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[2] mas
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
Database references
SIMBADdata
Exoplanet Archivedata
Extrasolar Planets
Encyclopaedia		data

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[7], 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.[8]

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[9]		 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.
  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. PMID 19713926.
  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.
  6. PlanetQuest: WASP-18 b
  7. 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. doi:10.1051/0004-6361/201423579.
  8. "NASA's Chandra X-ray Observatory Finds Planet That Makes Star Act Deceptively Old". Chandra X-ray Observatory. Retrieved 20 September 2014.
  9. 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.

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