−0.026
101.524+14.742
−31.503
°

See also

  • List of extrasolar planets

References

  1. 1.0 1.1 1.2 1.3 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode2012AstL...38..331A. 
  2. 2.0 2.1 2.2 2.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. 3.0 3.1 Houk, Nancy (1979). Michigan catalogue of two-dimensional spectral types for the HD stars. Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan. Bibcode1978mcts.book.....H. 
  4. 4.0 4.1 "HD 27894". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+27894. 
  5. 5.0 5.1 Soubiran, C. et al. (2018). "Gaia Data Release 2. The catalogue of radial velocity standard stars". Astronomy and Astrophysics 616: A7. doi:10.1051/0004-6361/201832795. Bibcode2018A&A...616A...7S. 
  6. 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 Moutou, C. et al. (2005). "The HARPS search for southern extra-solar planets IV. Three close-in planets around HD 2638, HD 27894 and HD 63454". Astronomy and Astrophysics 439 (1): 367–373. doi:10.1051/0004-6361:20052826. Bibcode2005A&A...439..367M. 
  7. 7.0 7.1 7.2 7.3 7.4 7.5 Bonfanti, A. et al. (2016). "Age consistency between exoplanet hosts and field stars". Astronomy & Astrophysics 585: 14. doi:10.1051/0004-6361/201527297. A5. Bibcode2016A&A...585A...5B. 
  8. Trevisan, M. et al. (November 2011). "Analysis of old very metal rich stars in the solar neighbourhood". Astronomy & Astrophysics 535: A42. doi:10.1051/0004-6361/201016056. Bibcode2011A&A...535A..42T. . See table 13.
  9. 9.0 9.1 9.2 Trifonov, T. et al. (2017). "Three planets around HD 27894. A close-in pair with a 2:1 period ratio and an eccentric Jovian planet at 5.4 AU". Astronomy & Astrophysics 602: L8. doi:10.1051/0004-6361/201731044. Bibcode2017A&A...602L...8T. 
  10. Nowakowski, Tomasz (June 12, 2017). "Two new massive planets detected around the star HD 27894". https://phys.org/news/2017-06-massive-planets-star-hd.html. Retrieved June 12, 2017. 
  11. 11.0 11.1 Feng, Fabo et al. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". The Astrophysical Journal Supplement Series 262 (21): 21. doi:10.3847/1538-4365/ac7e57. Bibcode2022ApJS..262...21F. 

Coordinates: Sky map 04h 20m 47.0473s, −59° 24′ 39.014″