W Aquilae (W Aql) is a variable star in the constellation of Aquila. It is a type of evolved star known as an S-type star. Due to its relatively close distance of 1,200 light-years (370 pc) and equatorial location, it is easy to observe and heavily studied.[9]
 W Aquilae showing the close companion Credit: Hubble Legacy Archive | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquila |
| Right ascension | 19h 15m 23.357s[1] |
| Declination | −07° 02′ 50.33″[1] |
| Apparent magnitude (V) | A: 7.0 - 14.6[2] B:14.8 [3] |
| Characteristics | |
| A | |
| Evolutionary stage | asymptotic giant branch[4] |
| Spectral type | S6/6e[4] (S3,9e - S6,9e[2]) |
| B−V color index | +2.58[5] |
| Variable type | Mira[2] |
| B | |
| Evolutionary stage | main sequence[4] |
| Spectral type | F8/9[4] |
| Astrometry | |
| Radial velocity (Rv) | −18.0[6] km/s |
| Proper motion (μ) | RA: 15.713[1] mas/yr Dec.: 0.103[1] mas/yr |
| Parallax (π) | 2.6735 ± 0.1392 mas[1] |
| Distance | 1,220 ± 60 ly (370 ± 20 pc) |
| Absolute magnitude (MV) | A: −0.7 to +6.9[3] B: +7.1[3] |
| Details | |
| A | |
| Mass | 1.04 - 3[4] M☉ |
| Radius | 444[7][a] R☉ |
| Luminosity | 7,500[8] L☉ |
| Temperature | 2,800[7] K |
| B | |
| Mass | 1.04 - 1.09[4] M☉ |
| Temperature | 5,900 - 6,170[4] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
Description
editW Aquilae is an S-type star with a spectral type of S3,9e to S6,9e, a red giant similar to M-type stars, but in which the dominant spectrum oxides are formed by metals of the fifth period of the periodic table. W Aquilae is also rich in the element technetium. Another feature of this class of stars is the stellar mass loss, in the case of W Aquilae is estimated at 4×10−6 solar masses per year.[10] Its effective temperature is about 2,800 K and its radius is equivalent to 440 solar radii.[7][a] It is also a very luminous star, 7,500 times more than the sun.[8]
Variability
edit
W Aquilae is a variable whose brightness oscillates between magnitude +7.3 and +14.3 over a period of 490.43 days. In Mira variables (which are named after Mira, the prototype), this instability comes from pulsation in the stellar surface, causing changes in color and brightness. W Aquilae, a Mira variable, shows silicon monoxide maser emission.[12]
Companion
editA magnitude 14.8 companion has been detected 0.47" SW of W Aquilae. This is fainter than W Aquilae at minimum and corresponds to an absolute magnitude of +7.1. Although that absolute magnitude would correspond to a K4 main sequence star, a spectrum was classified as F5 or F8. The separation between the two stars is 160 AU.[3]
Planet X
editA 2014 study of W Aquilae and α Centauri with the ALMA array claimed to have accidentally detected a previously-unknown Solar System object. This received widespread press coverage as a potential discovery of planet X. The paper was withdrawn without being accepted for peer-reviewed publication.[13]
Notes
editReferences
edit- ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b c 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.
- ^ a b c d Mayer, A.; Jorissen, A.; Kerschbaum, F.; Ottensamer, R.; Nowotny, W.; Cox, N. L. J.; Aringer, B.; Blommaert, J. A. D. L.; Decin, L.; Van Eck, S.; Gail, H.-P.; Groenewegen, M. A. T.; Kornfeld, K.; Mecina, M.; Posch, Thomas; Vandenbussche, B.; Waelkens, C. (2013). "Large-scale environments of binary AGB stars probed by Herschel. I. Morphology statistics and case studies of R Aquarii and W Aquilae". Astronomy & Astrophysics. 549: A69. arXiv:1211.3595. Bibcode:2013A&A...549A..69M. doi:10.1051/0004-6361/201219259. S2CID 55538633.
- ^ a b c d e f g Danilovich, T.; Olofsson, G.; Black, J. H.; Justtanont, K.; Olofsson, H. (2015). "Classifying the secondary component of the binary star W Aquilae". Astronomy & Astrophysics. 574: A23. arXiv:1501.00863. Bibcode:2015A&A...574A..23D. doi:10.1051/0004-6361/201423672. S2CID 15587164.
- ^ Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H. doi:10.1888/0333750888/2862. ISBN 0333750888.
- ^ Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode:1953GCRV..C......0W.
- ^ a b c Wallstrom, S. H. J.; Danilovich, T.; Muller, H. S. P.; Gottlieb, C. A.; Maes, S.; Van de Sande, M.; Decin, L.; Richards, A. M. S.; Baudry, A.; Bolte, J.; Ceulemans, T.; De Ceuster, F.; de Koter, A.; Mellah, I. El; Esseldeurs, M. (December 6, 2023). "ATOMIUM: Molecular inventory of 17 oxygen-rich evolved stars observed with ALMA". Astronomy & Astrophysics. 681: A50. arXiv:2312.03467. doi:10.1051/0004-6361/202347632. ISSN 0004-6361.
- ^ a b Brunner, M.; Danilovich, T.; Ramstedt, S.; Marti-Vidal, I.; De Beck, E.; Vlemmings, W. H. T.; Lindqvist, M.; Kerschbaum, F. (2018). "Molecular line study of the S-type AGB star W Aquilae". Astronomy & Astrophysics. 617: A23. arXiv:1806.01622. doi:10.1051/0004-6361/201832724. S2CID 67754573.
- ^ Danilovich, T.; et al. (2021). "ATOMIUM: Halide molecules around the S-type AGB star W Aquilae". Astronomy & Astrophysics. 655: A80. arXiv:2109.04747. Bibcode:2021A&A...655A..80D. doi:10.1051/0004-6361/202141757. S2CID 237485542.
- ^ Danilovich, T.; Bergman, P.; Justtanont, K.; Lombaert, R.; Maercker, M.; Olofsson, H.; Ramstedt, S.; Royer, P. (2014). "Detailed modelling of the circumstellar molecular line emission of the S-type AGB star W Aquilae". Astronomy & Astrophysics. 569: A76. arXiv:1408.1825. Bibcode:2014A&A...569A..76D. doi:10.1051/0004-6361/201322807. S2CID 55615864.
- ^ "Download Data". aavso.org. AAVSO. Retrieved 1 October 2021.
- ^ Ramstedt, Sofia; Vlemmings, Wouter; Mohamed, Shazrene; Choi, Yoon Kyung; Olofsson, Hans (July 2012). "TWINKLING STARS the disappearing SiO masers of W Aql". Proceedings of the International Astronomical Union. 287: 260–261. Bibcode:2012IAUS..287..260R. doi:10.1017/S1743921312007107. S2CID 123608578.
- ^ Vlemmings, W.; Ramstedt, S.; Maercker, M.; Davidsson, B. (2015). "The serendipitous discovery of a possible new solar system object with ALMA". arXiv:1512.02650 [astro-ph.SR].