AG Draconis

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AG Dra

AG Draconis
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
Right ascension 16h 01m 41.01124s
Declination +66° 48' 10.1382"'
Apparent magnitude (V) 9.8[1]
Spectral type K3IIIep[2]
U−B color index  ?
B−V color index  ?
Variable type nova variable
Radial velocity (Rv) -147.42±0.3 km/s
Proper motion (μ) RA: -7.66±0.82[3] mas/yr
Dec.: -5.49±0.99[3] mas/yr
Parallax (π) -0.85 ± 0.88[3] mas
Mass 1.5 / 0.5 M
Radius 0.9 R
Luminosity 1500 L
Surface gravity (log g) cgs
Temperature 3.500–5.000 K
Metallicity -1.3
Rotation ?
Age ? years
Companion AG Draconis B
Period (P) 1.516769336 yr
Semi-major axis (a) 0.01081″
Other designations
AG Dra, GCRV 9231, PPM 19692, TYC 4195-254-1, [[ AG]]+66° 715, RBS 1547, UBV 13635, BD+67° 922, GSC 04195-00254, 2RE J160133+664805, BPS BS 16087-0012, HIC 78512, 2RE J1601+664, 2E 1601.3+6656, HIP 78512, RX J1601.6+6648, AAVSO 1601+67, 2E 3573, IRAS 16013+6656, 1RXS J160141.2+664811, JP11 236, SAO 16931, 1ES 1601+66.9, 2MASS J16014101+6648101.
Database references

AG Draconis is a binary system consisting of an orange-red giant star and a white dwarf star that revolve around each other every 550 days. It has a baseline apparent magnitude of around 9.8 and flares up to around magnitude 7.3 and is one of the most-studied of symbiotic star systems and its variations in brightness have been observed for 124 years.[1] The outbursts occur every 15 years and last for 3–6 years.[4]

The larger star is thought to be an orange 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.[1] 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.[4]

The star is located in a spherical halo around the Milky Way, and is a nova variable, erupting every 10–15 years.


  1. ^ a b c Hric, L.; Gális, R.; Leedjärv, L.; Burmeister, M.; Kundra, E. (2014). "Outburst activity of the symbiotic system AG Dra". Monthly Notices of the Royal Astronomical Society. 443 (2): 1103–12. Bibcode:2014MNRAS.443.1103H. arXiv:1406.5505Freely accessible. doi:10.1093/mnras/stu1162. 
  2. ^ Shenavrin, V. I.; Taranova, O. G.; Nadzhip, A. E. (2011). "Search for and study of hot circumstellar dust envelopes". Astronomy Reports. 55 (1): 31–81. Bibcode:2011ARep...55...31S. doi:10.1134/S1063772911010070. 
  3. ^ a b c van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. Bibcode:2007A&A...474..653V. arXiv:0708.1752Freely accessible. doi:10.1051/0004-6361:20078357. Vizier catalog entry
  4. ^ a b Sion, Edward M.; Moreno, Jackeline; Godon, Patrick; Sabra, Bassem; Mikolajewska, Joanna (2012). "On the Nature of the Hot Component in the Symbiotic, Supersoft X-Ray Binary AG Draconis". The Astronomical Journal. 144 (6): 5. Bibcode:2012AJ....144..171S. arXiv:1210.1111Freely accessible. doi:10.1088/0004-6256/144/6/171. 171.