Some authors state that Theta Aurigae had no traditional name,[12]although Richard Hinckley Allen makes a passing reference about the name Mahasim, as a name also used, with various spellings, for Eta Aurigae and Lambda Herculis,[13] from the Arabic المِعْصَم al-miʽşam "the wrist" (of the charioteer). In 2016, the IAU organized a Working Group on Star Names (WGSN)[14] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[15] It approved the name Mahasim for the component Theta Aurigae A on 30 June 2017 and it is now so included in the List of IAU-approved Star Names.[10]
It is known as 五車四 (the Fourth Star of the Five Chariots) in Chinese[16]
The secondary, Theta Aurigae B, is a +7.2 magnitude companion, 4.5[3] magnitudes fainter than the primary, located at an angular separation of 3.91 arcseconds along a position angle of 304.9° as of 2002.[18] This is an F-typemain sequence star with a stellar classification in the range F2-5 V.[3]
The mean combined apparent magnitude of the system is +2.65 but the variation of the primary causes the system's brightness to range from magnitude +2.62 to +2.70 with a period of 1.37 days. The system is an X-ray source with a luminosity of 9.49 × 1026 erg s−1.[3]
^ abSamus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.
^ abJohnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
^Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick (eds.), Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, vol. 30, University of Toronto: International Astronomical Union, p. 57, Bibcode:1967IAUS...30...57E
^ abcdefSikora, J.; et al. (February 2019). "A volume-limited survey of mCP stars within 100 pc - I. Fundamental parameters and chemical abundances". Monthly Notices of the Royal Astronomical Society. 483 (2): 2300–2324. arXiv:1811.05633. Bibcode:2019MNRAS.483.2300S. doi:10.1093/mnras/sty3105.
^ abRice, J. B.; Holmgren, D. E.; Bohlender, D. A. (September 2004), "The distribution of oxygen on the surface of the Ap star θ Aur. An abundance Doppler image to compare with ɛ UMa", Astronomy and Astrophysics, 424: 237–244, Bibcode:2004A&A...424..237R, doi:10.1051/0004-6361:20035639
^Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
