# AG Draconis

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Star in the constellation Draco

AG Draconis A blue band light curve for AG Draconis, spanning 123 years, adapted from Gális et al. (2015)[1] Observation data Epoch J2000 Equinox J2000 Constellation Draco Right ascension 16h 01m 41.01257s[2] Declination +66° 48′ 10.1312″[2] Apparent magnitude (V) 7.9 - 10.3[3] Characteristics Spectral type K3 IIIep[4] + WD[5] B−V color index 1.425±0.094[6] Variable type Z And[7] Astrometry Radial velocity (Rv) −147.42±0.30[6] km/s Proper motion (μ) RA: −7.135[2] mas/yr Dec.: −5.602[2] mas/yr Parallax (π) 0.2101±0.0268 mas[2] Distance approx. 16,000 ly (approx. 4,800 pc) Orbit[8] Period (P) 549.73 d Eccentricity (e) 0.06 Periastron epoch (T) 2447622.28 JD Argument of periastron (ω) (secondary) 359.8° Semi-amplitude (K1) (primary) 4.67 km/s Details[5] AG Dra A Mass 1.5 M☉ Radius 35 R☉ Metallicity [Fe/H] −1.3 dex AG Dra B Luminosity ~ 103 L☉ Temperature ~ 105 K Other designations AG Dra, AAVSO 1601+67, AG+66° 715, BD+67°922, HIP 78512, SAO 16931[9] Database references SIMBAD data

**AG Draconis** is a [binary star](/source/Binary_star) system in the northern [constellation](/source/Constellation) of [Draco](/source/Draco_(constellation)). It consists of a [giant star](/source/Giant_star) and a [white dwarf](/source/White_dwarf) that revolve around each other every 550 days.

## Discovery

AG Draconis has been catalogued since mid 20th century, as BD+67°922. However, its unusual nature did not start to come to light until the middle of the century. It was noted as an emission-line object in 1943,[10] although its nature was not understood.[11] The [emission spectrum](/source/Emission_spectrum) was serendipitously discovered to be variable by [Nancy Grace Roman](/source/Nancy_Grace_Roman) when she observed the star and found that the spectrum had completely changed since earlier observations.[12] It was given the [variable star designation](/source/Variable_star_designation) AG Draconis in 1964.[13]

## Variability

AG Draconis spends most of its time in a quiescent phase near [visual magnitude](/source/Visual_magnitude) 9.8, with only small semi-regular variations thought to be due to pulsations of the giant star. At its faintest, it can reach magnitude 10.3.[3] The semi-regular variations have periods of 340 - 370 days. Variations at [ultraviolet](/source/Ultraviolet) wavelengths occur with a period of 550 days, which is the orbital period.[14]

Every 12-16 years, outbursts occur and last for several years.[5] The brightness can increase to visual magnitude 7.9,[3] although usually not this bright.[5]

## System

The *a* sin *i* value for the primary is 50.69 *R*☉, where *a* is the [semimajor axis](/source/Semimajor_axis) and *i* is the (unknown) [orbital inclination](/source/Orbital_inclination).[8] The larger star is thought to be an orange hued giant around 1.5 times as massive as the Sun that has swollen to around 35 times the diameter of the Sun with a spectral type measured at K3IIIep.[5] The smaller star is a compact hot white dwarf around 0.4 times as massive as the Sun, with a surface temperature of around 80,000 K.[15]

## References

1. **[^](#cite_ref-Gális_1-0)** Gális, R.; Hric, L.; Smelcer, L. (February 2015). ["AG Draconis - a symbiotic mystery"](https://ui.adsabs.harvard.edu/abs/2015OEJV..169....4G). *Open European Journal on Variable Stars*. **169**: 4–9. [Bibcode](/source/Bibcode_(identifier)):[2015OEJV..169....4G](https://ui.adsabs.harvard.edu/abs/2015OEJV..169....4G). Retrieved 2 January 2022.

1. ^ [***a***](#cite_ref-GaiaDR2_2-0) [***b***](#cite_ref-GaiaDR2_2-1) [***c***](#cite_ref-GaiaDR2_2-2) [***d***](#cite_ref-GaiaDR2_2-3) [***e***](#cite_ref-GaiaDR2_2-4) [Brown, A. G. A.](/source/Anthony_Brown_(scientist)); et al. ([Gaia collaboration](/source/Data_Processing_and_Analysis_Consortium)) (August 2018). ["*Gaia* Data Release 2: Summary of the contents and survey properties"](https://doi.org/10.1051%2F0004-6361%2F201833051). *[Astronomy & Astrophysics](/source/Astronomy_%26_Astrophysics)*. **616**. A1. [arXiv](/source/ArXiv_(identifier)):[1804.09365](https://arxiv.org/abs/1804.09365). [Bibcode](/source/Bibcode_(identifier)):[2018A&A...616A...1G](https://ui.adsabs.harvard.edu/abs/2018A&A...616A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201833051](https://doi.org/10.1051%2F0004-6361%2F201833051).

1. ^ [***a***](#cite_ref-vsx_3-0) [***b***](#cite_ref-vsx_3-1) [***c***](#cite_ref-vsx_3-2) ["AG Draconis"](https://www.aavso.org/vsx/index.php?view=detail.top&oid=13733). *Variable Star Index*. [AAVSO](/source/AAVSO). Retrieved 2020-04-29.

1. **[^](#cite_ref-Shenavrin2011_4-0)** Shenavrin, V. I.; et al. (2011). "Search for and study of hot circumstellar dust envelopes". *Astronomy Reports*. **55** (1): 31–81. [Bibcode](/source/Bibcode_(identifier)):[2011ARep...55...31S](https://ui.adsabs.harvard.edu/abs/2011ARep...55...31S). [doi](/source/Doi_(identifier)):[10.1134/S1063772911010070](https://doi.org/10.1134%2FS1063772911010070). [S2CID](/source/S2CID_(identifier)) [122700080](https://api.semanticscholar.org/CorpusID:122700080).

1. ^ [***a***](#cite_ref-Hric2014_5-0) [***b***](#cite_ref-Hric2014_5-1) [***c***](#cite_ref-Hric2014_5-2) [***d***](#cite_ref-Hric2014_5-3) [***e***](#cite_ref-Hric2014_5-4) Hric, L.; et al. (September 2014). ["Outburst activity of the symbiotic system AG Dra"](https://doi.org/10.1093%2Fmnras%2Fstu1162). *Monthly Notices of the Royal Astronomical Society*. **443** (2): 1103–1112. [arXiv](/source/ArXiv_(identifier)):[1406.5505](https://arxiv.org/abs/1406.5505). [Bibcode](/source/Bibcode_(identifier)):[2014MNRAS.443.1103H](https://ui.adsabs.harvard.edu/abs/2014MNRAS.443.1103H). [doi](/source/Doi_(identifier)):[10.1093/mnras/stu1162](https://doi.org/10.1093%2Fmnras%2Fstu1162). [S2CID](/source/S2CID_(identifier)) [119225658](https://api.semanticscholar.org/CorpusID:119225658).

1. ^ [***a***](#cite_ref-Anderson2012_6-0) [***b***](#cite_ref-Anderson2012_6-1) Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". *Astronomy Letters*. **38** (5): 331. [arXiv](/source/ArXiv_(identifier)):[1108.4971](https://arxiv.org/abs/1108.4971). [Bibcode](/source/Bibcode_(identifier)):[2012AstL...38..331A](https://ui.adsabs.harvard.edu/abs/2012AstL...38..331A). [doi](/source/Doi_(identifier)):[10.1134/S1063773712050015](https://doi.org/10.1134%2FS1063773712050015). [S2CID](/source/S2CID_(identifier)) [119257644](https://api.semanticscholar.org/CorpusID:119257644).

1. **[^](#cite_ref-gcvs_7-0)** Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017). "General catalogue of variable stars: Version GCVS 5.1". *Astronomy Reports*. **61** (1): 80. [Bibcode](/source/Bibcode_(identifier)):[2017ARep...61...80S](https://ui.adsabs.harvard.edu/abs/2017ARep...61...80S). [doi](/source/Doi_(identifier)):[10.1134/S1063772917010085](https://doi.org/10.1134%2FS1063772917010085). [S2CID](/source/S2CID_(identifier)) [125853869](https://api.semanticscholar.org/CorpusID:125853869).

1. ^ [***a***](#cite_ref-Gális2016_8-0) [***b***](#cite_ref-Gális2016_8-1) Gális, R.; Hric, L.; Friedjung, M.; Petrík, K. (1999). "Resonances as the general cause of the outbursts in the symbiotic system AG Draconis". *Astronomy and Astrophysics*. **348**: 533. [Bibcode](/source/Bibcode_(identifier)):[1999A&A...348..533G](https://ui.adsabs.harvard.edu/abs/1999A&A...348..533G).

1. **[^](#cite_ref-SIMBAD_9-0)** ["AG Dra"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=AG+Dra). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2 September 2018.

1. **[^](#cite_ref-janssen_10-0)** Janssen, Edith M.; Vyssotsky, A. N. (1943). "A Peculiar Emission-Line Object". *Publications of the Astronomical Society of the Pacific*. **55** (326): 244. [Bibcode](/source/Bibcode_(identifier)):[1943PASP...55..244J](https://ui.adsabs.harvard.edu/abs/1943PASP...55..244J). [doi](/source/Doi_(identifier)):[10.1086/125560](https://doi.org/10.1086%2F125560). [S2CID](/source/S2CID_(identifier)) [122605688](https://api.semanticscholar.org/CorpusID:122605688).

1. **[^](#cite_ref-wilson1950_11-0)** Wilson, Ralph E. (1950). "The Spectrum of HD 4174". *Publications of the Astronomical Society of the Pacific*. **62** (363): 14. [Bibcode](/source/Bibcode_(identifier)):[1950PASP...62...14W](https://ui.adsabs.harvard.edu/abs/1950PASP...62...14W). [doi](/source/Doi_(identifier)):[10.1086/126211](https://doi.org/10.1086%2F126211). [S2CID](/source/S2CID_(identifier)) [120390522](https://api.semanticscholar.org/CorpusID:120390522).

1. **[^](#cite_ref-roman_12-0)** Roman, Nancy G. (1953). "The Spectrum of BD+67°922". *The Astrophysical Journal*. **117**: 467. [Bibcode](/source/Bibcode_(identifier)):[1953ApJ...117..467R](https://ui.adsabs.harvard.edu/abs/1953ApJ...117..467R). [doi](/source/Doi_(identifier)):[10.1086/145717](https://doi.org/10.1086%2F145717).

1. **[^](#cite_ref-ibvs_13-0)** Robinson, L. J. (1964). "AG Draconis". *Information Bulletin on Variable Stars*. **73**: 1. [Bibcode](/source/Bibcode_(identifier)):[1964IBVS...73....1R](https://ui.adsabs.harvard.edu/abs/1964IBVS...73....1R).

1. **[^](#cite_ref-Meinunger1979_14-0)** Meinunger, L. (1979). "Discovery of a period in the symbiotic star AG Draconis". *Information Bulletin on Variable Stars*. **1611**: 2. [Bibcode](/source/Bibcode_(identifier)):[1979IBVS.1611....1M](https://ui.adsabs.harvard.edu/abs/1979IBVS.1611....1M).

1. **[^](#cite_ref-sion_15-0)** Sion, Edward M.; et al. (2012). "On the Nature of the Hot Component in the Symbiotic, Supersoft X-Ray Binary AG Draconis". *The Astronomical Journal*. **144** (6): 5. [arXiv](/source/ArXiv_(identifier)):[1210.1111](https://arxiv.org/abs/1210.1111). [Bibcode](/source/Bibcode_(identifier)):[2012AJ....144..171S](https://ui.adsabs.harvard.edu/abs/2012AJ....144..171S). [doi](/source/Doi_(identifier)):[10.1088/0004-6256/144/6/171](https://doi.org/10.1088%2F0004-6256%2F144%2F6%2F171). [S2CID](/source/S2CID_(identifier)) [118737620](https://api.semanticscholar.org/CorpusID:118737620). 171.

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