Theta1 Crucis

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θ1 Crucis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Crux
Right ascension 12h 03m 01.50130s[1]
Declination −63° 18′ 46.5406″[1]
Apparent magnitude (V) 4.30[2]
Spectral type A3(m)A8-A8[3]
U−B color index +0.03[2]
B−V color index +0.28[2]
Radial velocity (Rv)−2.4[4] km/s
Proper motion (μ) RA: −152.35[1] mas/yr
Dec.: +7.00[1] mas/yr
Parallax (π)13.88 ± 0.15[1] mas
Distance235 ± 3 ly
(72.0 ± 0.8 pc)
Absolute magnitude (MV)+1.29[5]
Period (P)24.4828 d
Eccentricity (e)0.61
Periastron epoch (T)2419453.3470 JD
Argument of periastron (ω)
Semi-amplitude (K1)
46.1 km/s
Semi-amplitude (K2)
56.1 km/s
Mass1.57[7] M
Luminosity81[8] L
Surface gravity (log g)3.76[7] cgs
Temperature7341±250[7] K
Age1.1[7] Gyr
Other designations
θ1 Cru, CPD−62° 2543, HD 104671, HIP 58758, HR 4599, SAO 251705.[9]
Database references

Theta1 Crucis1 Cru, Theta1 Crucis) is a spectroscopic binary star system in the southern constellation of Crux. It is visible to the naked eye with an apparent visual magnitude of 4.30m.[2] The distance to this star, as determined using parallax measurements,[1] is around 235 light years.

The pair orbit each other closely with a period of 24.5 days and an eccentricity of 0.61.[6] The primary component is an Am star, which is a chemically peculiar A-type star that shows anomalous variations in absorption lines of certain elements.[10] It has a stellar classification of A3(m)A8-A8.[3] With a mass 157% times that of the Sun,[7] it radiates 81[8] times the Sun's luminosity from its outer atmosphere at an effective temperature of 7341 K.[7] Unusually for a fully radiative A-type star, X-ray emissions have been detected, which may instead be coming from the orbiting companion.[11]


  1. ^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Mermilliod, J.-C. (1986), Compilation of Eggen's UBV data, transformed to UBV (unpublished), SIMBAD, Bibcode:1986EgUBV........0M. 
  3. ^ a b Houk, N.; Cowley, A. P. (1975), University of Michigan Catalogue of two-dimensional spectral types for the HD stars, 1, 
  4. ^ Wilson, Ralph Elmer (1953), General Catalogue of Stellar Radial Velocities, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W. 
  5. ^ Eggen, Olin J. (July 1998), "The Age Range of Hyades Stars", The Astronomical Journal, 116 (1): 284–292, Bibcode:1998AJ....116..284E, doi:10.1086/300413. 
  6. ^ a b Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy & Astrophysics, 424 (2): 727, arXiv:astro-ph/0406573Freely accessible, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213. 
  7. ^ a b c d e f David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154Freely accessible, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146. 
  8. ^ a b McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037Freely accessible, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x. 
  9. ^ "tet01 Cru". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-10-06. 
  10. ^ Renson, P.; Manfroid, J. (May 2009), "Catalogue of Ap, HgMn and Am stars", Astronomy and Astrophysics, 498 (3): 961–966, Bibcode:2009A&A...498..961R, doi:10.1051/0004-6361/200810788. 
  11. ^ Schröder, C.; Schmitt, J. H. M. M. (November 2007), "X-ray emission from A-type stars", Astronomy and Astrophysics, 475 (2): 677–684, Bibcode:2007A&A...475..677S, doi:10.1051/0004-6361:20077429.