Theta Mensae

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]

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

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]

References
  1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361.
  3. Zorec, J.; Royer, F. (January 2012). "Rotational velocities of A-type stars". Astronomy & Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691. eISSN 1432-0746. ISSN 0004-6361.
  4. Buscombe, W. (1 May 1969). "Line Strengths for Southern OB stars--II: Observations with Moderate Dispersion". Monthly Notices of the Royal Astronomical Society. 144 (1): 31–39. Bibcode:1969MNRAS.144...31B. doi:10.1093/mnras/144.1.31. ISSN 0035-8711.
  5. Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99–110. Bibcode:1966CoLPL...4...99J.
  6. Pedersen, May G.; et al. (8 February 2019). "Diverse Variability of O and B Stars Revealed from 2-minute Cadence Light Curves in Sectors 1 and 2 of the TESS Mission: Selection of an Asteroseismic Sample". The Astrophysical Journal. 872 (1): L9. arXiv:1901.07576. Bibcode:2019ApJ...872L...9P. doi:10.3847/2041-8213/ab01e1. eISSN 2041-8213.
  7. Kharchenko, N.V.; Scholz, R.-D.; Piskunov, A.E.; Röser, S.; Schilbach, E. (November 2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889–896. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. eISSN 1521-3994. ISSN 0004-6337. S2CID 119323941.
  8. Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. eISSN 1562-6873. ISSN 1063-7737. S2CID 119257644.
  9. Kervella, Pierre; Arenou, Frédéric; Thévenin, Frédéric (2022). "Stellar and substellar companions from Gaia EDR3". Astronomy & Astrophysics. 657: A7. arXiv:2109.10912. Bibcode:2022A&A...657A...7K. doi:10.1051/0004-6361/202142146. eISSN 1432-0746. ISSN 0004-6361.
  10. Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. eISSN 1538-3881.
  11. Paunzen, E.; Schnell, A.; Maitzen, H. M. (December 2005). "An empirical temperature calibration for the Δa photometric system I: The B-type stars". Astronomy & Astrophysics. 444 (3): 941–946. arXiv:astro-ph/0509049. Bibcode:2005A&A...444..941P. doi:10.1051/0004-6361:20053546. eISSN 1432-0746. ISSN 0004-6361.
  12. Barraza, L. F.; Gomes, R. L.; Messias, Y. S.; Leão, I. C.; Almeida, L. A.; Janot-Pacheco, E.; Brito, A. C.; Brito, F. A. C.; Santana, J. V.; Gonçalves, N. S.; das Chagas, M. L.; Teixeira, M. A.; De Medeiros, J. R.; Canto Martins, B. L. (1 January 2022). "Rotation Signature of TESS B-type Stars. A Comprehensive Analysis". The Astrophysical Journal. 924 (2): 117. arXiv:2202.01022. Bibcode:2022ApJ...924..117B. doi:10.3847/1538-4357/ac3335. eISSN 1538-4357. ISSN 0004-637X.
  13. Levato, H.; Grosso, M. (June 2004). "New Projected Rotational Velocities of All Southern B-type Stars of the Bright Star Catalogue". Astronomical Society of the Pacific. 215: 51. Bibcode:2004IAUS..215...51L.
  14. Gould, Benjamin Apthorp (1878). "Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas". Resultados del Observatorio Nacional Argentino. 1. Bibcode:1879RNAO....1.....G.
  15. "Theta Mensae". SIMBAD. Centre de données astronomiques de Strasbourg.
  16. Eggleton, P. P.; Tokovinin, A. A. (11 September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. eISSN 1365-2966. ISSN 0035-8711.
  17. Houk, N.; Cowley, A. P. (1975). University of Michigan Catalogue of two-dimensional spectral types for the HD stars. Volume I. Declinations −90° to −53°. Bibcode:1975mcts.book.....H.
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