Astronomy:LL Aquarii

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Short description: Binary star in the constellation Aquarius
LL Aquarii
Observation data
Equinox J2000.0]] (ICRS)
Constellation Aquarius[1]
Right ascension  22h 34m 42.153s[2]
Declination −03° 35′ 58.17″[2]
Apparent magnitude (V) 9.23[1]
Min I: 9.86
Min II: 9.59[3]
Characteristics
Evolutionary stage main sequence[4]
Spectral type F9 V + G3 V[5]
U−B color index 0.029[6]
B−V color index 0.601±0.037[1]
Variable type Algol[3]
Astrometry
Radial velocity (Rv)−9.59±0.46[7] km/s
Proper motion (μ) RA: 73.192[2] mas/yr
Dec.: −21.545[2] mas/yr
Parallax (π)7.297 ± 0.0219[2] mas
Distance447 ± 1 ly
(137.0 ± 0.4 pc)
Absolute magnitude (MV)3.95[1]
Orbit[4]
Period (P)20.178322(1) days
Semi-major axis (a)40.744±0.007 R☉[5]
Eccentricity (e)0.3163±0.0003
Inclination (i)89.545±0.003°
Longitude of the node (Ω)32.11±0.14[5]°
Periastron epoch (T)2460223.84444(1) BJD
Argument of periastron (ω)
(secondary)		155.69±0.12°
Semi-amplitude (K1)
(primary)		49.948±0.013[5] km/s
Semi-amplitude (K2)
(secondary)		57.736±0.014[5] km/s
Details[4]
Primary
Mass1.1947(9) M☉
Radius1.3180(13) R☉
Luminosity2.377 L☉
Surface gravity (log g)4.2755(9) cgs
Temperature6,242±50 K
Metallicity [Fe/H]0.075±0.030 dex
Rotation19.1±3.2 days
Rotational velocity (v sin i)3.5±0.5[5] km/s
Age3.01±0.12 Gyr
Secondary
Mass1.0334(6) M☉
Radius0.9927(8) R☉
Luminosity1.030 L☉
Surface gravity (log g)4.4587(8) cgs
Temperature5,839±44 K
Rotation14.0±1.7 days
Rotational velocity (v sin i)3.6±0.4[5] km/s
Age2.67±0.12 Gyr
Other designations
LL Aqr, BD−04°5706, HD 213896, HIP 111454, SAO 146171, PPM 206522[8]
Database references
SIMBADdata

LL Aquarii is an eclipsing binary star system in the equatorial constellation of Aquarius, abbreviated LL Aqr. At peak brightness it has a combined apparent visual magnitude of 9.23,[1] which is too dim to be visible to the naked eye. Based on parallax measurements, it is located at a distance of approximately 447 light years from the Sun.[2] The system is drifting closer with a heliocentric radial velocity of about −10 km/s.[7]

Observations

A light curve for LL Aquarii, plotted from TESS data.[9] The main plot shows the complete light curve, and the inset plot shows that primary (red) and secondary (green) minima with an expanded horizontal scale.

In 1996, this star was found to be an Algol-type eclipsing binary based on photometric observations made with the Hipparcos space observatory. It was assigned the variable-star designation LL Aqr in 1999.[10] This is a detached system forming a double-lined spectroscopic binary. In 2004, a more extensive light curve showed an eccentric orbit with a period of 20.1784 days. During the primary eclipse, the system dropped to magnitude 9.86, while the secondary eclipse showed a magnitude of 9.59.[11] The first orbital elements were published in 2008, showing an orbital eccentricity of 0.3095 with a mass ratio of 0.86. Stellar models indicated the stars are near the mid point of their main sequence lifetimes.[7]

The more massive member of the system, the primary component, has a stellar classification of F9 V,[5] matching an F-type main-sequence star. It has 19.5% more mass than the Sun and a 32% greater girth. This star is radiating 2.15 times the luminosity of the Sun from its photosphere at an effective temperature of around 6,080 K. It is spinning with a projected rotational velocity of 3.5±0.5 km/s. The metallicity, or abundance of elements with mass greater than helium, is very nearly Sun-like.[5]

The secondary component is considered a solar twin, which means its properties are close to Sun-like. It is a G-type main-sequence star with a class of G3 V.[5] Neither member of the system shows signs of stellar activity, being slowly rotating and not emitting X-rays. Tidal effects between the two stars is negligible;[12] they have an orbital separation of 40.7 times the radius of the Sun.[5]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 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 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. 
  4. ↑ 4.0 4.1 4.2 Miller, N. J.; Maxted, P. F. L.; Hahlin, A.; Graczyk, D. (2025-11-20), "Fundamental effective temperature measurements for eclipsing binary stars - VII. The solar twin in LL Aquarii", Monthly Notices of the Royal Astronomical Society, doi:10.1093/mnras/staf2078. 
  5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 Graczyk, D. et al. (October 2016), "A solar twin in the eclipsing binary LL Aquarii", Astronomy & Astrophysics 594: id. A92, doi:10.1051/0004-6361/201628918, Bibcode: 2016A&A...594A..92G. 
  6. ↑ Saputra, M. B. (April 2020), "Atmospheric model and synthetic spectrum of LL Aquarii using Kurucz model", Journal of Physics: Conference Series 1523 (1): id. 012021, doi:10.1088/1742-6596/1523/1/012021, Bibcode: 2020JPhCS1523a2021S. 
  7. ↑ 7.0 7.1 7.2 Ibanoǧlu, C. et al. (November 2008), "Spectroscopic and photometric observations of the selected Algol-type binaries - III. LL Aquarii, MP Delphini and NSV 20913", Monthly Notices of the Royal Astronomical Society 390 (3): 958–968, doi:10.1111/j.1365-2966.2008.13585.x, Bibcode: 2008MNRAS.390..958I. 
  8. ↑ "LL Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=LL+Aqr. 
  9. ↑ MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html, retrieved 29 December 2024. 
  10. ↑ Kazarovets, E. V. et al. (1999), "The 74th Special Name-list of Variable Stars", Information Bulletin on Variable Stars 4659: 1, Bibcode: 1999IBVS.4659....1K. 
  11. ↑ Otero, Sebastian A.; Dubovsky, Pavol A. (August 2004), "New Elements for 80 Eclipsing Binaries IV", Information Bulletin on Variable Stars 5557: 1, Bibcode: 2004IBVS.5557....1O. 
  12. ↑ Southworth, J. (September 2013), "The solar-type eclipsing binary system LL Aquarii*", Astronomy & Astrophysics 557: 557, doi:10.1051/0004-6361/201322195, A119, Bibcode: 2013A&A...557A.119S. 

Further reading

  • "Spectroscopic binary orbits from photoelectric radial velocities - Paper 230: Five Short-Period Double-Lined Binaries: HD 25788, HD 32704, HD 45191 (V455 Aur), and HD 213896 (LL Aqr)", The Observatory 133: 156–184, June 2013, Bibcode: 2013Obs...133..156G. 
  • Solonovich, A. P. et al. (2003), "Searches of the periods and variability type definition of new variable stars AL Ari, FM Leo, LL Aqr, V1125 Tau, V1366 Ori.", Odessa Astronomical Publications 16: 66, Bibcode: 2003OAP....16...66S. 



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