Eta Tucanae

Eta Tucanae
Location of η Tucanae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Tucana
Right ascension 23h 57m 35.07852s[1]
Declination −64° 17′ 53.6229″[1]
Apparent magnitude (V) +5.00[2]
Characteristics
Spectral type A1V[2]
U−B color index +0.08[3]
B−V color index +0.06[3]
Astrometry
Radial velocity (Rv)+32.50[4] km/s
Proper motion (μ) RA: +78.850[1] mas/yr
Dec.: −62.049[1] mas/yr
Parallax (π)21.2425 ± 0.3639 mas[1]
Distance154 ± 3 ly
(47.1 ± 0.8 pc)
Absolute magnitude (MV)1.62[5]
Details
Mass1.94[6] M☉
Radius1.8[7] R☉
Luminosity23[8] L☉
Surface gravity (log g)4.31[9] cgs
Temperature9,057[8] K
Rotational velocity (v sin i)190[6] km/s
Other designations
η Tuc, CPD–64° 4391, FK5 2026, GC 33223, HD 224392, HIP 118121, HR 9062, SAO 255609, GSC 09130-01766[10]
Database references
SIMBADdata

Eta Tucanae, Latinized from η Tucanae, is a probable binary star[6] system in the southern constellation of Tucana, a few degrees to the north of Epsilon Tucanae. It is visible to the naked eye as a dim, white-hued point of light with an apparent visual magnitude of +5.00.[2] parallax measurements provide a distance estimate of about 154 light years from the Sun, and it is drifting further away with a mean radial velocity of +32.5 km/s.[4] It is a member of the 30 million year old Tucana-Horologium association of co-moving stars.[6][2]

The radial velocity for Eta Tucanae displays strong oscillations, suggesting this is a spectroscopic binary system. A companion was directly detected in 2014, but this result has some unexplained anomalies.[6] The primary component is an A-type main-sequence star with a stellar classification of A1V.[2] It is spinning rapidly with a projected rotational velocity of 190 km/s,[6] giving it an equatorial bulge that is 15% larger than the polar radius.[11] The star has 1.9[6] times the mass of the Sun and 1.8[7] times the Sun's radius. It is radiating 23[8] times the luminosity of the Sun from its photosphere at an effective temperature of 9,057 K.[8]

  1. ^ a b c d e Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference aaa523_A73 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Mallama2014 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Kharchenko2007 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference XHIP was invoked but never defined (see the help page).
  6. ^ a b c d e f g Cite error: The named reference Borgniet2017 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference AllendePrieto was invoked but never defined (see the help page).
  8. ^ a b c d Cite error: The named reference Zorec2012 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference David2015 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 vanBelle2012 was invoked but never defined (see the help page).