AV Microscopii

AV Microscopii is a variable star in the southern constellation of Microscopium. It is a dim, red-hued star near the lower limit of visibility to the naked eye with a baseline apparent visual magnitude of 6.28.[2] The star is located approximately 740 light years away from the Sun, based on parallax,[1] but is moving closer with a radial velocity of −23 km/s.[2] It is a member of the Milky Way‘s old disk population.[6]

Star in the constellation Microscopium

AV Microscopii
Observation data
EpochJ2000.0      EquinoxJ2000.0 (ICRS)
Constellation Microscopium
Right ascension 20h 41m 24.66513s[1]
Declination −42° 08 01.6196[1]
Apparent magnitude (V) 6.28[2](6.25 – 6.35)[3]
Characteristics
Spectral type M4 III[4]
B−V color index 1.584±0.019[2]
Variable type LC:[3]
Astrometry
Radial velocity(Rv) −22.9±0.9[2] km/s
Proper motion(μ) RA: +46.627[1] mas/yr
Dec.: −32.891[1] mas/yr
Parallax(π) 4.3815 ± 0.1715[1] mas
Distance 740 ± 30 ly
(228 ± 9 pc)
Absolute magnitude (MV) −1.40[2]
Details
Radius 77.5+3.2
−16.4
[1] R
Luminosity 849±38[1] L
Temperature 3,539+448
−70
[1] K
Other designations
AV Mic, CD−42°15034, HD 196829, HIP 102096, SAO 230323[5]
Database references
SIMBAD data

Based upon a stellar classification of M4 III,[4] this is an aging red giant star,[4] having exhausted the supply of hydrogen at its core then expanded to around 78[1] times the Sun’s radius. Earlier it had been classed as M3 II,[7] with the luminosity class of a bright giant. Samus et al. (2017) have it tentatively classified as an irregular variable of subtype LC, suggesting this is a supergiant star.[3] It is a pulsating variable with multiple periods discovered,[8] ranging in apparent visual magnitude between 6.25 and 6.35.[3][9] The star radiates 849 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 3,539 K.[1]

Pulsation periods[8]
Period (days) 22.3 23.3 30.3 31.0 32.3 45.0 110.7
Amplitude (mag.) 0.038 0.050 0.017 0.027 0.019 0.025 0.018

. . . AV Microscopii . . .

  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. 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.
  3. Samus, N. N.; et al. (2017). “General Catalogue of Variable Stars”. Astronomy Reports. 5.1. 61 (1): 80–88. Bibcode:2017ARep…61…80S. doi:10.1134/S1063772917010085. S2CID 125853869.
  4. Houk, Nancy (1978). Michigan catalogue of two-dimensional spectral types for the HD stars. 2. Ann Arbor: Dept. of Astronomy, University of Michigan. Bibcode:1978mcts.book…..H.
  5. “AV Mic”. SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-08-11.
  6. Eggen, O. J. (August 1976). “A sample of old-disk-population red giants”. Publications of the Astronomical Society of the Pacific. 88: 426–443. Bibcode:1976PASP…88..426E. doi:10.1086/129965.
  7. Evans, David S.; et al. (1959). “Fundamental data for southern stars (Second List)”. Monthly Notices of the Royal Astronomical Society. 119 (6): 638. Bibcode:1959MNRAS.119..638E. doi:10.1093/mnras/119.6.638.
  8. Tabur, V.; et al. (December 2009). “Long-term photometry and periods for 261 nearby pulsating M giants”. Monthly Notices of the Royal Astronomical Society. 400 (4): 1945–1961. arXiv:0908.3228. Bibcode:2009MNRAS.400.1945T. doi:10.1111/j.1365-2966.2009.15588.x. S2CID 15358380.
  9. Watson, Christopher (28 September 2009). “AV Microscopii”. AAVSO Website. American Association of Variable Star Observers. Retrieved 20 March 2015.
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HD
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NGC

. . . AV Microscopii . . .

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. . . AV Microscopii . . .

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