15 Sagittae (15 Sge) is a star in the northern constellation Sagitta, located around 58 light years away from the Sun. It is visible to the naked eye as a faint, yellow-hued star with an apparent visual magnitude of 5.80.[2] Considered a solar analog, it was the target of the first radial velocity survey from Lick Observatory, which found a drift due to a companion.[6] In 2002, the cause of this was found to be brown dwarf companion B via direct imaging.[7]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Sagitta |
| Right ascension | 20h 04m 06.22091s[1] |
| Declination | +17° 04′ 12.6774″[1] |
| Apparent magnitude (V) | 5.80[2] |
| Characteristics | |
| Evolutionary stage | main sequence |
| Spectral type | G0V + L4[3] |
| B−V color index | 0.600±0.005[2] |
| Astrometry | |
| Radial velocity (Rv) | 4.57±0.1[4] km/s |
| Proper motion (μ) | RA: −387.590[1] mas/yr Dec.: −419.542[1] mas/yr |
| Parallax (π) | 56.426 ± 0.069 mas[1] |
| Distance | 57.80 ± 0.07 ly (17.72 ± 0.02 pc) |
| Absolute magnitude (MV) | 4.55[2] |
| Orbit[3] | |
| Period (P) | 73.3+2.2 −3.9 yr |
| Semi-major axis (a) | 18.3+0.4 −0.5 AU |
| Eccentricity (e) | 0.50±0.01 |
| Inclination (i) | 97.3+0.4 −0.5° |
| Details[3] | |
| 15 Sge A | |
| Mass | 1.08±0.04 M☉ |
| Radius | 1.115±0.021 R☉ |
| Luminosity | 1.338±0.032 L☉ |
| Surface gravity (log g) | 4.42±0.06 cgs |
| Temperature | 5,883±59 K |
| Metallicity [Fe/H] | 0.05±0.07 dex |
| Rotation | 17.5±2.3 |
| Rotational velocity (v sin i) | 4.42±0.06 km/s |
| Age | 2.5±1.8 Gyr |
| 15 Sge B | |
| Mass | 68.7+2.4 −3.1 MJup |
| Radius | 1.0±0.4 RJup |
| Luminosity | 0.000075±0.000016 L☉ |
| Temperature | 1,510–1,850 K |
| Other designations | |
| Database references | |
| SIMBAD | data |
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The companion is a high-mass substellar brown dwarf of spectral class L4 ± 1.5, only a few Jupiter masses below the limit for stars, in a long-period orbit around the primary star. Imaged by the Keck telescope, was the first brown dwarf candidate orbiting a sun-like star detected via imaging and is currently the only known companion brown dwarf which both has a significant radial velocity trend on the primary that has also been imaged.
The brown dwarf was originally thought to have a semi-major axis of 14 AU and a circular orbit viewed from pole-on,[8] but ten more years of observations found that the brown dwarf's orbit is viewed from nearly edge-on, is significantly eccentric and appeared to be moving in a circular orbit when first discovered, but is now approaching the primary as viewed from Earth.[3]
References
edit- ^ a b c d e Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ a b c d Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
- ^ a b c d Crepp, Justin R.; et al. (June 2012). "The Dynamical Mass and Three-Dimensional Orbit of HR7672B: A Benchmark Brown Dwarf with High Eccentricity". The Astrophysical Journal. 751 (2): 14. arXiv:1112.1725. Bibcode:2012ApJ...751...97C. doi:10.1088/0004-637X/751/2/97. S2CID 16113054. 97.
- ^ Nidever, David L.; et al. (August 2002). "Radial Velocities for 889 Late-Type Stars". The Astrophysical Journal Supplement Series. 141 (2): 503–522. arXiv:astro-ph/0112477. Bibcode:2002ApJS..141..503N. doi:10.1086/340570. S2CID 51814894.
- ^ "15 Sge". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-03-24.
- ^ Cumming, Andrew; et al. (December 1999). "The Lick Planet Search: Detectability and Mass Thresholds". The Astrophysical Journal. 526 (2): 890–915. arXiv:astro-ph/9906466. Bibcode:1999ApJ...526..890C. doi:10.1086/308020. S2CID 12560512.
- ^ "Brown dwarf found around nearby sun-like star" (Press release). Kamuela, Hawaii: W. M. Keck Observatory. January 1, 2002. Retrieved August 13, 2019.
- ^ Liu, Michael C.; et al. (May 2002). "Crossing the Brown Dwarf Desert Using Adaptive Optics: A Very Close L-Dwarf Companion to the Nearby Solar Analog HR 7672". The Astrophysical Journal. 571 (1): 519–527. arXiv:astro-ph/0112407. Bibcode:2002ApJ...571..519L. doi:10.1086/339845. S2CID 11405638.