AV Microscopii
Star in the constellation Microscopium
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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,[3] 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.[8]
A broad-band optical light curve for AV Microscopii, plotted from data published by Tabur et al. (2009)[1] | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Microscopium[2] |
| Right ascension | 20h 41m 24.66513s[3] |
| Declination | −42° 08′ 01.6196″[3] |
| Apparent magnitude (V) | 6.28[2] (6.25 – 6.35)[4] |
| Characteristics | |
| Spectral type | M4 III[5] |
| B−V color index | 1.584±0.019[2] |
| Variable type | LC:[4] |
| Astrometry | |
| Radial velocity (Rv) | −22.9±0.9[2] km/s |
| Proper motion (μ) | RA: +46.627[3] mas/yr Dec.: −32.891[3] mas/yr |
| Parallax (π) | 4.3815±0.1715 mas[3] |
| Distance | 740 ± 30 ly (228 ± 9 pc) |
| Absolute magnitude (MV) | −1.40[2] |
| Details | |
| Mass | 2.4[6] M☉ |
| Radius | 77.5+3.2 −16.4[3] R☉ |
| Luminosity | 849±38[3] L☉ |
| Surface gravity (log g) | 2.14[6] cgs |
| Temperature | 3,539+448 −70[3] K |
| Metallicity [Fe/H] | −0.10[6] dex |
| Other designations | |
| AV Mic, CD−42°15034, HD 196829, HIP 102096, SAO 230323[7] | |
| Database references | |
| SIMBAD | data |
Based upon a stellar classification of M4 III,[5] this is an aging red giant star,[5] having exhausted the supply of hydrogen at its core then expanded to around 78[3] times the Sun's radius. Earlier it had been classed as M3 II,[9] 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.[4] It is a pulsating variable with multiple periods discovered,[1] ranging in apparent visual magnitude between 6.25 and 6.35.[4][10] The star radiates 849 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 3,539 K.[3]
| 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 |