Omicron Coronae Borealis

o Coronae Borealis

Location of o Coronae Borealis (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Corona Borealis
Right ascension	15^h 20^m 08.559^s[1]
Declination	+29° 36′ 58.35″[1]
Apparent magnitude (V)	+5.53[2]
Characteristics
Spectral type	K0 III[3]
U−B color index	+0.786[2]
B−V color index	+1.009[2]
Astrometry
Radial velocity (Rv)	−54.15±0.20[4] km/s
Proper motion (μ)	RA: −117.98±0.18[1] mas/yr Dec.: −42.44±0.31[1] mas/yr
Parallax (π)	12.08 ± 0.44 mas[1]
Distance	270 ± 10 ly (83 ± 3 pc)
Absolute magnitude (MV)	+0.92[3]
Details[4]
Mass	1.07±0.19 M☉
Radius	10.13±0.40 R☉
Luminosity	50.1 L☉
Surface gravity (log g)	2.70±0.06 cgs
Temperature	4,812±13 K
Metallicity [Fe/H]	−0.24±0.01 dex
Rotational velocity (v sin i)	0.47±0.61 km/s
Age	5.54±2.79 Gyr
Other designations
o CrB, 1 Coronae Borealis, BD+30° 2647, HD 136512, HIP 75049, HR 5709, SAO 83768, WDS J15201+2937A, 2MASS J15200853+2936584
Database references
SIMBAD	data
Exoplanet Archive	data

Omicron Coronae Borealis, Latinized from o Coronae Borealis, is a star in the northern constellation of Corona Borealis. It is a faint star but visible to the naked eye on a dark night with an apparent visual magnitude of +5.53.^[2] The annual parallax shift of the star as seen from Earth is 12.08 mas, which provides a distance estimate of around 270 light years. It is moving closer to the Sun with a radial velocity of −54 km/s.^[4]

Based upon the spectrum of this star, it has a stellar classification of K0 III.^[3] This indicates this is an evolved K-type giant star that has exhausted the hydrogen at its core and has left the main sequence. This is a red clump star, which means it is now generating energy through helium fusion at its core. It has 107% of the mass of the Sun and has expanded to over ten times the Sun's radius. The star is radiating 50 times the Sun's luminosity from its expanded photosphere at an effective temperature of 4,812 K.^[5]

Planetary system

Omicron Coronae Borealis has one confirmed planet, believed to be, along with HD 100655 b, one of the two least massive planets known around red clump giants.^[5] The planet was detected by measuring changes in radial velocity of the host star caused by gravitational perturbation of the orbiting object. It is orbiting with a period of 188 days, at a semimajor axis 83% of the mean separation between the Earth and the Sun, and an eccentricity of 0.19.^[5]

The Omicron Coronae Borealis planetary system^[5]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	>1.5 MJ	0.83	187.83 ± 0.54	0.191 ± 0.085	—	—

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. Jennens, P. A.; Helfer, H. L. (September 1975), "A new photometric metal abundance and luminosity calibration for field G and K giants", Monthly Notices of the Royal Astronomical Society, 172 (3): 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667.
3. 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.
4. Jofré, E; et al. (2015), "Stellar parameters and chemical abundances of 223 evolved stars with and without planets", Astronomy & Astrophysics, 574: A50, arXiv:1410.6422, Bibcode:2015A&A...574A..50J, doi:10.1051/0004-6361/201424474, S2CID 53666931, A50.
5. Sato, Bun'ei; et al. (2012), "Substellar Companions to Seven Evolved Intermediate-Mass Stars", Publications of the Astronomical Society of Japan, 64 (6), 135, arXiv:1207.3141, Bibcode:2012PASJ...64..135S, doi:10.1093/pasj/64.6.135, S2CID 119197073.