HAT-P-4

HAT-P-4 is a wide binary star consisting of a pair of G-type main-sequence stars^[5] in the constellation of Boötes.^[1] It also has the BD designation BD+36°2593.

HAT-P-4

Observation data Epoch J2000      Equinox J2000
Constellation	Boötes[1]
HAT-P-4A
Right ascension	15h 19m 57.9204s[2]
Declination	+36° 13′ 46.738″[2]
Apparent magnitude (V)	11.159±0.010[3]
HAT-P-4B
Right ascension	15h 20m 00.0127s[4]
Declination	+36° 12′ 18.520″[4]
Apparent magnitude (V)	11.534±0.01[3]
Characteristics
HAT-P-4A
Spectral type	G0V[5]
B−V color index	0.771
Variable type	planetary transit[6]
HAT-P-4B
Spectral type	G2V[5]
Astrometry
HAT-P-4A
Radial velocity (Rv)	−1.13(37)[2] km/s
Proper motion (μ)	RA: −21.513(13) mas/yr[2] Dec.: −24.255(19) mas/yr[2]
Parallax (π)	3.1071±0.0154 mas[2]
Distance	1,050 ± 5 ly (322 ± 2 pc)
HAT-P-4B
Radial velocity (Rv)	−1.31(35)[4] km/s
Proper motion (μ)	RA: −21.424(13) mas/yr[4] Dec.: −24.182(20) mas/yr[4]
Parallax (π)	3.0777±0.0155 mas[4]
Distance	1,060 ± 5 ly (325 ± 2 pc)
Position (relative to HAT-P-4A)[5]
Component	HAT-P-4B
Epoch of observation	1999/02/07
Angular distance	91.760±0.099″
Position angle	163.97±0.06°
Projected separation	28446 AU
Details
HAT-P-4A
Mass	1.260+0.043 −0.042[7] M☉
Radius	1.573±0.015[7] R☉
Luminosity	2.8[2] L☉
Surface gravity (log g)	4.145±0.015[7] cgs
Temperature	5927+57 −47[7] K
Metallicity [Fe/H]	0.277±0.007[8] dex
Rotational velocity (v sin i)	5.6 ± 0.9[9] km/s
Age	~4.2 Gyr
HAT-P-4B
Mass	1.0[4] M☉
Radius	1.3[4] R☉
Luminosity	2.0[4] L☉
Surface gravity (log g)	4.38±0.14[8] cgs
Temperature	6037±37[8] K
Metallicity [Fe/H]	0.175±0.006[8] dex
Age	7.8[4] Gyr
Other designations
HAT-P-4A: BD+36°2593, SAO 64638, TYC 2569-1599-1, GSC 02569-01599, 2MASS J15195792+3613467[10]
HAT-P-4B: TYC 2569-744-1, 2MASS J15200001+3612185[11]
Database references
SIMBAD	A
	B
Data sources:
Hipparcos Catalogue, CCDM (2002), Bright Star Catalogue (5th rev. ed.)

The star exhibits an infrared excess of unknown origin.^[12]

Binary companion

The companion star is located at a distance of 28446 astronomical units and therefore has an orbital period that is extremely long.^[5]

Planetary system

The primary star is home to the transiting extrasolar planet HAT-P-4b.^[6] This planet is a fairly typical hot Jupiter type planet in a 3-day orbit.^[6]

The HAT-P-4A planetary system^[13][14]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	0.651+0.033 −0.037 MJ	0.04449+0.00083 −0.0012	3.0565254±0.0000012	<0.0073	—	1.28+0.016 −0.015[7] RJ

See also

• HATNet Project