HD 136118

HD 136118

Telescope image of HD 136118
Observation data Epoch J2000      Equinox J2000
Constellation	Serpens
Right ascension	15^h 18^m 55.47227^s[1]
Declination	−01° 35′ 32.5926″[1]
Apparent magnitude (V)	6.93[2]
Characteristics
Evolutionary stage	main sequence[3]
Spectral type	F7V[4]
B−V color index	0.553±0.007[2]
Astrometry
Radial velocity (Rv)	−3.07±0.13[1] km/s
Proper motion (μ)	RA: −123.024(31) mas/yr[1] Dec.: 22.180(30) mas/yr[1]
Parallax (π)	19.8116 ± 0.0341 mas[1]
Distance	164.6 ± 0.3 ly (50.48 ± 0.09 pc)
Absolute magnitude (MV)	3.60[5]
Details
Mass	1.84±0.23[6] M☉
Radius	1.70±0.02[7] R☉
Luminosity	3.717±0.018[7] L☉
Surface gravity (log g)	4.08[5] cgs
Temperature	6,148+38 −43[7] K
Metallicity [Fe/H]	−0.06±0.01[2] dex
Rotational velocity (v sin i)	8.5[5] km/s
Age	3.5±0.4[2] Gyr
Other designations
BD−01° 3045, HD 136118, HIP 74948, SAO 140452[8]
Database references
SIMBAD	data

HD 136118 is a star in the Serpens Caput section of the Serpens constellation. The star is too dim to be readily visible to the naked eye, having an apparent visual magnitude of 6.93.^[2] It is located at a distance of 165 light years from the Sun based on parallax,^[1] and is drifting closer with a radial velocity of −3 km/s.^[2]

This object is an F-type main-sequence star with a stellar classification of F7V.^[4] The absolute visual magnitude of this star suggests that it has begun to evolve away from the main sequence.^[3] The abundances of the stellar atmosphere are similar to the Sun, and it has only a modest level of chromospheric activity.^[9] HD 136118 has 84% more mass compared to the Sun,^[6] and is 70%^[7] larger in radius. The star is an estimated 3.5^[2] billion years old and is spinning with a projected rotational velocity of 8.5 km/s.^[5]

Brown dwarf companion

The astronomer Debra Fischer discovered a substellar companion, originally thought to be a very massive exoplanet, which was announced on February 7, 2002.^[3] Designated HD 136118 b, it is orbiting the host star with a period of 3.25 years.^[9] This object has a minimum mass of 11.9 M_J.^[3] On November 25, 2009, its inclination was calculated to be 163.1° and its true mass 42 M_J, classifying it as a brown dwarf.^[9] Later studies in 2022 and 2023 found true masses of about 13-16 M_J, closer to the minimum mass, but still classifying the companion as a brown dwarf by most definitions.^[10][11]

Due to its high mass the object is likely to be very hot and possibly glowing faintly. The orbit of the object has a semimajor axis of 1.45 astronomical units from the parent star, taking 1,188 days (3.25 years) to complete one eccentric orbit.

The HD 136118 planetary system^[11]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (years)	Eccentricity	Inclination	Radius
b	16.5+1.7 −1.8 MJ	2.353+0.046 −0.045	3.262+0.053 −0.051	0.35+0.027 −0.026	134.0+4.7 −7.5°	—

See also

• List of brown dwarfs

References

1. 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.
2. 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.
3. Fischer, Debra A.; et al. (2002). "Planetary Companions to HD 136118, HD 50554, and HD 106252". Publications of the Astronomical Society of the Pacific. 114 (795): 529–535. Bibcode:2002PASP..114..529F. doi:10.1086/341677. JSTOR 10.1086/341677.
4. Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars". Michigan Spectral Survey. 5. Bibcode:1999MSS...C05....0H.
5. Luck, R. Earle (January 2017). "Abundances in the Local Region II: F, G, and K Dwarfs and Subgiants". The Astronomical Journal. 153 (1): 19. arXiv:1611.02897. Bibcode:2017AJ....153...21L. doi:10.3847/1538-3881/153/1/21. S2CID 119511744. 21.
6. Stassun, Keivan G.; et al. (2017). "Accurate Empirical Radii and Masses of Planets and Their Host Stars with Gaia Parallaxes". The Astronomical Journal. 153 (3): 136. arXiv:1609.04389. Bibcode:2017AJ....153..136S. doi:10.3847/1538-3881/aa5df3. S2CID 119219062.
7. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
8. "HD 81040". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-07-13.
9. Martioli, Eder; et al. (January 2010). "The Mass of the Candidate Exoplanet Companion to HD 136118 from Hubble Space Telescope Astrometry and High-Precision Radial Velocities". The Astrophysical Journal. 708 (1): 625–634. arXiv:0911.4645. Bibcode:2010ApJ...708..625M. doi:10.1088/0004-637X/708/1/625. S2CID 119183677.
10. 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.
11. Xiao, Guang-Yao; Liu, Yu-Juan; et al. (May 2023). "The Masses of a Sample of Radial-Velocity Exoplanets with Astrometric Measurements". Research in Astronomy and Astrophysics. 23 (5): 055022. arXiv:2303.12409. Bibcode:2023RAA....23e5022X. doi:10.1088/1674-4527/accb7e. S2CID 257663647.

External links

• "Notes for star HD 136118". Extrasolar Planets Encyclopaedia. Archived from the original on November 6, 2007. Retrieved 2008-08-20.