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]
^
abHill, G.; et al. (1975), "MK Classifications of some Northern Hemisphere Binary Systems", Memoirs of the Royal Astronomical Society, 79: 131,
Bibcode:
1975MmRAS..79..131H.
^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.
^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.
^Kaluzny, J. (1986), "Contact binaries with components in poor thermal contact. IV. AG Virginis", Acta Astronomica, 36: 121–129,
Bibcode:
1986AcA....36..121K.
Djurašević, Gojko (August 1993), "An Analysis of Close Binaries Based on Photometric Measurements - Part Four - an Interpretation of CB Lightcurve Ag-Virginis by Using the Inverse-Problem Method", Astrophysics and Space Science, 206 (1): 119–127,
Bibcode:
1993Ap&SS.206..119D,
doi:
10.1007/BF00658388,
S2CID128295945.
Bell, S. A.; et al. (December 1990), "Spots on AG Virginis - paradigm or panacea?", Monthly Notices of the Royal Astronomical Society, 247: 632,
Bibcode:
1990MNRAS.247..632B.
Michaels, E. J. (June 1988), "AG Virginis: New Times of Minima and Period Study", Information Bulletin on Variable Stars, 3202: 1,
Bibcode:
1988IBVS.3202....1M.
Niarchos, P. G. (August 1985), "Photoelectric light curves and elements of AG Virginis", Astronomy and Astrophysics Supplement Series, 61: 313–318,
Bibcode:
1985A&AS...61..313N.