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 mas[1]
Distance	42.00 ± 0.02 ly (12.878 ± 0.005 pc)
Details[5]
Mass	1.029 M☉
Radius	5,960[a] km
Luminosity	0.013182 L☉
Surface gravity (log g)	8.67 cgs
Temperature	12540±143 K
Age	(as white dwarf) 1.138 Gyr
Other designations
GJ 742, AC +70 8247, G 260-15, LFT 1446, LHS 3424, LTT 15585, Grw+70 8247, WD 1900+705[2][6]
Database references
SIMBAD	data
ARICNS	data

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.^[7] This makes it the fifth or sixth white dwarf discovered.^[b] At first, its spectrum was thought to be almost featureless,^[7] but later observation showed it to have unusual broad, shallow absorption bands.^[11][12] 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.^[13][14] In the 1980s, it was realized that the unusual absorption bands could be explained as hydrogen absorption lines shifted by the Zeeman effect.^[6][15][16]

Notes

1. Applying the Stefan–Boltzmann law with a nominal solar effective temperature of 5,772 K:

   ${\displaystyle {\sqrt {{\biggl (}{\frac {5,772}{11,880}}{\biggr )}^{4}\cdot 10^{-2.88}}}=0.00857\ R_{\odot }}$.

2. The star EGGR 37 was suspected to be a white dwarf by April 1934,^[8] but this was not confirmed until 1938.^[9][10]

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. S2CID 122605705.
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. "GJ 742". Montreal White Dwarf Database. Retrieved 2024-05-30.
6. 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. Bibcode:1985ApJ...289L..25G. doi:10.1086/184427.{{cite journal}}: CS1 maint: multiple names: authors list (link)
7. G. P. Kuiper (October 1934). "Two New White Dwarfs of Large Parallax". Publications of the Astronomical Society of the Pacific. 46 (273): 287–290. Bibcode:1934PASP...46..287K. doi:10.1086/124496. S2CID 123421818.
8. 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 (6): 508–518, at p. 517. Bibcode:1934MNRAS..94..508V. doi:10.1093/mnras/94.6.508.
9. Jöran M. Ramberg (May 1938). "Zwei weiße Zwerge unter den physischen Hyadenmigliedern". Astronomische Nachrichten (in German). 265 (6–7): 111–112. Bibcode:1938AN....265..111R. doi:10.1002/asna.19382650609.
10. See also Gerard P. Kuiper (August 1941). "List of Known White Dwarfs". Publications of the Astronomical Society of the Pacific. 53 (314): 248–252. Bibcode:1941PASP...53..248K. doi:10.1086/125335. S2CID 123040354.
11. 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. Bibcode:1938MWOAR..10....1A.
12. 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. Bibcode:1957ApJ...126...14G. doi:10.1086/146364.
13. 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. Bibcode:1970ApJ...161L..77K. doi:10.1086/180574.{{cite journal}}: CS1 maint: multiple names: authors list (link)
14. 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.
15. 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. Bibcode:1985ApJ...292..260A. doi:10.1086/163156.{{cite journal}}: CS1 maint: multiple names: authors list (link)
16. 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. Bibcode:1988ApJ...327..222W. doi:10.1086/166184.