VLBI Astrometry of the Semiregular Variable RX Bootis

Kamezaki, Tatsuya; Nakagawa, Akiharu; Omodaká, Toshihiro; Kurayama, Tomoharu; Imai, Hiroshi; Tafoya, Daniel; Matsui, Makoto; Nishida, Yukari; Nagayama, Tomonori; Honma, Mareki; Kobayashi, Hideyuki; Miyaji, Takeshi; Takeuti, M.

doi:10.1093/pasj/64.1.7

Cited by 21 publications

(10 citation statements)

References 33 publications

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“…(Kamezaki et al 2012). Of particular interest are the astrometric measurements for the symbiotic system R Aqr (Kamohara et al 2010) and the parallax distance of 218…”

Section: Asymptotic Giant Branch Starsmentioning

confidence: 99%

Microarcsecond Radio Astrometry

Reid

Honma

2014

Annu. Rev. Astron. Astrophys.

177

191

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Astrometry provides the foundation for astrophysics. Accurate positions are required for the association of sources detected at different times or wavelengths, and distances are essential to estimate the size, luminosity, mass, and ages of most objects. Very Long Baseline Interferometry at radio wavelengths, with diffraction-limited imaging at sub-milliarcsec resolution, has long held the promise of micro-arcsecond astrometry. However, only in the past decade has this been routinely achieved. Currently, parallaxes for sources across the Milky Way are being measured with ∼ 10 µas accuracy and proper motions of galaxies are being determined with accuracies of ∼ 1 µas y −1 . The astrophysical applications of these measurements cover many fields, including star formation, evolved stars, stellar and super-massive black holes, Galactic structure, the history and fate of the Local Group, the Hubble constant, and tests of general relativity. This review summarizes the methods used and the astrophysical applications of micro-arcsecond radio astrometry.

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“…(Kamezaki et al 2012). Of particular interest are the astrometric measurements for the symbiotic system R Aqr (Kamohara et al 2010) and the parallax distance of 218…”

Section: Asymptotic Giant Branch Starsmentioning

confidence: 99%

Microarcsecond Radio Astrometry

Reid

Honma

2014

Annu. Rev. Astron. Astrophys.

177

191

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“…All references are given in Tables A.1-A.4. For the S-type stars, a comparison between the IRAM 30 m line intensities published in Wallerstein et al (2011) and in Ramstedt et al (2009) Kamezaki et al (2012). (b) Vlemmings et al (2003).…”

Section: Co Radio Line Observationsmentioning

confidence: 99%

The¹²CO/¹³CO ratio in AGB stars of different chemical type

Ramstedt

Olofsson

2014

A&A

103

137

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Aims. The aim of this paper is to investigate the evolution of the 12 C/ 13 C ratio along the AGB through the circumstellar 12 CO/ 13 CO abundance ratio. This is the first time a sample including a significant number of M-and S-type stars is analysed together with a carbon-star sample of equal size, making it possible to investigate trends among the different types and establish evolutionary effects. Methods. The circumstellar 12 CO/ 13 CO abundance ratios are estimated through a detailed radiative transfer analysis of single-dish radio line emission observations. Several different transitions have been observed for each source to ensure that a large extent of the circumstellar envelope is probed and the radiative transfer model is well constrained. The radiative transfer model is based on the Monte Carlo method and has been benchmarked against a set of similar codes. It assumes that the radiation field is non-local and solves the statistical equilibrium equations in full non-local thermodynamic equilibrium. The energy balance equation, determining the gas temperature distribution, is solved self-consistently, and the effects of thermal dust radiation (as estimated from the spectral energy distribution) are taken into account. First, the 12 CO radiative transfer is solved, assuming an abundance (dependent on the chemical type of the star), to give the physical parameters of the gas, i.e. mass-loss rate,Ṁ, gas expansion velocity, υ e , and gas temperature distribution. Then, the 13 CO radiative transfer is solved using the results of the 12 CO model giving the 13 CO abundance. Finally, the 12 CO/ 13 CO abundance ratio is calculated. Results. The circumstellar 12 CO/ 13 CO abundance ratio differs between the three spectral types. This is consistent with what is expected from stellar evolutionary models assuming that the spectral types constitute an evolutionary sequence; however, this is the first time this has been shown observationally for a relatively large sample covering all three spectral types. The median value of the 13 CO abundance in the inner circumstellar envelope is 1.6 × 10 −5 , 2.3 × 10 −5 , and 3.0 × 10 −5 for the M-type, S-type, and carbon stars of the sample, respectively, corresponding to 12 CO/ 13 CO abundance ratios of 13, 26, and 34, respectively. The spread in the 13 CO abundance, quantified by the ratio between the 90th and 10th percentile, is 4, 3, and 15 for the M-type, S-type, and carbon stars, respectively. Interestingly, the abundance ratio spread of the carbon stars is much larger than for the M-and S-type stars, even when excluding J-type carbon stars, in line with what could be expected from evolution on the AGB. We find no correlation between the isotopologue ratio and the mass-loss rate, as would be expected if both increase as the star evolves.

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“…An apparent K−band magnitude of −1.85 is converted to an absolute magnitude of −7.35 +0.15 −0.14 mag based on the parallax measurement. This source is reported to have different pulsation periods pulsation periods, which are summarised in table 4 of Kamezaki et al (2012). We found that they can be classified into two typical values, ∼160 days and over ∼ 320 days.…”

Section: Semi-regular Variable Rx Boomentioning

confidence: 79%

“…From the position of the source on log P − M K plane, one can study the stellar structure and pulsation properties. Kamezaki et al (2012) compared the M K and dual periods with the P-L relation in the Magellanic Clouds (Ita et al, 2004). Then it was found that RX Boo belongs to the sequence C (pulsating in fundamental mode) at longer period, and belongs to the sequence C' (pulsating in first-over tone mode) at shorter period.…”

Section: Semi-regular Variable Rx Boomentioning

confidence: 99%

Young and Intermediate-Age Distance Indicators

et al. 2017

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Distance measurements beyond geometrical and semi-geometrical methods, rely mainly on standard candles. As the name suggests, these objects have known luminosities by virtue of their intrinsic proprieties and play a major role in our understanding of modern cosmology. The main caveats associated with standard candles are their absolute calibration, contamination of the sample from other sources and systematic uncertainties. The absolute calibration mainly de-

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VLBI Astrometry of the Semiregular Variable RX Bootis

Cited by 21 publications

References 33 publications

Microarcsecond Radio Astrometry

Microarcsecond Radio Astrometry

The¹²CO/¹³CO ratio in AGB stars of different chemical type

Young and Intermediate-Age Distance Indicators

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VLBI Astrometry of the Semiregular Variable RX Bootis

Cited by 21 publications

References 33 publications

Microarcsecond Radio Astrometry

Microarcsecond Radio Astrometry

The12CO/13CO ratio in AGB stars of different chemical type

Young and Intermediate-Age Distance Indicators

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Product

Resources

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The¹²CO/¹³CO ratio in AGB stars of different chemical type