BY Draconis
 Visual band light curves for BY Draconis from six different years, adapted from Pettersen et al. (1992) | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Draco |
| AB | |
| Right ascension | 18h 33m 55.7721s |
| Declination | +51° 43′ 08.898″ |
| Apparent magnitude (V) | 8.20 |
| Characteristics | |
| Spectral type | K4Ve + K7.5Ve + M5 |
| U−B color index | +0.99 |
| B−V color index | +1.19 |
| Variable type | BY Dra + UV Cet |
| Astrometry | |
| AB | |
| Radial velocity (Rv) | −25.484±0.046 km/s |
| Proper motion (μ) | RA: +185.715 mas/yr Dec.: −325.475 mas/yr |
| Parallax (π) | 60.3814±0.0352 mas |
| Distance | 54.02 ± 0.03 ly (16.561 ± 0.010 pc) |
| Absolute magnitude (MV) | 7.48 / 8.63 |
| Orbit | |
| Primary | BY Dra A |
| Secondary | BY Dra B |
| Period (P) | 5.9751139±0.0000046 d |
| Semi-major axis (a) | (4.4472±0.0091)×10−3" (7.907±0.016 R☉) |
| Eccentricity (e) | 0.30014±0.00062 |
| Inclination (i) | 154.41±0.29° |
| Longitude of the node (Ω) | 152.3±0.1° |
| Periastron epoch (T) | JD 2453999.2144±0.0021 |
| Argument of periastron (ω) (secondary) | 230.33±0.17° |
| Semi-amplitude (K1) (primary) | 28.394±0.060 km/s |
| Semi-amplitude (K2) (secondary) | 32.284±0.061 km/s |
| Details | |
| BY Dra A | |
| Mass | 0.792±0.026 M☉ |
| Radius | 0.695±0.025 R☉ |
| Temperature | 4,000 K |
| Metallicity | +0.0 |
| Rotation | 3.8285 days |
| Age | 1–2 Gyr |
| BY Dra B | |
| Mass | 0.697±0.023 M☉ |
| Radius | 0.61±0.02 R☉ |
| Temperature | 4,000 K |
| Metallicity | +0.0 |
| Rotation | 3.8285 days |
| Age | 1–2 Gyr |
| Other designations | |
| BY Dra, BD+51 2402, GJ 719, HD 234677, HIP 91009, SAO 31048, LTT 15477 | |
| Database references | |
| SIMBAD | BY Dra AB |
| BY Dra C | |
| ARICNS | data |
BY Draconis is a multiple star system in the constellation Draco, consisting of at least three main sequence stars. Components A and B form a close binary star system with a short orbital period of only 5.98 days. Their individual spectroscopic classifications are dK5e and dK7e. They form the prototype of a class of variable stars known as BY Draconis variables.
The third component (C) is widely separated from the A-B pair, by an angular distance of 17 arcseconds which corresponds to 260 AU at the estimated distance of this star system—where an AU is the average distance from the Earth to the Sun. Component C is an M5 class red dwarf star. There may be a fourth component to the system, orbiting with a ≤1000‑day period, responsible for the eccentricity of the 5.98-day orbit, but this has not been visually confirmed.
The variability of BY Draconis is caused by activity in the stellar photosphere called starspots, which are comparable to sunspots on the Sun but much larger on BY Dra, in combination with rapid rotation that changes the viewing angle of the activity relative to the observer. This variation has an average periodicity of 3.8285 days, but the brightness also changes over the course of several years—depending on the level of surface activity. Most observers believe that the primary star (A) is responsible for the variability as the secondary produces only a third of the total luminosity from the system. However, spots may occur on both stars. Unlike the Sun, these spots may occur in the polar regions of the stars.
References
- 1 2 3 Pettersen, B. R.; Olah, K.; Sandmann, W. H. (1992). "Longterm behaviour of starspots. II - A decade of new starspot photometry of BY Draconis and EV Lacertae". Astronomy and Astrophysics Supplement Series. 96 (3): 497–504. Bibcode:1992A&AS...96..497P.
- 1 2 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.
- 1 2 3 4 5 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.
- 1 2 "V* BY Dra". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2008-04-18.
- 1 2 Epps, E. A. (1972). "UBV photoelectric observations. I. Stars within 25 parasecs of the Sun. II. Stars in quasar, galaxy fields. III. Stars in Kapteyn selected areas. IV. Miscellaneous stars". Royal Observatory Bulletin. 176: 77–115. Bibcode:1972RGOB..176..127E.
- ↑ Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
- 1 2 3 4 5 Hełminiak, K.G. (2012). "New high-precision orbital and physical parameters of the double-lined low-mass spectroscopic binary BY Draconis". Monthly Notices of the Royal Astronomical Society. 419 (2): 1285–1293. arXiv:1109.5059. Bibcode:2012MNRAS.419.1285H. doi:10.1111/j.1365-2966.2011.19785.x. S2CID 19002972.
- 1 2 Boden, A. F.; Lane, B. F. (2001). "A Preliminary Visual Orbit of BY Draconis". The Astrophysical Journal. 547 (2): 1071–1076. arXiv:astro-ph/0001138. Bibcode:2001ApJ...547.1071B. doi:10.1086/318394. S2CID 10704476.
- 1 2 Pettersen, B. R.; Olah, K.; Sandmann, H. W. (December 1992). "Longterm behaviour of starspots. II. A decade of new starspots of photometry of BY Draconis and EV Lacertae". Astronomy and Astrophysics Supplement Series. 96. Bibcode:1992A&AS...96..497P. ISSN 0365-0138.
External links
- "BY Draconis star". The Internet Encyclopedia of Science. Archived from the original on 4 March 2008. Retrieved 2008-04-18.
