AG Virginis

A visual band light curve for AG Virginis, plotted from ASAS data[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Virgo
Right ascension 12h 01m 03.504s[2]
Declination 13° 00′ 30.01″[2]
Apparent magnitude (V) 8.51[3]
Characteristics
Spectral type A7V-A9V[4]
B−V color index 0.289±0.017[3]
Variable type W UMa[5]
Astrometry
Proper motion (μ) RA: −2.740 mas/yr[2]
Dec.: −18.255 mas/yr[2]
Parallax (π)3.9564 ± 0.0621 mas[2]
Distance820 ± 10 ly
(253 ± 4 pc)
Orbit[6]
Period (P)0.6426507 d
Semi-major axis (a)4.477 R☉[7]
Eccentricity (e)0.00 (assumed)
Inclination (i)84.40[7]°
Periastron epoch (T)53,501.5388±0.0013 MJD
Semi-amplitude (K1)
(primary)		93.39±1.06 km/s
Semi-amplitude (K2)
(secondary)		244.24±1.97 km/s
Details
Component 1
Mass2.179[7] M☉
Radius2.185[7] R☉
Luminosity19.0[7] L☉
Temperature8,150[7] K
Metallicity [Fe/H]−0.08±0.09[8] dex
Age2.252[7] Gyr
Component 2
Mass0.739[7] M☉
Radius1.356[7] R☉
Luminosity3.85[7] L☉
Temperature6,915[7] K
Other designations
AG Vir, BD+13°2481, HD 104350, HIP 58605, SAO 99908, PPM 128717[9]
Database references
SIMBADdata

AG Virginis is an eclipsing binary star system in the equatorial constellation of Virgo. With a maximum apparent visual magnitude of 8.51[3] it is too faint to be visible to the naked eye. The system is located at a distance of approximately 820 light years from the Sun based on parallax measurements.[2]

The variability of this system was first reported by P. Guthnick and R. Prager in 1929. R. S. Dugan determined the periodicity in 1933.[10] C. Blanco and F. Catalano in 1970 proposed that this is a semidetached binary where the primary component has filled its Roche lobe, thereby allowing mass transfer. They noted that the orbital period appeared to vary slightly with a ~40 year cycle,[11] which could be explained by a third component.[12] In 1986, J. Kaluzny produced a model for the light curve which suggested this is instead a contact binary. Multiple observers noted a permanent asymmetry to the light curve, with the primary minimum appearing distorted. A localized "hot spot" hypothesis was proposed to explain this feature.[13]

This is a close binary system with an orbital period of 15.4 hours. It is classified as a W Ursae Majoris variable,[6] which means the components are in near contact with each other and their mutual gravitational influence is distorting their shapes. The components are separated by just 4.5 times the radius of the Sun, and the orbital plane is inclined at an angle of 84.4° to the line of sight from the Earth.[7] This causes the two stars to eclipse each other during every orbit. The net visual brightness decreases by 0.58 in magnitude during the primary eclipse and by 0.45 during the secondary eclipse.[14]

The combined spectrum of the system has a varying stellar classification in the range of A7V-A9V,[4] matching an A-type main-sequence star. The primary component has 2.2 times the mass and radius of the Sun, while the secondary has 74% of the Sun's mass and 136% of the radius of the Sun.[7]

References

  1. ^ "ASAS All Star Catalogue". The All Sky Automated Survey. Retrieved 8 December 2021.
  2. ^ a b c d e Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  3. ^ a b c 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, S2CID 119257644.
  4. ^ a b Hill, G.; et al. (1975), "MK Classifications of some Northern Hemisphere Binary Systems", Memoirs of the Royal Astronomical Society, 79: 131, Bibcode:1975MmRAS..79..131H.
  5. ^ Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  6. ^ a b Pribulla, Theodor; et al. (August 2006), "Radial Velocity Studies of Close Binary Stars. XI.", The Astronomical Journal, 132 (2): 769–780, arXiv:astro-ph/0605357, Bibcode:2006AJ....132..769P, doi:10.1086/505536, S2CID 2156235.
  7. ^ a b c d e f g h i j k l m Latković, Olivera; et al. (May 2021), "Statistics of 700 Individually Studied W UMa Stars", The Astrophysical Journal Supplement Series, 254 (1): 18, arXiv:2103.06693, Bibcode:2021ApJS..254...10L, doi:10.3847/1538-4365/abeb23, S2CID 232185576, 10.
  8. ^ Rucinski, Slavek M.; et al. (September 2013), "Spectroscopic Metallicity Determinations for W UMa-type Binary Stars", The Astronomical Journal, 146 (3): 20, arXiv:1308.0184, Bibcode:2013AJ....146...70R, doi:10.1088/0004-6256/146/3/70, S2CID 119243235, 70.
  9. ^ "AG Vir", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2022-06-07.
  10. ^ Binnendijk, L. (October 1969), "The light variation and orbital elements of AG Virginis", Astronomical Journal, 74: 1024–1031, Bibcode:1969AJ.....74.1024B, doi:10.1086/110898.
  11. ^ Blanco, C.; Catalano, F. (1970), "Light curve and elements of AG Vir", Memorie della Società Astronomia Italiana, vol. 41, p. 343, Bibcode:1970MmSAI..41..343B.
  12. ^ Avvakumova, E. A.; et al. (2014), "Observations of two unusual eclipsing binaries, FN Cam and AG Vir", Baltic Astronomy, 23 (3–4): 255–259, Bibcode:2014BaltA..23..255A, doi:10.1515/astro-2017-0188, hdl:10995/92262, S2CID 185752291.
  13. ^ Kaluzny, J. (1986), "Contact binaries with components in poor thermal contact. IV. AG Virginis", Acta Astronomica, 36: 121–129, Bibcode:1986AcA....36..121K.
  14. ^ Avvakumova, E. A.; et al. (October 2013), "Eclipsing variables: Catalogue and classification", Astronomische Nachrichten, 334 (8): 860, Bibcode:2013AN....334..860A, doi:10.1002/asna.201311942, hdl:10995/27061.

Further reading

Categories