WASP-8

WASP-8 is a binary star system of 9.9 magnitude. The star system is much younger than the Sun at 300 million to 1.2 billion years age, and is heavily enriched in heavy elements, having nearly twice the 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 mas[3]
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 magnitude 9.9 main-sequence yellow dwarf star. It is reported to be a G-type star with a temperature of 5600 K and has mass 1.093±0.024, a radius 0.976±0.020 and a luminosity of 0.79 times that of the Sun. 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 close to pointing one of the poles to the Earth.[8]

Planetary system

The primary star is orbited by two known extrasolar planets, designated WASP-8b and WASP-8c. WASP-8b was discovered in 2010 by the astronomical transit method and was catalogued as part of the SuperWASP mission.[7] WASP-8c was discovered in late 2013 with the 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. Bohn, A. J.; Southworth, J.; Ginski, C.; Kenworthy, M. A.; Maxted, P. F. L.; Evans, D. F. (2020), "A multiplicity study of transiting exoplanet host stars", Astronomy & Astrophysics, 635: A73, arXiv:2001.08224, Bibcode:2020A&A...635A..73B, doi:10.1051/0004-6361/201937127, S2CID 210861118
  3. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  4. Southworth, J.; Bohn, A. J.; Kenworthy, M. A.; Ginski, C.; Mancini, L. (2020), "A multiplicity study of transiting exoplanet host stars", Astronomy & Astrophysics, 635: A74, arXiv:2001.08225, Bibcode:2020A&A...635A..74S, doi:10.1051/0004-6361/201937334, S2CID 210860775
  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. Bourrier, V.; Cegla, H. M.; Lovis, C.; Wyttenbach, A. (2016), "Refined architecture of the WASP-8 system: A cautionary tale for traditional Rossiter-Mc Laughlin analysis", Astronomy & Astrophysics, 599: A33, arXiv:1611.07985, Bibcode:2017A&A...599A..33B, doi:10.1051/0004-6361/201629973, S2CID 118864447
  9. Knutson, Heather A.; Fulton, Benjamin J.; Montet, Benjamin T.; Kao, Melodie; Ngo, Henry; Howard, Andrew W.; Crepp, Justin R.; Hinkley, Sasha; Bakos, Gaspar Á.; Batygin, Konstantin; Johnson, John Asher; Morton, Timothy D.; Muirhead, Philip S. (2013), "Friends of Hot Jupiters. I. A Radial Velocity Search for Massive, Long-Period Companions to Close-In Gas Giant Planets", The Astrophysical Journal, 785 (2): 126, arXiv:1312.2954, doi:10.1088/0004-637X/785/2/126, S2CID 42687848
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