Upsilon2 Cassiopeiae is a barium star, showing an excess of the element barium in its spectrum. This can occur from mass transfer from a more-evolved companion star that later became a white dwarf, although no companion has been detected.[6] It is 2.2 billion years old with 1.44 times the mass of the Sun.[5] The star is radiating 55[1] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,937 K.[5]
Nomenclature
υ2 Cassiopeiae is the star's Bayer designation. In 2016, the IAU organized a Working Group on Star Names (WGSN)[8] to catalog and standardize proper names for stars. The WGSN approved the name Castula for this star on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[7]
^ abKeenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
^ abBergeat, J.; Knapik, A. (May 1997), "The barium stars in the Hertzsprung-Russel diagram.", Astronomy and Astrophysics, 321: L9, Bibcode:1997A&A...321L...9B.