AG Draconis

AG Draconis
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
Right ascension 16h 01m 41.01257s[1]
Declination +66° 48′ 10.1312″[1]
Apparent magnitude (V) 9.76[2]
Characteristics
Spectral type K3 IIIep[3] + WD[4]
B−V color index 1.425±0.094[2]
Variable type Z And[5]
Astrometry
Radial velocity (Rv)−147.42±0.30[2] km/s
Proper motion (μ) RA: −7.135[1] mas/yr
Dec.: −5.602[1] mas/yr
Parallax (π)0.2101 ± 0.0268[1] mas
Distanceapprox. 16,000 ly
(approx. 4,800 pc)
Orbit[6]
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[4]
AG Dra A
Mass1.5 M☉
Radius35 R☉
Metallicity [Fe/H]−1.3 dex
AG Dra B
Luminosity~ 103 L☉
Temperature~ 105 K
Other designations
AG Dra, BD+67° 922, HIP 78512, SAO 16931[7]
Database references
SIMBADdata

AG Draconis is a binary star system in the northern constellation of Draco. It consists of a giant star and a white dwarf 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.[4] The outbursts occur every 15 years and last for 3–6 years.[8]

The a sin i value for the primary is 50.69 R☉, where a is the semimajor axis and i is the (unknown) orbital inclination.[6] 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.[4] 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.[8]

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

References

  1. 1 2 3 4 5 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  2. 1 2 3 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015.
  3. ↑ Shenavrin, V. I.; et al. (2011). "Search for and study of hot circumstellar dust envelopes". Astronomy Reports. 55 (1): 31–81. Bibcode:2011ARep...55...31S. doi:10.1134/S1063772911010070.
  4. 1 2 3 4 Hric, L.; et al. (September 2014). "Outburst activity of the symbiotic system AG Dra". Monthly Notices of the Royal Astronomical Society. 443 (2): 1103–1112. arXiv:1406.5505. Bibcode:2014MNRAS.443.1103H. doi:10.1093/mnras/stu1162.
  5. ↑ 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:2017ARep...61...80S. doi:10.1134/S1063772917010085.
  6. 1 2 Gális, R.; et al. (March 2016). "Resonances as the general cause of the outbursts in the symbiotic system AG Draconis". Monthly Notices of the Royal Astronomical Society. 456 (3): 2558–2565. arXiv:1512.03209. Bibcode:2016MNRAS.456.2558L. doi:10.1093/mnras/stv2807.
  7. ↑ "AG Dra". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2 September 2018.
  8. 1 2 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:1210.1111. Bibcode:2012AJ....144..171S. doi:10.1088/0004-6256/144/6/171. 171.
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