Both components are blue-white B-typemain-sequence stars that do not fill their Roche lobes. The system has a mean apparent magnitude of +6.15. However, the orbit of the stars are oriented in such a way that they periodically eclipse each other, so AR Aurigae is a variable star and its brightness varies from magnitude +6.15 to +6.82 with a period of 4.13 days.[6] In 1931, H. N. Pendersen and J. C. Steensgard became the first persons to detect these eclipses.[11][12] When an eclipse is not occurring, the star will be faintly visible to the naked eye under very good observing conditions.
The primary component of AR Aurigae is known to be a mercury-manganese star, also known as an HgMn star. As the name implies, these stars have over-abundances of the elements mercury and manganese, and also often xenon and other elements.[4] Because AR Aurigae is an eclipsing binary (in fact, it is the only known eclipsing binary with a mercury-manganese star), accurate characterization of its parameters has been made possible. Based on the light-time effect observed from the stars, it is inferred that there is a third star with a mass of 0.54 M☉, orbiting at a separation of 13 AU every 23.7 years.[4]
References
^Johansen, K. T. (January 1970). "Light curve and photometric elements of AR Aurigae". Astronomy & Astrophysics. 4: 1–10. Bibcode:1970A&A.....4....1J.
^Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27 –L30. Bibcode:2000A&A...355L..27H.
^ abNicolet, B. (1978). "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System". Astronomy and Astrophysics Supplement Series. 34: 1–49. Bibcode:1978A&AS...34....1N.
^ 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. Bibcode:2009yCat....102025S.
^Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode:1953GCRV..C......0W.
^ abcNordstrom, B.; Johansen, K. T. (1994). "Radii and masses for the young star AR Aurigae". Astronomy and Astrophysics. 282: 787. Bibcode:1994A&A...282..787N.
^ abcdEker, Z.; Bilir, S.; Soydugan, F.; Gökçe, E. Yaz; Soydugan, E.; Tüysüz, M.; Şenyüz, T.; Demircan, O. (2014). "The Catalogue of Stellar Parameters from the Detached Double-Lined Eclipsing Binaries in the Milky Way". Publications of the Astronomical Society of Australia. 31. arXiv:1403.1583. Bibcode:2014PASA...31...24E. doi:10.1017/pasa.2014.17. S2CID119238300.