AR Aurigae
Triple star system in the constellation Auriga
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AR Aurigae (AR Aur), also known by its Flamsteed designation 17 Aurigae, is a triple star in the constellation Auriga. Based on parallax measurements made by the Gaia spacecraft, it is approximately 461 light-years from Earth.[1]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Auriga |
| Right ascension | 05h 18m 18.896s[1] |
| Declination | +33° 46â² 02.52â³[1] |
| Apparent magnitude (V) | 6.144[2] |
| Characteristics | |
| Evolutionary stage | Main sequence[3] |
| Spectral type | B9V + B9.5V[4] + M[5] |
| UâB color index | â0.18[6] |
| BâV color index | â0.06[6] |
| Variable type | Eclipsing[3] |
| Astrometry | |
| Radial velocity (Rv) | 28.65±0.09[7] km/s |
| Proper motion (μ) | RA: +15.254[1] mas/yr Dec.: â29.225[1] mas/yr |
| Parallax (Ï) | 7.0735±0.0461 mas[1] |
| Distance | 461 ± 3 ly (141.4 ± 0.9 pc) |
| Absolute magnitude (MV) | 1.11/1.17[8] |
| Orbit[3] | |
| Primary | AR Aur A |
| Name | AR Aur B |
| Period (P) | 4.134581 days |
| Semi-major axis (a) | 0.08564±0.00018 AU |
| Inclination (i) | 88.6000±0.0072° |
| Semi-amplitude (K1) (primary) | 108.36±0.18[7] km/s |
| Semi-amplitude (K2) (secondary) | 116.92±0.17[7] km/s |
| Orbit[5] | |
| Primary | AR Aur AB |
| Name | AR Aur C |
| Period (P) | 23.365±0.090 years |
| Semi-major axis (a) | 14.351 ± 0.042 AU |
| Eccentricity (e) | 0.268±0.022 |
| Inclination (i) | 88.510° |
| Argument of periastron (Ï) (secondary) | 13.4±4.6° |
| Details[3] | |
| AR Aur A | |
| Mass | 2.5444±0.0086 Mâ |
| Radius | 1.8433±0.0022 Râ |
| Luminosity | 44.1+2.5 â2.4 Lâ |
| Surface gravity (log g) | 4.3125±0.0008 cgs |
| Temperature | 10,950±150[4] K |
| Rotational velocity (v sin i) | 22.555±0.027 km/s |
| Age | 33±3 Myr |
| AR Aur B | |
| Mass | 2.3581±0.0085 Mâ |
| Radius | 1.7658±0.0026 Râ |
| Luminosity | 32.2+1.9 â1.8 Lâ |
| Surface gravity (log g) | 4.3169±0.0011 cgs |
| Temperature | 10,350±150[4] K |
| Rotational velocity (v sin i) | 21.604±0.032 km/s |
| Age | 33±3 Myr |
| AR Aur C | |
| Mass | 0.5122±0.0087[5] Mâ |
| Other designations | |
| 17 Aur, BD+33°1002, HD 34364, HIP 24740, HR 1728, SAO 57858, PPM 70158 | |
| Database references | |
| SIMBAD | data |
Characteristics
The two inner components of this pair form an eclipsing binary system. This make AR Aurigae a variable star, with its brightness varying from magnitude +6.15 to +6.82 with a period of 4.13 days.[10] Both components are blue-white B-type main-sequence stars that do not fill their Roche lobes.[3]
The primary component of AR Aurigae is known to be a mercury-manganese star, also known as an HgMn star. As the name implies, these stars have over-abundances of the elements mercury and manganese, and also often xenon and other elements.[4] Because AR Aurigae is an eclipsing binary (in fact, it is the only known eclipsing binary with a mercury-manganese star), accurate characterization of its parameters has been made possible.
In 1931, H. N. Pendersen and J. C. Steensgard became the first persons to detect these eclipses.[11] When an eclipse is not occurring, the star will be faintly visible to the naked eye under very good observing conditions.
The third component has been detected by analysing the difference between the observed and the predicted time of eclipses, which is caused by the light-time effect of its orbital motion around the pair. This star has a mass of 0.54 Mâ and is orbiting at a separation of 13 AU every 23.7 years.[4]