Astronomy:15 Sagittae
250px 15 Sagittae and its companion Credit: Keck Observatory | |
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| 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[5] mas |
| 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 astronomical unit|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 | |
| Database references | |
| SIMBAD | data |
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
- ↑ 1.0 1.1 1.2 1.3 1.4 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A XHIP record for this object at VizieR.
- ↑ 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 3.0 3.1 3.2 3.3 3.4 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. doi:10.1088/0004-637X/751/2/97. 97. Bibcode: 2012ApJ...751...97C.
- ↑ Nidever, David L. et al. (August 2002). "Radial Velocities for 889 Late-Type Stars". The Astrophysical Journal Supplement Series 141 (2): 503–522. doi:10.1086/340570. Bibcode: 2002ApJS..141..503N.
- ↑ 5.0 5.1 5.2 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 et al. (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. doi:10.3847/1538-3881/adf730. Bibcode: 2025AJ....170..211K.
- ↑ "15 Sge". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=15+Sge.
- ↑ Cumming, Andrew et al. (December 1999). "The Lick Planet Search: Detectability and Mass Thresholds". The Astrophysical Journal 526 (2): 890–915. doi:10.1086/308020. Bibcode: 1999ApJ...526..890C.
- ↑ "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. doi:10.1086/339845. Bibcode: 2002ApJ...571..519L.
- ↑ 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. https://books.google.com/books?id=TYLvAAAAMAAJ&q=7664. Retrieved 2025-11-16.
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