Epsilon Aquilae
Template:Location mark Location of ε Aquilae (circled) | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquila |
| Right ascension | Template:RA[1] |
| Declination | Template:DEC[1] |
| Apparent magnitude (V) | +4.02[2] |
| Characteristics | |
| Spectral type | K1-IIICN0.5[3] |
| U−B Template:Engvar | +1.04[2] |
| B−V Template:Engvar | +1.08[2] |
| R−I Template:Engvar | +0.52 |
| Astrometry | |
| Radial velocity (Rv) | Script error: No such module "val".[4] km/s |
| Proper motion (μ) | RA: Script error: No such module "val". mas/yr[1] Dec.: Script error: No such module "val". mas/yr[1] |
| Parallax (π) | 18.1821±0.3319 mas[1] |
| Distance | Template:Rnd ± Template:Rnd ly (Template:Rnd ± Template:Rnd pc) |
| Absolute bolometric magnitude (Mbol) | +0.30[5] |
| Orbit[6] | |
| Period (P) | Script error: No such module "val". |
| Semi-major axis (a) | ≥ Script error: No such module "convert". |
| Eccentricity (e) | 0.272±0.026 |
| Periastron epoch (T) | Script error: No such module "val". |
| Argument of periastron (ω) (secondary) | Script error: No such module "val".° |
| Semi-amplitude (K1) (primary) | Script error: No such module "val". km/s |
| Details | |
| ε Aql Aa | |
| Mass | Script error: No such module "val".[7] Template:Solar mass |
| Radius | Script error: No such module "val".[8] Template:Solar radius |
| Luminosity | Script error: No such module "val".[9] Template:Solar luminosity |
| Surface gravity (log g) | 2.91[9] cgs |
| Temperature | 4,760[9] K |
| Metallicity [Fe/H] | 0.00[9] dex |
| Rotational velocity (v sin i) | 4.4[10] km/s |
| ε Aql Ab | |
| Mass | Script error: No such module "val".[7] Template:Solar mass |
| Metallicity [Fe/H] | {{{metal_fe2}}} dex |
| Other designations | |
| Template:Odlist[11] | |
| Database references | |
| SIMBAD | data |
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Epsilon Aquilae is a binary star[12] system in the equatorial constellation of Aquila, near the western constellation boundary with Hercules. Its name is a Bayer designation that is Latinized from ε Aquilae, and abbreviated Epsilon Aql or ε Aql. The system has an apparent visual magnitude of 4.02[2] and is visible to the naked eye. Based upon an annual parallax of Script error: No such module "val".,[1] Epsilon Aquilae lies at a distance of approximately Script error: No such module "convert". from Earth, but is drifting closer with a radial velocity of −46 km/s.[4]
It has the traditional name Deneb el Okab Template:IPAc-en, from an Arabic term ذنب العقاب ðanab al-ʽuqāb "the tail of the eagle", and the Mandarin names Woo Template:IPAc-en and Yuë Template:IPAc-en, derived from and represent the state Wú (吳), an old state was located at the mouth of the Yangtze River, and Yuè (越), an old state in Zhejiang province[13] (together with 19 Capricorni in Twelve States asterism). According to the R.H. Allen's works, it shares names with ζ Aquilae.[14] Epsilon Aquilae could be more precisely called Deneb el Okab Borealis, because is situated to the north of Zeta Aquilae, which can therefore be called Deneb el Okab Australis.[15]
Properties
The binary nature of this system was reported by German astronomer F. Kustner in 1914, but it was not confirmed until 1974. It is a single-lined spectroscopic binary system;[7] the pair orbit each other over a period of 1,271 days (3.5 years) with an eccentricity (ovalness) of 0.27.[6] There are two visual companions to Epsilon Aquilae, both reported by German astronomer R. Engelmann in 1887. Component B is a magnitude 10.56 star at an angular separation of Script error: No such module "val". along a position angle (PA) of 184° relative to the primary, as of 2014. At magnitude 11.25, component C is at a separation of Script error: No such module "val". with a PA of 159°, as of 2015.[16]
The primary component of this system is an evolved giant star with a stellar classification of K1-III CN0.5,[3] showing a mild overabundance of the CN molecule in the spectrum. The chemical abundances of the star suggest it has gone through first dredge-up.[17] It has more than double the mass of the Sun[7] and has expanded to ten times the Sun's radius.[8] The star shines with 54 times the Sun's luminosity, which is being radiated from its outer envelope at an effective temperature of 4,760 K.[9] At this heat, it glows with the orange-hue of a K-type star.[18]
This has been designated a barium star, meaning its atmosphere is extremely enriched with barium and other heavy elements. However, this is disputed, with astronomer Andrew McWilliam (1990) finding normal abundances from an s-process.[7]
References
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- ↑ a b c d e Template:Cite Gaia DR3
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- ↑ a b c d e Script error: No such module "citation/CS1".
- ↑ a b Script error: No such module "citation/CS1".
- ↑ a b c d e Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ Template:Cite simbad
- ↑ Script error: No such module "citation/CS1".
- ↑ Template:In lang English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name Template:Webarchive, Hong Kong Space Museum. Accessed on line November 23, 2010.
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
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