AH Virginis

AH Virginis

A visual band light curve for AH Virginis, plotted from INTEGRAL-OMC data[1]
Observation data
Epoch J2000      Equinox J2000
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 mas/yr[2]
Dec.: −107.737 mas/yr[2]
Parallax (π)9.6552 ± 0.0203 mas[2]
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]

  1. ^ Cite error: The named reference OMCarchive was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference dr3a was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Anderson_Francis_2012 was invoked but never defined (see the help page).
  4. ^ a b c d e f Cite error: The named reference Lu_Rucinski_1993 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Bilir_et_al_2005 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Latković_et_al_2021 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Eggen_1969 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Hussey_1905 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference dr3b was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Guthnick_Prager_1929 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Lause_1935 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Chang_1948 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Binnendijk_1960 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Bakos_1977 was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference Kaluzny_1984 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference Demircan_et_al_1991 was invoked but never defined (see the help page).
  19. ^ a b Cite error: The named reference Chen_et_al_2015 was invoked but never defined (see the help page).