GRW +70 8247

From Wikipedia, the free encyclopedia
  (Redirected from GJ 742)
Jump to: navigation, search
GRW +70 8247
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Draco
Right ascension 19h 00m 10.25s[1]
Declination +70° 39′ 51.2″[1]
Apparent magnitude (V) 13.2[1]
Characteristics
Spectral type DA:w[1]
B−V color index 0.0[1]
Astrometry
Proper motion (μ) RA: 105[1] mas/yr
Dec.: 479[1] mas/yr
Parallax (π) 76 ± 4[1] mas
Distance 43 ± 2 ly
(13.2 ± 0.7 pc)
Other designations
GJ 742, AC +70 8247, G 260-15, LFT 1446, LHS 3424, LTT 15585, Grw+70 8247, WD 1900+705[1][2]
Database references
SIMBAD data

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[edit]

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.[3] This makes it the fifth or sixth white dwarf discovered.[4] At first, its spectrum was thought to be almost featureless,[3] but later observation showed it to have unusual broad, shallow absorption bands.[5], p. 28; [6] In 1970, when light it emitted was observed to be circularly polarized, it became the first white dwarf known to have a magnetic field.[7] In the 1980s it was realized that the unusual absorption bands could be explained as hydrogen absorption lines shifted by the Zeeman effect.[2][8][9]

Notes and references[edit]

  1. ^ a b c d e f g h i Gliese 742, entry in SIMBAD. Accessed on line November 5, 2007.
  2. ^ a b 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.
  3. ^ a b 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.
  4. ^ 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).
  5. ^ 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.
  6. ^ 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.
  7. ^ 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.
  8. ^ 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.
  9. ^ 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.