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KOI-81 is an eclipsing binary star in the constellation of Cygnus. The primary star is a late B-type or early A-type main-sequence star with a temperature of 10,000 K (9,700 °C; 17,500 °F). It lies in the field of view of the Kepler Mission and was determined to have an object in orbit around it which is smaller and hotter than the main star.[4]

Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension  19h 35m 08.577s[1]
Declination +45° 01′ 06.58″[1]
Apparent magnitude (V) 11.349[2]
Spectral type B9-A0V[3]
B−V color index 0.204[2]
[3] M
Radius2.93 ± 0.14[3] R
Luminosity77.3 ± 9.6[3] L
Temperature10000[3] K
Other designations
KIC 8823868, 2MASS J19350857+4501065, GSC2.3 N2K9001230
Database references


KOI-81b is a hot compact object orbiting KOI-81. It was discovered in 2010 by the Kepler Mission and came to attention because of its small size and high temperature of 17,000 K (16,700 °C; 30,100 °F).[4] The orbit of KOI-81b around the main star takes 23.8776 days to complete. Analysis of relativistic effects in the Kepler light curve suggests that it is a low-mass white dwarf of approximately 0.3 solar masses, produced by a previous stage of mass transfer during the object's giant phase.[3]

See alsoEdit


  1. ^ a b Cutri R.M.; Skrutskie M.F.; Van Dyk S.; Beichman C.A.; Carpenter J.M.; Chester T.; Cambresy L.; Evans T.; Fowler J.; Gizis J.; Howard E.; Huchra J.; Jarrett T.; Kopan E.L.; Kirkpatrick J.D.; Light R.M.; Marsh K.A.; McCallon H.; Schneider S.; Stiening R.; Sykes M.; Weinberg M.; Wheaton W.A.; Wheelock S.; Zacarias N. (2003). "2MASS J19350857+4501065". 2MASS All-Sky Catalog of Point Sources. Retrieved 2010-06-19.
  2. ^ a b "GSC2.3 N2K9001230". Guide Star Catalog 2.3. Retrieved 2010-06-19.
  3. ^ a b c d e f van Kerkwijk, Marten H.; Rappaport, Saul A.; Breton, René P.; Justham, Stephen; Podsiadlowski, Philipp; Han, Zhanwen (2010). "Observations of Doppler Boosting in Kepler Light Curves". The Astrophysical Journal. 715 (1): 51–58. arXiv:1001.4539. Bibcode:2010ApJ...715...51V. doi:10.1088/0004-637X/715/1/51.
  4. ^ a b Rowe, Jason F.; Borucki, William J.; Koch, David; Howell, Steve B.; Basri, Gibor; Batalha, Natalie; Brown, Timothy M.; Caldwell, Douglas; Cochran, William D.; Dunham, Edward; Dupree, Andrea K.; Fortney, Jonathan J.; Gautier, Thomas N.; Gilliland, Ronald L.; Jenkins, Jon; Latham, David W.; Lissauer, Jack J.; Marcy, Geoff; Monet, David G.; Sasselov, Dimitar; Welsh, William F. (2010). "Kepler Observations of Transiting Hot Compact Objects". The Astrophysical Journal Letters. 713 (2): L150–L154. arXiv:1001.3420. Bibcode:2010ApJ...713L.150R. doi:10.1088/2041-8205/713/2/L150.

Coordinates:   19h 35m 08.57s, +45° 01′ 06.6″