Tau Ursae Majoris

Tau Ursae Majoris
Diagram showing star positions and boundaries of the Ursa Major constellation and its surroundings
Location of τ Ursae Majoris (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Ursa Major
Right ascension 09h 10m 55.06553s[1]
Declination +63° 30′ 49.0553″[1]
Apparent magnitude (V) 4.66[2]
Characteristics
Spectral type kA5hF0mF5 II[3]
U−B color index +0.14[2]
B−V color index +0.35[2]
Astrometry
Radial velocity (Rv)−9.80±0.30[4] km/s
Proper motion (μ) RA: +102.37[1] mas/yr
Dec.: −63.55[1] mas/yr
Parallax (π)25.82 ± 0.54 mas[1]
Distance126 ± 3 ly
(38.7 ± 0.8 pc)
Absolute magnitude (MV)+1.73[5]
Orbit[6]
Period (P)1,062.4 d
Eccentricity (e)0.48
Periastron epoch (T)2425721.6 JD
Argument of periastron (ω)
(secondary)		349.4°
Semi-amplitude (K1)
(primary)		3.9 km/s
Details
τ UMa A
Mass1.8±0.1[7] M☉
Luminosity16[8] L☉
Surface gravity (log g)3.86±0.43[9] cgs
Temperature7,343±100[9] K
Metallicity [Fe/H]+0.57±0.15[9] dex
Rotational velocity (v sin i)21[10] km/s
Other designations
τ UMa, 14 Ursae Majoris, BD+64°723, FK5 2727, HD 78362, HIP 45075, HR 3624, SAO 14796, WDS J09109+6331A[11]
Database references
SIMBADdata

Tau Ursae Majoris (τ UMa) is the Bayer designation for a binary star in the northern circumpolar constellation of Ursa Major. It is visible to the naked eye, having an apparent visual magnitude of 4.66.[2] With an annual parallax shift of 25.82 mas,[1] it is located about 126 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction factor of 0.19 due to interstellar dust.[9]

This is a single-lined spectroscopic binary star system with an orbital period of 2.9 years and an eccentricity of 0.48.[6] The primary member, component A, is an evolved bright giant with a stellar classification of kA5hF0mF5 II.[3] This notation indicates the star's spectrum shows the calcium K lines of an A5 star, the hydrogen lines of an F0 star, and the metallic lines of an F5 star.[12] It is an evolved Am star of the ρ Puppis type, a class of evolved stars showing the Am chemical peculiarities.[13] It is located in the instability strip of the Hertzsprung–Russell diagram but is not thought to be variable.[7]

  1. ^ a b c d e f Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Mermilliod1986 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Gray2006 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference deBruijne2012 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Pourbaix2004 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Burkhart2005 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Mcdonald2012 was invoked but never defined (see the help page).
  9. ^ a b c d Cite error: The named reference Koleva2012 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Royer2002 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference gray_corbally2009 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Zaremba1979 was invoked but never defined (see the help page).