Zeta Coronae Borealis
Binary star in the constellation Corona Borealis
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ζ Coronae Borealis, Latinised as Zeta Coronae Borealis, is the Bayer designation of a double star in the constellation Corona Borealis. The two components are separated by six arc-seconds and share the same Hipparcos catalogue number and Flamsteed designation. Each of the two is also a spectroscopic multiple system, with a total of five stars in the group.
 | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Corona Borealis |
| ζ1 | |
| Right ascension | 15h 39m 22.244s[1] |
| Declination | +36° 38′ 12.59″[1] |
| Apparent magnitude (V) | 5.95[2] |
| ζ2 | |
| Right ascension | 15h 39m 22.672s[3] |
| Declination | +36° 38′ 08.92″[3] |
| Apparent magnitude (V) | 4.99[2] |
| Characteristics | |
| ζ1 | |
| Evolutionary stage | Main sequence |
| Spectral type | B9 V[2] |
| ζ2 | |
| Evolutionary stage | Main sequence |
| Spectral type | B6 V + B7 V[2] |
| Astrometry | |
| ζ1 | |
| Radial velocity (Rv) | −18.43+0.50 −0.51[4] km/s |
| Proper motion (μ) | RA: −14.011 mas/yr[1] Dec.: −3.919 mas/yr[1] |
| Parallax (π) | 6.2190±0.0685 mas[1] |
| Distance | 524 ± 6 ly (161 ± 2 pc) |
| ζ2 | |
| Radial velocity (Rv) | −30.79±0.66[4] km/s |
| Proper motion (μ) | RA: −15.510 mas/yr[3] Dec.: −7.465 mas/yr[3] |
| Parallax (π) | 6.4259±0.0960 mas[3] |
| Distance | 508 ± 8 ly (156 ± 2 pc) |
| Orbit[4] | |
| Primary | ζ1 A |
| Name | ζ1 B |
| Period (P) | 4.06±0.01 days |
| Semi-major axis (a) | ≥0.49±0.10 R☉ (A) |
| Eccentricity (e) | 0.16+0.14 −0.16 |
| Periastron epoch (T) | 2,460,429.46±0.14 JD |
| Argument of periastron (ω) (secondary) | 262+66 −51° |
| Semi-amplitude (K1) (primary) | 6.1±0.8 km/s |
| Orbit[4] | |
| Primary | ζ2 A |
| Name | ζ2 B |
| Period (P) | 1.7236±0.0002 days |
| Semi-major axis (a) | ≥2.98±0.05 R☉ (A) ≥3.16±0.05 R☉ (B) |
| Eccentricity (e) | 0 |
| Inclination (i) | ~38[5]° |
| Periastron epoch (T) | 2,460,428.92±0.01 JD |
| Semi-amplitude (K1) (primary) | 87.19+1.10 −1.09 km/s |
| Semi-amplitude (K2) (secondary) | 92.86±1.10 km/s |
| Orbit[5] | |
| Primary | ζ2 AB |
| Name | ζ2 C |
| Period (P) | 251.5±0.6 days |
| Semi-major axis (a) | ≥124±7 R☉ |
| Eccentricity (e) | 0.48±0.03 |
| Periastron epoch (T) | 2,449,373.5±1.7 JD |
| Argument of periastron (ω) (secondary) | 191.8±2.9° |
| Semi-amplitude (K1) (primary) | 28.5±2.0 km/s |
| Details | |
| ζ1 A | |
| Mass | 3.24[6] M☉ |
| Radius | 2.63±0.06[1] R☉ |
| Luminosity | 194.5+3.7 −4.0[1] L☉ |
| Surface gravity (log g) | 4.043+0.014 −0.016[1] cgs |
| Temperature | 13,292+58 −72[1] K |
| Rotational velocity (v sin i) | 15[7] km/s |
| ζ2 A | |
| Mass | 4.13[8] M☉ |
| Radius | 2.38[5] R☉ |
| Rotation | 1.7 days[8] |
| Rotational velocity (v sin i) | 46±7[8] km/s |
| ζ2 B | |
| Mass | 3.73[8] M☉ |
| Rotational velocity (v sin i) | 7.5±2[8] km/s |
| ζ2 C | |
| Mass | 3.78[8] M☉ |
| Other designations | |
| 7 Coronae Borealis, HIP 76669, BD+37°2665, CCDM J15394+3638, WDS J15394+3638 | |
| ζ1: ζ CrB B, HR 5833, HD 139891 | |
| ζ2: ζ CrB A, HR 5834, HD 139892 | |
| Database references | |
| SIMBAD | ζ |
| ζ1 | |
| ζ2 | |
Nomenclature
ζ Coronae Borealis has the Flamsteed designation 7 Coronae Borealis and the Hipparcos catalogue number HIP 76669. As a double star, the brighter component is designated A (e.g. WDS J15394+3638 A) while the fainter of the two is designated B. The brighter star is also known as ζ2 Coronae Borealis and the fainter as ζ1 Coronae Borealis.
Each of the pair has its own Bright Star Catalogue and Henry Draper Catalogue numbers: HR 5833 and 5834, and HD 139891 and 139892 for ζ1 and ζ2 respectively.
System
ζ1 Coronae Borealis is a single-lined spectroscopic binary, with an orbital period of about 9.5 days. The nature of the companion is unknown.[9]
The brighter star, ζ2 Coronae Borealis, is a spectroscopic triple system, consisting of three massive stars. The inner pair orbit in 1.7 days, while the outer pair orbit in 251 days.[9]