HD 187923

HD 187923 is a suspected variable star[5] in the equatorial constellation of Aquila. It is a dim star that is just visible to the naked eye, having an apparent visual magnitude of 6.148.[2] Based upon an annual parallax shift of 37.04 mas,[1] it is located 88 light years away. The star is moving closer to the Earth with a heliocentric radial velocity of −20.7 km/s.[2] It has a relatively high proper motion, traversing the celestial sphere at the rate of 0.480″ per year.[9]

HD 187923
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension  19h 52m 03.43853s[1]
Declination +11° 37′ 41.9725″[1]
Apparent magnitude (V) 6.148[2]
Characteristics
Spectral type G0 V[3]
U−B color index +0.12[4]
B−V color index +0.65[4]
Variable type suspected[5]
Astrometry
Radial velocity (Rv)−20.7±0.2[2] km/s
Proper motion (μ) RA: −344.185[1] mas/yr
Dec.: -334.608[1] mas/yr
Parallax (π)37.0427 ± 0.0529[1] mas
Distance88.0 ± 0.1 ly
(27.00 ± 0.04 pc)
Absolute magnitude (MV)3.94[2]
Details[6]
Mass1.28±0.17 or 1.02[7] M☉
Radius1.44±0.04 R☉
Luminosity2.09+0.10
−0.09 L☉
Surface gravity (log g)4.23 cgs
Temperature5,774 K
Metallicity [Fe/H]−0.11 dex
Rotational velocity (v sin i)0.1 km/s
Age8.8±0.7 or 10.2[7] Gyr
Other designations
NSV 12490, BD+11° 4019, GJ 4126, HD 187923, HIP 97767, HR 7569, SAO 105348, WDS J19521+1138A, LTT 15805[8]
Database references
SIMBADdata

This is an ordinary G-type main-sequence star with a stellar classification of G0 V.[3] It has some similarities to the Sun, and thus is considered a solar analog.[10] Brewer et al. (2016) estimate the star has 1.3 times the mass of the Sun and 1.44 times the Sun's radius. It is thought to be around 9 billion years old and is spinning slowly with a projected rotational velocity of 0.1 km/s. The star is radiating double the Sun's luminosity from its photosphere at an effective temperature of 5,774 K.[6] Casagrande et al. (2011) gave a much lower mass estimate of 1.02 times the Sun's mass with an age of around 10.2 billion years.[7]

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.
  2. Nordström, B.; et al. (May 2004), "The Geneva-Copenhagen survey of the Solar neighbourhood: Ages, metallicities, and kinematic properties of 14,000 F and G dwarfs", Astronomy and Astrophysics, 418: 989–1019, arXiv:astro-ph/0405198, Bibcode:2004A&A...418..989N, doi:10.1051/0004-6361:20035959.
  3. Cenarro, A. J.; et al. (July 2009), "Mg and TiO spectral features at the near-IR: spectrophotometric index definitions and empirical calibrations", Monthly Notices of the Royal Astronomical Society, 396 (4): 1895–1914, arXiv:0903.4835, Bibcode:2009MNRAS.396.1895C, doi:10.1111/j.1365-2966.2009.14839.x.
  4. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data. SIMBAD, Bibcode:1986EgUBV........0M.
  5. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, GCVS 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S.
  6. Brewer, John M.; et al. (2016), "Spectral Properties of Cool Stars: Extended Abundance Analysis of 1,617 Planet-Search Stars", The Astrophysical Journal Supplement Series, 225 (2): 32, arXiv:1606.07929, Bibcode:2016ApJS..225...32B, doi:10.3847/0067-0049/225/2/32.
  7. Casagrande, L.; et al. (June 2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy and Astrophysics, 530: A138, arXiv:1103.4651, Bibcode:2011A&A...530A.138C, doi:10.1051/0004-6361/201016276.
  8. "HD 187923". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 6, 2018.
  9. Lépine, Sébastien; Shara, Michael M. (March 2005), "A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)", The Astronomical Journal, 129 (3): 1483–1522, arXiv:astro-ph/0412070, Bibcode:2005AJ....129.1483L, doi:10.1086/427854.
  10. Galeev, A. I.; et al. (June 2004), "Chemical Composition of 15 Photometric Analogues of the Sun", Astronomy Reports, 48 (6): 492–510, Bibcode:2004ARep...48..492G, doi:10.1134/1.1767216.
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