TZ Cassiopeiae explained

TZ Cassiopeiae (TZ Cas, HIP 117763, SAO 20912) is a variable star in the constellation Cassiopeia with an apparent magnitude of around +9 to +10. It is approximately 8,400 light-years away from Earth. The star is a red supergiant star with a spectral type of M3 and a temperature around .

TZ Cassiopeiae was reported as being variable by Williamina Fleming and published posthumously in 1911.^[1] It is a slow irregular variable star with a possible period of 3,100 days.^[2] It is over 90,000 times the luminosity of the Sun, and it is 767 times larger than the Sun. It is a member of the Cas OB5 stellar association, together with the nearby red supergiant PZ Cassiopeiae.^[3]

The initial mass of TZ Cassiopeiae has been estimated from its position relative to theoretical stellar evolutionary tracks to be around .^[4]

TZ Cas is losing mass through a powerful stellar wind at two millionths of a solar mass each year.^[5] It is unclear whether this is sufficient to cause the star to lose its atmosphere and become a blue supergiant before the core exhausts its fuel and collapses as a supernova. Either as a red or blue supergiant, or a Wolf–Rayet star, it will inevitably end its life violently in a supernova explosion when the core collapse occurs.^[6]

Notes and References

1. 1911HarCi.167....1F. Stars Having Peculiar Spectra. 31 New Variable Stars. Harvard College Observatory Circular. 167. 1. Fleming. Williamina. Pickering. Edward C.. 1911.
2. Kiss . L. L. . Szabó . G. M. . Bedding . T. R. . 10.1111/j.1365-2966.2006.10973.x . Variability in red supergiant stars: Pulsations, long secondary periods and convection noise . Monthly Notices of the Royal Astronomical Society . 372 . 4 . 1721–1734 . 2006 . astro-ph/0608438 . 2006MNRAS.372.1721K . 5203133 .
3. 1978ApJS...38..309H. Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way. Astrophysical Journal. 38. 309. Humphreys. R. M.. 1978. 10.1086/190559.
4. 10.1051/0004-6361:20066353. Atmospheric dynamics and the mass loss process in red supergiant stars. Astronomy and Astrophysics. 469. 2. 671. 2007. Josselin . E.. Plez . B.. 2007A&A...469..671J. 0705.0266 . 17789027.
5. 1010.5369v1. Mauron. Nicolas. The mass-loss rates of red supergiants and the de Jager prescription. Astronomy & Astrophysics. 526. A156. Josselin. Eric. 2010. 10.1051/0004-6361/201013993. 2011A&A...526A.156M . 119276502.
6. 2015A&A...575A..60M. 1410.8721. Impact of mass-loss on the evolution and pre-supernova properties of red supergiants. Astronomy & Astrophysics. 575. A60. Meynet. G.. Chomienne. V.. Ekström. S.. Georgy. C.. Granada. A.. Groh. J.. Maeder. A.. Eggenberger. P.. Levesque. E.. Massey. P.. 2015. 10.1051/0004-6361/201424671. 38736311.