Kappa Lupi

Kappa Lupi is a binary star^[18] in the constellation of Lupus. With a combined apparent magnitude of 3.70,^[19] it is visible to the naked eye. The average distance to this system, based on parallax measurements, is 180 light-years.

Kappa Lupi

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Lupus[1][2]
κ1 Lup
Right ascension	15h 11m 56.07286s[3]
Declination	−48° 44′ 16.1692″[3]
Apparent magnitude (V)	3.86[4]
κ2 Lup
Right ascension	15h 11m 57.67537s[5]
Declination	−48° 44′ 37.2684″[5]
Apparent magnitude (V)	5.70[2]
Characteristics
κ1 Lup
Spectral type	B9.5 Vne[6]
U−B color index	−0.08[4]
B−V color index	−0.05[4]
κ2 Lup
Evolutionary stage	main sequence[5]
Spectral type	A3/5V[7]
B−V color index	+0.144±0.008[2]
Astrometry
κ1 Lup
Radial velocity (Rv)	−6.6±2.9[8] km/s
Proper motion (μ)	RA: −96.50[3] mas/yr Dec.: −49.86[3] mas/yr
Parallax (π)	18.12±0.47 mas[3]
Distance	180 ± 5 ly (55 ± 1 pc)
κ2 Lup
Radial velocity (Rv)	+0.0±3.7[9] km/s
Proper motion (μ)	RA: −98.497 mas/yr[5] Dec.: −43.645 mas/yr[5]
Parallax (π)	17.906±0.0587 mas[5]
Distance	182.1 ± 0.6 ly (55.8 ± 0.2 pc)
Absolute magnitude (MV)	+1.84[10]
Details
κ1 Lup
Mass	2.89±0.03[11] M☉
Radius	3.0[12] R☉
Luminosity	90[12] L☉
Surface gravity (log g)	3.99±0.14[13] cgs
Temperature	10,280[12] K
Rotational velocity (v sin i)	191±16[11] km/s
Age	121[13] Myr
κ2 Lup
Mass	2.0[12] M☉
Radius	1.8[12] R☉
Luminosity	13[12] L☉
Surface gravity (log g)	4.26[12] cgs
Temperature	8,255[12] K
Metallicity [Fe/H]	−0.01[14] dex
Rotational velocity (v sin i)	160.4±1.0[15] km/s
Age	653[5] Myr
Other designations
κ1 Lup: CD−48°9704, FK5 1398, HD 134481, HIP 74376, HR 5646, SAO 225525[16]
κ2 Lup: BD−48°9705, HD 134482, HIP 74380, HR 5647, SAO 225526[17]
Database references
SIMBAD	κ1 Lup
SIMBAD	κ2 Lup

The stars in the system are separated by an angular separation of 26.44″.^[18] At their distance, this corresponds to a projected separation of 1,450 astronomical units.^[20] They are members of the Hyades Stream, which is a moving group that is coincident with the proper motions of the Hyades cluster.^[21]

The primary, Kappa¹ Lupi, has an apparent magnitude of 3.86.^[4] It is a B-type main sequence star with a stellar classification of B9.5 Vne.^[6] The 'n' suffix indicates the spectrum shows "nebulous" absorption lines due to rapid rotation, while the 'e' means this is a Be star that displays Balmer series emission lines. With an estimated age of 195 million years,^[6] it is about 75% of the way through its life span on the main sequence.^[11] The star is rotating with a projected rotational velocity of 191 km/s.^[11] This rate of spin is giving the star an oblate shape with an equatorial bulge that is an estimated 9% larger than the polar radius.^[22]

The secondary, Kappa² Lupi, has an apparent magnitude of 5.70.^[2] It is an A-type main-sequence star with a stellar classification of A3/5V.^[7] The star has a high rotation rate, showing a projected rotational velocity of 160 km/s.^[15] It is 2.0 times more massive and 1.8 times larger than the Sun, with 13 times the Sun's luminosity and an effective temperature of 8,255 K.^[12]

In Chinese astronomy, Kappa¹ Lupi is called 騎陣將軍, Pinyin: Qízhènjiāngjūn, meaning Chariots and Cavalry General, because this star is marking itself and stand alone in Chariots and Cavalry General asterism, Root mansion (see : Chinese constellation).^[23]