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U Aquilae 
Summary
U Aquilae is a binary star system in the constellation Aquila, Located approximately 614 parsecs (2,000 ly) away from Earth.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquila |
| Right ascension | 19h 29m 21.3603s[2] |
| Declination | −07° 02′ 38.710″[2] |
| Apparent magnitude (V) | 6.61[3] (6.08 - 6.86[4]) |
| Characteristics | |
| Spectral type | F5-G1 I-II[5] + B9.8V[6] |
| U−B color index | 0.70[3] |
| B−V color index | 1.10[3] |
| Variable type | δ Cep[4] |
| Astrometry | |
| Radial velocity (Rv) | -6.5[2] km/s |
| Proper motion (μ) | RA: -0.99[2] mas/yr Dec.: -9.14[2] mas/yr |
| Parallax (π) | 3.63 ± 0.96 mas[2] |
| Distance | 614[6] pc |
| Absolute magnitude (MV) | −3.68[6] |
| Orbit[7] | |
| Period (P) | 1,856 |
| Semi-major axis (a) | 1.311" (6.1 AU) |
| Eccentricity (e) | 0.165 |
| Inclination (i) | 74° |
| Longitude of the node (Ω) | 190° |
| Details | |
| A | |
| Mass | 5.7[6] M☉ |
| Radius | 55[7] R☉ |
| Luminosity | 2,570[6] L☉ |
| Surface gravity (log g) | 1.3[8] cgs |
| Temperature | 5,440-6,640[8] K |
| Metallicity [Fe/H] | 0.17[9] dex |
| B | |
| Mass | 2.3[6] M☉ |
| Radius | 2.1[7] R☉ |
| Temperature | 9,300[7] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
The primary star (component A) is a yellow supergiant with a radius of 55 R☉ and a luminosity of 2,570 L☉. The secondary (component B) is a blue main-sequence star, twice the mass of the sun and around thirty times more luminous. It is hotter than the primary star at 9,300 K, but much smaller and fainter. The two stars orbit every five years and their separation varies from five to seven astronomical units in a mildly eccentric orbit.
u Aql A is a classical Cepheid variable star ranging between magnitudes 6.08 and 6.86 over a period of 7.02 days. It is an evolved star which has exhausted its core hydrogen and is now fusing helium into carbon.[10]
References edit
- ^ Kiss, Laszlo L. (July 1998). "A photometric and spectroscopic study of the brightest northern Cepheids - I. Observations". Monthly Notices of the Royal Astronomical Society. 297 (3): 825. Bibcode:1998MNRAS.297..825K. doi:10.1046/j.1365-8711.1998.01559.x.
- ^ a b c d e f Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
- ^ a b c Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
- ^ 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.
- ^ Simpson, P. (2012). "The Eagle and its Errands". Guidebook to the Constellations. Patrick Moore's Practical Astronomy Series. pp. 373–399. doi:10.1007/978-1-4419-6941-5_9. ISBN 978-1-4419-6940-8.
- ^ a b c d e f Evans, Nancy Remage (2013). "Binary Cepheids: Separations and Mass Ratios in 5M☉Binaries". The Astronomical Journal. 146 (4): 93. arXiv:1307.7123. Bibcode:2013AJ....146...93E. doi:10.1088/0004-6256/146/4/93. S2CID 34133110.
- ^ a b c d Welch, D. L.; Evans, N. R.; Lyons, R. W.; Harris, H. C.; Barnes, T. G., I. I.; Slovak, M. H.; Moffett, T. J. (1987). "The orbit of the classical Cepheid U Aquilae". Publications of the Astronomical Society of the Pacific. 99: 610. Bibcode:1987PASP...99..610W. doi:10.1086/132022.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b Kiss, L. L.; Szatmary, K. (1998). "A photometric and spectroscopic study of the brightest northern Cepheids -- II. Fundamental physical parameters". Monthly Notices of the Royal Astronomical Society. 300 (2): 616. Bibcode:1998MNRAS.300..616K. doi:10.1046/j.1365-8711.1998.01943.x.
- ^ Groenewegen, M. A. T. (2013). "Baade-Wesselink distances to Galactic and Magellanic Cloud Cepheids and the effect of metallicity". Astronomy & Astrophysics. 550: A70. arXiv:1212.5478. Bibcode:2013A&A...550A..70G. doi:10.1051/0004-6361/201220446. S2CID 118665355.
- ^ Kiss, L. L. (1998). "A photometric and spectroscopic study of the brightest northern Cepheids -- I. Observations". Monthly Notices of the Royal Astronomical Society. 297 (3): 825–838. Bibcode:1998MNRAS.297..825K. doi:10.1046/j.1365-8711.1998.01559.x.