Kappa Lupi
Binary star in the constellation Lupus
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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.
 | |
| Observation data Epoch J2000.0 Equinox 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: CD−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]