35 Sextantis
Triple star system in Sextans
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35 Sextantis (68 G. Sextantis; HD 92841; HR 4193), or simply 35 Sex, is a triple star system located in the equatorial constellation Sextans. The primary has an apparent magnitude of 6.09,[2] making it barely visible to the naked eye, even under ideal conditions. The companion has an apparent magnitude of 7.01,[2] making it readily visible in binoculars, but not to the naked eye. The system is located relatively far at a distance of approximately 700 light-years but it is drifting closer with a combined heliocentric radial velocity of −2.18 km/s.[17]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Sextans |
| A | |
| Right ascension | 10h 43m 20.92086s[1] |
| Declination | +04° 44′ 51.6121″[1] |
| Apparent magnitude (V) | 6.09±0.01[2] |
| B | |
| Right ascension | 10h 43m 20.52732s[3] |
| Declination | +04° 44′ 48.2184″[3] |
| Apparent magnitude (V) | 7.01±0.01[2] |
| Characteristics | |
| U−B color index | +1.09[4] |
| B−V color index | +1.17[4] |
| A | |
| Spectral type | K2.5 III[5] |
| B | |
| Spectral type | K1 II-III[6] |
| Astrometry | |
| A | |
| Radial velocity (Rv) | −3.15±0.16[7] km/s |
| Proper motion (μ) | RA: +22.430 mas/yr[1] Dec.: −33.285 mas/yr[1] |
| Parallax (π) | 4.6773±0.1457 mas[1] |
| Distance | 700 ± 20 ly (214 ± 7 pc) |
| B | |
| Radial velocity (Rv) | −1.49±0.98[7] km/s |
| Proper motion (μ) | RA: +24.384 mas/yr[3] Dec.: −37.384 mas/yr[3] |
| Parallax (π) | 4.5442±0.15 mas[3] |
| Distance | 720 ± 20 ly (220 ± 7 pc) |
| Orbit[8] | |
| Primary | A |
| Name | B |
| Period (P) | 23,302 yr |
| Semi-major axis (a) | 6.80" (1,460 AU) |
| Orbit[9] | |
| Primary | Ba |
| Name | Bb |
| Period (P) | 1,568.7±2.2 d |
| Semi-major axis (a) | 0.021" (4.64 AU) |
| Eccentricity (e) | 0.388±0.057 |
| Periastron epoch (T) | 2,451,911±27 JD |
| Argument of periastron (ω) (secondary) | 311.8±3.3° |
| Semi-amplitude (K1) (primary) | 5.55±0.15 km/s |
| Details | |
| A | |
| Mass | 2.45[8] M☉ |
| Radius | 25.39+0.8 −2.2[10] R☉ |
| Luminosity | 240±7[10] L☉ |
| Temperature | 4,512±122[11] K |
| Metallicity [Fe/H] | −0.17[12] dex |
| Rotational velocity (v sin i) | 3.7±0.3[7] km/s |
| Ba | |
| Mass | 2.44[8] M☉ |
| Radius | 10.15+0.34 −0.30[13] R☉ |
| Luminosity | 57.2±1.2[13] L☉ |
| Temperature | 5,030±122[11] K |
| Metallicity [Fe/H] | −0.16[12] dex |
| Rotational velocity (v sin i) | 4.1±0.5[7] km/s |
| Bb | |
| Mass | 0.58[8] M☉ |
| Other designations | |
| 10 H. Sextantis,[14] 35 Sex, 68 G. Sextantis[15], AG+05°1556, BD+05°2384, GC 14745, HD 92841, HIP 52452, HR 4193, SAO 118449, CCDM J10433+0443, TIC 374350811[16] | |
| Database references | |
| SIMBAD | The system |
| A | |
| B | |
The System
| A | |||||||||||||
| Separation = 6.8″ Period = 23,000 y | |||||||||||||
| Ba | |||||||||||||
| Separation = 0.021″ Period = 1,580 d | |||||||||||||
| Bb | |||||||||||||
Hierarchy of orbits in the 35 Sextantis system[9]
The system was first observed by Friedrich Georg Wilhelm von Struve in 1821.[18] The separation between the A and B component was initially 7.90 arcseconds,[18] but it has since decreased to 6.62".[19] Thanks to this separation, the components 35 Sextantis can be distinguished using a telescope. Observations from Tokovinin & Gorynya (2007) revealed that the B component is a single-lined spectroscopic binary.[9] The primary and secondary both take 23,302 years to orbit each other while the secondary and its close companion take 1,568 days to revolve around each other in a relatively eccentric orbit.[9]
Physical characteristic
35 Sextantis A has a stellar classification of K2.5 III,[5] indicating that it is an evolved K-type giant star that has exhausted hydrogen at its core and left the main sequence. 35 Sextantis B has a classification of K1 II-III,[6] indicating that it is a hotter, more evolved K-type star that has the luminosity class intermediate between a bright giant and giant star. The primary has 2.45 times the mass of the Sun[8] but it has expanded to 25.39 times the radius of the Sun.[10] It radiates 240 times the luminosity of the Sun[10] from its enlarged photosphere at an effective temperature of 4,512 K,[11] giving it an orange-hued when viewed in the night sky.
The secondary has a similar mass to the primary[8] but it is smaller, having a radius 10.15 times that of the Sun.[13] 35 Sextantis B radiates 57.2 times the luminosity of the Sun[13] from its photosphere at an effective temperature of 5030 K.[11] Both stars are metal deficient with iron abundances of [Fe/H] = −0.17 and [Fe/H] = −0.16 respectively.[12] They spin modestly with projected rotational velocities of 3.7 km/s and 4.1 km/s.[7] The close companion has a mass 58% that of the Sun's,[8] suggesting that it may be a K-type main-sequence star.