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 165light years from the Sun based on parallax,[1] and is drifting closer with a radial velocity of −3km/s.[2]
Yellow-white hued middle-aged star in the constellation Serpens
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 8.5km/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 11.9MJ.[3] On November 25, 2009, its inclination was calculated to be 163.1° and its true mass 42MJ, classifying it as a brown dwarf.[9] A 2022 study estimated a true mass of 13.1MJ, closer to the minimum mass.[10]
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.
Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars". Michigan Spectral Survey. 5. Bibcode:1999MSS...C05....0H.
Stassun, Keivan G.; etal. (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. S2CID119219062.
"HD 81040". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-07-13.
Martioli, Eder; etal. (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. S2CID119183677.
Feng, Fabo; Butler, R. Paul; etal. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". The Astrophysical Journal Supplement Series. 262 (21). arXiv:2208.12720. Bibcode:2022arXiv220812720F. doi:10.3847/1538-4365/ac7e57.
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