Nu2 Boötis

Nu² Boötis is a white-hued binary star^[11] system in the northern constellation of Boötes. Its name is a Bayer designation that is Latinized from ν² Boötis, and abbreviated Nu² Boo or ν² Boo. This system is faintly visible to the naked eye as a point of light with a combined apparent visual magnitude of 5.02.^[3] Based upon an annual parallax shift of 7.86 mas as seen from the Earth,^[2] it is located approximately 441 light-years (135 pc)  light years from the Sun. The system is moving closer to the Sun with a radial velocity of −16.6 km/s.^[6]

For other stars with this Bayer designation, see ν Boötis.

Nu² Boötis

ν1 (right) and ν2 (left) Boötis in optical light
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Boötes[1]
Right ascension	15h 31m 46.983s[2]
Declination	+40° 53′ 57.61″[2]
Apparent magnitude (V)	5.02[3] (5.80 + 5.80)[4]
Characteristics
Spectral type	A5 V[5]
U−B color index	+0.11[3]
B−V color index	+0.07[3]
R−I color index	0.04
Astrometry
Radial velocity (Rv)	−16.6±3.7[6] km/s
Proper motion (μ)	RA: −22.887 mas/yr[2] Dec.: −12.041 mas/yr[2]
Parallax (π)	7.3894±0.1816 mas[7]
Distance	440 ± 10 ly (135 ± 3 pc)
Absolute magnitude (MV)	−0.59[1]
Orbit[8]
Period (P)	9.026±0.017 yr
Semi-major axis (a)	0.0615±0.0007″
Eccentricity (e)	0.006±0.015
Inclination (i)	109.7±1.2°
Longitude of the node (Ω)	199.4±0.9°
Periastron epoch (T)	2000.75±0.24
Argument of periastron (ω) (secondary)	293±9°
Details
Mass	2.84±0.11[9] M☉
Radius	6.21+1.07 −0.81[7] R☉
Luminosity	135±3[7] L☉
Temperature	7894+574 −600[7] K
Rotational velocity (v sin i)	217[9] km/s
Other designations
ν2 Boo, ψ Her, 53 Boötis, BD+41°2611, GC 20883, HD 138629, HIP 76041, HR 5774, SAO 45590, ADS 9688, CCDM 15318+4054, WDS J15318+4054AB[10]
Database references
SIMBAD	data
Data sources:
Hipparcos Catalogue, CCDM (2002), Bright Star Catalogue (5th rev. ed.)

This stellar pair have a nearly circular orbit with a period of nine years and a semimajor axis of 0.0615 arc seconds.^[11] They are both of visual magnitude 5.80 and display a similar spectrum, with the primary, component A, being an A-type main sequence star with a stellar classification of A5 V.^[5] This has been identified as an A-type shell star, suggesting there is a circumstellar disk of gas orbiting one or both stars.^[12] There are two other stars that appear close to the pair, termed C and D, but they are physically unrelated.^[13]

Ptolemy considered Nu Boötis to be shared by Hercules, and Bayer assigned it a designation in both constellations: Nu Boötis (ν Boo) and Psi Herculis (ψ Her). When the modern constellation boundaries were fixed in 1930, the latter designation dropped from use.^[14]