15 Sagittarii
Star in the constellation Sagittarius
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15 Sagittarii is a blue-hued binary star[10] system in the southern zodiac constellation of Sagittarius. The estimated distance based upon photometry is around 4,200 ly (1,300 pc).[7] It is faintly visible to the naked eye with an apparent visual magnitude of 5.37.[2] The system is moving closer to the Sun with a heliocentric radial velocity of around â6 km/s.[6]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 15m 12.90641s[1] |
| Declination | â20° 43â² 41.7738â³[1] |
| Apparent magnitude (V) | 5.37[2] |
| Characteristics | |
| Spectral type | O9.7 Iab[3] or B0 Iab[4] |
| BâV color index | 0.007±0.004[5] |
| Astrometry | |
| Radial velocity (Rv) | â6.3±2.8[6] km/s |
| Proper motion (μ) | RA: +1.60[1] mas/yr Dec.: â1.51[1] mas/yr |
| Parallax (Ï) | 0.10±0.45 mas[1] |
| Distance | 4,200±650[7] ly (1,300±200 pc) |
| Details[8] | |
| 15 Sgr Aa | |
| Mass | ~30[4] Mâ |
| Radius | 28.6±12.5 Râ |
| Luminosity | 4.47+3.85 â2.07Ã105 Lâ |
| Surface gravity (log g) | 3.10 cgs |
| Temperature | 28,000±1,000 K |
| Rotational velocity (v sin i) | 83±7[4] km/s |
| Other designations | |
| 15 Sgr, BDâ20° 5054, HD 167264, HIP 89439, HR 6822, SAO 186543, WDS J18152-2044[9] | |
| Database references | |
| SIMBAD | data |
Chini et al. (2012) identify this as a double-lined spectroscopic binary star system.[10] It shows a stellar classification of O9.7 Iab,[3] matching a massive O-type supergiant star. Along with the O-type star 16 Sgr (HD 167263), it is ionizing an H II region along the western edge of the molecular cloud L291.[11]
The Washington Double Star Catalog lists four companions within a 2 arcsecond angular radius.[12]