R Aquarii

R Aquarii (R Aqr) is a variable star in the constellation Aquarius.[8]

R Aquarii
Location of R Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 23h 43m 49.46201s[1]
Declination −15° 17′ 04.1385″[1]
Apparent magnitude (V) 5.2 - 12.4[2]
Characteristics
Spectral type M5e-M8.5e + pec[2]
U−B color index −0.62[3]
B−V color index +1.98[3]
Variable type Mira + Z And[2]
Astrometry
Radial velocity (Rv)-22.0[4] km/s
Proper motion (μ) RA: +37.13 ± 0.47[5] mas/yr
Dec.: −28.62 ± 0.44[5] mas/yr
Parallax (π)4.59 ± 0.24[5] mas
Distance710 ± 40 ly
(220 ± 10 pc)
Orbit[6]
Period (P)15,943 ± 471
Semi-major axis (a)0.071 - 0.084"
(14.2 - 16.8 AU)
Eccentricity (e)0.25 ± 0.07
Inclination (i)70°
Details
A
Mass1 - 1.5[6] M☉
Radius430[6] R☉
Luminosity4,780[7] L☉
Surface gravity (log g)−0.5[7] cgs
Temperature2,800[7] K
B
Mass0.6 - 1[6] M☉
Other designations
R Aqr, BD−16°6352, HD 222800, HIP 117054, HR 8992, SAO 165849
Database references
SIMBADdata
Data sources:
Hipparcos Catalogue,
CCDM (2002),
Bright Star Catalogue (5th rev. ed.)

R Aquarii is a symbiotic star believed to contain a white dwarf and a Mira-type variable in a binary system. The orbital period is approximately 44 years.[6] The main Mira-type star is a red giant, and varies in brightness by a factor of several hundred and with a period of slightly more than a year; this variability was discovered by Karl Ludwig Harding in 1810. It has a distance of about 200 parsec, and is one of the nearest symbiotic stars and a well-known jet source.[9] The two components have been resolved at a separation of 55 mas.[10]

By its gravitational pull, the white dwarf draws in material from the red giant and occasionally ejects some of the surplus in weird loops to form the nebula seen in the linked image.[11] The whole system appears reddened because it is situated in a very dusty region of space, and its blue light is absorbed before reaching Earth.

The nebula around R Aquarii is also known as Cederblad 211.[12] It is possible that the nebula is the remnant of a nova-like outburst, which may have been observed by Japanese astronomers, in the year 930 AD.[13] It is reasonably bright but small and dominated by its central star. Visual observations are difficult and rare.[14] The central region of the jet shows an ejection that took place around 190 years ago, as well as much younger structures.[15]

The giant primary star is a Mira variable, a star that pulsates and changes temperature, leading to very large visual brightness changes. The total range of 5.2 - 12.4 is a variation of 750 times in brightness, from a naked eye star to one beyond the range of binoculars. The pulsations occur every 390 days but are not entirely regular.[2]

  • R Aquarii peculiar stellar relationship captured by SPHERE.[16]
  • R Aquarii as seen in 2012 by ESO's Very Large Telescope.[17]
  • R Aquarii and its surrounding nebulosity
  • Artist's impression of R Aquarii during an outburst
  • The jet and central regions of the nebula around R Aquarii
  • HST image of R Aquarii

References
  1. Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  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. Celis s., L. (1982). "Red variable stars. I - UBVRI photometry and photometric properties". Astronomical Journal. 87: 1791. Bibcode:1982AJ.....87.1791C. doi:10.1086/113268.
  4. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode:1953GCRV..C......0W.
  5. Min, Cheulhong; Matsumoto, Naoko; Kim, Mi Kyoung; Hirota, Tomoya; Shibata, Katsunori M.; Cho, Se-Hyung; Shizugami, Makoto; Honma, Mareki (2014). "Accurate parallax measurement toward the symbiotic star R Aquarii". Publications of the Astronomical Society of Japan. 66 (2): 38. arXiv:1401.5574. Bibcode:2014PASJ...66...38M. doi:10.1093/pasj/psu003. S2CID 118691801.
  6. M. Gromadzki & J. Mikołajewska (March 2009). "The spectroscopic orbit and the geometry of R Aquarii". Astronomy & Astrophysics. 495 (3): 931–936. arXiv:0804.4139. Bibcode:2009A&A...495..931G. doi:10.1051/0004-6361:200810052. S2CID 2034734.
  7. 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.
  8. "R Aquarii | aavso.org". www.aavso.org. Retrieved 2018-07-11.
  9. Stute, Matthias; Sahai, Raghvendra. "Hydrodynamical Simulations of the Jet in the Symbiotic Star MWC 560". The Astrophysical Journal. The American Astronomical Society. hdl:2014/41009.
  10. Hollis, J. M.; Pedelty, J. A.; Lyon, R. G. (1997). "Spatial Resolution of the R Aquarii Binary System". The Astrophysical Journal. 482 (1): L85–L88. Bibcode:1997ApJ...482L..85H. doi:10.1086/310687.
  11. "Aladin previewer". CDS.
  12. Cederblad, S (1946). "Studies of bright diffuse galactic nebulae with special regard to their spatial distribution". Lund Medd. Astron. Obs. Ser. II. 119: 1. Bibcode:1946MeLuS.119....1C.
  13. Kafatos, Minas; Michalitsianos, Andrew G (1982). "The peculiar variable star R Aquarii and its jet". Nature. 298 (5874): 540. Bibcode:1982Natur.298..540K. doi:10.1038/298540a0. S2CID 4238750.
  14. "The Drama-Ridden Couple of R Aquarii". Sky & Telescope. Retrieved 2018-01-18.
  15. Paresce, Francesco; Hack, Warren (1994). "New HST observations of the core of R Aquarii. 1: Imaging". Astronomy and Astrophysics. 287: 154. Bibcode:1994A&A...287..154P.
  16. "Dancing with the Enemy - ESO's R Aquarii Week continues with the sharpest R Aquarii image ever". www.eso.org. Retrieved 12 December 2018.
  17. "VLT view of binary system R Aquarii from 2012". www.eso.org. Retrieved 10 December 2018.
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