WASP-2

WASP-2 is a binary star system located about 496 light-years away in the Delphinus constellation.^[12] The primary is a magnitude 12 orange dwarf star, orbited by a red dwarf star on a wide orbit.^[8][13] The star system shows an infrared excess noise of unknown origin.^[14]

WASP-2

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Delphinus[1]
A[2]
Right ascension	20h 30m 54.1282s[3]
Declination	+06° 25′ 46.341″[3]
Apparent magnitude (V)	+11.98[4]
C[a 1]
Right ascension	~20h 30m 54s[2]
Declination	~+06° 25′ 46″[2]
Characteristics
Spectral type	K1.5V + K2-M3[5]
Apparent magnitude (J)	10.166±0.027[6]
Apparent magnitude (H)	9.752±0.026[6]
Apparent magnitude (K)	9.632±0.024[6]
Variable type	planetary transit[7]
Astrometry
Radial velocity (Rv)	−27.70±0.46[3] km/s
Proper motion (μ)	RA: 5.631 mas/yr[3] Dec.: −48.491 mas/yr[3]
Parallax (π)	6.5777±0.0270 mas[3]
Distance	496 ± 2 ly (152.0 ± 0.6 pc)
Orbit[8]
Primary	WASP-2A
Companion	WASP-2B
Semi-major axis (a)	106″
Details
WASP-2A
Mass	0.843±0.033[9] M☉
Radius	0.821±0.013[9] R☉
Luminosity	0.507+0.023 −0.029[10] L☉
Surface gravity (log g)	4.536±0.015[9] cgs
Temperature	5170±60[9] K
Metallicity [Fe/H]	0.1±0.2[11] dex
Rotational velocity (v sin i)	0.9±0.5[11] km/s
Age	7.6+2.5 −3.3[9] Gyr
WASP-2B
Mass	0.40±0.02[9] M☉
Temperature	3523+28 −19[9] K
Other designations
V357 Del, TOI-5797, TIC 374530847, WASP-2, GSC 00522-01199, 2MASS J20305413+0625463, 1SWASP J203054.12+062546.4, USNO-B1.0 0964-00543604, UCAC2 34018636[12]
Database references
SIMBAD	A
	B
Exoplanet Archive	data

The primary star hosts one known exoplanet, WASP-2b.^[15] Since the planet transits the star, the star is classified as a planetary transit variable and has received the variable star designation V357 Delphini.^[7]

Binary star

In 2008 a study was undertaken of fourteen stars with exoplanets that were originally discovered using the transit method through relatively small telescopes. These systems were re-examined with the 2.2 m (87 in) reflector telescope at the Calar Alto Observatory in Spain. This star system, along with two others, was determined to be a previously unknown binary star system. The previously unknown secondary star is a dim magnitude 15 M-type star separated by about 111 AU from the primary, appearing offset from the primary by about one arc second in the images. This discovery resulted in a recalculation of parameters for both the planet and the primary star.^[2]

A re-examination of the WASP-2 spectrum in 2015 resulted in the measurement of the stellar companion's temperature as 3513±28 K, and an angular separation of 0.73 arcseconds.^[16]

Planetary system

The primary star has one exoplanet, WASP-2b, a hot Jupiter detected by the SuperWASP project in 2006 using the transit method.^[15]

The WASP-2 planetary system^[11][9]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	0.892±0.027 MJ	0.0308±0.0004	2.15222163(42)	<0.013	84.81+0.35 −0.27°	1.060±0.024 RJ

See also

• WASP-1

Notes

1. The secondary star is identified with a "C" suffix so as to not confuse it with the planetary designation suffix "b".^[2]