HR 5553

HR 5553 is a binary star system located thirty-eight light-years away from the Sun, in the northern constellation Boötes. It has the variable star designation DE Boötis, and is classified as an RS Canum Venaticorum variable that ranges in apparent visual magnitude from 5.97 down to 6.04,[4] which is bright enough to be dimly visible to the naked eye. The system is drifting closer to the Sun with a radial velocity of −30 km/s,[6] and is expected to come as close as 26.9 light-years in 210,000 years.[13]

HR 5553

A visual band light curve for DE Boötes, adapted from Henry et al. (1995)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Boötes
Right ascension	14h 53m 23.76674s[2]
Declination	+19° 09′ 10.0813″[2]
Apparent magnitude (V)	6.00[3] (5.97 to 6.04)[4]
Characteristics
Spectral type	K0 V[5]
U−B color index	+0.49[5]
B−V color index	+0.84[5]
Variable type	RS CVn[4]
Astrometry
Radial velocity (Rv)	−29.82±0.15[6] km/s
Proper motion (μ)	RA: −442.23[2] mas/yr Dec.: +217.61[2] mas/yr
Parallax (π)	86.88 ± 0.46 mas[2]
Distance	37.5 ± 0.2 ly (11.51 ± 0.06 pc)
Absolute magnitude (MV)	5.69[7]
Orbit[8]
Period (P)	125.396±0.001 d
Semi-major axis (a)	0.19±0.03 AU
Eccentricity (e)	0.51±0.001
Inclination (i)	93.4±4.2°
Longitude of the node (Ω)	248.3±3.6°
Argument of periastron (ω) (secondary)	219±0.1°
Details
HR 5553 A
Mass	0.84[9] M☉
Radius	0.86[9] R☉
Luminosity	0.498[9] L☉
Surface gravity (log g)	4.57[10] cgs
Temperature	5,313[10] K
Metallicity [Fe/H]	0.10[10] dex
Rotation	10.4[10]
Rotational velocity (v sin i)	4.0[10] km/s
Age	0.7–1.3[11] Gyr
HR 5553 B
Mass	0.45[5] M☉
Other designations
DE Boo, BD+19°2881, GJ 567, HD 131511, HIP 72848, LHS 5279[12]
Database references
SIMBAD	data

Orbital elements for this single-lined spectroscopic binary was first calculated in 1981 using radial velocity measurements from David Dunlap Observatory combined with older measurements from Mount Wilson Observatory and Dominion Astrophysical Observatory.[14] The two stars orbit each other with a period of 125 days and a large eccentricity of 0.51.[5]

The primary, designated component A, is a K-type main sequence star with a stellar classification of K0 V. It is around one[11] billion years old and is spinning with a projected rotational velocity of 4 km/s.[10]The star has 84% of the mass of the Sun and 86% of the Sun's radius.[9] It is radiating 50%[9] of the luminosity of the Sun from its photosphere at an effective temperature of 5,313 K.[10] Component B has an estimated 45% of the mass of the Sun.[5]

An infrared excess has been detected around this system, most likely indicating the presence of a circumstellar disk at a radius of 34.2 AU. The temperature of this dust is 40 K.[10] The estimated mass of the dust is 0.0002 times the mass of the Earth. It is aligned to within 10° of the plane of the binary system.[9][8]