Astronomy:WASP-21

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Short description: Star in the constellation Pegasus
WASP 21 / Tangra
WASP-21.jpg
Size comparison between Sun and WASP-21
Observation data
Equinox J2000.0]] (ICRS)
Constellation Pegasus
Right ascension  23h 09m 58.25s[1]
Declination +18° 23′ 45.9″[1]
Apparent magnitude (V) 11.58 ± 0.08[1]
Characteristics
Spectral type G3V
Astrometry
Radial velocity (Rv)-89.45 [1] km/s
Proper motion (μ) RA: 17.597 ± 0.074 [2] mas/yr
Dec.: 18.867 ± 0.05 [2] mas/yr
Parallax (π)3.8412 ± 0.0427[2] mas
Distance849 ± 9 ly
(260 ± 3 pc)
Absolute magnitude (MV)4.97
Details
Mass0.89 ± 0.071[3] M☉
Radius1.136 ± 0.049[3] R☉
Surface gravity (log g)4.277 ± 0.025[3] cgs
Temperature5800 ± 100[1] K
Metallicity-0.4 ± 0.1 [1]
Metallicity [Fe/H]-0.46 ± 0.11 [1] dex
Rotational velocity (v sin i)1.5 ± 0.6 [1] km/s
Age12 ± 5[1] Gyr
Other designations
Tangra, GSC 01715-00679, 2MASS J23095825+1823459, Gaia DR2 2831084391023184128
Database references
SIMBADdata

WASP-21 is a G-type star (spectral type G3V) that is reaching the end of its main sequence lifetime[4][5] approximately 850 light years from Earth in the constellation of Pegasus. The star is relatively metal-poor, having 40% of heavy elements compared to the Sun.[5] Kinematically, WASP-21 belongs to the thick disk of the Milky Way.[1] It has an exoplanet named WASP-21b. [6]

The survey in 2012 have failed to find any stellar companions to WASP-21.[7]

Naming

In 2019 the WASP-21 system was chosen as part of the NameExoWorlds campaign organised by the International Astronomical Union, which assigned each country a star and planet to be named. WASP-21 was assigned to Bulgaria. The winning proposal named the star Tangra after a deity worshipped by the early Bulgars, and the planet Bendida after a deity worshipped by the Thracians.[8]

Planetary System

In 2010 WASP-21 was discovered to host a hot Jupiter type planet by the Wide Angle Search for Planets (WASP).[1] and confirmed by radial velocity by the WASP team in 2010.

Transit-timing variation analysis in 2015 did not find an additional planets in the system.[5]

In 2020, spectroscopic analysis has found the WASP-21 b atmosphere is mostly cloudless and contains sodium.[9]

The WASP-21 planetary system[3][5]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b / Bendida 0.276 ± 0.018 MJ 0.0499 ± 0.0013 4.322482 0.0 [1] 86.97 ± 0.33° 1.162 RJ

References

  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 Bouchy, F.; Hebb, L.; Skillen, I.; Collier Cameron, A.; Smalley, B.; Udry, S.; Anderson, D. R.; Boisse, I. et al. (2010). "WASP-21b: A hot-Saturn exoplanet transiting a thick disc star". Astronomy and Astrophysics 519: A98. doi:10.1051/0004-6361/201014817. Bibcode: 2010A&A...519A..98B. 
  2. ↑ 2.0 2.1 2.2 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 3.3 Ciceri, S.; Mancini, L.; Southworth, J.; Nikolov, N.; Bozza, V.; Bruni, I.; Calchi Novati, S.; d'Ago, G. et al. (2013). "Simultaneous follow-up of planetary transits: Revised physical properties for the planetary systems HAT-P-16 and WASP-21". Astronomy & Astrophysics 557: A30. doi:10.1051/0004-6361/201321669. Bibcode: 2013A&A...557A..30C. 
  4. ↑ Barros, S. C. C.; Pollacco, D. L.; Gibson, N. P.; Howarth, I. D.; Keenan, F. P.; Simpson, E. K.; Skillen, I.; Steele, I. A. (2011). "A lower mass for the exoplanet WASP-21b". Monthly Notices of the Royal Astronomical Society 416 (4): 2593–2599. doi:10.1111/j.1365-2966.2011.19210.x. Bibcode: 2011MNRAS.416.2593B. 
  5. ↑ 5.0 5.1 5.2 5.3 Seeliger, M.; Kitze, M.; Errmann, R.; Richter, S.; Ohlert, J. M.; Chen, W. P.; Guo, J. K.; Göğüş, E. et al. (2015), "Ground-based transit observations of the HAT-P-18, HAT-P-19, HAT-P-27/WASP40 and WASP-21 systems", Monthly Notices of the Royal Astronomical Society 451 (4): 4060–4072, doi:10.1093/mnras/stv1187, Bibcode: 2015MNRAS.451.4060S 
  6. ↑ "Exoplanet-catalog" (in en). https://exoplanets.nasa.gov/exoplanet-catalog/5375/wasp-21-b/. 
  7. ↑ Ginski, C.; Mugrauer, M.; Seeliger, M.; Eisenbeiss, T. (2012), "A lucky imaging multiplicity study of exoplanet host stars", Monthly Notices of the Royal Astronomical Society 421 (3): 2498–2509, doi:10.1111/j.1365-2966.2012.20485.x, Bibcode: 2012MNRAS.421.2498G 
  8. ↑ "Bulgaria | NameExoworlds" (in en). 2019-12-17. http://www.nameexoworlds.iau.org/bulgaria. 
  9. ↑ Chen, G.; Casasayas-Barris, N.; Pallé, E.; Welbanks, L.; Madhusudhan, N.; Luque, R.; Murgas, F. (2020), "Detection of Na in WASP-21b's lower and upper atmosphere", Astronomy & Astrophysics 642: A54, doi:10.1051/0004-6361/202038661, Bibcode: 2020A&A...642A..54C 

Coordinates: Sky map 23h 09m 58.25s, +18° 23′ 45.9″



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