KOI-74

KOI-74 (KIC 6889235^[7]) is an eclipsing binary star in the constellation of Cygnus. The primary star is an A-type main-sequence star with a temperature of 9,400 K (9,130 °C; 16,460 °F). It lies in the field of view of the Kepler Mission and was determined to have a companion object in orbit around it which is smaller and hotter than the main star.^[8]

KOI-74

A light curve for KOI-74, adapted from van Kerkwijk et al. (2010)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Cygnus[2]
Right ascension	19h 53m 17.810s[3]
Declination	+42° 23′ 18.51″[3]
Apparent magnitude (V)	10.715[4]
Characteristics
Spectral type	A1V[1]
B−V color index	0.154[4]
Astrometry
Radial velocity (Rv)	−41.97±0.32[5] km/s
Proper motion (μ)	RA: +1.328[3] mas/yr Dec.: −41.497[3] mas/yr
Parallax (π)	1.328±0.144 mas[3]
Distance	approx. 2,500 ly (approx. 750 pc)
Orbit[1]
Period (P)	5.18875 days
Eccentricity (e)	0
Inclination (i)	88.8°
Semi-amplitude (K1) (primary)	14.7 km/s
Details
primary
Mass	2.22+0.10 −0.14[1] M☉
Radius	1.90+0.04 −0.05[1] R☉
Luminosity	25.6±2.4[1] L☉
Temperature	9,400±150[1] K
white dwarf
Mass	0.22±0.01[1] M☉
Radius	0.043±0.004[1] R☉
Luminosity	0.05±0.02[1] L☉
Temperature	13,000±1,000[1] K
Other designations
KIC 6889235, 2MASS J19531781+4223185, GSC2.3 N2J3000844[6]
Database references
SIMBAD	data
KIC	data

KOI-74b

KOI-74b is a hot compact object orbiting KOI-74. It was discovered in 2010 by the Kepler Mission and came to attention because of its small size (its radius is only 4.3% of the solar radius) and high temperature of 13,000 K (12,700 °C; 22,900 °F).^[8] The orbit of KOI-74b around the main star takes 5.18875 days to complete. Analysis of relativistic boosting of light in the Kepler data indicates that it is likely to be a low mass white dwarf of approximately 0.22 solar masses, resulting from an earlier phase of mass transfer in a binary system when the object underwent its giant phase.^[1]

See also

• KOI-81, a similar system also discovered by the Kepler Mission.
• Kepler Object of Interest, stars observed to have transits by the Kepler Mission