WASP-8

WASP-8 is a binary star system of 9.9 magnitude. The star system is much younger than Sun at 0.3+0.9
−0 billion years age, and is heavily enriched in heavy elements, having nearly twice concentration of iron compared to the Sun.[4]

WASP-8
Observation data
Epoch J2000      Equinox J2000
Constellation Sculptor
Right ascension 23h 59m 36.0711s[1]
Declination −35° 01′ 52.920″[1]
Apparent magnitude (V) 9.9
Characteristics
WASP-8A
Evolutionary stage main-sequence
Spectral type G6
WASP-8B
Spectral type M[2]
Astrometry
Radial velocity (Rv)-1.9±0.6[3] km/s
Proper motion (μ) RA: 109.752[3] mas/yr
Dec.: 7.615[3] mas/yr
Parallax (π)11.1052 ± 0.0175[3] mas
Distance293.7 ± 0.5 ly
(90.0 ± 0.1 pc)
Position (relative to WASP-8A)[2]
ComponentWASP-8B
Epoch of observation2016
Angular distance4.520±0.005″
Position angle170.9±0.1°
Observed separation
(projected)		408 AU
Details[4]
WASP-8A
Mass1.093±0.024 M☉
Radius0.976±0.020 R☉
Luminosity0.79 L☉
Temperature5600±80 K
Metallicity [Fe/H]0.29±0.03 dex
Rotational velocity (v sin i)1.90±0.05[5] km/s
Age0.3+0.9
−0[4] Gyr
WASP-8B
Mass0.53±0.02 M☉
Temperature3758+47
−43 K
Other designations
TYC 7522-505-1, WDS J23596-3502A, 2MASS J23593607-3501530, Gaia DR2 2312679845530628096, CD-35 16019[6]
WASP-8A: Gaia EDR3 2312679845530628096
WASP-8B: Gaia EDR3 2312679845529776128
Database references
SIMBADdata

The primary, WASP-8A, is a 9.9 main-sequence yellow dwarf star. It is reported to be a G-type star of temperature 5600 K, mass of 1.093±0.024 solar masses, radius of 0.976±0.020 solar radius, and a luminosity of 0.79 of solar luminosity. There is a companion star WASP-8B located 4.5 arcseconds away with the same proper motion indicating a stellar binary system.[7] The binarity was confirmed in 2020.[2] The axis orientation of the primary star is uncertain, but it is a close to pointing one of the poles to the Earth.[8]

Planetary system

The primary star is orbited by two known extrasolar planet, designated WASP-8b and WASP-8c. Planet WASP-8b was catalogued as part of the SuperWASP mission and discovered in 2010 by the astronomical transit method.[7] WASP-8c was discovered in late 2013 by radial velocity method.[9]


The WASP-8 planetary system[4]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 2.216±0.035 MJ 0.0817±0.0006 8.159 0.3082 88.52° 1.165±0.032 RJ
c ≥9.45 MJ 5.28 4323 — — —

See also
Artist's impression of a star like WASP-8.

References
  1. Brown, A. G. A; et al. (2016). "Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties". Astronomy and Astrophysics. 595. A2. arXiv:1609.04172. Bibcode:2016A&A...595A...2G. doi:10.1051/0004-6361/201629512. S2CID 1828208.Gaia Data Release 1 catalog entry
  2. A multiplicity study of transiting exoplanet host stars. I. High-contrast imaging with VLT/SPHERE, 2020, arXiv:2001.08224
  3. Brown, A. G. A.; et al. (Gaia collaboration). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics (in press). arXiv:2012.01533. doi:10.1051/0004-6361/202039657. S2CID 227254300. Gaia EDR3 record for this source at VizieR.
  4. A multiplicity study of transiting exoplanet host stars. II. Revised properties of transiting planetary systems with companions, 2020, arXiv:2001.08225
  5. Bourrier, V.; et al. (2017). "Refined architecture of the WASP-8 system: A cautionary tale for traditional Rossiter-McLaughlin analysis". Astronomy and Astrophysics. 599. A33. arXiv:1611.07985. Bibcode:2017A&A...599A..33B. doi:10.1051/0004-6361/201629973. S2CID 118864447.
  6. "NAME WASP-8 A -- Star in double system". SIMBAD Astronomical Database. Centre de données astronomiques de Strasbourg. Retrieved 2014-09-29.
  7. Queloz, D.; et al. (2010). "WASP-8b: a retrograde transiting planet in a multiple system". Astronomy and Astrophysics. 517. L1. arXiv:1006.5089. Bibcode:2010A&A...517L...1Q. doi:10.1051/0004-6361/201014768. S2CID 35774603.
  8. Refined architecture of the WASP-8 system: a cautionary tale for traditional Rossiter-McLaughlin analysis, 2016, arXiv:1611.07985
  9. FRIENDS OF HOT JUPITERS I: A RADIAL VELOCITY SEARCH FOR MASSIVE, LONG-PERIOD COMPANIONS TO CLOSE-IN GAS GIANT PLANETS, 2013, arXiv:1312.2954

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