HD 27894

HD 27894

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Reticulum[1]
Right ascension	04^h 20^m 47.046^s[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 mas/yr[2] Dec.: 270.012±0.017 mas/yr[2]
Parallax (π)	22.8888 ± 0.0121 mas[2]
Distance	142.50 ± 0.08 ly (43.69 ± 0.02 pc)
Absolute magnitude (MV)	6.225[6]
Details
Mass	0.83±0.03[7] M☉
Radius	0.79±0.02[7] R☉
Luminosity	0.33±0.01[7] L☉
Surface gravity (log g)	4.56±0.03[7] cgs
Temperature	4,923±32[7] K
Metallicity [Fe/H]	+0.30±0.07[6] dex
Rotation	44 days[6]
Rotational velocity (v sin i)	≤ 1.5[6] km/s
Age	7.7±2.3[8] Gyr
Other designations
CD−59° 829, HD 27894, HIP 20277, LTT 1953[4]
Database references
SIMBAD	data

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. 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.
2. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
3. Houk, Nancy (1979). Michigan catalogue of two-dimensional spectral types for the HD stars. Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan. Bibcode:1978mcts.book.....H. LCCN 78010745.
4. "HD 27894". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2024-01-14.
5. Soubiran, C.; et al. (2018). "Gaia Data Release 2. The catalogue of radial velocity standard stars". Astronomy and Astrophysics. 616: A7. arXiv:1804.09370. Bibcode:2018A&A...616A...7S. doi:10.1051/0004-6361/201832795. S2CID 52952408.
6. 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. Bibcode:2005A&A...439..367M. doi:10.1051/0004-6361:20052826.
7. Bonfanti, A.; et al. (2016). "Age consistency between exoplanet hosts and field stars". Astronomy & Astrophysics. 585: 14. arXiv:1511.01744. Bibcode:2016A&A...585A...5B. doi:10.1051/0004-6361/201527297. S2CID 53971692. A5.
8. Trevisan, M.; et al. (November 2011). "Analysis of old very metal rich stars in the solar neighbourhood". Astronomy & Astrophysics. 535: A42. arXiv:1109.6304. Bibcode:2011A&A...535A..42T. doi:10.1051/0004-6361/201016056. S2CID 49565866.. See table 13.
9. 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. arXiv:1706.00509. Bibcode:2017A&A...602L...8T. doi:10.1051/0004-6361/201731044. S2CID 119105619.
10. Nowakowski, Tomasz (June 12, 2017). "Two new massive planets detected around the star HD 27894". Retrieved June 12, 2017.
11. Feng, Fabo; Butler, R. Paul; et al. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". The Astrophysical Journal Supplement Series. 262 (21): 21. arXiv:2208.12720. Bibcode:2022ApJS..262...21F. doi:10.3847/1538-4365/ac7e57. S2CID 251864022.