KT Lupi
Visual binary star system in the constellation of Lupus
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KT Lupi is a visual binary star[4] system in the constellation Lupus. It is visible to the naked eye with a combined apparent visual magnitude of 4.55.[1] As of 1983, the pair had an angular separation of 2.19″±0.03″.[9] Based upon an annual parallax shift of 7.6 mas[2] as seen from Earth's orbit, it is located 430 light-years from the Sun. The system is moving further from the Earth with a heliocentric radial velocity of +6.5 km/s.[6] It is a member of the Upper Centaurus-Lupus sub-group of the Scorpius–Centaurus association.[4]
  | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Lupus[1] |
| Right ascension | 15h 35m 53.24806s[2] |
| Declination | −44° 57′ 30.1982″[2] |
| Apparent magnitude (V) | 4.55[1] (4.66 + 6.62)[3] |
| Characteristics | |
| Spectral type | B3 V + B6 V[4] |
| B−V color index | −0.175±0.003[1] |
| Variable type | Be[5] |
| Astrometry | |
| Radial velocity (Rv) | +6.5±2.8[6] km/s |
| Proper motion (μ) | RA: −20.53[2] mas/yr Dec.: −21.23[2] mas/yr |
| Parallax (π) | 7.62±0.43 mas[2] |
| Distance | 430 ± 20 ly (131 ± 7 pc) |
| Absolute magnitude (MV) | −1.03[1] |
| Details | |
| KT Lup A | |
| Mass | 5.9±0.1[7] M☉ |
| Radius | 3.00±0.06[8] R☉ |
| Luminosity | 794+791 −396[9] L☉ |
| Surface gravity (log g) | 3.50±0.04[8] cgs |
| Temperature | 18,400±184[8] K |
| Rotational velocity (v sin i) | 30±0.6[8] km/s |
| Age | 21.0±10.6[7] Myr |
| KT Lup B | |
| Mass | 2.79[10] M☉ |
| Other designations | |
| d Lup, KT Lup, CD−44°10239, HD 138769, HIP 76371, HR 5781, SAO 225950, WDS J15359-4457AB[11] | |
| Database references | |
| SIMBAD | data |
The primary, component A, is a variable Be star,[5] with the variation being modulated by rotation.[13] It is visual magnitude 4.66[3] with a stellar classification of B3 V,[4] matching a B-type main-sequence star. Hiltner et al. (1969) gave a class of B3 IVp,[14] which is still used in some studies.[7][8][9] It is a helium-weak chemically peculiar star showing an enhanced silicon patch near the equator and a silicon-weak region close to the pole.[9] The star is about 21 million years old with nearly six[7] times the mass of the Sun and three times the Sun's radius.[8] It is radiating roughly 794[9] times the Sun's luminosity from its photosphere at an effective temperature of 18,400 K.[8]
The secondary companion, component B, is of magnitude 6.62[3] with a class of B6 V.[4] It has 2.79 times the Sun's mass.[10]