Delta Aquilae
 Location of δ Aquilae (circled) near the center |
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| Observation data Epoch J2000 Equinox J2000 |
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|---|---|
| Constellation | Aquila |
| Right ascension | 19h 25m 29.90139s[1] |
| Declination | +03° 06′ 53.2061″[1] |
| Apparent magnitude (V) | 3.365[2] |
| Characteristics | |
| Spectral type | F0 IV[3] + K[4] |
| U−B color index | +0.031[2] |
| B−V color index | +0.319[2] |
| R−I color index | +0.16 |
| Variable type | δ Sct[5] |
| Astrometry | |
| Radial velocity (Rv) | –30.1[6] km/s |
| Proper motion (μ) | RA: +254.54[1] mas/yr Dec.: +82.51[1] mas/yr |
| Parallax (π) | 64.41 ± 1.00[1] mas |
| Distance | 50.6 ± 0.8 ly (15.5 ± 0.2 pc) |
| Absolute magnitude (MV) | 2.46[7] |
| Orbit[8] | |
| Period (P) | 3.426 ± 0.006 yr |
| Semimajor axis (a) | 0.0539 ± 0.0040" |
| Eccentricity (e) | 0.36 ± 0.07 |
| Inclination (i) | 150 ± 11° |
| Longitude of the node (Ω) | 337 ± 9° |
| Periastron epoch (T) | 1954.58 ± 0.13 |
| Argument of periastron (ω) (secondary) |
191 ± 14° |
| Details | |
| δ Aql A | |
| Mass | 1.65[4] M☉ |
| Radius | 2.04[4] R☉ |
| Luminosity | 6.8[9]–7.9[10] L☉ |
| Temperature | 7,016[7] K |
| Rotational velocity (v sin i) | 87.3[11] km/s |
| δ Aql B | |
| Mass | 0.67[4] M☉ |
| Radius | 0.61[4] R☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
| Data sources: | |
| Hipparcos Catalogue, CCDM (2002), Bright Star Catalogue (5th rev. ed.) |
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Delta Aquilae (δ Aql, δ Aquilae) is a binary star system in the equatorial constellation of Aquila. The traditional name for this star is Denebokab. It has an apparent visual magnitude of 3.4[2] and, based upon parallax measurements, is located about 50.6 light-years (15.5 parsecs) from Earth.
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[edit] Properties
Delta Aquilae is an astrometric binary with an orbital period of 3.422 years and an eccentricity of about 0.36.[8] The primary, Delta Aquilae A, is a subgiant star with a stellar classification of F0 IV,[3] which indicates it is in the process of exhausting the supply of hydrogen at its core and evolving into a giant star. The mass of the star is 65% greater than the Sun and it has expanded to more than double the Sun's radius.[4] It is radiating around 7–8 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 7,016 K.[7]
Delta Aquilae A is a Delta Scuti variable that exhibits variations in luminosity from pulsations in its outer envelope.[5] It is spinning rapidly with a projected rotational velocity of about 87 km s–1, giving a lower bound on the azimuthal velocity along the star's equator.[11]
The secondary component, Delta Aquilae B, is a smaller star with about 67% of the Sun's mass and 61% of the radius of the Sun.[4] It may be a K-type star.[4]
[edit] Etymology
This star is sometimes called by the name Denebokab, meaning the tail of eagle in Arabic. In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Djenubi Menkib al Nesr (منكب ألنسر ألخنوبي - mankib al-nasr al-janúbii), which was translated into Latin as Australior Humerus Vulturis, meaning the southern shoulder of the eagle.[13]
In Chinese, 右旗 (Yòu Qí), meaning Right Flag, refers to an asterism consisting of δ Aquilae, μ Aquilae, σ Aquilae, ν Aquilae, ι Aquilae, 42 Aquilae, HD 184701, κ Aquilae and 56 Aquilae.[14] Consequently, δ Aquilae itself is known as 右旗三 (Yòu Qí sān, English: the Third Star of Right Flag.)[15]
This star, along with η Aql and θ Aql (Tseen Foo) and, were Al Mizān (ألميزان), the Scale-beam.[16] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Mizān were the title for three stars :δ Aql as Al Mizān I, η Aql as l Mizān II and θ Aql as Al Mizān III.[17]
[edit] References
- ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, Bibcode 2007A&A...474..653V, doi:10.1051/0004-6361:20078357
- ^ a b c d Cousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars 8: 59, Bibcode 1984SAAOC...8...59C
- ^ a b Cowley, Anne; Fraquelli, Dorothy (February 1974), "MK Spectral Types for Some Bright F Stars", Publications of the Astronomical Society of the Pacific 86 (509): 70, Bibcode 1974PASP...86...70C, doi:10.1086/129562
- ^ a b c d e f g h Fuhrmann, Klaus (February 2008), "Nearby stars of the Galactic disc and halo - IV", Monthly Notices of the Royal Astronomical Society 384 (1): 173–224, Bibcode 2008MNRAS.384..173F, doi:10.1111/j.1365-2966.2007.12671.x
- ^ a b Mantegazza, L.; Poretti, E. (June 2005), "Projected rotational velocities of some Delta Scuti and Gamma Doradus stars", Communications in Asteroseismology 146: 37–39, Bibcode 2005CoAst.146...37M, doi:10.1553/cia146s37
- ^ Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick, eds., The Revision of the General Catalogue of Radial Velocities, University of Toronto: International Astronomical Union, Bibcode 1967IAUS...30...57E
- ^ a b c Reiners, A. (January 2006), "Rotation- and temperature-dependence of stellar latitudinal differential rotation", Astronomy and Astrophysics 446 (1): 267-277, arXiv:astro-ph/0509399, Bibcode 2006A&A...446..267R, doi:10.1051/0004-6361:20053911
- ^ a b Kamper, Karl W.; Legget, David; McCarthy, Donald W., Jr. (August 1989), "Astrometric-spectroscopic binary star orbits. III - Alpha Ophiuchi and Delta Aquilae", Astronomical Journal 98: 686–691, Bibcode 1989AJ.....98..686K, doi:10.1086/115169
- ^ Malagnini, M. L.; Morossi, C. (November 1990), "Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars", Astronomy and Astrophysics Supplement Series 85 (3): 1015–1019, Bibcode 1990A&AS...85.1015M
- ^ do Nascimento, J. D., Jr. et al. (July 2003), "On the link between rotation, chromospheric activity and Li abundance in subgiant stars", Astronomy and Astrophysics 405: 723-731, arXiv:astro-ph/0307196, Bibcode 2003A&A...405..723D, doi:10.1051/0004-6361:20030633
- ^ a b Schröder, C.; Reiners, A.; Schmitt, J. H. M. M. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo", Astronomy and Astrophysics 493 (3): 1099−1107, Bibcode 2009A&A...493.1099S, doi:10.1051/0004-6361:200810377
- ^ "del Aql -- Variable Star", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Delta+Aquilae, retrieved 2012-02-06
- ^ Knobel, E. B. (June 1895), "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket", Monthly Notices of the Royal Astronomical Society 55: 429, Bibcode 1895MNRAS..55..429K
- ^ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 9789867332257.
- ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
- ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 61. ISBN 0486210790. http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Aquila*.html. Retrieved 2010-12-12.
- ^ Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology, http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720005197_1972005197.pdf, retrieved 2012-02-06
[edit] External links
- Jim Kaler's Stars, University of Illinois: DELTA AQL (Delta Aquilae)
- An Atlas of the Universe: Multiple Star Orbits
- Image δ Aquilae
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