KOI-81
 A light curve for KOI-81, adapted from van Kerkwijk et al. (2010).[1] The inset plot shows the eclipse on an expanded scale. | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus[2] |
| Right ascension | 19h 35m 08.576s[3] |
| Declination | +45° 01′ 06.46″[3] |
| Apparent magnitude (V) | 11.349[4] |
| Characteristics | |
| Evolutionary stage | main sequence + subdwarf[5] |
| Spectral type | B9-A0V[1] |
| B−V color index | 0.204[4] |
| Astrometry | |
| Radial velocity (Rv) | −21.02±0.13[6] km/s |
| Proper motion (μ) | RA: +0.318[3] mas/yr Dec.: −2.541[3] mas/yr |
| Parallax (π) | 0.5633±0.0302 mas[3] |
| Distance | 5,800 ± 300 ly (1,780 ± 100 pc) |
| Orbit[5] | |
| Period (P) | 23.8760923 days |
| Eccentricity (e) | 0 (assumed) |
| Inclination (i) | 88.97° |
| Semi-amplitude (K1) (primary) | 6.74 km/s |
| Semi-amplitude (K2) (secondary) | 101.18 km/s |
| Details | |
| primary | |
| Mass | 2.916[5] M☉ |
| Radius | 2.447[5] R☉ |
| Luminosity | 77.3±9.6[1] L☉ |
| Surface gravity (log g) | 4.13[5] cgs |
| Temperature | 11,700[5] K |
| Rotational velocity (v sin i) | 296[5] km/s |
| subdwarf | |
| Mass | 0.194[5] M☉ |
| Radius | 0.0911[5] R☉ |
| Luminosity | 0.9±0.4[1] L☉ |
| Surface gravity (log g) | 5.81[5] cgs |
| Temperature | >19,400[5] K |
| Rotational velocity (v sin i) | <10[5] km/s |
| Other designations | |
| KIC 8823868, 2MASS J19350857+4501065, GSC2.3 N2K9001230 | |
| Database references | |
| SIMBAD | data |
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.[7]
KOI-81b
[edit]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).[7] 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,[1] or the immediate progenitor of such a white dwarf, a hot subdwarf.[5] This small hot star was produced by mass transfer when the primary stripped the outer layers when the secondary expanded after leaving the main sequence.[5]
See also
[edit]- KOI-74, a similar system also discovered by the Kepler Mission.
- Kepler Object of Interest, stars observed to have transits by the Kepler Mission
References
[edit]- ^ a b c d e 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. S2CID 15893663.
- ^ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific. 99 (617): 695. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Constellation record for this object at VizieR.
- ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b "GSC2.3 N2K9001230". Guide Star Catalog 2.3. Retrieved 2010-06-19.
- ^ a b c d e f g h i j k l m n Matson, Rachel A.; Gies, Douglas R.; Guo, Zhao; Quinn, Samuel N.; Buchhave, Lars A.; Latham, David W.; Howell, Steve B.; Rowe, Jason F. (2015). "HST/COS Detection of the Spectrum of the Subdwarf Companion of KOI-81". The Astrophysical Journal. 806 (2): 155. arXiv:1505.00817. Bibcode:2015ApJ...806..155M. doi:10.1088/0004-637X/806/2/155.
- ^ Zhang, Li-yun; Su, Tianhao; Misra, Prabhakar; Han, Xianming L.; Meng, Gang; Pi, Qingfeng; Yang, Jiawei (2023). "Stellar Parameters and Spectroscopic Properties of TESS Objects Observed in the LAMOST Low- and Medium-resolution Spectral Survey". The Astrophysical Journal Supplement Series. 264 (1): 17. Bibcode:2023ApJS..264...17Z. doi:10.3847/1538-4365/ac9b28.
- ^ 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. S2CID 118578253.