WASP-1

WASP-1 is a magnitude 12 binary star system located about 1,250 light-years away^[2] in the Andromeda constellation.^[7] The binary system consists of a metal-rich F-type main-sequence star, named WASP-1A, and a distant low-mass star, named WASP-1B. WASP-1A has one known transiting hot Jupiter exoplanet named WASP-1b.

WASP-1

Telescope photo of WASP-1
Observation data Epoch J2000      Equinox J2000
Constellation	Andromeda[1]
Right ascension	00h 20m 40.0746s[2]
Declination	+31° 59′ 23.955″[2]
Apparent magnitude (V)	11.68 ± 0.05[3]
Characteristics
WASP-1A
Evolutionary stage	main-sequence star
Spectral type	F7V[4]
Apparent magnitude (B)	~12.0[5]
Apparent magnitude (V)	11.68 ± 0.05[3]
WASP-1B
Apparent magnitude (H)	15.130 ± 0.046[6]
Apparent magnitude (K)	15.116 ± 0.055[6]
Astrometry
WASP-1A
Radial velocity (Rv)	−13.90(59)[2] km/s
Proper motion (μ)	RA: −4.692(22) mas/yr[2] Dec.: −3.320(20) mas/yr[2]
Parallax (π)	2.6108±0.0218 mas[2]
Distance	1,250 ± 10 ly (383 ± 3 pc)
Absolute magnitude (MV)	3.63+0.13 −0.14[3]
Details[3]
WASP-1A
Mass	1.301+0.049 −0.047 M☉
Radius	1.515+0.052 −0.045 R☉
Luminosity	2.88+0.36 −0.30 L☉
Surface gravity (log g)	4.190+0.020 −0.022 cgs
Temperature	6110±75 K
Metallicity [Fe/H]	0.26±0.08 dex
Age	3.0±0.6 Gyr
WASP-1B
Mass	~0.3[6]: 13  M☉
Surface gravity (log g)	~4.97[6]: 13  cgs
Temperature	~3400[6]: 13  K
Position (relative to WASP-1A)[6]: 11, 13
Component	WASP-1B
Epoch of observation	2013–2014
Angular distance	~4.58″
Position angle	~1.9°
Projected separation	1587+160 −16 AU
Other designations
1SWASP J002040.07+315923.7, USNO-B1.0 1219-00005465, TOI-6014, TIC 57984377, WASP-1, TYC 2265-107-1, GSC 02265-00107, 2MASS J00204007+3159239[5]
Database references
SIMBAD	data
Exoplanet Archive	data

Stellar companion

WASP-1A has a distant companion star, named WASP-1B. WASP-1B is a low-mass star that is around 0.3 times as massive as the Sun and has an effective temperature of about 3400 K.^[6]: 24 WASP-1B is located northward of WASP-1A at an angular separation of about 4.6 arcseconds, corresponding to a projected distance of 1587 AU.^{[6]: 13, 15} WASP-1B was first identified in observations from 2006 and confirmed in further observations from 2012 to 2014, which showed that it shares the proper motion of WASP-1A, indicating the two stars are gravitationally bound to each other.^[6]: 15

Planetary system

In 2006, an extrasolar planet was discovered by the Wide Angle Search for Planets team using the transit method.^[4] The planet has a density of 0.31 to 0.40 g/cm³, making it about half as dense as Saturn, and one third as dense as water. The orbit of WASP-1b is inclined to the rotational axis of the star by 79.0^+4.3
_−4.5 degrees, making it a nearly "polar" orbit.^[8]

Two searches for additional planets using transit-timing variations have yielded negative results.^[9][10]

The WASP-1 planetary system^[11]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	0.948+0.029 −0.028 MJ	0.03958+0.00047 −0.00049	2.51994480±0.00000050	<0.013	90.0+0.0 −2.9°	1.514+0.052 −0.047 RJ

See also

• SuperWASP
• List of extrasolar planets