Visual band light curves for BY Draconis from six different years, adapted from Pettersen et al. (1992)[1]
Observation data Epoch J2000 Equinox J2000
Constellation
Draco
Right ascension
18h 33m 55.7728s[2]
Declination
+51° 43′ 08.905″[2]
Apparent magnitude (V)
8.07[2]
Characteristics
Spectral type
K6Ve[2]
U−B color index
+0.99[3]
B−V color index
+1.19[3]
Variable type
BY Dra + UV Cet[4]
Astrometry
Radial velocity (Rv)
−25.484±0.046[5] km/s
Proper motion (μ)
RA: 185.759[2] mas/yr Dec.: −325.590[2] mas/yr
Parallax (π)
60.59 ± 0.28 mas[2]
Distance
53.8 ± 0.2 ly (16.50 ± 0.08 pc)
Absolute magnitude (MV)
7.48 / 8.63[6]
Orbit[5]
Primary
BY Dra A
Companion
BY Dra B
Period (P)
5.9751139 ± 0.0000046 d
Semi-major axis (a)
4.4472 ± 0.0091 mas
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[5]
BY Dra A
Mass
0.792 ± 0.026 M☉
BY Dra B
Mass
0.697 ± 0.023 M☉
Other designations
BY Dra, GJ 719, BD+51 2402, HD 234677, LTT 15477, SAO 31048, HIP 91009.
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 components. Components A and B are main sequence stars,[5] and form a close binary star system with a short orbital period of only 5.98 days. Their individual spectroscopic classifications are dK5e and dK7e.[1] They form the prototype of a class of variable stars known as BY Draconis variables.[6]
The third component (C) is, by comparison, 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.[5]
The variability of BY Draconis is caused by activity in the stellar photosphere called starspots, which are comparable to sunspots on the Sun, 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, the spots may occur on both stars. Unlike the Sun, these spots may occur in the polar regions of the stars.[1]
^ abcPettersen, 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.
^ abcdefg"V* BY Dra". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2008-04-18.
^ abEpps, 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.
^ abcdeHełminiak, 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.
^ abBoden, 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.
Gamma Draconis (γ Draconis, abbreviated Gamma Dra, γ Dra), formally named Eltanin /ɛlˈteɪnɪn/, is a star in the northern constellation of Draco. Contrary...
BYDraconis is a multiple star system in the constellation Draco, consisting of at least three components. Components A and B are main sequence stars...
exceptions to the planetary rulerships were the figures Cauda Draconis and Caput Draconis, which were assigned to the northern and southern lunar nodes...
developed by Larian Studios. Its first release in 2009 was subtitled Ego Draconis and was published by dtp entertainment and in the United States by cdv Software...
The phrase caput draconis means "dragon's head" (or "head of the dragon") in Latin. Caput Draconis may also refer to: The "head" of the constellation...
Sigma Draconis is a single star in the northern constellation of Draco. It has the proper name Alsafi /ælˈseɪfi/, while Sigma Draconis, which is latinised...
Thuban (/ˈθjuːbæn/), with Bayer designation Alpha Draconis or α Draconis, is a binary star system in the northern constellation of Draco. A relatively...
Bayer designation Psi Draconis (ψ Dra / ψ Draconis) is shared by two star systems, in the constellation Draco: ψ1 Draconis ψ2 Draconis This article includes...
Beta Draconis, a name Latinized from β Draconis, is a binary star system and the third-brightest star in the northern circumpolar constellation of Draco...
BYDraconis variables are variable stars of late spectral types, usually K or M, and typically belong to the main sequence. The name comes from the archetype...
Mu Draconis (μ Draconis, abbreviated Mu Dra, μ Dra) is a multiple star system near the head of the constellation of Draco. With a combined magnitude of...
Iota Draconis (ι Draconis, abbreviated Iota Dra, ι Dra), also named Edasich /ˈɛdəsɪk/, is a star in the northern circumpolar constellation of Draco. A...
Zeta Draconis (ζ Draconis, abbreviated Zet Dra, ζ Dra) is a binary star in the northern circumpolar constellation of Draco. With an apparent visual magnitude...
Eta Draconis (η Draconis, abbreviated Eta Dra, η Dra) is a binary star in the northern circumpolar constellation of Draco. Despite having an apparent visual...
Nu Draconis (also known as 𝜈 Dra, 𝜈 Draconis, where 𝜈 is the Greek letter nu, or traditionally as Kuma /ˈkjuːmə/) is a double star in the constellation...
Omicron Draconis (Latinised as ο Draconis, abbreviated to ο Dra) is a giant star in the constellation Draco located 322.93 light years from the Earth...
frigid, ice covered planet unnamed in Dune 2000 but later called Sigma Draconis IV in Emperor: Battle for Dune. As they import their goods from nearby...
Delta Draconis (δ Draconis, abbreviated Delta Dra, δ Dra), formally named Altais /ælˈteɪ.ɪs/, is a yellow star in the constellation of Draco. It has an...
Chi Draconis (χ Dra, χ Draconis, Chi Draconis) is a magnitude 3.6 binary star in the constellation Draco. It also has the Flamsteed designation 44 Draconis...
Lambda Draconis (λ Draconis, abbreviated Lam Dra, λ Dra), also named Giausar (/ˈdʒɔːzɑːr/ JAW-zar), is a solitary, orange-red star in the northern circumpolar...
Draconis, Latinized from ε Draconis, is a fourth-magnitude star in the constellation Draco. This star along with Delta Draconis (Altais), Pi Draconis...
Kappa Draconis, Latinized from κ Draconis, is a blue giant star located in the northern circumpolar constellation of Draco. At an apparent magnitude of...
Xi Draconis (ξ Draconis, abbreviated Xi Dra, ξ Dra) is a double or binary star in the northern circumpolar constellation of Draco. It has an apparent visual...
Psi1 Draconis (ψ1 Draconis, abbreviated Psi1 Dra, ψ1 Dra), also designated 31 Draconis, is a triple star system in the northern constellation of Draco...
Pictoris is the south pole star of Mercury while Omicron Draconis is its north star. 42 Draconis is the closest star to the north pole of Venus. Eta1 Doradus...
Theta Draconis, a name Latinized from θ Draconis, is a binary star system in the northern circumpolar constellation of Draco. It is faintly visible to...
Global Information