15 Sagittae
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Sagitta[1] |
| Right ascension | 20h 04m 06.22077s[2] |
| Declination | +17° 04′ 12.6766″[2] |
| Apparent magnitude (V) | 5.80[1] |
| Characteristics | |
| Evolutionary stage | main sequence[2] |
| Spectral type | G0V + L4[3] |
| B−V color index | 0.600±0.005[1] |
| Astrometry | |
| Radial velocity (Rv) | 4.57±0.1[4] km/s |
| Proper motion (μ) | RA: −387.472[2] mas/yr Dec.: −419.497[2] mas/yr |
| Parallax (π) | 56.2724±0.0094 mas[5] |
| Distance | 57.960 ± 0.010 ly (17.771 ± 0.003 pc) |
| Absolute magnitude (MV) | 4.55[1] |
| Orbit[5] | |
| Period (P) | 63.77+0.63 −0.61 yr |
| Semi-major axis (a) | 16.88±0.10 AU |
| Eccentricity (e) | 0.4683+0.0032 −0.0031 |
| Inclination (i) | 97.73±0.31° |
| Longitude of the node (Ω) | 330.88±0.21° |
| Periastron epoch (T) | 2,457,070±11 |
| Argument of periastron (ω) (secondary) | 266.23±0.45° |
| Details[5] | |
| 15 Sge A | |
| Mass | 1.114±0.013 M☉ |
| Radius | 1.051±0.010 R☉ |
| Luminosity | 1.224±0.043 L☉ |
| Surface gravity (log g) | 4.442±0.010 cgs |
| Temperature | 5,932±81 K |
| Metallicity [Fe/H] | +0.051±0.057 dex |
| Rotation | 14.8±1.3 days |
| Rotational velocity (v sin i) | 4.42±0.06[3] km/s |
| Age | 2.26±0.40 Gyr |
| 15 Sge B | |
| Mass | 75.39±0.67 MJup |
| Radius | 0.82+0.10 −0.07[6] RJup |
| Luminosity | 0.000075±0.000016[3] L☉ |
| Temperature | 1,510–1,850[3] K |
| Other designations | |
| 15 Sge, BD+16°4121, GJ 779, HD 190406, HIP 98819, HR 7672, SAO 105635, LFT 1517, LHS 3515, LTT 15872, Wolf 866[7] | |
| Database references | |
| SIMBAD | data |
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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.[1] 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.[8] In 2002, the cause of this was found to be brown dwarf companion B via direct imaging.[9]
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, it 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,[10] 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]
John Flamsteed labelled this star as z Sagittae, but the designation was dropped by later authors and is now largely unknown.[11]
References
- ^ a b c d e 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. XHIP record for this object at VizieR.
- ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b c d e 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.
- ^ a b c Li, Yaguang; Liu, Michael C.; Dupuy, Trent J.; Huber, Daniel; Zhang, Jingwen; Hey, Daniel; Costa, R. R.; Larsen, Jens Reersted; Ong, J. M. Joel (2025-12-05). "A Test of Substellar Evolutionary Models with High-Precision Ages from Asteroseismology and Gyrochronology for the Benchmark System HR 7672AB". arXiv:2512.06083 [astro-ph.SR].
- ^ Kasagi, Yui; Kawashima, Yui; Kawahara, Hajime; Kotani, Takayuki; Masuda, Kento; Ahn, Kyohoon; Guyon, Olivier; Hirano, Teruyuki; Jovanovic, Nemanja (2025-08-02). "Unveiling the Atmosphere of HR 7672 B from the Near-Infrared High-Resolution Spectrum Using REACH/Subaru". The Astronomical Journal. 170 (4): 211. arXiv:2508.01281. Bibcode:2025AJ....170..211K. doi:10.3847/1538-3881/adf730.
- ^ "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.
- ^ Wagman, Morton (2003). Lost Stars: Lost, Missing, and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas-Louis de Lacaille, John Flamsteed, and Sundry Others. McDonald & Woodward Publishing Company. ISBN 978-0-939923-78-6. Retrieved 2025-11-16.
