XY Ursae Majoris

XY Ursae Majoris

A light curve for XY Ursae Majoris, plotted from TESS data[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
Right ascension 09h 09m 55.935s[2]
Declination +54° 29′ 17.72″[2]
Apparent magnitude (V) 9.50[3]
Characteristics
Evolutionary stage Main sequence
Spectral type G2V + K5V[4]
B−V color index 0.765±0.039[3]
Variable type Detached eclipsing binary, RS CVn[5]
Astrometry
Radial velocity (Rv)−9.98±0.83[6] km/s
Proper motion (μ) RA: −49.781 mas/yr[2]
Dec.: −182.641 mas/yr[2]
Parallax (π)14.7223 ± 0.0137 mas[2]
Distance221.5 ± 0.2 ly
(67.92 ± 0.06 pc)
Absolute magnitude (MV)5.41[3]
Orbit[7]
Period (P)0.4789961 d
Semi-major axis (a)3.05±0.01 R☉[8]
Eccentricity (e)0.0
Inclination (i)79.81[8]°
Periastron epoch (T)2,453,821.6344±0.0002
Semi-amplitude (K1)
(primary)		124.74±0.28 km/s
Details
Primary
Mass1.01±0.01[8] M☉
Radius1.22±0.01[8] R☉
Luminosity1.10±0.02[8] L☉
Temperature5,780[4] K
Secondary
Mass0.65±0.01[8] M☉
Radius0.58±0.01[8] R☉
Luminosity0.09±0.01[8] L☉
Temperature3,850[4] K
Other designations
XY UMa, AG+54 702, BD+55 1317, HD 237786, HIP 44998, SAO 27143, PPM 32024[9]
Database references
SIMBADdata

XY Ursae Majoris is a short period binary star system in the northern circumpolar constellation of Ursa Major. It is an eclipsing binary with a baseline apparent visual magnitude of 9.50.[3] The system is located at a distance of 221.5 light years from the Sun based on parallax measurements,[2] but is drifting closer with a radial velocity of −10 km/s.[6] It has a relatively high proper motion, traversing the celestial sphere at the angular rate of 0.191″·yr−1.[10]

The variability of this system was discovered by W. Strohmeier and its period was determined by R. Kippenhahn, with the findings announced in 1955.[11] It was found to be a detached eclipsing binary system, and by 1963 a variable primary component had been noted.[12] E. H. Geyer made intermittent light curve studies of the system starting with its discovery up until 1975,[11] ascribing variability in the light curve to star spot activity on the primary component. The orbital period of the pair was determined to be 0.479 d,[13] with the orbital plane inclined at an angle of 79.84° to the line of sight from the Earth.[8]

By 1990, enough data had been collected to identify a long term variation of the period, and it was hypothesized this was caused by a third body in the system orbiting the close binary.[14] The orbital period of this component was estimated to be ~30 years in 2001,[15] then refined to 26.7 years by 2010. If the orbital plane of this component is the same as the inner pair, its mass would be 18% of the mass of the Sun. An alternative solution to the period change suggests magnetic activity causes shifts in the angular momentum of the system, but this is considered less likely.[8]

This is a double-lined spectroscopic binary star system with an orbital period of 11.5 h.[7] The primary component is a G-type main-sequence star with a stellar classification of G2V.[4] It is an RS Canum Venaticorum-type variable that is magnetically active[5] and a bright X-ray source.[16] Despite this, relatively few optical flares have been observed.[16] The cooler secondary is a K-type main-sequence star of class K5V that is smaller and less massive than the primary.[4]

  1. ^ Cite error: The named reference MAST was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference GaiaEDR3 was invoked but never defined (see the help page).
  3. ^ a b c d Cite error: The named reference Anderson_Francis_2012 was invoked but never defined (see the help page).
  4. ^ a b c d e Cite error: The named reference Lister_et_al_2001 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Karataș_et_al_2004 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Pribulla_et_al_2007 was invoked but never defined (see the help page).
  8. ^ a b c d e f g h i j Cite error: The named reference Yuan2010 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Lepine_Shara_2005 was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference Geyer1976 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Lorenzi_Scaltriti_1977 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Geyer1977 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Pojmanski_Geyer_1990 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Chochol_et_al_2001 was invoked but never defined (see the help page).
  16. ^ a b Cite error: The named reference Gong_et_al_2016 was invoked but never defined (see the help page).