GRW +70 8247

GRW +70 8247 is a white dwarf star located 42 light-years from Earth[1] in the constellation Draco. With a magnitude of about 13 it is visible only through a large telescope.

GRW +70 8247
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Draco
Right ascension 19h 00m 10.2534s[1]
Declination +70° 39′ 51.418″[1]
Apparent magnitude (V) 13.19[2]
Characteristics
Spectral type DAP4.5[3]
U−B color index -0.85[4]
B−V color index +0.05[4]
Astrometry
Proper motion (μ) RA: +85.774[1] mas/yr
Dec.: +505.050[1] mas/yr
Parallax (π)77.6525 ± 0.0317[1] mas
Distance42.00 ± 0.02 ly
(12.878 ± 0.005 pc)
Other designations
GJ 742, AC +70 8247, G 260-15, LFT 1446, LHS 3424, LTT 15585, Grw+70 8247, WD 1900+705[2][5]
Database references
SIMBADdata
ARICNSdata

Properties

Although photographed in the 19th century as part of the Carte du Ciel project, the star was not determined to be a white dwarf until G. P. Kuiper observed it in 1934.[6] This makes it the fifth or sixth white dwarf discovered.[lower-alpha 1] At first, its spectrum was thought to be almost featureless,[6] but later observation showed it to have unusual broad, shallow absorption bands.[10][11] In 1970, when light that it emitted was observed to be circularly polarized, it became the first white dwarf known to have a magnetic field.[12][13] In the 1980s, it was realized that the unusual absorption bands could be explained as hydrogen absorption lines shifted by the Zeeman effect.[5][14][15]

Notes
  1. The star EGGR 37 was suspected to be a white dwarf by April 1934,[7] but this was not confirmed until 1938.[8][9]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. "LAWD 73". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 5, 2007.
  3. Wesemael, F.; Greenstein, J. L.; Liebert, James; Lamontagne, R.; Fontaine, G.; Bergeron, P.; Glaspey, J. W. (1993). "An atlas of optical spectra of white-dwarf stars". Publications of the Astronomical Society of the Pacific. 105: 761. Bibcode:1993PASP..105..761W. doi:10.1086/133228.
  4. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  5. Jesse L. Greenstein, Ronald J. W. Henry, and R. F. O'Connell (February 15, 1985). "Further identifications of hydrogen in Grw +70°8247". Astrophysical Journal. 289: L25–L29.CS1 maint: multiple names: authors list (link)
  6. G. P. Kuiper (October 1934). "Two New White Dwarfs of Large Parallax". Publications of the Astronomical Society of the Pacific. 46 (273): 287–290.
  7. P. J. van Rhijn and J. J. Raimond (April 1934). "Some new members of the Hyades cluster". Monthly Notices of the Royal Astronomical Society. 94: 508–518, at p. 517.
  8. Jöran M. Ramberg (May 1938). "Zwei weiße Zwerge unter den physischen Hyadenmigliedern". Astronomische Nachrichten (in German). 265: 111–112.
  9. See also Gerard P. Kuiper (August 1941). "List of Known White Dwarfs". Publications of the Astronomical Society of the Pacific. 53 (314): 248–252.
  10. Walter S. Adams and Frederick H. Seahes (1938). "Annual Report of the Director of the Mount Wilson Observatory (1937-1938)". Mount Wilson Observatory Annual Report. 10: 28.
  11. Jesse L. Greenstein and Mildred S. Matthews (July 1957). "Studies of the White Dwarfs. I. Broad Features in White Dwarf Spectra". Astrophysical Journal. 126: 14–18.
  12. James C. Kemp, John B. Swedlund, J. D. Landstreet, and J. R. P. Angel (August 1970). "Discovery of Circularly Polarized Light from a White Dwarf". Astrophysical Journal. 161: L77–L79.CS1 maint: multiple names: authors list (link)
  13. Angel, J.R.P.; Landstreet, J.D.; Oke, J.B. (1972). "The Spectral Dependence of Circular Polarization in Grw+70°8247". Astrophysical Journal. 171: L11–L15. Bibcode:1972ApJ...171L..11A. doi:10.1086/180857.
  14. J. R. P. Angel, James Liebert, and H. S. Stockman (May 1, 1985). "The optical spectrum of hydrogen at 160-350 million gauss in the white dwarf Grw +70°8247". Astrophysical Journal. 292: 260–266.CS1 maint: multiple names: authors list (link)
  15. D. T. Wickramasinghe and Lilia Ferrario (April 1, 1988). "A centered dipole model for the high field magnetic white dwarf GRW +70°8247". Astrophysical Journal. 327: 222–233.


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