* Astronomy

Blobrana · L

RE: R Aquarii

Blobrana · L

Maximum of R Aquarii variable star on the 12th January, 2011.

Magnitude=5.8
Minimum=12.4
Period=387.0 days

Position(2000): RA=23 43 49.4616, Dec=-15 17 04.202

Blobrana · L

Title: The spectroscopic orbit and the geometry of R Aqr
Authors: M. Gromadzki, J. Mikolajewska
(Version v2)

R Aqr is one of the closest symbiotic binaries and the only D-type system with radial velocity data suitable for orbital parameters estimation. The aims of our study are to derive a reliable spectroscopic orbit of the Mira component, and to establish connections between the orbital motion and other phenomena shown by R Aqr. We reanalyse velocity data recently published by McIntosh & Rustan complemented by three additional historical velocities. We find an eccentric orbit (e=0.4) with a period 40.9 yr. This solution is in agreement with a resolved VLA observation of this system. We demonstrate that the last 1974-1981 increase of extinction towards the Mira occurred during its superior spectroscopic conjunction, and can be due to obscuration by a neutral material in the accreting stream. We also show that jet ejection is not connected with the orbital position.

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Blobrana · L

R Aquarii is a symbiotic star believed to contain a white dwarf and a Mira-type variable in a binary system. It is thought that outbursts occur near or on the surface of the hot, compact, and probably very old star that has already shed its outer layers to become a white dwarf. This star is violently reactivated by large quantities of fresh material falling onto it from its nearby stellar companion.
R Aquarii is one of the closest stars known to undergo violent eruptions that throw out large quantities of processed nuclear material into the surrounding space.
The symbiotic star is at a distance of only 700 lightyears

HR 8992, HD 222800
Mag. max : 5.8
Mag. min : 12.4
Period (day) : 386.96
Spectrum: M5e-M8.5e+pec

Position(2000): RA: 23h43m49.5s, Dec: -15°17m4.0s

Blobrana · L

Title: First Images of R Aquarii and its Asymmetric H_{2}O Shell
Authors: S. Ragland, H. Le Coroller, E. Pluzhnik, W. D. Cotton, W. C. Danchi, J. D. Monnier, W. A. Traub, L. A. Willson, J.-P. Berger, M. G. Lacasse

We report imaging observations of the symbotic long-period Mira variable R Aquarii (R Aqr) at near-infrared and radio wavelengths. The near-infrared observations were made with the IOTA imaging interferometer in three narrow-band filters centred at 1.51, 1.64, and 1.78 \mu m, which sample mainly water, continuum, and water features, respectively. Our near-infrared fringe visibility and closure phase data are analysed using three models. (a) A uniform disk model with wavelength-dependent sizes fails to fit the visibility data, and is inconsistent with the closure phase data. (b) A three- component model, comprising a Mira star, water shell, and an off-axis point source, provide a good fit to all data. (c) A model generated by a constrained image reconstruction analysis provides more insight, suggesting that the water shell is highly non-uniform, i.e., clumpy. The VLBA observations of SiO masers in the outer molecular envelope show evidence of turbulence, with jet-like features containing velocity gradients.

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