BY Draconis

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Double star
BY Draconis
Observation
dates equinox :  J2000.0 , epoch : J2000.0
AladinLite
Constellation Dragon
Apparent brightness  8.04 mag
Position of the companion
Angular distance C: 16 ″ , 7th
Position angle C: Δα = +11 ", 9; Δδ +11 ", 8
Astrometry
Radial velocity (−25.43 ± 0.08) km / s
parallax AB: 60.56 ± 0.04
C: 60.62 ± 0.06 mas
distance  54 ly
(16.5 pc )
Proper movement :
Rec. Share: AB: +185.79 ± 0.08
C: +199.80 ± 0.15 mas / a
Dec. portion: AB: −325.81 ± 0.06
C: −339.06 ± 0.13 mas / a
orbit 
period AB: 5.98 d
Major semi-axis AB: 4.45 mas
eccentricity AB: 0.30
Orbit inclination AB: 154 °
Argument of the node AB: 152 °
Epoch of the periastron AB: JD 2453999
Argument of the periapsis AB: 230 °
Individual data
Names FROM; C.
Observation data:
Right ascension FROM 183355.77218 h 33 m 55,772 s
C. 183357.07418 h 33 m 57.074 p
declination FROM 2514308.903+ 51 ° 43 ′ 08.903 ″
C. 2514320.761+ 51 ° 43 ′ 20.761 ″
Apparent brightness FROM 8.04 (8.04 to 8.48) mag
C. approx. 16 mag
Typing:
Spectral class FROM A: K4 Ve
B: K7 Ve
C. approx M5
B − V color index FROM +1.19
U − B color index FROM +0.99
Physical Properties:
Absolute vis.
Brightness M vis 		FROM A: +7.48 mag
B: +8.63 mag
C.
Dimensions FROM A: 0.79 M ☉
B: 0.70 M ☉
C.
Effective temperature FROM 4620 K
C.
Metallicity [Fe / H] FROM +0.2
C.
Other names
and catalog entries
Bonn survey BD + 51 ° 2402
Henry Draper Catalog HD 234677 [1]
SAO catalog SAO 31048 [2]
Tycho catalog TYC 3539-2623-1 [3]
Hipparcos catalog HIP 91009 [4]
Further designations:
BY Draconis, 2MASS J18335574 + 5143094, WDS J18339 + 5144A, GJ 719 BY Draconis C, 2MASS J18335703 + 5143213, WDS J18339 + 5144B

Template: Infobox double star / maintenance / RekDekSizeLeerTemplate: Infobox double star / maintenance / single coordinates

BY Draconis is a multiple system at a distance of just over 50  light years . The components A and B orbit each other closely in just 5.98 days and form the prototype of the BY-Draconis stars , which belong to the rotationally variable stars . Component C is a faint red dwarf and orbits AB at a distance of 260  AU .

BY Draconis AB has star spots comparable to the sunspots of the sun . In combination with the rapid rotation, these spots migrate rapidly and thus cause the variability . The mean period of these fluctuations is 3.8 days, with long-term trends over the years. It is believed that the variability is mainly caused by the lighter component A, but component B could also be contributing.

Web links

Individual evidence

  1. ↑ a b c d e f g h i BY Dra. In: SIMBAD. Center de Données astronomiques de Strasbourg, accessed February 6, 2019 .
  2. ↑ BY Dra. In: VSX. AAVSO , accessed February 6, 2019 .
  3. ↑ a b BY Dra C. In: SIMBAD. Center de Données astronomiques de Strasbourg, accessed February 6, 2019 .
  4. ↑ a b K.G. Hełminiak: New high-precision orbital and physical parameters of the double-lined low-mass spectroscopic binary BY Draconis . In: Monthly Notices of the Royal Astronomical Society . 419, 2012, pp. 1285-1293. arxiv : 1109.5059 . bibcode : 2012MNRAS.419.1285H . doi : 10.1111 / j.1365-2966.2011.19785.x .
  5. ↑ ZUC 16. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed February 6, 2019 .
  6. ^ AF Boden, BF Lane: A Preliminary Visual Orbit of BY Draconis . In: The Astrophysical Journal . 547, No. 2, 2001, pp. 1071-1076. arxiv : astro-ph / 0001138 . bibcode : 2001ApJ ... 547.1071B . doi : 10.1086 / 318394 .
  7. ^ BR Pettersen, K. Olah, WH Sandmann: Long-term behavior of starspots. II - A decade of new starspot photometry of BY Draconis and EV Lacertae . In: Astronomy and Astrophysics Supplement Series . 96, No. 3, 1992, pp. 497-504. bibcode : 1992A & AS ... 96..497P .