74 Aquarii
Triple star system in the constellation Aquarius
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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.
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| 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 |
| Name | 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 |
| Name | 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 | |
| HI Aqr, BD−12 6371, HD 216494, HIP 113031, HR 8704, SAO 165359[11] | |
| Database references | |
| SIMBAD | data |
Jean Manfroid and Gautier Mathys reported that 74 Aquarii is a variable star in 1985.[13] Based on that result it was given its variable star designation in 1987.[14]
Visual binary
74 Aquarii is a double star with the two components separated by about 0.1″.[15] 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]
Spectroscopic binary
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.[16] A refined orbit was calculated in 2004 by Italian astronomers Giovanni Catanzaro and Paolo Leto. The orbital period is 3.4 days and the orbit is nearly circular.[8]
Components
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][17][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.[15] 74 Aquarii is an α2 CVn variable star, with a total amplitude of just 0.01 magnitudes,[3] and a period of 3.5892 days.[18]