W Aquilae

W Aquilae (W Aql) is a variable star in the constellation of Aquila.

W Aquilae

W Aquilae showing the close companion
Credit: Hubble Legacy Archive
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension  19h 15m 23.347s[1]
Declination 07° 02′ 50.35″[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[1]
Variable type Mira[2]
B
Evolutionary stage main sequence[4]
Spectral type F8/9[4]
Astrometry
Radial velocity (Rv)−18.0[5] km/s
Proper motion (μ) RA: 14.901 mas/yr
Dec.: −1.517 mas/yr
Parallax (π)3.1128 ± 0.2018[6] mas
Distance1,050 ± 70 ly
(320 ± 20 pc)
Absolute magnitude (MV)A: −0.7 to +6.9[3]
B: +7.1[3]
Details
A
Mass1.04 - 3[4] M☉
Radius400[7] - 480[8] R☉
Luminosity7,500[9] L☉
Temperature2,300[9] - 3,000[7] K
B
Mass1.04 - 1.09[4] M☉
Temperature5,900 - 6,170[4] K
Other designations
W Aql, IRAS 19126-0708, TYC 5142-2895-1, 2MASS J19152335-0702503, AAVSO 1910-07
Database references
SIMBADdata

Description

W 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 varies between 2,300 and 3,000 K and its diameter between 400 and 480 solar radii.[7][8] It is also a very luminous star, 7,500 times more than the sun.[9]

Variability

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.

Companion

A 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

A 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.[11]

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References
  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode:1953GCRV..C......0W.
  6. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  7. Ramstedt, S.; Mohamed, S.; Vlemmings, W. H. T.; Danilovich, T.; Brunner, M.; De Beck, E.; Humphreys, E. M. L.; Lindqvist, M.; Maercker, M.; Olofsson, H.; Kerschbaum, F.; Quintana-Lacaci, G. (2017). "The circumstellar envelope around the S-type AGB star W Aql". Astronomy & Astrophysics. 605: A126. arXiv:1709.07327. doi:10.1051/0004-6361/201730934. PMC 5683349. PMID 29142327.
  8. Ramstedt, S.; Schöier, F. L.; Olofsson, H. (2009). "Circumstellar molecular line emission from S-type AGB stars: mass-loss rates and SiO abundances". Astronomy and Astrophysics. 499 (2): 515. arXiv:0903.1672. Bibcode:2009A&A...499..515R. doi:10.1051/0004-6361/200911730. S2CID 17942939. 515-527.
  9. 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.
  10. 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.
  11. Vlemmings, W.; Ramstedt, S.; Maercker, M.; Davidsson, B. (2015). "The serendipitous discovery of a possible new solar system object with ALMA". 1512: arXiv:1512.02650. arXiv:1512.02650. Bibcode:2015arXiv151202650V. Cite journal requires |journal= (help)
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