# KOI-256

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Double star in the constellation Draco

KOI-256 Artist's impression of the white dwarf companion gravitationally bending the starlight of KOI-256 Observation data Epoch J2000 Equinox J2000 Constellation Draco[1] Right ascension 19h 00m 44.42489s[2] Declination +49° 33′ 55.2489″[2] 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 Astrometry Proper motion (μ) RA: −6.796±0.030 mas/yr[2] Dec.: −14.373±0.030 mas/yr[2] Parallax (π) 5.6681±0.0228 mas[2] Distance 575 ± 2 ly (176.4 ± 0.7 pc) Orbit[3] Name KOI-256 B Period (P) 1.3786548±0.00001 d Semi-major axis (a) 0.0250±0.0018 AU Eccentricity (e) 0 Inclination (i) 89.01±0.65° Periastron epoch (T) 2455373.635498±0.000036 Argument of periastron (ω) (primary) 90° Semi-amplitude (K1) (primary) 106.5±1.8 km/s Details[3] KOI-256 A Mass 0.51±0.15 M☉ Radius 0.54±0.014 R☉ Temperature 3450±50 K Metallicity +0.31±0.10 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 KIC 11548140, 2MASS J19004443+4933553 Database references SIMBAD data Exoplanet Archive data KIC data

**KOI-256** is a [double star](/source/Double_star) located in the constellation [Draco](/source/Draco_(constellation)) approximately 575 [light-years](/source/Light-year) (176 [pc](/source/Parsec)) from Earth.[2] While observations by the [*Kepler*](/source/Kepler_(spacecraft)) spacecraft suggested the system contained a gas giant [exoplanet](/source/Exoplanet) orbiting a [red dwarf](/source/Red_dwarf), later studies determined that KOI-256 was a binary system composed of the red dwarf orbiting a [white dwarf](/source/White_dwarf).[4][5]

## Name

KOI-256

The acronym "KOI" comes from *[Kepler object of interest](/source/Kepler_object_of_interest)* and means that the object has been cataloged by the *[Kepler](/source/Kepler_(spacecraft))* spacecraft during its search for extrasolar planets using the [transit method](/source/Transit_method). The "256" is the number of the object.

## Characteristics

A [light curve](/source/Light_curve) for KOI-256, plotted from *Kepler* data.[6]  The inset plot (adapted from Muirhead *et al.*[3]) shows the time near the occultation of the white dwarf.

Initial observations by the *Kepler* spacecraft suggested a central [red dwarf](/source/Red_dwarf) with a mass of 0.65 [M☉](/source/Solar_mass), a radius of 1.1 [*R*☉](/source/Solar_radius), and a temperature of 3,639 [K](/source/Kelvin) (3,366 [°C](/source/Celsius); 6,091 [°F](/source/Fahrenheit)). Its candidate [exoplanet](/source/Exoplanet) was estimated to have a mass of 14.8 [M🜨](/source/Earth_mass), a radius of 25.34 [R🜨](/source/Earth_radius), an orbital period of 1.38 days, a temperature of 1,160 K (890 °C; 1,630 °F), and a [semi-major axis](/source/Semi-major_axis) of 0.021 [astronomical units](/source/Astronomical_unit).[7][8] 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.[9]

Muirhead *et al.* (2013) performed additional observations with the [Hale Telescope](/source/Hale_Telescope) at [Palomar Observatory](/source/Palomar_Observatory). Using the [radial velocity method](/source/Doppler_spectroscopy) for exoplanet detection, Muirhead's team found that the red dwarf was wobbling too much to be caused by a [planetary mass object](/source/Planetary_mass_object), and was more likely being influenced by a [white dwarf](/source/White_dwarf). Using ultraviolet data from the [GALEX](/source/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](/source/Gravitational_lens). 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.[4]

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).[3]

## References

1. **[^](#cite_ref-constellation_1-0)** [Roman, Nancy G.](/source/Nancy_Roman) (1987). ["Identification of a constellation from a position"](https://doi.org/10.1086%2F132034). *[Publications of the Astronomical Society of the Pacific](/source/Publications_of_the_Astronomical_Society_of_the_Pacific)*. **99** (617): 695. [Bibcode](/source/Bibcode_(identifier)):[1987PASP...99..695R](https://ui.adsabs.harvard.edu/abs/1987PASP...99..695R). [doi](/source/Doi_(identifier)):[10.1086/132034](https://doi.org/10.1086%2F132034). [Constellation record for this object](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?source=VI%2F42%2Fout&%2F%2Ftables=VI%2F42%2Fout&-c=KOI-256&-c.eq=J2000&-c.r=++2&-c.u=arcmin&-c.geom=r&-source=&-source=VI%2F42%2Fout&-out=RA1875&-out=DE1875&-out=Cst) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-GaiaDR3_2-0) [***b***](#cite_ref-GaiaDR3_2-1) [***c***](#cite_ref-GaiaDR3_2-2) [***d***](#cite_ref-GaiaDR3_2-3) [***e***](#cite_ref-GaiaDR3_2-4) Vallenari, A.; et al. (Gaia collaboration) (2023). ["*Gaia* Data Release 3. Summary of the content and survey properties"](https://doi.org/10.1051%2F0004-6361%2F202243940). *Astronomy and Astrophysics*. **674**: A1. [arXiv](/source/ArXiv_(identifier)):[2208.00211](https://arxiv.org/abs/2208.00211). [Bibcode](/source/Bibcode_(identifier)):[2023A&A...674A...1G](https://ui.adsabs.harvard.edu/abs/2023A&A...674A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202243940](https://doi.org/10.1051%2F0004-6361%2F202243940). [S2CID](/source/S2CID_(identifier)) [244398875](https://api.semanticscholar.org/CorpusID:244398875). [Gaia DR3 record for this source](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-source=+I%2F355&-from=nav&-nav=cat%3AI%2F355%26tab%3A%7BI%2F355%2Fgaiadr3%7D%26key%3Asource%3D1355%2Fgaiadr3%26HTTPPRM%3A%26-out.add%3D.%26Source%3D%3D%3D2132027576829358208%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-Muirhead2013_3-0) [***b***](#cite_ref-Muirhead2013_3-1) [***c***](#cite_ref-Muirhead2013_3-2) [***d***](#cite_ref-Muirhead2013_3-3) Muirhead, Philip S.; Vanderburg, Andrew; Shporer, Avi; Becker, Juliette; Swift, Jonathan J.; et al. (April 2013). "Characterizing the Cool KOIs. V. KOI-256: A Mutually Eclipsing Post-common Envelope Binary". *The Astrophysical Journal*. **767** (2). 111. [arXiv](/source/ArXiv_(identifier)):[1304.1165](https://arxiv.org/abs/1304.1165). [Bibcode](/source/Bibcode_(identifier)):[2013ApJ...767..111M](https://ui.adsabs.harvard.edu/abs/2013ApJ...767..111M). [doi](/source/Doi_(identifier)):[10.1088/0004-637X/767/2/111](https://doi.org/10.1088%2F0004-637X%2F767%2F2%2F111). [S2CID](/source/S2CID_(identifier)) [30368826](https://api.semanticscholar.org/CorpusID:30368826).

1. ^ [***a***](#cite_ref-nasa20130404_4-0) [***b***](#cite_ref-nasa20130404_4-1) ["Gravity-Bending Find Leads to Kepler Meeting Einstein"](https://web.archive.org/web/20150705131007/http://www.nasa.gov/mission_pages/kepler/news/kepler20130404.html). [NASA](/source/NASA). 4 April 2013. Archived from [the original](https://www.nasa.gov/mission_pages/kepler/news/kepler20130404.html) on 5 July 2015. Retrieved 29 August 2015.

1. **[^](#cite_ref-discover20130404_5-0)** O'Neill, Ian (4 April 2013). ["Kepler Watches White Dwarf Warp Spacetime"](https://web.archive.org/web/20150915004704/http://news.discovery.com/space/alien-life-exoplanets/kepler-watches-white-dwarfs-gravity-warp-spacetime-13040.htm). *[Discovery.com](/source/Discovery.com)*. Archived from [the original](http://news.discovery.com/space/alien-life-exoplanets/kepler-watches-white-dwarfs-gravity-warp-spacetime-13040.htm) on 15 September 2015. Retrieved 29 August 2015.

1. **[^](#cite_ref-MAST_6-0)** ["MAST: Barbara A. Mikulski Archive for Space Telescopes"](https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html). Space Telescope Science Institute. Retrieved 27 August 2024.

1. **[^](#cite_ref-Borucki2011_7-0)** Borucki, William J.; Koch, David G.; Basri, Gibor; Batalhi, Natalie; Brown, Timothy M.; et al. (July 2011). "Characteristics of Planetary Candidates Observed by *Kepler*. II. Analysis of the First Four Months of Data". *[The Astrophysical Journal](/source/The_Astrophysical_Journal)*. **736** (1). 19. [arXiv](/source/ArXiv_(identifier)):[1102.0541](https://arxiv.org/abs/1102.0541). [Bibcode](/source/Bibcode_(identifier)):[2011ApJ...736...19B](https://ui.adsabs.harvard.edu/abs/2011ApJ...736...19B). [doi](/source/Doi_(identifier)):[10.1088/0004-637X/736/1/19](https://doi.org/10.1088%2F0004-637X%2F736%2F1%2F19). [S2CID](/source/S2CID_(identifier)) [15233153](https://api.semanticscholar.org/CorpusID:15233153).

1. **[^](#cite_ref-Szabo2013_8-0)** Szabó, R.; Szabó, Gy. M.; Dálya, G.; Simon, A. E.; Hodosán, G.; et al. (May 2013). "Multiple planets or exomoons in Kepler hot Jupiter systems with transit timing variations?". *[Astronomy and Astrophysics](/source/Astronomy_and_Astrophysics)*. **553**. A17. [arXiv](/source/ArXiv_(identifier)):[1207.7229](https://arxiv.org/abs/1207.7229). [Bibcode](/source/Bibcode_(identifier)):[2013A&A...553A..17S](https://ui.adsabs.harvard.edu/abs/2013A&A...553A..17S). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201220132](https://doi.org/10.1051%2F0004-6361%2F201220132). [S2CID](/source/S2CID_(identifier)) [118791908](https://api.semanticscholar.org/CorpusID:118791908).

1. **[^](#cite_ref-Muirhead2012_9-0)** Muirhead, Philip S.; Hamren, Katherine; Schlawin, Everett; Rojas-Ayala, Bárbara; Covey, Kevin R.; et al. (May 2012). "Characterizing the Cool Kepler Objects of Interests. New Effective Temperatures, Metallicities, Masses, and Radii of Low-mass Kepler Planet-candidate Host Stars". *The Astrophysical Journal Letters*. **750** (2). L37. [arXiv](/source/ArXiv_(identifier)):[1109.1819](https://arxiv.org/abs/1109.1819). [Bibcode](/source/Bibcode_(identifier)):[2012ApJ...750L..37M](https://ui.adsabs.harvard.edu/abs/2012ApJ...750L..37M). [doi](/source/Doi_(identifier)):[10.1088/2041-8205/750/2/L37](https://doi.org/10.1088%2F2041-8205%2F750%2F2%2FL37). [S2CID](/source/S2CID_(identifier)) [27131741](https://api.semanticscholar.org/CorpusID:27131741).

v t e Constellation of Draco List of stars in Draco Draco in Chinese astronomy Stars Bayer α (Thuban) β (Rastaban) γ (Eltanin) δ (Altais) ε (Tyl) ζ (Aldhibah) η (Athebyne) θ ι (Edasich) κ λ (Giausar) μ (Alrakis) ν (Kuma) ξ (Grumium) ο π ρ σ (Alsafi) τ υ φ χ ψ1 (Dziban) ψ2 ω Flamsteed 4 6 7 (Tianyi) 8 (Taiyi) 10 (i) 15 (A) 18 (g) 19 (h) 26 36 39 (b) 42 (Fafnir) 45 (d) 50 59 64 (e) 68 Variable TW YY AG BY CL CM CX DO EK HP V581 HR 3751 4126 4934 5811 6237 6518 6618 (Alruba) 6817 7137 7783 HD 109246 (Funi) 101364 128717 147379 156279 158259 176693 191939 Other 2MASS 1237+6526 2MASS J17554042+6551277 G 240-72 GD 356 Gliese 420 Gliese 625 Gliese 687 GRW +70 8247 Kepler-4 Kepler-10 Kepler-12 Kepler-90 Kepler-296 KOI-256 LP 71-82 Qatar-1 SDSS J1240+6710 Struve 2398 TOI-1136 WD 1856+534 WISE 1647+5632 WISE 1841+7000 Exoplanets HD 139357 b HD 167042 b ι Dra b (Hypatia) Kepler-4b Kepler-10b c Kepler-12b Kepler-90e f g h i Kepler-296b c d e f TOI-1452 b TrES-2b Star clusters LAMOST 1 Nebulae Cat's Eye Nebula NGC 6742 Galaxies NGC 3147 3197 3735 4121 4125 4221 4236 4319 4331 4332 4363 4441 4513 4545 4589 5678 5777 5866 5866B 5879 5905 5907 5949 5963 5965 5982 5985 6090 6248 6285 6286 6338 6340 6365 6373 6394 6412 6503 6505 6566 6621 6622 6670 6676 6786 6789 Other 1ES 1927+654 1ES 1959+650 3C 249.1 3C 305 3C 319 3C 343 3C 343.1 3C 351 3C 356 3C 371 3C 380 3C 390.3 3C 401 4C +72.26 4C 73.08 8C 1241+735 Abell 2218 BCG Bean galaxy Beaver galaxy BZQ J1727+5510 Draco Dwarf Draco II GB 1508+5714 Goldfish galaxy H1821+643 HFLS3 IERS B1946+708 IRAS F17179+5444 IRAS 18580+6527 J120011.1+680924.8 KKR 25 Markarian 817 Markarian 876 Original TRG PGC 39058 Porphyrion QSO B1823+568 RGZ J172749.5+534647 S5 1803+784 S5 2007+777 SDSS J1715+6008 Tadpole Galaxy UGC 9391 UGC 9405 UGC 11241 UGC 11411 WISEA J145223.62+611707.5 WN B1851+5707 Galaxy clusters Abell 2218 CL1358+62 Draco Supercluster NGC 5866 Group Astronomical events SN 2003jb SN 2005B SN 2016aps Swift J1644+57 Category

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Adapted from the Wikipedia article [KOI-256](https://en.wikipedia.org/wiki/KOI-256) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/KOI-256?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.