  | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Microscopium [1] |
| A | |
| Right ascension | 21h 27m 01.62303s [2] |
| Declination | −42° 32′ 52.5560″ [2] |
| Apparent magnitude (V) | 5.58±0.01 [3] |
| B | |
| Right ascension | 21h 27m 01.75500s [4] |
| Declination | −42° 32′ 55.0458″ [4] |
| Apparent magnitude (V) | 8.09±0.01 [3] |
| Characteristics | |
| A | |
| Evolutionary stage | subgiant [5] |
| Spectral type | kA4 hF0 V mF6 [6] |
| U−B color index | +0.15 [7] |
| B−V color index | +0.39 [7] |
| B | |
| Evolutionary stage | main sequence [8] |
| Spectral type | F8 V [9] |
| U−B color index | +0.06 [9] |
| B−V color index | +0.55 [9] |
| Astrometry | |
| Radial velocity (Rv) | 18.3±2.8 [10] km/s |
| A | |
| Proper motion (μ) | RA: −48.257 mas/yr [2] Dec.: +13.160 mas/yr [2] |
| Parallax (π) | 18.489±0.0498 mas [2] |
| Distance | 176.4 ± 0.5 ly (54.1 ± 0.1 pc) |
| Absolute magnitude (MV) | +1.74 [11] |
| B | |
| Proper motion (μ) | RA: −53.002 mas/yr [4] Dec.: +15.410 mas/yr [4] |
| Parallax (π) | 18.5325±0.0349 mas [4] |
| Distance | 176.0 ± 0.3 ly (54.0 ± 0.1 pc) |
| Absolute magnitude (MV) | +4.00 [9] |
| Details | |
| A | |
| Mass | 1.73 [2] M☉ |
| Radius | 1.09 [8] R☉ |
| Luminosity | 12.8 [2] L☉ |
| Surface gravity (log g) | 3.86±0.08 [12] cgs |
| Temperature | 6,778 [13] K |
| Rotational velocity (v sin i) | 85 [14] km/s |
| Age | 1.36±0.19 [2] Gyr |
| B | |
| Mass | 1.02 [15] M☉ |
| Radius | 1.09±0.21 [16] R☉ |
| Luminosity | 1.29 [8] L☉ |
| Surface gravity (log g) | 4.29 [15] cgs |
| Temperature | 6,235±115 [17] K |
| Metallicity [Fe/H] | −0.11 [18] dex |
| Rotational velocity (v sin i) | 72.8 [19] km/s |
| Age | 3.46 [18] Gyr |
| Other designations | |
| 69 G. Microscopii [20] , CD−43°14539, CPD−43°9451, GC 30021, HD 204018, HIP 105913, HR 8202, SAO 230692, WDS J21270-4233AB [21] | |
| Database references | |
| SIMBAD | The system |
| A | |
| B | |
HD 204018, also designated as HR 8202, is a visual binary located in the southern constellation of Microscopium. The primary has an apparent magnitude of 5.58, [3] making it faintly visible to the naked eye under ideal conditions. The companion has an apparent magnitude of 8.09. [3] The system is located relatively close at a distance of 176 light years based on Gaia DR3 parallax measurements [2] [4] but is receding with a heliocentric radial velocity of 18.3 km/s . [10] At its current distance, HD 204018's combined brightness is diminished by 0.13 magnitudes due to interstellar dust. [22]
HD 204018A is an Am star with a stellar classification of kA4hF0 VmF6, [6] indicating that it has the calcium K-line of an A4 star, the hydrogen lines of a F0 main-sequence star and the metallic lines of a F6 star. It has 1.73 imes the mass of the Sun [2] and 2.42 times the Sun's radius. [2] It radiates 12.8 times the luminosity of the Sun [2] from its photosphere at an effective temperature of 6,778 K , [13] giving it a yellowish-white hue. At an age of 1.5 billion years, HD 2014018A is estimated to be on the subgiant branch. [5] An alternate model places it on the main sequence at an age of 1,35 billion years. [2] The object spins at a moderate speed with a projected rotational velocity of 85 km/s . [14]
The companion is an F8 main sequence star [9] located 2+1⁄2" away along a position angle of 151°. [23] It has an angular diameter of 0.186±0.035 arcseconds , [17] which yields a radius of 1.09 R☉ at its estimated distance. [16] It has 102% times the mass of the Sun [15] and an effective temperature of 6,235 K . [17] HD 204018B is estimated to be 3.46 billion years old and is slightly metal deficient. [18]
There is a magnitude 12 co-moving companion located 295.3" away from the system along a position angle of 75°. [23] It is a red dwarf with an estimated spectral class of K6 and any orbit would take over a million years. [24]
