The variability of this star was first reported by
O. J. Eggen in 1971, who classified it as an ultra-short period
cepheid – a proposed category of
pulsating stars in the
instability strip.[14] It was subsequently grouped in the class of
Delta Scuti variables, which show a pulsation period of less than a day.[15] Observations in 1984 by
P. Lopez de Coca showed at least one pulsation period with a cycle of 1.9 hours.[16]L. Mantegazza and associates in 1994 were able to detect seven or more pulsation modes, with the previously detected dominant mode being a radial pulsation with a frequency of 12.72 cycles per day.[17]
The star became of interest to
astroseismology study because of its relatively slow rotation rate and the numerous modes of pulsation. A multi-site campaign involving the
Whole Earth Telescope network was conducted in 1993 to observe this star, which detected ten modes.[1] This was increased to 24 frequencies in 1998,[18] then 67 independent frequencies with 79 total by 2005. Evidence suggests there are many more such modes.[19]
This is an
A-type main-sequence star with a
stellar classification of A8/9V,[5] but is near the end of its main sequence lifetime.[11] It is classified as a Delta Scuti variable that varies in brightness with an
amplitude of 0.040 in visual magnitude and a period of 1.89 hours.[6]Element abundances are similar to the Sun, although there is a slight overabundance of barium and underabundances of sulfur and carbon.[20] It has a
projected rotational velocity of 21 km/s, but the actual rotational velocity is likely much higher at around 80 km/s.[11]
References
^
abBreger, M.; et al. (May 1995), "The δ Scuti star FG Virginis. I. Multiple pulsation frequencies determined with a combined DSN/WET campaign", Astronomy & Astrophysics, 297: 473,
Bibcode:
1995A&A...297..473B.
^
abHouk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5,
Bibcode:
1999MSS...C05....0H.
^
abcBreger, M.; Lenz, P. (February 2019), "Photometric data by the Delta Scuti Network. II. EE Cam, FG Vir, 44 Tau", The Journal of Astronomical Data, 25 (1): 6,
Bibcode:
2019JAD....25....1B.
^Eitter, J. J.; Beavers, W. I. (June 1979), "Lunar occultation summary. III", Astrophysical Journal Supplement Series, 40: 475–486,
Bibcode:
1979ApJS...40..475E,
doi:10.1086/190595.
See event no. 528.
^Eggen, O. J. (December 1971), "The Nature of the Blue Stragglers in the Old Disk Population", Publications of the Astronomical Society of the Pacific, 83 (496): 762,
Bibcode:
1971PASP...83..762E,
doi:
10.1086/129212,
S2CID120025134.
^Lopez de Coca, P.; et al. (January 1984), "Narrow Band Photometry of FG Vir", Information Bulletin on Variable Stars, 2465: 1,
Bibcode:
1984IBVS.2465....1L.
^Mantegazza, L.; et al. (July 1994), "Simultaneous intensive photometry and high resolution spectroscopy of δ Scuti stars I. Mode typing of HD 106384 = FG Virginis", Astronomy & Astrophysics, 287: 95–104,
Bibcode:
1994A&A...287...95M.
^Breger, M.; et al. (January 1999), "The delta Scuti star FG Virginis. IV. Mode identifications and pulsation modelling", Astronomy & Astrophysics, 341: 151–162,
arXiv:astro-ph/9811338,
Bibcode:
1999A&A...341..151B.
Haas, P. (2011), "Analyses of Crawford's uvby β calibrations using the pulsational variations of FG Vir", Communications in Asteroseismology, 162: 3,
Bibcode:
2011CoAst.162....3H,
doi:10.1553/cia162s3.
Lenz, P.; et al. (April 2008), "Determination of intrinsic mode amplitudes of the δ Scuti stars FG Vir and 44 Tau", Communications in Asteroseismology, 153: 40–48,
Bibcode:
2008CoAst.153...40L,
doi:10.1553/cia_153s40.
Zima, W. (July 2001), "The Spectroscopic and Photometric DSN Campaign 2002 of FG Vir", Communications in Asteroseismology, 140: 57–58,
Bibcode:
2001CoAst.140...57Z.
Dziembowski, W. A.; et al. (November 1998), Kjeldsen, H.; Bedding, T. R. (eds.), "Oscillations in XX Pyx and FG VIR and the prospects for asteroseismology of delta Scuti stars from space", The First MONS Workshop: Science with a Small Space Telescope, held in Aarhus, Denmark, June 29–30, 1998, Aarhus Universitet, p. 127,
Bibcode:
1998mons.proc..127D.
Viskum, M.; et al. (July 1998), "Oscillation mode identifications and models for the delta Scuti star FG Virginis", Astronomy & Astrophysics, 335: 549–560,
arXiv:astro-ph/9804218,
Bibcode:
1998A&A...335..549V.
Breger, M.; et al. (March 1998), "The delta Scuti star FG Vir. III. The 1995 multisite campaign and the detection of 24 pulsation frequencies", Astronomy & Astrophysics, 331: 271–279,
Bibcode:
1998A&A...331..271B.
Breger, M.; et al. (May 1996), "The δ Scuti star FG Virginis. II. A search for high pulsation frequencies", Astronomy & Astrophysics, 309: 197–202,
Bibcode:
1996A&A...309..197B.
Guzik, J. A.; Bradley, P. A. (September 1995), "Models and mode identifications of the Delta Scuti Star FG Vir", Delta Scuti Star Newsletter, 9 (9): 7–14,
Bibcode:
1995DSSN....9....7G.
Breger, M. (September 1995), "The 1995 FG VIR campaign: will 550 hours of new data and 19 frequencies be enough to do asteroseismology?", Delta Scuti Star Newsletter, 9 (9): 14–17,
Bibcode:
1995DSSN....9...14B.
Dawson, D. W.; et al. (June 1995), "A Photometric Study of the delta Scuti Star FG Virginis Undertaken during 1985/6", Publications of the Astronomical Society of the Pacific, 107: 517–520,
Bibcode:
1995PASP..107..517D,
doi:
10.1086/133585,
S2CID123547347.
Dawson, D. W. (March 1990), "The Period Structure of FG Virginis", Bulletin of the American Astronomical Society, 22: 831,
Bibcode:
1990BAAS...22..831D.
Gonzalez-Bedolla, S. F.; Rodriguez, E. (February 1990), "FG Vir, Additional Photoelectric Observations", Information Bulletin on Variable Stars, 3426: 1,
Bibcode:
1990IBVS.3426....1G.