HD 159176
Variable star in the constellation Scorpius
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HD 159176, also known as Boss 4444 and V1036 Scorpii, is a variable star about 2,800 light years from the Earth, in the constellation Scorpius.[2] It is a 5th magnitude star, so it should be visible to the naked eye of an observer far from city lights. HD 159176 is the brightest star in the young open cluster NGC 6383.[4] It is a binary star composed of two nearly identical O stars in a circular orbit.[8]
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Scorpius[1] |
| Right ascension | 17h 34m 42.49213s[2] |
| Declination | −32° 34′ 53.9955″[2] |
| Apparent magnitude (V) | 5.71 - 5.79[3] |
| Characteristics | |
| Spectral type | O6.5V + O7V[4] |
| U−B color index | −0.86[5] |
| B−V color index | +0.04[5] |
| Variable type | Rotating ellipsoidal[3] |
| Astrometry | |
| Proper motion (μ) | RA: 2.621±0.083[2] mas/yr Dec.: −0.798±0.058[2] mas/yr |
| Parallax (π) | 1.1666±0.0707 mas[2] |
| Distance | 2,800 ± 200 ly (860 ± 50 pc) |
| Absolute magnitude (MV) | −4.53[5] |
| Orbit[6] | |
| Period (P) | 3.366767 d |
| Eccentricity (e) | 0.0 |
| Periastron epoch (T) | 2448885.420±0.003 |
| Semi-amplitude (K1) (primary) | 215.7±1.4 km/s |
| Semi-amplitude (K2) (secondary) | 218.1±1.5 km/s |
| Details | |
| Primary | |
| Mass | 46.4+14.3 −9.5[4] M☉ |
| Luminosity | 105.50±0.10[4] L☉ |
| Temperature | 38,000[4] K |
| Secondary | |
| Mass | 44.2+13.6 −9.1[4] M☉ |
| Luminosity | 105.41±0.10[4] L☉ |
| Temperature | 36,750[4] K |
| Other designations | |
| V1036 Scorpii, HIP 86011, HR 6535, SAO 208977, Boss 4444[7] | |
| Database references | |
| SIMBAD | data |
In 1930, Robert Trumpler discovered that HD 159176 is a spectroscopic binary. He noted that the two stars have very nearly the same brightness and spectral type. In addition, he was observing at the Lick Observatory, so the far southern declination of the star meant it could only be observed near transit. Those three things together prevented him from unambiguously measuring the orbital period.[10] The first full set of orbital elements, including the 3.3664±0.0003 day period, was derived by Peter Conti et al. in 1975.[11] Also in 1975, photometric observations by J. C. Thomas showed that HD 159176 is a rotating ellipsoidal variable.[12][13] The star's spectra exhibit the Struve–Sahade effect.[4] HD 159176 was given the variable star designation V1036 Scorpii, in 1997.[14]
Although HD 159176 was long considered to be a non-eclipsing binary,[4][8][15][16] data from the Transiting Exoplanet Survey Satellite does show eclipses.[17]
HD 159176 has an X-ray luminosity far higher than would be expected from two isolated O stars. The excess X-rays may arise from interacting stellar winds.[8]