Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Aquarius |
Right ascension | 22h 53m 28.70492s [2] |
Declination | −11° 36′ 59.4532″ [2] |
Apparent magnitude (V) | 5.8 [3] |
Characteristics | |
Spectral type | B8IV/V [4] (B9pHgMn) [3]) |
U−B color index | −0.245 [5] |
B−V color index | −0.082 [5] |
Variable type | a2 CVn [3] |
Astrometry | |
Proper motion (μ) |
RA: +21.539
[2]
mas/
yr Dec.: +2.282 [2] mas/ yr |
Parallax (π) | 5.5008 ± 0.6556 mas [2] |
Distance | approx. 590
ly (approx. 180 pc) |
Absolute magnitude (MV) | −1.19 [6] |
Orbit [7] | |
Primary | 74 Aquarii A |
Companion | 74 Aquarii B |
Period (P) | 9.479±0.044 yr |
Semi-major axis (a) | 0.0460±0.0061″ |
Eccentricity (e) | 0.862±0.029 |
Inclination (i) | 29.8±17.4° |
Longitude of the node (Ω) | 40.9±20.3° |
Periastron epoch (T) | 2010.039±0.134 |
Argument of periastron (ω) (secondary) | 70.7±16.1° |
Orbit [8] | |
Primary | 74 Aquarii Aa |
Companion | 74 Aquarii Ab |
Period (P) | 3.429616±0.000004 d |
Eccentricity (e) | 0.05±0.02 |
Periastron epoch (T) | 2452909.150±0.007 JD |
Argument of periastron (ω) (secondary) | 86.5±0.8° |
Semi-amplitude (K1) (primary) | 95±2 km/s |
Semi-amplitude (K2) (secondary) | 113±2 km/s |
Details | |
Aa | |
Mass | 2.72 [9] M☉ |
Rotational velocity (v sin i) | 20 [10] km/s |
Ab | |
Mass | 2.53 [9] M☉ |
B | |
Mass | 3.11 [9] M☉ |
Other designations | |
Database references | |
SIMBAD | data |
74 Aquarii (abbreviated 74 Aqr) is a triple star [12] system in the constellation of Aquarius. 74 Aquarii is its Flamsteed designation and it also bears the variable star designation HI Aquarii. The combined apparent visual magnitude is 5.8, [5] although it is very slightly variable, [3] and it is located at a distance of 590 light-years (180 parsecs) from Earth.
74 Aquarii is a double star with the two components separated by about 0.1 ″. [13] The two components are referred to as A and B or AB and C in different publications. [7] [8] The pair form a binary with a period of 9.5 years at a typical angular separation of 0.046″, but the orbit is highly eccentric. [7] In 2010, this component was at an angular separation of 0.069 arcseconds along a position angle of 285.9°. This is equivalent to a projected separation of 13.9±2.4 AU. [12]
The primary star of the visual pair is a double-lined spectroscopic binary, where the presence of both components is revealed from the Doppler shift of their spectral lines, meaning 74 Aquarii is a triple system. The spectroscopic binary was discovered and the orbit calculated by Richard J. Wolff of the University of Hawaii in 1974. [14] A refined orbit was calculated in 2004 by Italian astronomers Giovanni Catanzaro and Paolo Leto in 2004. The orbital period is 3.4 days and the orbit is nearly circular. [8]
The three stars have a combined spectral type of B8 or B9 and all three are thought to be similar. It is unclear whether the stars are on the main sequence, subgiants, or giant stars. [9] [15] [4] The two visual components are both chemically peculiar stars, the brighter of the two being a mercury-manganese star and the fainter an Ap/Bp star with an excess of mercury. [13] 74 Aquarii is an a2 CVn variable star, with a total amplitude of just 0.01 magnitudes, [3] and a period of 3.5892 days. [16]