Astronomy:AH Virginis

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Short description: Star in the constellation Virgo
AH Virginis
AHVirLightCurve.png
A visual band light curve for AH Virginis, plotted from INTEGRAL-OMC data[1]
Observation data
Equinox J2000.0]] (ICRS)
Constellation Virgo
Right ascension  12h 14m 20.996s[2]
Declination +11° 49′ 09.39″[2]
Apparent magnitude (V) 9.18[3]
Characteristics
Spectral type G8V[4]
B−V color index 0.81±0.25[3]
Variable type Eclipsing W UMa[5]
Astrometry
Radial velocity (Rv)6.6±0.9[6] km/s
Proper motion (μ) RA: 47.828[2] mas/yr
Dec.: −107.737[2] mas/yr
Parallax (π)9.6552 ± 0.0203[2] mas
Distance337.8 ± 0.7 ly
(103.6 ± 0.2 pc)
Absolute magnitude (MV)4.25±0.16[4]
Absolute bolometric
magnitude (Mbol)		4.07±0.16[4]
Orbit[4]
Period (P)0.4075 d
Semi-major axis (a)2.796±0.017 R☉
Eccentricity (e)0.0 (assumed)
Inclination (i)85.2±1.2°
Periastron epoch (T)2,448,765 JD
Argument of periastron (ω)
(secondary)		0.0°
Semi-amplitude (K1)
(primary)		79.6±1.6 km/s
Semi-amplitude (K2)
(secondary)		263.5±1.9 km/s
Details[7]
Primary
Mass1.360 M☉
Radius1.397 R☉
Luminosity1.860 L☉
Temperature5,300 K
Age4.622 Gyr
Secondary
Mass0.412 M☉
Radius0.826 R☉
Luminosity0.634 L☉
Temperature5,671 K
Other designations
AH Vir, BD+12°2437A, HD 106400A, HIP 59683A, SAO 100003A, WDS 12143+1149A[8]
Database references
SIMBADdata

AH Virginis is a contact binary[7] star system in the equatorial constellation of Virgo, abbreviated AH Vir. It is a variable star with a brightness that peaks at an apparent visual magnitude of 9.18, making it too faint to be viewed with the naked eye.[3] The distance to this system is approximately 338 light years based on parallax measurements, and it is drifting further away with a mean radial velocity of 7 km/s.[6] O. J. Eggen in 1969 included this system as a probable member of the Wolf 630 group of co-moving stars.[9]

In 1905, this source was identified as an optical double star by W. J. Hussey, with the pair showing an angular separation of 1.27″ along a position angle of 15.2°.[10] Gaia Data Release 3 astrometry for the companion is flagged as potentially unreliable but shows a similar parallax and proper motion to AH Virginis.[11]

The brighter visual component was found to be variable by P. Guthnick and R. Prager in 1929, and designated AH Vir.[12][4] This component was determined to be a W Ursae Majoris variable, and an orbital period of 9.78 hours was found by F. Lause in 1934–1935.[13] Y. C. Chang computed orbital elements of this close binary in 1948 and found the system is eclipsing.[14]

In 1960, L. Binnendijk interpreted the particular shape of the light curve for AH Vir as being due to a sub-luminous region on the primary.[15] Multiple observers noted frequent changes to the light curve and period over time, and in 1977 G. A. Bakos found emission in the calcium K line that suggested mass transfer is taking place.[16] The amplitude of these changes compared to the overall brightness variation is among the largest known among W UMa-type variables. The primary eclipse is total with a duration of around 43 minutes.[17] It was proposed in 1991 that the observed variations in the light curve may be caused by magnetic activity and magnetic interactions between the components.[18]

There has been uncertainty as to whether the two stars are in direct contact with each other, or if the system is semi-detached with only the primary being close to its Roche lobe. The evidence now suggests that they are an overcontact system. The orbital period is showing a increase over time of (2.1869±0.0161)×10−7 d·yr−1, combined with a cyclical variation with a period of 37.19 years. The system shows a strong level of magnetic activity,[19] with the primary being the more active component.[4] The mean magnetic field strength of the primary is estimated as 1.487 kG. The cyclical variation in orbital period may be related to the activity on the primary.[19]

References

  1. ↑ OMC Archive, The Astronomical Data Centre at CAB, https://sdc.cab.inta-csic.es/omc/secure/form_busqueda.jsp?resetForm=true, retrieved 19 December 2021. 
  2. ↑ 2.0 2.1 2.2 2.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Lu, W. -X.; Rucinski, S. M. (July 1993), "Spectral-Line Broadening Functions of W UMa-Type Binaries. II. AH Vir", Astronomical Journal 106: 361, doi:10.1086/116645, Bibcode: 1993AJ....106..361L. 
  5. ↑ Samus, N. N. et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1 61 (1): 80–88, doi:10.1134/S1063772917010085, Bibcode: 2017ARep...61...80S. 
  6. ↑ 6.0 6.1 Bilir, S. et al. (2005), "Kinematics of W Ursae Majoris type binaries and evidence of the two types of formation", Monthly Notices of the Royal Astronomical Society 357 (2): 497–517, doi:10.1111/j.1365-2966.2005.08609.x, Bibcode: 2005MNRAS.357..497B. 
  7. ↑ 7.0 7.1 Latković, Olivera et al. (2021), "Statistics of 700 Individually Studied W UMa Stars", The Astrophysical Journal Supplement Series 254 (1): 10, doi:10.3847/1538-4365/abeb23, Bibcode: 2021ApJS..254...10L. 
  8. ↑ "AH Vir". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=AH+Vir. 
  9. ↑ Eggen, Olin J. (October 1969), "Stellar Groups in the Old Disk Population", Publications of the Astronomical Society of the Pacific 81 (482): 553, doi:10.1086/128823, Bibcode: 1969PASP...81..553E. 
  10. ↑ Hussey, William Joseph (1905), "Observations of one hundred new double stars : eleventh catalogue", Lick Observatory Bulletin (Berkeley: The University Press) 81: 151–158, doi:10.5479/ADS/bib/1905LicOB.3.151H, Bibcode: 1905LicOB...3..151H.  Identified as HU 1137.
  11. ↑ Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  12. ↑ Guthnick, P.; Prager, R. (December 1929), "Benennung von veränderlichen Sternen" (in de), Astronomische Nachrichten 237 (10): 169, doi:10.1002/asna.19292371002, Bibcode: 1929AN....237..169G. 
  13. ↑ Lause, Friedrich (December 1935), "Beobachtungen von Bedeckungsveräderlichen V", Astronomische Nachrichten 257 (13): 211–214, doi:10.1002/asna.19352571304, Bibcode: 1935AN....257..211L. 
  14. ↑ Chang, Y. C. (January 1948), "Spectrographic Observations of the Eclipsing Binaries of the W Ursae Majoris Type: AH Virginis and TZ Bootis", Astrophysical Journal 107: 96, doi:10.1086/144990, Bibcode: 1948ApJ...107...96C. 
  15. ↑ Binnendijk, L. (August 1960), "The light variation and orbital elements of AH Virginis", Astronomical Journal 65: 358–373, doi:10.1086/108270, Bibcode: 1960AJ.....65..358B. 
  16. ↑ Bakos, G. A. (1977), "Variations of the Light Curve and the Period of AH VIR", Bulletin of the Astronomical Institute of Czechoslovakia 28: p. 157, Bibcode: 1977BAICz..28..157B. 
  17. ↑ Kaluzny, J. (1984), "Determination of parameters of W UMa-type systems : V757 Cen, GW Cep, BX Peg, AH Vir", Acta Astronautica 34: 217–224, Bibcode: 1984AcA....34..217K. 
  18. ↑ Demircan, O. et al. (January 1991), "A Period Analysis of AH Virginis", Astronomical Journal 101: 201, doi:10.1086/115679, Bibcode: 1991AJ....101..201D. 
  19. ↑ 19.0 19.1 Chen, Ming; Xiang, Fu-Yuan; Yu, Yun-Xia; Xiao, Ting-Yu (February 2015), "The orbital period variations of AH Virginis", Research in Astronomy and Astrophysics 15 (2): 275–280, doi:10.1088/1674-4527/15/2/010, 275-280, Bibcode: 2015RAA....15..275C. 

Further reading

  • Demircan, Osman (July 1987), "BV Observations of W-Ursae Type Binaries - CK-Bootis, BI-Canum, and AH-Virginis", Astrophysics and Space Science 135 (1): 169–174, doi:10.1007/BF00644471, Bibcode: 1987Ap&SS.135..169D. 
  • Niarchos, P. G. (July 1983), "Light curves and elements of AH Virginis", Astronomy and Astrophysics Supplement Series 53: 13–19, Bibcode: 1983A&AS...53...13N. 
  • Hoffmann, M. (March 1981), "B and Mg Band Observations of AH Vir in 1977", Information Bulletin on Variable Stars 1933: 1, Bibcode: 1981IBVS.1933....1H. 
  • Hopp, U.; Witzigmann, S. (August 1981), "Note on the Period of the W UMa Star AH Vir", Information Bulletin on Variable Stars 2005: 1, Bibcode: 1981IBVS.2005....1H. 
  • Landolt, Arlo U. (June 1972), "A Time of Minimum for AH Virginis", Publications of the Astronomical Society of the Pacific 84 (499): 448, doi:10.1086/129312, Bibcode: 1972PASP...84..448L. 
  • Sievers, J. R. (October 1963), "A Photoelectric Study of AH Virginis", Publications of the Astronomical Society of the Pacific 75 (446): 446, 418, doi:10.1086/127995, Bibcode: 1963PASP...75..418S. 
  • Kitamura, M. et al. (1957), "Photoelectric Observations of AH Virginis and the Interpretation of its Color Changes at Light Minima", Publications of the Astronomical Society of Japan 9: 119, Bibcode: 1957PASJ....9..119K. 




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