Phi Draconis
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Draco |
Right ascension | 18h 20m 45.43224s[1] |
Declination | 71° 20′ 16.1499″[1] |
Apparent magnitude (V) | 4.2004[1] |
Characteristics | |
Spectral type | B8VpSi[2] + A4V + B9V[3] |
U−B color index | −0.38[4] |
B−V color index | −0.10[4] |
Variable type | α2 CVn[5] |
Astrometry | |
Radial velocity (Rv) | -16[6] km/s |
Proper motion (μ) | RA: -5.03[1] mas/yr Dec.: 37.86[1] mas/yr |
Parallax (π) | 10.77 ± 0.38[1] mas |
Distance | 300 ± 10 ly (93 ± 3 pc) |
Absolute magnitude (MV) | −0.74 (−0.48/+0.94)[3] |
Orbit[3] | |
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[3] | |
Primary | Aa |
Companion | Ab |
Period (P) | 127.9902 d |
Eccentricity (e) | 0.707 |
Inclination (i) | ~50° |
Semi-amplitude (K1) (primary) | 29.0 km/s |
Details | |
Aa | |
Mass | 3.3[3] 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 | 1.71649[7] |
Age | 245[3] Myr |
B | |
Mass | 2.93[3] M☉ |
Age | 330[3] 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.[5]
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″.[3]
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.[8]
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).[9]
References[]
- ^ a b c d e f van Leeuwen, F. (November 2007). "Hipparcos, the New Reduction" (VizieR). Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Retrieved 2010-11-22.
- ^ Gray, R. O.; Corbally, C. J. (2014). "An Expert Computer Program for Classifying Stars on the MK Spectral Classification System". The Astronomical Journal. 147 (4): 80. Bibcode:2014AJ....147...80G. doi:10.1088/0004-6256/147/4/80.
- ^ a b c d e f g h i Liška, J. (2016). "Analysis of the multiple system with chemically peculiar component φ Draconis". Monthly Notices of the Royal Astronomical Society. 461 (1): 939–947. arXiv:1606.01333. Bibcode:2016MNRAS.461..939L. doi:10.1093/mnras/stw1355.
- ^ a b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. (PDF) origin: SIMBAD: 0. Bibcode:1986EgUBV........0M.
- ^ a b Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
- ^ Evans, D. S. (1967). "The Revision of the General Catalogue of Radial Velocities". Determination of Radial Velocities and Their Applications. 30: 57. Bibcode:1967IAUS...30...57E.
- ^ a b c d e North, P. (June 1998), "Do SI stars undergo any rotational braking?", Astronomy and Astrophysics, 334: 181–187, arXiv:astro-ph/9802286, Bibcode:1998A&A...334..181N
- ^ Prvák, M.; Liška, J.; Krtička, J.; Mikulášek, Z.; Lüftinger, T. (2015). "Modelling of variability of the chemically peculiar star ϕ Draconis". Astronomy and Astrophysics. 584: A17. arXiv:1510.01192. Bibcode:2015A&A...584A..17P. doi:10.1051/0004-6361/201526647.
- ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 10 日
External links[]
- Jim Kaler's Stars, University of Illinois: PHI DRA (Phi Draconis)
- An Atlas of the Universe: Multiple Star Orbits
Coordinates: 18h 20m 45.43s, +71° 20′ 16.13″
- Draco (constellation)
- Ap stars
- Bayer objects
- Flamsteed objects
- Henry Draper Catalogue objects
- Stars with proper names
- Astronomy in China
- Hipparcos objects
- HR objects
- Durchmusterung objects
- Alpha2 Canum Venaticorum variables
- B-type main-sequence stars
- Binary stars