KOI-256
 White dwarf companion gravitationally bending the starlight of KOI-256 | ||
| Observation data J2000
| ||
|---|---|---|
| Constellation | Cygnus | |
| Right ascension | 19h 00m 44.42489s[1] | |
| Declination | +49° 33′ 55.2489″[1] | |
| Characteristics | ||
| KOI-256 A | ||
| Evolutionary stage | Red dwarf | |
| Spectral type | M3V | |
| Apparent magnitude (Kepler) | 15.37 | |
| Apparent magnitude (J) | 12.701±0.024 | |
| Apparent magnitude (H) | 12.001±0.019 | |
| Apparent magnitude (Ks) | 11.783±0.023 | |
| Apparent magnitude (r) | 15.754 | |
| Apparent magnitude (i) | 14.636 | |
| Apparent magnitude (z) | 14.059 | |
| R−I color index | 1.118 | |
| J−H color index | 0.700±0.031 | |
| J−K color index | 0.918±0.033 | |
| KOI-256 B | ||
| Evolutionary stage | White dwarf | |
| Spectral type | D | |
| Apparent magnitude (Kepler) | 19.45 | |
Semi-amplitude (K1)(primary) | 106.5±1.8 km/s | |
| Details Rotational velocity (v sin i) 19.79±0.52 km/s | | |
| KOI-256 B | ||
| Mass | 0.592±0.084 M☉ | |
| Radius | 0.01345±0.00091 R☉ | |
| Temperature | 7100±800 K | |
| Other designations | ||
| Database references | ||
Exoplanet Archive | data | |
| KIC | data | |
KOI-256 is a
Kepler spacecraft suggested the system contained a gas giant exoplanet orbiting a red dwarf, later studies determined that KOI-256 was a binary system composed of the red dwarf orbiting a white dwarf.[3][4]
Name
The acronym "KOI" comes from transit method. The "256" is the number of the object.
Characteristics
Initial observations by the Kepler spacecraft suggested a central
semi-major axis of 0.021 astronomical units.[5][6] Further studies by Muirhead et al. (2012) refined the candidate exoplanet parameters to a radius of 5.60±0.76 R🜨, a temperature of 726 K (453 °C; 847 °F), and a semi-major axis of 0.016 AU.[7]
Muirhead et al. (2013) performed additional observations with the
planetary mass object, and was more likely being influenced by a white dwarf. Using ultraviolet data from the GALEX spacecraft, it was seen that the red dwarf was significantly active, further suggesting perturbations by a white dwarf. The team re-analyzed Kepler's data, and found that when the white dwarf passed in front of the red dwarf, the red dwarf's light noticeably warped and brightened, an effect called gravitational lensing. While only being slightly larger than the Earth, the white dwarf has such large mass that the physically larger red dwarf orbits around its smaller companion.[3]
With the new observations, the red dwarf was shown to have a mass of 0.51±0.15 M☉, a radius of 0.540±0.014 R☉, and a temperature of 3,450 ± 50 K (3,180 ± 50 °C; 5,750 ± 90 °F). The white dwarf has a mass of 0.592±0.084 M☉, a radius of 0.01345±0.00091 R☉, and a temperature of 7,100 ± 800 K (6,800 ± 800 °C; 12,300 ± 1,400 °F).[2]
References
- ^ S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ S2CID 30368826.
- ^ a b "Gravity-Bending Find Leads to Kepler Meeting Einstein". NASA. 4 April 2013. Archived from the original on 5 July 2015. Retrieved 29 August 2015.
- Discovery.com. Archived from the originalon 15 September 2015. Retrieved 29 August 2015.
- S2CID 15233153.
- S2CID 118791908.
- S2CID 27131741.