Astronomy:W Aquilae

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Short description: Variable star in the constellation Aquila
W Aquilae
280px
W Aquilae showing the close companion
Credit: Hubble Legacy Archive
Observation data
Equinox J2000.0]] (ICRS)
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[1] mas
Distance1,220 ± 60 ly
(370 ± 20 pc)
Absolute magnitude (MV)A: −0.7 to +6.9[3]
B: +7.1[3]
Details
A
Mass1.04 - 3[4] M☉
Radius444[7][lower-alpha 1] R☉
Luminosity7,500[8] L☉
Temperature2,800[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, Gaia DR2 420492505899016640
Database references
SIMBADdata

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]

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 is about 2,800 K and its radius is equivalent to 440 solar radii.[7][lower-alpha 1] It is also a very luminous star, 7,500 times more than the sun.[8]

Variability

In 1893, Leo Anton Carl de Ball announced that the then unnamed star was a variable star, whose brightness varied by at least one magnitude.[11] It was listed with its variable star designation, W Aquilae, in Annie Jump Cannon's 1907 Second Catalogue of Variable Stars.[12]

The visual band light curve of W Aquilae, from AAVSO data[13]

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.[14]

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.[15]

Notes

  1. ↑ 1.0 1.1 Radius calculated with angular diameter and distance in Table 1

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 Samus, N. N. 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. ↑ 3.0 3.1 3.2 3.3 Mayer, A.; Jorissen, A.; Kerschbaum, F.; Ottensamer, R.; Nowotny, W.; Cox, N. L. J.; Aringer, B.; Blommaert, J. A. D. L. et al. (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. doi:10.1051/0004-6361/201219259. Bibcode: 2013A&A...549A..69M. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 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. doi:10.1051/0004-6361/201423672. Bibcode: 2015A&A...574A..23D. 
  5. ↑ Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P. et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27. doi:10.1888/0333750888/2862. ISBN 0333750888. Bibcode: 2000A&A...355L..27H. 
  6. ↑ Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode: 1953GCRV..C......0W. 
  7. ↑ 7.0 7.1 7.2 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. et al. (December 6, 2023). "ATOMIUM: Molecular inventory of 17 oxygen-rich evolved stars observed with ALMA". Astronomy & Astrophysics 681: A50. doi:10.1051/0004-6361/202347632. ISSN 0004-6361. 
  8. ↑ 8.0 8.1 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. doi:10.1051/0004-6361/201832724. 
  9. ↑ Danilovich, T. et al. (2021). "ATOMIUM: Halide molecules around the S-type AGB star W Aquilae". Astronomy & Astrophysics 655: A80. doi:10.1051/0004-6361/202141757. Bibcode: 2021A&A...655A..80D. 
  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. doi:10.1051/0004-6361/201322807. Bibcode: 2014A&A...569A..76D. 
  11. ↑ de Ball, Leo (August 1893). "Über einen neuen veränderlichen Stern in Aquila". Astronomische Nachrichten 133: 215. Bibcode: 1893AN....133..215D. https://articles.adsabs.harvard.edu/pdf/1893AN....133..215D. Retrieved 23 November 2024. 
  12. ↑ Cannon, Annie J. (1907). "Second catalogue of variable stars". Annals of Harvard College Observatory 55: 1–94. Bibcode: 1907AnHar..55....1C. https://articles.adsabs.harvard.edu/pdf/1907AnHar..55....1C. Retrieved 21 November 2024. 
  13. ↑ "Download Data". AAVSO. https://www.aavso.org/data-download. 
  14. ↑ 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. doi:10.1017/S1743921312007107. Bibcode: 2012IAUS..287..260R. 
  15. ↑ 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].



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