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 4×10−6solar 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
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 monoxidemaser emission.[12]
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planet X. The paper was withdrawn without being accepted for peer-reviewed publication.[13]
Notes
^
abRadius calculated with angular diameter and distance in Table 1
^
abcSamus, 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.
^
abcdMayer, 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.
S2CID55538633.
^
abBrunner, 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.
S2CID67754573.
^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.
S2CID55615864.
^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].