WASP-18

WASP-18 is a magnitude 9 star located in the Phoenix constellation of the southern hemisphere.[1] It has a mass of 1.25 solar masses.[6]

WASP-18
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Phoenix[1]
Right ascension 01h 37m 25.0335s[2]
Declination −45° 40′ 40.377″[2]
Apparent magnitude (V) 9.273[3]
Characteristics
Spectral type F6V[4]
Astrometry
Proper motion (μ) RA: 25.243±0.030[2] mas/yr
Dec.: 20.597±0.034[2] mas/yr
Parallax (π)8.0694 ± 0.0241 mas[2]
Distance404 ± 1 ly
(123.9 ± 0.4 pc)
Details
Mass1.256±0.13[4] M☉
Radius1.216+0.067
−0.054[4] R☉
Surface gravity (log g)4.37±0.03[5] cgs
Temperature6368±66[5] K
Metallicity [Fe/H]0.11±0.08[5] dex
Rotational velocity (v sin i)11.9±1.2[5] km/s
Age0.5–1.5[4] Gyr
Other designations
HD 10069, HIP 7562, PPM 306061, SAO 215585, 2MASS J15595095-2803422, Gaia DR2 4955371367334610048, TOI 185
Database references
SIMBADdata
Exoplanet Archivedata
Extrasolar Planets
Encyclopaedia		data

The star, although similar to Sun in terms of overall contents of heavy elements, is depleted of carbon. Carbon to oxygen molar ratio of 0.23±0.05 for WASP-18 is well below solar ratio of 0.55.[7]

Planetary system

In 2009, the SuperWASP project announced that a large, hot Jupiter type extrasolar planet, WASP-18b, was orbiting very close to this star.[4]

Observations from the Chandra X-ray Observatory failed to find any X-rays coming from WASP-18,[8] and it is thought that this is caused by WASP-18b disrupting the star's magnetic field by causing a reduction in convection in the star's atmosphere. Tidal forces from the planet may also explain the higher amounts of lithium measured in earlier optical studies of WASP-18.[9]

The WASP-18 planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b ~10[4] MJ 0.020206 0.94145455+0.00000087
−0.00000132[10]		 0.0092 — —

See also

References
  1. "WASP-18b". Exoplanet Transit Database. Retrieved 2009-08-29.
  2. 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.
  3. Maxted, P. F. L.; et al. (2011). "UBV(RI)C photometry of transiting planet hosting stars". Monthly Notices of the Royal Astronomical Society. 418 (2): 1039–1042. arXiv:1108.0349. Bibcode:2011MNRAS.418.1039M. doi:10.1111/j.1365-2966.2011.19554.x. S2CID 117056033.
  4. Hellier, Coel; et al. (2009). "An orbital period of 0.94days for the hot-Jupiter planet WASP-18b" (PDF). Nature. 460 (7259): 1098–1100. Bibcode:2009Natur.460.1098H. doi:10.1038/nature08245. hdl:2268/28276. PMID 19713926. S2CID 205217669.
  5. Torres, Guillermo; et al. (2012). "Improved Spectroscopic Parameters for Transiting Planet Hosts". The Astrophysical Journal. 757 (2). 161. arXiv:1208.1268. Bibcode:2012ApJ...757..161T. doi:10.1088/0004-637X/757/2/161. S2CID 16580774.
  6. PlanetQuest: WASP-18 b
  7. Polanski, Alex S.; Crossfield, Ian J. M.; Howard, Andrew W.; Isaacson, Howard; Rice, Malena (2022), Chemical Abundances for 25 JWST Exoplanet Host Stars with KeckSpec, arXiv:2207.13662
  8. Pillitteri, I.; et al. (July 2014). "No X-rays from WASP-18. Implications for its age, activity, and the influence of its massive hot Jupiter". Astronomy & Astrophysics. 567: A128. arXiv:1406.2620. Bibcode:2014A&A...567A.128P. doi:10.1051/0004-6361/201423579. S2CID 118527777.
  9. "NASA's Chandra X-ray Observatory Finds Planet That Makes Star Act Deceptively Old". Chandra X-ray Observatory. Retrieved 20 September 2014.
  10. McDonald, I.; Kerins, E. (2018). "Pre-discovery transits of the exoplanets WASP-18b and WASP-33b from Hipparcos". Monthly Notices of the Royal Astronomical Society: Letters. 477 (1): L21–L24. arXiv:1803.06187. Bibcode:2018MNRAS.477L..21M. doi:10.1093/mnrasl/sly045. S2CID 49547292.


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