H Orionis

h Orionis
	Location of h Orionis (circled in red)
Observation data; Epoch J2000 Equinox ICRS
Constellation	Orion
Right ascension	05h 09m 19.6433s
Declination	+09° 49′ 46.503″
Apparent magnitude (V)	+5.43
Characteristics
Evolutionary stage	main sequence
Spectral type	kA2hF1mF3
B−V color index	0.249±0.010
Astrometry
Radial velocity (Rv)	+43.9119±0.0036 km/s
Proper motion (μ)	RA: +60.769 mas/yr ; Dec.: −7.443 mas/yr
Parallax (π)	18.7710±0.1981 mas
Distance	174 ± 2 ly ; (53.3 ± 0.6 pc)
Absolute magnitude (MV)	+1.74
Orbit
Period (P)	155.87±0.03 days
Semi-major axis (a)	0.75 au
Eccentricity (e)	0.553±0.015
Inclination (i)	29±2 or 151±2°
Periastron epoch (T)	2,400,012.3±0.8 BJD
Argument of periastron (ω); (secondary)	275.2±1.5°
Semi-amplitude (K1); (primary)	6.89±0.13 km/s
Details
Aa
Mass	1.76 M☉
Radius	2.2 R☉
Luminosity	15.0 L☉
Surface gravity (log g)	4.07 cgs
Temperature	7,500 K
Metallicity [Fe/H]	+0.28 dex
Rotational velocity (v sin i)	12.6 km/s
Age	1.12±0.05 Gyr
Ab
Mass	0.53 M☉
Radius	0.50 R☉
Temperature	3,900 K
Age	1.12±0.05 Gyr
Other designations
	16 Ori, BD+09°743, HD 33254, HIP 23983, HR 1672, TYC 702-2789-1
Database references
SIMBAD	data

h Orionis is a binary star in the constellation Orion. At an apparent magnitude of +5.43, it is faintly visible to the naked eye in locations far from light pollution. Parallax measurements give a distance of 174 light-years (53.3 parsecs).

Characteristics

This is a single-lined spectroscopic binary, first spotted in 1969 by Peter S. Conti. The components take 155.87 days to orbit around each other, following a moderately-eccentric path with an eccentricity of 0.553 and a semi-major axis of 0.75 astronomical units.

The primary is an A or F-type star and an Am star, with its spectrum matching a spectral class of kA2hF1mF3. The star has 1.76 times the mass of the Sun and 2.2 times the Sun's radius. It has an effective temperature of 7,500 K, which gives it the white hue typical of an A or early F-type star.

The secondary is a red dwarf with about half the size of the Sun and an effecitve temperature of 3,900 K.

h Orionis has been suspected to be a member of the Hyades cluster based on its stellar kinematics. However, the estimated age of the system, 1.12 billion years, is almost twice that of the cluster. The red dwarf also does not emit the amount of X-rays expected for an object of the Hyades' age, further arguing against the system's membership of the cluster.

References

1 2 3 4 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. XHIP record for this object at VizieR.
1 2 3 4 5 6 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.
1 2 Abt, H. A.; Levy, S. G. (1985). "Improved study of metallic-line binaries". The Astrophysical Journal Supplement Series. 59: 229. Bibcode:1985ApJS...59..229A. doi:10.1086/191070.
↑ Leão, I. C.; Pasquini, L.; Ludwig, H.-G.; De Medeiros, J. R. (2019). "Spectroscopic and astrometric radial velocities: Hyades as a benchmark". Monthly Notices of the Royal Astronomical Society. 483 (4): 5026. arXiv:1811.08771. Bibcode:2019MNRAS.483.5026L. doi:10.1093/mnras/sty3215.
1 2 Torres, Guillermo; Stefanik, Robert P.; Latham, David W. (2026). "Long-term Spectroscopic Survey of the Hyades Cluster: The Binary Population". The Astrophysical Journal Supplement Series. 283 (2): 81. arXiv:2603.00229. Bibcode:2026ApJS..283...81T. doi:10.3847/1538-4365/ae4fbb. Table with properties, entry 575.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Waisberg, Idel; Klein, Ygal; Katz, Boaz (2026). "Hidden Companions to Intermediate-mass Stars. XXXVII. Uncovering a 0.53M_⊙, 0.75 au Companion to h Orionis". Research Notes of the American Astronomical Society. 10 (5): 125. Bibcode:2026RNAAS..10..125W. doi:10.3847/2515-5172/ae6eec.
1 2 Stassun, Keivan G.; et al. (2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467.
1 2 Takeda, Yoichi; Han, Inwoo; Kang, Dong-Il; Lee, Byeong-Cheol; Kim, Kang-Min (2019). "Compositional differences between the component stars of eclipsing close binary systems showing chemical peculiarities". Monthly Notices of the Royal Astronomical Society. 485 (1): 1067. arXiv:1902.04766. Bibcode:2019MNRAS.485.1067T. doi:10.1093/mnras/stz449.
↑ "16 Ori". SIMBAD. Centre de données astronomiques de Strasbourg.
↑ Conti, Peter S. (1969). "Zeeman Observations of Metallic-Line Stars". The Astrophysical Journal. 156: 661. Bibcode:1969ApJ...156..661C. doi:10.1086/149996. ISSN 0004-637X.
↑ "The Colour of Stars". Australia Telescope, Outreach and Education. Commonwealth Scientific and Industrial Research Organisation. December 21, 2004. Archived from the original on 2013-12-03. Retrieved 2012-01-16.

[XHIP-1] 1 2 3 4 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. XHIP record for this object at VizieR.

[DR3-2] 1 2 3 4 5 6 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.

[abt1985-3] 1 2 Abt, H. A.; Levy, S. G. (1985). "Improved study of metallic-line binaries". The Astrophysical Journal Supplement Series. 59: 229. Bibcode:1985ApJS...59..229A. doi:10.1086/191070.

[Leão2019-4] Leão, I. C.; Pasquini, L.; Ludwig, H.-G.; De Medeiros, J. R. (2019). "Spectroscopic and astrometric radial velocities: Hyades as a benchmark". Monthly Notices of the Royal Astronomical Society. 483 (4): 5026. arXiv:1811.08771. Bibcode:2019MNRAS.483.5026L. doi:10.1093/mnras/sty3215.

[Torres2026-5] 1 2 Torres, Guillermo; Stefanik, Robert P.; Latham, David W. (2026). "Long-term Spectroscopic Survey of the Hyades Cluster: The Binary Population". The Astrophysical Journal Supplement Series. 283 (2): 81. arXiv:2603.00229. Bibcode:2026ApJS..283...81T. doi:10.3847/1538-4365/ae4fbb. Table with properties, entry 575.

[Waisberg2026-6] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Waisberg, Idel; Klein, Ygal; Katz, Boaz (2026). "Hidden Companions to Intermediate-mass Stars. XXXVII. Uncovering a 0.53M_⊙, 0.75 au Companion to h Orionis". Research Notes of the American Astronomical Society. 10 (5): 125. Bibcode:2026RNAAS..10..125W. doi:10.3847/2515-5172/ae6eec.

[tic-7] 1 2 Stassun, Keivan G.; et al. (2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467.

[takeda2019-8] 1 2 Takeda, Yoichi; Han, Inwoo; Kang, Dong-Il; Lee, Byeong-Cheol; Kim, Kang-Min (2019). "Compositional differences between the component stars of eclipsing close binary systems showing chemical peculiarities". Monthly Notices of the Royal Astronomical Society. 485 (1): 1067. arXiv:1902.04766. Bibcode:2019MNRAS.485.1067T. doi:10.1093/mnras/stz449.

[SIMBAD-9] "16 Ori". SIMBAD. Centre de données astronomiques de Strasbourg.

[Conti1969-10] Conti, Peter S. (1969). "Zeeman Observations of Metallic-Line Stars". The Astrophysical Journal. 156: 661. Bibcode:1969ApJ...156..661C. doi:10.1086/149996. ISSN 0004-637X.

[csiro-11] "The Colour of Stars". Australia Telescope, Outreach and Education. Commonwealth Scientific and Industrial Research Organisation. December 21, 2004. Archived from the original on 2013-12-03. Retrieved 2012-01-16.