Fifty Years of Observations of Grw+70◦8247

Fifty Years of Observations of Grw+70◦8247

S. Bagnulo

Among white dwarfs, Grw+708247 stands as a particularly interesting object for various reasons. It is the first white dwarf in which a magnetic field was discovered. It is one of the stars with the longest rotation period (probably between 100 and 1000 yr). It shows one of the most unusual optical spectra ever seen because spectral lines are produced in presence of one of the strongest magnetic fields ever measured in the universe (∼ 400 MG). Most importantly, this star has been the subject of a number of scientific articles co-authored by John Landstreet, from the one reporting the discovery of its magnetic field in 1970, to a very recent paper which presents new spectropolarimetric observations obtained from the William Herschel Telescope. Here I will show how the polarisation spectra of the star have changed during John’s career, and what we have learnt from the observations of this star.

Proceedings of the Polish Astronomical Society, vol. 11, 15-24 (2020)

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