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Theta Mensae

θ Mensae
Location of θ Mensae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Mensa
Right ascension 06h 56m 34.47434s[1]
Declination −79° 25′ 12.6918″[1]
Apparent magnitude (V) 5.45±0.01[2]
Characteristics
Evolutionary stage main sequence[3]
Spectral type B9.5 V[4]
U−B color index −0.07[5]
B−V color index +0.05[5]
Variable type suspected SPB[6]
Astrometry
Radial velocity (Rv)6±7.4[7] km/s
Proper motion (μ) RA: −2.270 mas/yr[1]
Dec.: −1.240 mas/yr[1]
Parallax (π)8.4632 ± 0.0405 mas[1]
Distance385 ± 2 ly
(118.2 ± 0.6 pc)
Absolute magnitude (MV)+0.28[8]
Details
Mass2.87±0.03[3] M☉
Radius4.37[9] R☉
Luminosity124+8
−6[10] L☉
Surface gravity (log g)3.64±0.06[10] cgs
Temperature9,938±282[11] K
Rotation1.266 d[12]
Rotational velocity (v sin i)209[13] km/s
Age266±4[3] Myr
Other designations
θ Mensae, 42 G. Mensae[14], CPD−79°238, FK5 2545, GC 9278, HD 54239, HIP 33384, HR 2689, SAO 256355[15]
Database references
SIMBADdata

θ Mensae, Latinized to Theta Mensae, is a star located in the southern circumpolar constellation Mensa. It has an apparent magnitude of 5.45,[2] making it faintly visible to the naked eye if viewed under ideal conditions. Based on parallax measurements from Gaia Data Release 3, the object is estimated to be 385 light years distant.[1] The value is horribly constrained, but it appears to be receding with a heliocentric radial velocity of 6 km/s.[7]

This is a solitary,[16] B-type main-sequence star with a stellar classification of B9.5 V.[4] Houk and Cowley (1975) give it a class of B9.5/A0 III/IV,[17] indicating that it is a B9.5-A0 star with the blended luminosity class of a giant star and a subgiant. Nevertheless, Theta Mensae has 2.87 times the Sun’s mass[3] and a enlarged radius of 4.37 R☉.[9] It radiates 124 solar luminosities[10] from its photosphere and it has an effective temperature of 9,938 K,[11] giving it a bluish-white hue. It is estimated to be 266 million years old, having completed 85.2% of its main sequence lifetime,[3] hence the large radius. Like most hot stars, it spins rapidly, having a projected rotational velocity of 209 km/s.[13]

Data from the Transiting Exoplanet Survey Satellite suggests that Theta Mensae may be a slowly pulsating B-type star plus a variable star with rotation modulations[6]

  1. ^ a b c d e Cite error: The named reference GaiaDR3 was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference Tycho2000 was invoked but never defined (see the help page).
  3. ^ a b c d e Cite error: The named reference Zorec2012 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Buscombe1969 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Johnson1966 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Pedersen2019 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Kharchenko2007 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Kervella2021 was invoked but never defined (see the help page).
  10. ^ a b c Cite error: The named reference Stassun2019 was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference Pauzen2005 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Barraza2022 was invoked but never defined (see the help page).
  13. ^ a b Cite error: The named reference Levato2004 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Gould1879 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference Houk1975 was invoked but never defined (see the help page).
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