AX Circini
AX Circini is a binary star system in the southern constellation of Circinus. It has a nominal magnitude of 5.91, which is bright enough to be visible to the naked eye. Based upon an annual parallax shift of 1.7 mas, it is located roughly 1,900 light-years from the Earth. The system is moving closer with a heliocentric radial velocity of −21 km/s.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Circinus |
| Right ascension | 14h 52m 35.25324s |
| Declination | −63° 48′ 35.4172″ |
| Apparent magnitude (V) | 5.91 (5.69–6.19) |
| Characteristics | |
| Spectral type | F8 II + B6 V |
| U−B color index | +0.2 |
| B−V color index | +0.8 |
| Variable type | δ Cep |
| Astrometry | |
| Radial velocity (Rv) | −20.9±4.6 km/s |
| Proper motion (μ) | RA: −4.779 mas/yr Dec.: −5.108 mas/yr |
| Parallax (π) | 1.7449 ± 0.3450 mas |
| Distance | approx. 1,900 ly (approx. 600 pc) |
| Absolute magnitude (MV) | −3.37 |
| Orbit | |
| Period (P) | 6,532±25 d |
| Eccentricity (e) | 0.19±0.02 |
| Longitude of the node (Ω) | 231±8° |
| Periastron epoch (T) | 2,448,500±60 JD |
| Semi-amplitude (K1) (primary) | 10.0±0.5 km/s |
| Details | |
| AX Cir A | |
| Mass | 11.56 M☉ |
| Radius | 45.68 R☉ |
| Luminosity | 2,050 L☉ |
| Surface gravity (log g) | 2.00 cgs |
| Temperature | 5,443±21 K |
| Metallicity [Fe/H] | −0.05 dex |
| Rotational velocity (v sin i) | 7.4±0.4 km/s |
| AX Cir B | |
| Mass | 5.57 M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is a spectroscopic binary with an orbital period of 17.88 years and an eccentricity of 0.19. A binary companion was first suspected in 1960, as the spectrum was considered to be composite and there is an ultraviolet excess. The companion was confirmed in 1982, and it was resolved using long baseline interferometry in 2014 and 2015. The system has an a sin i value of 6.05 AU, where a is the semimajor axis and i is the (unknown) orbital inclination.
The primary, component A, is a yellow-white-hued bright giant with a stellar classification of F8 II, and it is a classical Cepheid variable. The combined apparent magnitude of the system ranges from 5.69 to 6.19 over 5.273 days. The secondary companion, component B, is a main-sequence star with a class of B6 V and an absolute magnitude of about −0.12.