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Added by
Denise R. Goncalves
Publication date
2003
fields
Physics
and research's language is
English
Authors
D.R. Goncalves
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The first results on new optical data for R Aquarii (based on observations obtained with the 2.5m INT, the 2.5m NOT and the 3.5m NTT) are presented. The morphology and kinematics of the nebula, based on data obtained with the NTT from 1991 to 2000, are discussed. Physical parameters of the outer nebula and the knotty jet are derived using spectra obtained with the INT in 2001. From the analysis of all these data we propose that the spectacular knotty inner structure of R Aqr could result from the interaction of a highly collimated pulsating young jet with the older hourglass inner nebula.
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We analyse the optical spectra and the UV spectral evolution of the jets and of the HII region inside the R Aquarii binary system by the code SUMA which consistently accounts for shock and photoionization. The temperature of the hot star results 80,000 K as for a white dwarf. We find that the shock velocity in the NE jet increased between 1983 and 1989. The spectral evolution between 1989 and 1991 of the SW jet indicates that a larger contribution from low density-velocity matter affects the 1991 spectra. The evolution of the UV spectra from 8/11/1980 to 26/5/1991 in the HII region indicates that the reverse shock is actually a standing shock. The results obtained by modelling the line spectra are cross-checked by the fit of the continuum SED. It is found that a black-body temperature of 2800 K reproduces the radiation from the red giant. A black-body emission component corresponding to 1000 K is emitted by dust in the surrounding of the red giant. Model calculations confirm that the radio emission is of thermal origin. We found that the NE jet bulk emission is at a distance of about 2 (15) cm from the internal system, while the distance of the SW jet bulk is about 6 (14) cm. The distance of the reverse shock from the hot source in the internal region is < 9 (13) cm.
Multi-epoch phase-referencing VLBI (Very Long Baseline Interferometry) observations with VERA (VLBI Exploration of Radio Astrometry) were performed for the symbiotic star R Aquarii (R Aqr) from September 2005 to Oct 2006. Tracing one of the $v=2$, $J=1-0$ SiO maser spots, we measured an annual parallax of $pi = 4.59pm0.24$ mas, corresponding to a distance of $218_{-11}^{+12}$ pc. Our result is consistent with earlier distance measurements, but yields the highest accuracy of about $5%$ level. Applying our distance, we derived an absolute K-band magnitude of $M_{mathrm{K}} = -7.71 pm 0.11$, which is consistent with the recent Period-Luminosity relation by VLBI parallax measurements for 5 OH-Mira variables. In addition, the expansion age of an inner nebulae around R Aqr is found to be about 240 years, corresponds to about the year 1773.
In this proceeding, we present a short review of the fascinating nebulosities of symbiotic binary R Aquarii. The R Aquarii system, comprising the central binary and surrounding nebular material, has been the subject of near-continuous study since its discovery, with a few hundred papers listed in ADS. As such, it is impossible to provide here the comprehensive review that R Aquarii deserves, instead we chose to focus on the nebulosities -- covering both our own research and other relevant results from the literature.
R Aqr is known to be a symbiotic binary system with an associated extended emission nebula, possibly produced by a historic outburst. To find the associated historic records, we searched for and compiled all Guest Star and Peculiar Star records in three Korean official history books that cover almost two thousand years, Samguksagi, Goryeosa, Joseonwangjosillok. In addition to the record of A.D. 1073, previously noted by Li (1985), we have found in Goryeosa another candidate record of A.D. 1074, which has the same positional description as that of A.D. 1073 with an additional brightness description. We examined various aspects of the two records and conclude that they both are likely to be the records of outburst of R Aqr. This means that there were two successive outbursts in A.D. 1073 and in A.D. 1074, separated by approximately one year. Based on these records, we estimate the distance to R Aqr to be 273 pc if the expansion of the nebula has been at a constant rate. The brightness record of A.D. 1074 corresponds to the absolute magnitude at outburst of M_(outburst) = -6.2 mag. ~ -5.2 mag. at this distance. The two Korean records associated with R Aqr may provide astronomically meaningful constraints to the outburst model of R Aqr and the formative process of its nebulosity.
This survey paper examines the effective model theory obtained with the BSS model of real number computation. It treats the following topics: computable ordinals, satisfaction of computable infinitary formulas, forcing as a construction technique, effective categoricity, effective topology, and relations with other models for the effective theory of uncountable structures.
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