HD 136118

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 168 light years from the Sun based on parallax,[1] and is drifting closer with a radial velocity of −3 km/s.[2]

HD 136118
Observation data
Epoch J2000      Equinox J2000
Constellation Serpens
Right ascension 15h 18m 55.4719s[1]
Declination −01° 35′ 32.590″[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)−2.97±0.12[2] km/s
Proper motion (μ) RA: −123.748±0.112[1] mas/yr
Dec.: +22.522±0.151[1] mas/yr
Parallax (π)19.4132 ± 0.0741[1] mas
Distance168.0 ± 0.6 ly
(51.5 ± 0.2 pc)
Absolute magnitude (MV)3.60[5]
Details
Mass1.84±0.23[6] M☉
Radius1.70±0.02[1] R☉
Luminosity3.717±0.018[1] L☉
Surface gravity (log g)4.08[5] cgs
Temperature6,148+38
−43[1] K
Metallicity [Fe/H]−0.06±0.01[2] dex
Rotational velocity (v sin i)8.5[5] km/s
Age3.5±0.4[2] Gyr
Other designations
BD−01° 3045, HD 136118, HIP 74948, SAO 140452[7]
Database references
SIMBADdata

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.[8] HD 136118 has 84% more mass compared to the Sun,[6] and is 70%[1] 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
HD 136118 b
Discovery
Discovered byFischer "et al."[3]
Discovery site California
Discovery dateFebruary 7, 2002
Doppler Spectroscopy
Orbital characteristics
Apastron1.96 AU (293,000,000 km)
Periastron0.94 AU (141,000,000 km)
1.45 ± 0.25 AU (217,000,000 ± 37,000,000 km)
Eccentricity0.352 ± 0.006
1209 ± 24 d
3.31 y
Inclination163.1 ± 3
2450610.5 ± 3.7
316.4 ± 0.6
StarHD 136118
Physical characteristics
Mass42+11
−18 MJ

    The astronomer Debra Fischer discovered a substellar companion, originally thought to be a very massive exoplanet, which was announced on February 7, 2002. This object has a minimum mass of 11.9 MJ.[3] On November 25, 2009, its inclination was calculated to be 163.1° and its true mass 42 MJ, classifying it as a brown dwarf.[8] Designated HD 136118 b, it is orbiting the host star with a period of 3.25 years.[8]

    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[8]
    Companion
    (in order from star)    		 Mass Semimajor axis
    (AU)    		 Orbital period
    (days)    		 Eccentricity Inclination Radius
    b 42+11
    −18     MJ    		 1.45±0.25[3] 1,188±2 0.34±0.01 163.1±3.0° —

    See also

    References
    1. 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.
    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.
    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. 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.
    7. "HD 81040". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-07-13.
    8. 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.

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