Lambda Geminorum

Lambda Geminorum, Latinized from λ Geminorum, is a candidate multiple star system in the constellation Gemini. It is visible to the naked eye at night with a combined apparent visual magnitude of 3.57.[2] The distance to this system is 101 light years based on parallax,[6] and it is drifting closer with a radial velocity of –7.4 km/s.[5] It is a member of what is suspected to be a trailing tidal tail of the Hyades Stream.[12]

Lambda Geminorum
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Gemini
Right ascension 07h 18m 05.58012s[1]
Declination +16° 32′ 25.3964″[1]
Apparent magnitude (V) 3.571[2]
Characteristics
Spectral type A3V[3]
U−B color index +0.167[2]
B−V color index +0.113[2]
Variable type Constant[4]
Astrometry
Radial velocity (Rv)–7.40[5] km/s
Proper motion (μ) RA: –44.43[6] mas/yr
Dec.: –36.61[6] mas/yr
Parallax (π)32.33 ± 0.20 mas[6]
Distance100.9 ± 0.6 ly
(30.9 ± 0.2 pc)
Absolute magnitude (MV)+1.13[7]
Details
Mass2.098[3] M☉
Radius2.7773±0.0469[3] R☉
Luminosity27.3901±0.3416[3] L☉
Temperature7,932±62[3] K
Metallicity [Fe/H]−0.04±0.04[8] dex
Rotational velocity (v sin i)154[9] km/s
Age0.8 Gyr[3]
0.5[10] Gyr
Other designations
λ Gem, 54 Geminorum, NSV 3512, BD+16 1443, FK5 277, HD 56537, HIP 35350, HR 2763, SAO 96746, WDS J07181+1632A[11]
Database references
SIMBADdata

Components A and B of this system form a wide binary.[13] The secondary, component B, is a magnitude 10.7 stellar companion at an angular separation of 9.29″ from the primary along a position angle of 35.72°, as of 2009. The primary was identified as a spectroscopic binary by E. B. Frost in 1924.[14] This companion was confirmed during a lunar occultation with a separation of 14.1±0.7 mas and magnitude 6.8.[15]

The primary, designated component A, typically has been assigned a stellar classification of A3V,[3] which indicates this is an A-type main-sequence star that generates energy from core hydrogen fusion. However, in 1970 D. C. Barry classed it as A4IV,[16] suggesting this may be a subgiant star that has begun evolving into a giant star. It was catalogued a suspected variable star, but is now confirmed as constant.[4]

This star is less than a billion years in age with a rapid spin, showing a projected rotational velocity of 154 km/s[9] It is larger and hotter than the Sun, with twice the Sun's mass and 2.8 times the radius of the Sun. The star is radiating 27 times the Sun's luminosity from its photosphere at an effective temperature of 7,932 K.[3]

The primary displays a significant infrared excess in the K-band, which indicates an orbiting circumstellar disk of dust. A model fit to the data shows an inner radius between 0.08 AU and 0.14 AU, and an outer radius of up to 0.65 AU.[10]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Gutierrez-Moreno, Adelina; et al. (1966), "A System of photometric standards", Publications of the Department of Astronomy University of Chile, Publicaciones Universidad de Chile, Department de Astronomy, 1: 1–17, Bibcode:1966PDAUC...1....1G.
  3. Boyajian, Tabetha S.; et al. (July 2013), "Stellar Diameters and Temperatures. III. Main-sequence A, F, G, and K Stars: Additional High-precision Measurements and Empirical Relations", The Astrophysical Journal, 771 (1): 40, arXiv:1306.2974, Bibcode:2013ApJ...771...40B, doi:10.1088/0004-637X/771/1/40, S2CID 14911430.
  4. "Lam Gem". The International Variable Star Index. AAVSO – American Association of Variable Star Observers. Retrieved March 29, 2017.
  5. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
  6. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
  7. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  8. Cheng, Kwang-Ping; et al. (April 2016), "Utilizing Synthetic UV Spectra to Explore the Physical Basis for the Classification of Lambda Boötis Stars", The Astronomical Journal, 151 (4): 17, Bibcode:2016AJ....151..105C, doi:10.3847/0004-6256/151/4/105, S2CID 124045100, 105.
  9. Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID 18475298.
  10. Kirchschlager, Florian; et al. (May 2017), "Constraints on the structure of hot exozodiacal dust belts", Monthly Notices of the Royal Astronomical Society, 467 (2): 1614–1626, arXiv:1701.07271, Bibcode:2017MNRAS.467.1614K, doi:10.1093/mnras/stx202.
  11. "* lam Gem". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-12-09.
  12. Röser, Siegfried; et al. (January 2019), "Hyades tidal tails revealed by Gaia DR2", Astronomy & Astrophysics, 621: 5, arXiv:1811.03845, Bibcode:2019A&A...621L...2R, doi:10.1051/0004-6361/201834608, S2CID 118909033, L2.
  13. Rodriguez, David R.; et al. (May 2015), "Stellar multiplicity and debris discs: an unbiased sample", Monthly Notices of the Royal Astronomical Society, 449 (3): 3160–3170, arXiv:1503.01320, Bibcode:2015MNRAS.449.3160R, doi:10.1093/mnras/stv483, S2CID 119237891.
  14. Frost, E. B. (December 1924), "Fourteen spectroscopic binaries", Astrophysical Journal, 60: 319–320, Bibcode:1924ApJ....60..319F, doi:10.1086/142868.
  15. Richichi, A.; et al. (October 1999), "New binary stars discovered by lunar occultations. IV", Astronomy and Astrophysics, 350: 491−496, Bibcode:1999A&A...350..491R.
  16. Barry, Don C. (January 1970), "Spectral Classification of a and F Stars", Astrophysical Journal Supplement, 19: 281, Bibcode:1970ApJS...19..281B, doi:10.1086/190209.
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