R Aquarii

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Double star
R Aquarii
R Aquarii.jpg
Observation
dates equinox :  J2000.0 , epoch : J2000.0
AladinLite
Constellation Aquarius
Right ascension 23 h 43 m 49.462 s
declination −15 ° 17 ′ 04.184 ″
Apparent brightness  7.7 (5.2-12.4) mag
Astrometry
Radial velocity -22.0 km / s
parallax 3.12 ± 0.27 mas
distance  1040 ± 100 ly
(320 ± 30 pc )
Proper movement :
Rec. Share: +27.33 ± 0.42 mas / a
Dec. portion: -29.86 ± 0.40 mas / a
orbit 
period 15943 ± 471 d
Major semi-axis 0.071-0.084 "/ 14.2-16.8 AU
eccentricity 0.25 ± 0.07
Orbit inclination 70 °
Individual data
Names A; B.
Typing:
Spectral class A. M5e to M8.5e
B. pec
Physical Properties:
Dimensions A. 1 - 1.5 M ☉
B. 0.6 -1 M ☉
radius A. 430 R ☉
B.
Other names
and catalog entries
Bonn survey BD −16 ° 6352
Bright Star Catalog HR 8992 [1]
Henry Draper Catalog HD 222800 [2]
SAO catalog SAO 165849 [3]
Tycho catalog TYC 6404-77-1 [4]
Hipparcos catalog HIP 117054 [5]
Further designations: R Aquarii

Template: Infobox double star / maintenance / RekDekSizeLeer

R Aquarii also R Aqr is a symbiotic star , consisting of an M7 III Mira star and a white dwarf , in the constellation Aquarius .

The system is surrounded by complex, nebulous structures that extend over several angular minutes . On a large scale, R Aqr appears as a bipolar, hourglass-shaped nebula with a predominant toroidal structure at the waist, in which there is a curved, S-shaped structure.

Karl Ludwig Harding discovered the variability of R Aquarii as early as 1810, and thus this star was considered a normal Mira star for over 100 years . In 1919 it was demonstrated by a spectrum, and documented by photograph in 1921, that the system is surrounded by a nebula known as Cederblad 211 . In 1922 the system was identified as a double star with a white dwarf partner.

The hourglass nebula of R Aqr was first discovered by Carl Otto Lampland in 1922, and repeated observations have shown that - as a first approximation - it expands ballistically. The expansion of the large-scale nebula was used to calculate a kinematic age of 600 years. In 1985, this age was more precisely estimated to be 640 years by assuming a model using an hourglass geometry with an equatorial expansion speed of 55 km s −1 .

Observations of the jet

The presence of a central jet in R Aqr was first noted in 1980, and the jet was found to be present as early as 1934 photographs. Since these earlier observations, the large-scale S-shape of the jet has remained virtually unchanged, while on smaller scales its appearance varies greatly even on short time scales.

A symmetrical radio jet extends at least an apparent length of 10 arc seconds from the binary system. In addition, observations in the ultraviolet spectrum with the Faint Object Camera of the Hubble Space Telescope show mass movements of the gas in the inner 5 angular seconds of the northeast jet with tangential velocities in the range of 36 to 235 km s −1 .

Observations with the Chandra - X-ray Telescope and the Very Large Array in 2004 resulted in significant changes in the period of 3 to 4 years to earlier observations with the VLA in 1999 and with Chandra in the 2000th

The emission of the outer collision fronts of the X-ray jet are further away from the central binary system than those of the visible gas flow and originate from material that was heated to approx. 10 6 K by the collision , which indicates a collision between the jet and a relatively dense part of the interstellar Medium (ISM) at this point. In such a collision, the ultraviolet-emitting area coincides with the adiabatic area in the form of a high-temperature, low-density envelope that surrounds the cooled radio-emitting area after the shock. Between 2000 and 2004, the northeast outer X-ray jet moved away from the central double axis with an apparent projected movement of 580 km s −1 . The southwest's outer X-ray jet almost completely disappeared between 2000 and 2004, presumably due to adiabatic expansion and cooling. The northeastern radio emission nebula also moved away from the central area between 2000 and 2004, but at a lower apparent speed than its southwestern counterpart.

Proper movement of the system

The orbital period is about 44 years. The primary star is a red giant and usually varies from 6th to 11th magnitude (5.2 m to 12.4 m ) with a period of 387 days. It then shines orange-red, especially at a minimum. Due to the strong inflation and the corresponding stellar wind, it hurls a lot of matter into space. At a distance of about 320 parsecs, it is one of the closest symbiotic stars. The two components were resolved with a distance of 55 mas .

The white dwarf orbits its partner in a strongly elliptical orbit, and thus comes very close to him every 44 years. Due to its gravitation, it pulls a lot of matter out of the outer layers of the red giant and accumulates this gas in an accretion disk in the periapsis with significantly increased amounts. Occasionally a supercritical accumulation of mass is ejected in strange loops that form the Cederblad 211 Nebula. Bipolar jets emanating from the white dwarf can be seen on images taken by the system (from the VLT and HST ) .

outbreaks

So far, two nova and dwarf nova outbreaks have been detected in 1073 and 1773. These eruptions are of a recurring nature and the next one could therefore occur in 2400. In addition, a large dark cloud seems to encircle the white dwarf or its accretion disk and, through its expansion, influences the change in light of the red giant through its cover over the years. The next eclipse should occur from 2018 to 2026, with the middle of the event forecast for 2022.

The entire system appears red because it is in a very dusty region of the room, the blue part of its light spectrum is absorbed before it reaches the earth.

It is possible that the Cederblad 211 Nebula is the remnant of a nova-like eruption that may have been observed by Japanese astronomers in AD 930. It is reasonably bright, but small and dominated by its central star. Visual observations are difficult and rare. The central area of ​​the jets shows an ejection that took place around 190 years ago, as well as much more recent structures.

Picture gallery

Web links

Commons : R Aquarii  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b R Aqr. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed December 14, 2018 .
  2. ↑ Ralph Elmer Wilson: General catalog of stellar radial velocities. In: Carnegie Institute Washington DC Publication . 1953, bibcode : 1953GCRV..C ...... 0W .
  3. ↑ a b c T. Zwitter, C. Zurbach, S. Zucker, S. Zschocke, J. Zorec: Gaia Data Release 2 - Summary of the contents and survey properties . In: Astronomy & Astrophysics . tape 616 , August 1, 2018, ISSN  1432-0746 , p. A1 , doi : 10.1051 / 0004-6361 / 201833051 ( aanda.org [accessed December 11, 2018]).
  4. ↑ CAL Bailer-Jones, J. Rybizki, M. Fouesneau, G. Mantelet, R. Andrae: Estimating Distance from Parallaxes. IV. Distances to 1.33 Billion Stars in Gaia Data Release 2 . In: The Astronomical Journal . tape 156 , no. 2 , July 20, 2018, ISSN  1538-3881 , p. 58 , doi : 10.3847 / 1538-3881 / aacb21 .
  5. ↑ a b c d J. Mikołajewska, M. Gromadzki: The spectroscopic orbit and the geometry of R Aquarii . In: Astronomy & Astrophysics . tape 495 , no. 3 , March 1, 2009, ISSN  1432-0746 , p. 931-936 , doi : 10.1051 / 0004-6361: 200810052 ( aanda.org [accessed December 10, 2018]).
  6. ↑ R Aqr. In: VSX. AAVSO, accessed December 14, 2018 .
  7. ^ R Aquarii. In: Kerri Malatesta, AAVSO. April 13, 2010, accessed September 18, 2019 .
  8. ^ Solf, J .; Ulrich, H .: The structure of the R Aquarii nebula . In: Astronomy and Astrophysics (ISSN 0004-6361), vol. 148, no. 2, July 1985, p. 274-288 . July 2, 1985. bibcode : 1985A & A ... 148..274S .
  9. ^ JM Hollis et al .: The R Aquarii Jet in Hindsight . In: The Astrophysical Journal, Volume 514, Number 2 . July 13, 1998. doi : 10.1086 / 306979 .
  10. ↑ a b E. Kellogg et al .: Outer Jet X-Ray and Radio Emission in R Aquarii: 1999.8 to 2004.0 . In: The Astrophysical Journal, Volume 664, Number 2 . April 15, 2007. doi : 10.1086 / 518877 .
  11. ^ JM Hollis et al .: Lateral Shock of the R Aquarii Jet . In: The Astrophysical Journal, Volume 490, Number 1 . June 27, 1997. doi : 10.1086 / 304844 .
  12. ↑ Raghvendra Sahai, Matthias mare: Hydrodynamical simulations of the jet in the Symbiotic Star MWC 560. III. application to x-ray jets in symbiotic stars . August 10, 2007 ( nasa.gov [accessed December 10, 2018]).
  13. ↑ JM Hollis, JA Pedelty, RG Lyon: Spatial resolution of the R Aquarii Binary System . In: The Astrophysical Journal Letters . tape 482 , no. 1 , 1997, ISSN  1538-4357 , pp. L85 , doi : 10.1086 / 310687 ( iop.org [accessed December 10, 2018]).
  14. ↑ a b R Aquarii - more than a normal pulsating Mira star. In: Federal German Working Group for Changeable Stars (BAV) eV August 18, 2019, accessed on September 16, 2019 .
  15. ^ Andrew G. Michalitsianos, Minas Kafatos: The peculiar variable star R Aquarii and its jet . In: Nature . tape 298 , no. 5874 , August 1982, ISSN  1476-4687 , pp. 540-542 , doi : 10.1038 / 298540a0 ( nature.com [accessed December 10, 2018]).
  16. ^ Alan MacRobert: The Drama-Ridden Couple of R Aquarii. In: Sky & Telescope. October 7, 2017. Retrieved December 10, 2018 (American English).
  17. ↑ Francesco Paresce, Warren Hack: New HST observations of the core of R Aquarii. 1: Imaging . In: Astronomy and Astrophysics . tape 287 , July 1, 1994, ISSN  0004-6361 , bibcode : 1994A & A ... 287..154P .