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GRW +70 8247
GRW +70 8247 is a white dwarf located about 43 light years from Earth in the constellation Draco. With a magnitude of about 13 it is visible only through a large telescope.
==Properties==
Although photographed in the 19th century as part of the Carte du Ciel project, it was not determined to be a white dwarf until observed in 1934 by G. P. Kuiper.〔(Two New White Dwarfs of Large Parallax ), G. P. Kuiper, ''Publications of the Astronomical Society of the Pacific'' 46, #273 (October 1934), pp. 287–290.〕 This makes it the fifth or sixth white dwarf discovered.〔The star EGGR 37 was suspected to be a white dwarf by April 1934 ((Some new members of the Hyades cluster ), P. J. van Rhijn and J. J. Raimond, ''Monthly Notices of the Royal Astronomical Society'' 94 (April 1934), pp. 508–518, at p. 517) but this was not confirmed until 1938 ((Zwei weiße Zwerge unter den physischen Hyadenmigliedern ), Jöran M. Ramberg, ''Astronomische Nachrichten'' 265 (May 1938), pp. 111–112; see also (List of Known White Dwarfs ), Gerard P. Kuiper, ''Publications of the Astronomical Society of the Pacific'' 53, #314 (August 1941), pp. 248–252).〕 At first, its spectrum was thought to be almost featureless,〔 but later observation showed it to have unusual broad, shallow absorption bands.〔(Annual Report of the Director of the Mount Wilson Observatory (1937-1938) ), Walter S. Adams and Frederick H. Seahes, ''Mount Wilson Observatory Annual Report'' 10 (1938), pp. 1–40.〕, p. 28; 〔(Studies of the White Dwarfs. I. Broad Features in White Dwarf Spectra ), Jesse L. Greenstein and Mildred S. Matthews, ''Astrophysical Journal'' 126 (July 1957), pp. 14–18.〕 In 1970, when light it emitted was observed to be circularly polarized, it became the first white dwarf known to have a magnetic field.〔(Discovery of Circularly Polarized Light from a White Dwarf ), James C. Kemp, John B. Swedlund, J. D. Landstreet, and J. R. P. Angel, ''Astrophysical Journal'' 161 (August 1970), pp. L77–L79.〕 In the 1980s it was realized that the unusual absorption bands could be explained as hydrogen absorption lines shifted by the Zeeman effect.〔(Further identifications of hydrogen in Grw +70°8247 ), Jesse L. Greenstein, Ronald J. W. Henry, and R. F. O'Connell, ''Astrophysical Journal'' 289 (February 15, 1985), pp. L25–L29.〕〔(The optical spectrum of hydrogen at 160-350 million gauss in the white dwarf Grw +70°8247 ), J. R. P. Angel, James Liebert, and H. S. Stockman, ''Astrophysical Journal'' 292 (May 1, 1985), pp. 260–266.〕〔(A centered dipole model for the high field magnetic white dwarf GRW +70°8247 ), D. T. Wickramasinghe and Lilia Ferrario, ''Astrophysical Journal'' 327 (April 1, 1988), pp. 222–233.〕
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