HD 181342

HD 181342 is a star in the constellation of Sagittarius. With an apparent magnitude of 7.55,[2] it cannot be seen with the naked eye. Parallax measurements made by Gaia spacecraft put the star at a distance of 394 light-years (121 parsecs) away.[1]

HD 181342
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension 19h 21m 04.2304s[1]
Declination −23° 37′ 10.4513″[1]
Apparent magnitude (V) 7.55[2]
Characteristics
Spectral type K0 III[3]
B−V color index +1.02[2]
Astrometry
Radial velocity (Rv)−0.76 ± 0.07[4] km/s
Proper motion (μ) RA: −46.597±0.088[1] mas/yr
Dec.: −30.158±0.074[1] mas/yr
Parallax (π)8.2778 ± 0.0475[1] mas
Distance394 ± 2 ly
(120.8 ± 0.7 pc)
Absolute magnitude (MV)2.2 ± 0.2[2]
Details[4]
Mass1.78 ± 0.11 M☉
Radius4.55 ± 0.49 R☉
Luminosity16.2 L☉
Surface gravity (log g)3.42 ± 0.07 cgs
Temperature4976 ± 26 K
Metallicity [Fe/H]+0.22 ± 0.05 dex
Rotational velocity (v sin i)1.92 ± 0.23 km/s
Age1.56 ± 0.28 Gyr
Other designations
CD−23° 15307, CPD−23° 7442, HD 181342, HIP 95124, SAO 188005[5]
Database references
SIMBADdata

The survey in 2015 have ruled out the existence of any additional stellar companions at projected distances from 138 to 762 astronomical units.[6]

The star HD 181342 is named Belel. The name was selected in the NameExoWorlds campaign by Senegal, during the 100th anniversary of the IAU. Belel is a rare source of water in the north of Senegal.[7][8]

HD 181342 is a K-type red giant star.[3] It was formerly an A-type main-sequence star,[2] but at an age of 1.56 billion years it has swelled up to a size of 4.55 solar radii.[4] It is currently 1.78 times the mass of the Sun, 16.2 times as luminous, and its surface temperature is 4976 K.[4]

Planetary system

HD 181342 is known to have one planet, detected with Doppler spectroscopy.[2] The planet, HD 181342 b, orbits at a distance of 1.59 astronomical units (au), every 564 days (almost 2 years). Its mass is at least two and a half times that of Jupiter.[9]

The HD 181342 planetary system[9]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b ≥2.54±0.19 MJ 1.592±0.091 564.1±4.1 0.022±0.051 — —

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. Johnson, John Asher; et al. (2010). "Retired a Stars and Their Companions. IV. Seven Jovian Exoplanets from Keck Observatory". Publications of the Astronomical Society of the Pacific. 122 (892): 701–711. arXiv:1003.3445. Bibcode:2010PASP..122..701J. doi:10.1086/653809.
  3. Houk, N.; Smith-Moore, M. (1988). "Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 4, Declinations -26°.0 to -12°.0". Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. 4. Bibcode:1988mcts.book.....H.
  4. Jofré, E.; Petrucci, R.; Saffe, C.; Saker, L.; de la Villarmois, E. Artur; Chavero, C.; Gómez, M.; Mauas, P. J. D. (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.
  5. "HD 181342". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-09-19.
  6. Mugrauer, M.; Ginski, C. (12 May 2015). "High-contrast imaging search for stellar and substellar companions of exoplanet host stars". Monthly Notices of the Royal Astronomical Society. 450 (3): 3127–3136. doi:10.1093/mnras/stv771. Retrieved 19 June 2020.
  7. "Approved names". NameExoworlds. Retrieved 2020-01-02.
  8. "International Astronomical Union | IAU". www.iau.org. Retrieved 2020-01-02.
  9. Luhn, Jacob K.; et al. (2019). "Retired A Stars and Their Companions. VIII. 15 New Planetary Signals around Subgiants and Transit Parameters for California Planet Search Planets with Subgiant Hosts". The Astronomical Journal. 157 (4). 149. arXiv:1811.03043. Bibcode:2019AJ....157..149L. doi:10.3847/1538-3881/aaf5d0. S2CID 102486961.
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