84 Ursae Majoris

84 Ursae Majoris

A light curve for CR Ursae Majoris, plotted from TESS data.[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
Right ascension 13h 46m 35.65679s[2]
Declination +54° 25′ 57.6436″[2]
Apparent magnitude (V) 5.65 - 5.70[3]
Characteristics
Spectral type B9pe[4]
B−V color index -0.04[4]
Variable type α2 CVn[3]
Astrometry
Radial velocity (Rv)−2.4±1.6[5] km/s
Proper motion (μ) RA: −18.559±0.041[2] mas/yr
Dec.: −4.742±0.039[2] mas/yr
Parallax (π)10.7417 ± 0.0418 mas[2]
Distance304 ± 1 ly
(93.1 ± 0.4 pc)
Absolute magnitude (MV)0.98±0.12[6]
Details
Primary
Mass2.60+0.17
−0.25[7] M☉
Radius2.28±0.10[7] R☉
Luminosity44.9±4.3[7] L☉
Surface gravity (log g)4.07[8] cgs
Temperature9865±370[7] K
Metallicity [Fe/H]3.14±0.17[9] dex
Rotation1.39 d[7]
Age0.24+0.15
−0.11[7] Gyr
Other designations
CR Ursae Majoris, BD+55 1634, HIP 67231, HD 120198, HR 5187, SAO 28885[10]
Database references
SIMBADdata

84 Ursae Majoris, also known as HD 120198, is a star about 300 light years from the Earth, in the constellation Ursa Major.[2] It is a 5th magnitude star, making it faintly visible to the naked eye of an observer far from city lights. It is an Ap star with an 1,100 gauss magnetic field,[7] and an α2 CVn variable star, varying in brightness from magnitude 5.65 to 5.70, over a period of 1.37996 days.[3] 84 Ursae Majoris is located just 70 arcseconds from the star LDS 2914, but that star is believed to be a background star not physically associated with 84 Ursae Majoris.[11]

Gerhard Jackisch discovered that 84 Ursae Majoris is a variable star, with a period greater than one day, in 1972.[12] It was given the variable star designation CR Ursae Majoris in 1974.[13]

In 1994 John Rice and William Wehlau used Doppler imaging to map the distribution of iron and chromium on the surface of 84 Ursae Majoris. They found that the distribution of those elements across the surface was similar, and the abundances of those elements varied by a factor of 15 across the surface. Chromium was found to be about 600 times more abundant than on the Sun in the regions of the 84 Ursae Majoris surface with the minimum chromium abundance.[14]

The size of 84 Ursae Majoris was measured in red light during 2015 and 2016, using the CHARA array. The limb darkened angular diameter was 0.226±0.008 milliarcseconds.[4]

  1. ^ Cite error: The named reference MAST was invoked but never defined (see the help page).
  2. ^ a b c d e f Cite error: The named reference dr3 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference gcvs was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference Perraut2020 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Kochukhov2006 was invoked but never defined (see the help page).
  7. ^ a b c d e f g Cite error: The named reference Deal2021 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Adelman2000 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Sikora2019 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Roberts2007 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Jackisch1972 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Kukarkin1975 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Rice1994 was invoked but never defined (see the help page).