U Aquilae
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquila |
| Right ascension | 19h 29m 21.3603s[1] |
| Declination | −07° 02′ 38.710″[1] |
| Apparent magnitude (V) | 6.08 - 6.86[2] |
| Characteristics | |
| Spectral type | F5-G1 I-II[3] + B9.8V[4] |
| U−B color index | 0.70[5] |
| B−V color index | 1.10[5] |
| Variable type | δ Cep[2] |
| Astrometry | |
| Radial velocity (Rv) | −6.5[1] km/s |
| Proper motion (μ) | RA: −0.99[1] mas/yr Dec.: −9.14[1] mas/yr |
| Parallax (π) | 3.63±0.96 mas[1] |
| Distance | 1,931 ± 62 ly (592±19 pc)[6] |
| Absolute magnitude (MV) | −3.68[4] |
| Orbit[6] | |
| Primary | Aa |
| Name | Ab |
| Period (P) | 1,831.4±6.5 days |
| Semi-major axis (a) | (10.06±0.16)×10−3" (5.94±0.22 AU) |
| Eccentricity (e) | 0.193±0.005 |
| Inclination (i) | 115.4±0.7° |
| Longitude of the node (Ω) | 133.8±4.4° |
| Periastron epoch (T) | 2,457,575.3±8.4 JD |
| Argument of periastron (ω) (secondary) | 167.1±1.9° |
| Semi-amplitude (K1) (primary) | 8.41±0.04 km/s |
| Semi-amplitude (K2) (secondary) | 24.05±1.24 km/s |
| Details | |
| Aa | |
| Mass | 6.2±0.8[6] M☉ |
| Radius | 55[7] R☉ |
| Luminosity | 2,570[4] L☉ |
| Surface gravity (log g) | 1.3[8] cgs |
| Temperature | 5,440-6,640[8] K |
| Metallicity [Fe/H] | 0.17[9] dex |
| Ab | |
| Mass | 2.2±0.2[6] M☉ |
| Radius | 2.1[7] R☉ |
| Temperature | 9,300[7] K |
| Other designations | |
| U Aql, AAVSO 1924-07, BD−07°4968, GC 26905, HD 183344, HIP 95820, HR 7402, SAO 143454, ADS 12503, CCDM J19294-0703 | |
| Database references | |
| SIMBAD | data |
U Aquilae is a binary star system in the constellation Aquila, Located approximately 592 parsecs (1,930 ly) away from Earth.
U Aquilae is a spectroscopic binary. The primary star is a yellow supergiant with a radius of 55 R☉ and a luminosity of 2,570 L☉. The secondary 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. An 11th-magnitude star 1.6″ from the spectroscopic pair, is assumed to be related but would have an orbit of several thousand years.[11]
Discovery of the variability of U Aquilae was announced by Edwin Forrest Sawyer in 1886. In his announcement, he called the star 50 Aquilae, which is its designation in Uranometria Argentina. Sawyer had begun observing the star in late 1882, and had derived a period of "about one week".[12] It was listed with its variable star designation, U Aquilae, in Annie Jump Cannon's 1907 Second Catalogue of Variable Stars.[13]
U Aquilae Aa 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.[14]
References
[edit]- ^ 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 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 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 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 c d Gallenne, A.; Kervella, P.; Borgniet, S.; Mérand, A.; Pietrzyński, G.; Gieren, W.; Monnier, J. D.; Schaefer, G. H.; Evans, N. R.; Anderson, R. I.; Baron, F.; Roettenbacher, R. M.; Karczmarek, P. (February 2019). "Multiplicity of Galactic Cepheids from long-baseline interferometry. IV. New detected companions from MIRC and PIONIER observations". Astronomy and Astrophysics. 622: A164. Bibcode:2019A&A...622A.164G. doi:10.1051/0004-6361/201834614. ISSN 0004-6361.
- ^ a b c Welch, D. L.; Evans, N. R.; Lyons, R. W.; Harris, H. C.; Barnes, T. G., III; 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.
- ^ 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, 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.
- ^ Tokovinin, Andrei (2018). "The Updated Multiple Star Catalog". The Astrophysical Journal Supplement Series. 235 (1): 6. arXiv:1712.04750. Bibcode:2018ApJS..235....6T. doi:10.3847/1538-4365/aaa1a5.
- ^ Sawyer, Edwin F. (December 1886). "A new short-period variable in Aquila". Astronomical Journal. 7 (147): 22. Bibcode:1886AJ......7...22S. doi:10.1086/100847.
- ^ Cannon, Annie J. (1907). "Second catalogue of variable stars". Annals of Harvard College Observatory. 55: 1–94. Bibcode:1907AnHar..55....1C.
- ^ 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.
