A near-infrared (J band)light curve for U Carinae, adpated from Laney and Stobie (1992)[9]
U Car is aδ Cepheid variable with a period of 38.7681 days.Isaac Roberts discovered that the star's brightness varies in 1891,[10] and it was one of the earliest Cepheids to be discovered. It has also one of the longest periods, and hence is one of the most luminous in the class.[11] There are still only a few Cepheids with longer periods, includingRS Puppis,SV Vulpeculae, and the unusualS Vulpeculae.[2]
The brightness variation in U Car is caused byfundamental mode pulsations. The radius and temperature both vary, with the radius changing by 42 R☉ during each cycle.[12] The temperature variation causes the spectral type to vary between F6 and G7.
^abcdSamus, 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.
^Shapley, H. (1918). "Studies based on the colors and magnitudes in stellar clusters. VIII. The luminosities and distances of 139 Cepheid variables".Astrophysical Journal.48: 279.Bibcode:1918ApJ....48..279S.doi:10.1086/142435.
