Astronomy:W Aquilae

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W Aquilae (W Aql / SAO 143184 / GC 2525) is a variable star in the constellation of Aquila.

Description

W Aquilae is an S-type star with a spectral type of S39e to S69e, 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 ~ 4×10−7 solar masses per year. Its effective temperature varies between 2,250 and 3,175 K and its diameter between 430 and 473 solar radii. It is also a very luminous star, between 9,740 and 28,885 times more than the sun.

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.[1]

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 This received widespread press coverage as a potential discovery of planet X. The paper was withdrawn without being accepted for peer-reviewed publication.[2]

References

  1. 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. Bibcode2013A&A...549A..69M. 
  2. Vlemmings, W.; Ramstedt, S.; Maercker, M.; Davidsson, B. (2015). The serendipitous discovery of a possible new solar system object with ALMA. 1512. pp. arXiv:1512.02650. Bibcode2015arXiv151202650V. 

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