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.[7] It is 2.2billion years old with 1.44 times the mass of the Sun.[6] The star is radiating 55 times the luminosity of the Sun[8] from its enlarged photosphere at an effective temperature of 4,937K.[6]
Nomenclature
Upsilon2 Cassiopeiae, Latinised from υ2 Cassiopeiae, is the star's Bayer designation, abbreviated Upsilon2 Cas or υ2 Cas.
This star bore the name Castula in Bayer's Uranometria, which is Latin for a type of woman's tunic.[11] In 2016, the IAU organized a Working Group on Star Names (WGSN)[12] 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.[10]
12Keenan, 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.
12Bergeat, J.; Knapik, A. (May 1997), "The barium stars in the Hertzsprung-Russel diagram.", Astronomy and Astrophysics, 321: L9, Bibcode:1997A&A...321L...9B.
