Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Draco |
Right ascension | 18h 20m 45.43224s [1] |
Declination | 71° 20′ 16.1499″ [1] |
Apparent magnitude (V) | 4.22 [2] |
Characteristics | |
Spectral type | B8VpSi [3] + A4V + B9V [4] |
U−B color index | −0.38 [5] |
B−V color index | −0.10 [5] |
Variable type | α2 CVn [2] |
Astrometry | |
Radial velocity (Rv) | −16.44 [6] km/s |
Proper motion (μ) |
RA: −5.03
[1]
mas/
yr Dec.: +37.86 [1] mas/ yr |
Parallax (π) | 10.77 ± 0.38 mas [1] |
Distance | 300 ± 10
ly (93 ± 3 pc) |
Absolute magnitude (MV) | −0.74 (−0.48/+0.94) [4] |
Orbit [4] | |
Primary | A |
Companion | B |
Period (P) | 307.8 yr |
Semi-major axis (a) | 0.965" (89.60 au) |
Eccentricity (e) | 0.752 |
Inclination (i) | 95.6° |
Orbit [6] | |
Primary | Aa |
Companion | Ab |
Period (P) | 127.914 d |
Eccentricity (e) | 0.6725 |
Inclination (i) | 48° |
Semi-amplitude (K1) (primary) | 33.87 km/s |
Details | |
Aa | |
Mass | 3.3 [4] M☉ |
Radius | 2.7±0.2 [7] R☉ |
Luminosity | 107 [7] L☉ |
Surface gravity (log g) | 4.21±0.08 [7] cgs |
Temperature | 11,429 [7] K |
Rotation | 1.7165 [6] |
Rotational velocity (v sin i) | 81.5 [6] km/s |
Age | 245 [4] Myr |
Ab | |
Mass | 1.36 [8] M☉ |
B | |
Mass | 2.25 [8] M☉ |
Age | 330 [4] Myr |
Other designations | |
Database references | |
SIMBAD | data |
Phi Draconis (φ Dra / φ Draconis) is a fourth-magnitude variable star in the constellation Draco. It has the Flamsteed designation 43 Draconis. It is also a triple star system where the brightest component is a chemically peculiar Ap star.
The brightness of φ Draconis varies by about 0.04 of a magnitude every 1.7 days. This is due to very strong magnetic fields at the surface of the star, and it is classified as an α2 Canum Venaticorum variable. [2]
φ Draconis is a multiple star system containing three stars. The inner pair form a single-lined spectroscopic binary in an eccentric 128-day orbit. The outermost star orbits the inner pair every 308 years. The outer pair can be resolved visually and have a semi-major axis of 0.752 ″. A fourth component, C, is also listed in multiple star catalogues, but is only a chance alignment with the triple system. [4]
Phi Draconis Aa is a main-sequence Ap star with a spectral class of B8. The main abundance excess is silicon, although iron and chromium and also notably elevated. [10]
In Chinese astronomy, φ Draconis is called 柱史 ( Pinyin: Zhùshǐ), meaning Official of Royal Archives, because this star is marking itself and stand alone in Official of Royal Archives asterism, Purple Forbidden enclosure (see: Chinese constellations). [11]
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Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Draco |
Right ascension | 18h 20m 45.43224s [1] |
Declination | 71° 20′ 16.1499″ [1] |
Apparent magnitude (V) | 4.22 [2] |
Characteristics | |
Spectral type | B8VpSi [3] + A4V + B9V [4] |
U−B color index | −0.38 [5] |
B−V color index | −0.10 [5] |
Variable type | α2 CVn [2] |
Astrometry | |
Radial velocity (Rv) | −16.44 [6] km/s |
Proper motion (μ) |
RA: −5.03
[1]
mas/
yr Dec.: +37.86 [1] mas/ yr |
Parallax (π) | 10.77 ± 0.38 mas [1] |
Distance | 300 ± 10
ly (93 ± 3 pc) |
Absolute magnitude (MV) | −0.74 (−0.48/+0.94) [4] |
Orbit [4] | |
Primary | A |
Companion | B |
Period (P) | 307.8 yr |
Semi-major axis (a) | 0.965" (89.60 au) |
Eccentricity (e) | 0.752 |
Inclination (i) | 95.6° |
Orbit [6] | |
Primary | Aa |
Companion | Ab |
Period (P) | 127.914 d |
Eccentricity (e) | 0.6725 |
Inclination (i) | 48° |
Semi-amplitude (K1) (primary) | 33.87 km/s |
Details | |
Aa | |
Mass | 3.3 [4] M☉ |
Radius | 2.7±0.2 [7] R☉ |
Luminosity | 107 [7] L☉ |
Surface gravity (log g) | 4.21±0.08 [7] cgs |
Temperature | 11,429 [7] K |
Rotation | 1.7165 [6] |
Rotational velocity (v sin i) | 81.5 [6] km/s |
Age | 245 [4] Myr |
Ab | |
Mass | 1.36 [8] M☉ |
B | |
Mass | 2.25 [8] M☉ |
Age | 330 [4] Myr |
Other designations | |
Database references | |
SIMBAD | data |
Phi Draconis (φ Dra / φ Draconis) is a fourth-magnitude variable star in the constellation Draco. It has the Flamsteed designation 43 Draconis. It is also a triple star system where the brightest component is a chemically peculiar Ap star.
The brightness of φ Draconis varies by about 0.04 of a magnitude every 1.7 days. This is due to very strong magnetic fields at the surface of the star, and it is classified as an α2 Canum Venaticorum variable. [2]
φ Draconis is a multiple star system containing three stars. The inner pair form a single-lined spectroscopic binary in an eccentric 128-day orbit. The outermost star orbits the inner pair every 308 years. The outer pair can be resolved visually and have a semi-major axis of 0.752 ″. A fourth component, C, is also listed in multiple star catalogues, but is only a chance alignment with the triple system. [4]
Phi Draconis Aa is a main-sequence Ap star with a spectral class of B8. The main abundance excess is silicon, although iron and chromium and also notably elevated. [10]
In Chinese astronomy, φ Draconis is called 柱史 ( Pinyin: Zhùshǐ), meaning Official of Royal Archives, because this star is marking itself and stand alone in Official of Royal Archives asterism, Purple Forbidden enclosure (see: Chinese constellations). [11]
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