A self-consistent model of a 22 GHz water maser in a dusty environment near late-type stars

Babkovskaia, Natalia; Poutanen, Juri

doi:10.1051/0004-6361:20053609

Cited by 7 publications

(8 citation statements)

References 35 publications

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“…According to our calculations, the gain in the 22.2-GHz maser line is less than 10 −14 cm −1 for such densities. Note that Babkovskaia and Poutanen (2006) showed that the pumping of 22.2-GHz maser in the circumstellar envelopes is more efficient at H 2 number densities 10 7 -10 8 cm −3 and high H 2 O relative abundances, which agrees with our results.…”

Section: Discussionsupporting

confidence: 92%

H2O maser emission in circumstellar envelopes around AGB stars: Physical conditions in gas-dust clouds

Nesterenok

2013

Astron. Lett.

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The pumping of 22.2-GHz H 2 O masers in the circumstellar envelopes of asymptotic giant branch stars has been simulated numerically. The physical parameters adopted in the calculations correspond to those of the circumstellar envelope around IK Tau. The one-dimensional plane-parallel structure of the gas-dust cloud is considered. The statistical equilibrium equations for the H 2 O level populations and the thermal balance equations for the gas-dust cloud are solved self-consistently. The calculations take into account 410 rotational levels belonging to the five lowest vibrational levels of H 2 O. The stellar radiation field is shown to play an important role in the thermal balance of the gas-dust cloud due to the absorption of emission in rotational-vibrational H 2 O lines. The dependence of the gain in the 22.2-GHz maser line on the gas density and H 2 O number density in the gas-dust cloud is investigated. Gas densities close to the mean density of the stellar wind, 10 7 -10 8 cm −3 , and a high relative H 2 O abundance, more than 10 −4 , have been found to be the most likely physical conditions in maser sources.

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Section: Discussionsupporting

confidence: 92%

H2O maser emission in circumstellar envelopes around AGB stars: Physical conditions in gas-dust clouds

Nesterenok

2013

Astron. Lett.

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“…With water closer to the star, it is less susceptible to external forces like interstellar UV radiation that convert water to OH. Also unlike 1612-MHz OH maser emission, water masers are pumped by both radiation and collisions with H2 molecules (Babkovskaia & Poutanen 2006). It is possible that the relative strengths of the maser pumping mechanisms may differ at lower metallicity.…”

Section: Oh Abundancementioning

confidence: 99%

A dearth of OH/IR stars in the Small Magellanic Cloud

Goldman

Loon

Gómez

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present the results of targeted observations and a survey of 1612-, 1665-, and 1667-MHz circumstellar OH maser emission from asymptotic giant branch (AGB) stars and red supergiants (RSGs) in the Small Magellanic Cloud (SMC), using the Parkes and Australia Telescope Compact Array radio telescopes. No clear OH maser emission has been detected in any of our observations targeting luminous, long-period, large-amplitude variable stars, which have been confirmed spectroscopically and photometrically to be mid-to late-M spectral type. These observations have probed 3 − 4 times deeper than any OH maser survey in the SMC. Using a bootstrapping method with LMC and Galactic OH/IR star samples and our SMC observation upper limits, we have calculated the likelihood of not detecting maser emission in any of the two sources considered to be the top maser candidates to be less than 0.05%, assuming a similar pumping mechanism as the LMC and Galactic OH/IR sources. We have performed a population comparison of the Magellanic Clouds and used Spitzer IRAC and MIPS photometry to confirm that we have observed all high luminosity SMC sources that are expected to exhibit maser emission. We suspect that, compared to the OH/IR stars in the Galaxy and LMC, the reduction in metallicity may curtail the dusty wind phase at the end of the evolution of the most massive cool stars. We also suspect that the conditions in the circumstellar envelope change beyond a simple scaling of abundances and wind speed with metallicity.

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“…The gas and dust temperatures in the cloud depend on cooling and heating processes such as gasdust collisions, radiative cooling and heating by starlight. We use the calculation results from [10,11]. The dust and gas temperatures are taken to be equal 400 K and 600 K, respectively.…”

Section: Physical Modelmentioning

confidence: 99%

Simulation of pumping mechanism of H₂O-masers in circumstellar envelopes of late-type stars

Nesterenok¹

2013

J. Phys.: Conf. Ser.

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The radiative transfer problem is considered in dense gas-dust clouds. Physical parameters are adopted in simulations corresponding to gas-dust clouds in the circumstellar envelopes of late-type stars. An one-dimensional plane-parallel slab geometry of the cloud is considered. The radiative transfer problem is solved using the accelerated lambda iteration technique. The rotational levels of the five lowest vibrational levels of H 2 O-molecule are considered in the simulations. The level populations of H 2 O-molecule are computed as a function of distance in the cloud. The conditions of the level population inversion occurrence are investigated. In particular, the factors controlling the population inversion in the 22.2 GHz maser line are considered. A radiative excitation of the molecules by external radiation field of a star is considered together with the collisional pumping of the maser.

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A self-consistent model of a 22 GHz water maser in a dusty environment near late-type stars

Cited by 7 publications

References 35 publications

H2O maser emission in circumstellar envelopes around AGB stars: Physical conditions in gas-dust clouds

H2O maser emission in circumstellar envelopes around AGB stars: Physical conditions in gas-dust clouds

A dearth of OH/IR stars in the Small Magellanic Cloud

Simulation of pumping mechanism of H₂O-masers in circumstellar envelopes of late-type stars

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A self-consistent model of a 22 GHz water maser in a dusty environment near late-type stars

Cited by 7 publications

References 35 publications

H2O maser emission in circumstellar envelopes around AGB stars: Physical conditions in gas-dust clouds

H2O maser emission in circumstellar envelopes around AGB stars: Physical conditions in gas-dust clouds

A dearth of OH/IR stars in the Small Magellanic Cloud

Simulation of pumping mechanism of H2O-masers in circumstellar envelopes of late-type stars

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Product

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Simulation of pumping mechanism of H₂O-masers in circumstellar envelopes of late-type stars