AI canis minoris, a pulsating low-mass supergiant at an early transition phase from the AGB to the post-AGB stage of evolution

Архипова, В. П.; Иконникова, Н. П.; Есипов, В. Ф.; Комиссарова, Г. В.

doi:10.1134/s1063773717060019

Cited by 4 publications

(2 citation statements)

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“…The period of light variations ranges from several dozen days (Arkhipova et al, 2010;Hrivnak et al2015;2018) to Π ≈ 200 day (Arkhipova et al, 2009;Ikonnikova et al, 2018). Moreover, the pulsating variable AI CMi with period Π ≈ 310 day seems to be the early post-AGB star (Arkhipova et al, 2017). A common feature of post-AGB stars is a lack of strict repetition in light variations, so that observational estimates of the period are often highly uncertain.…”

Section: Introductionmentioning

confidence: 99%

“…The period of light variations ranges from several dozen days (Arkhipova et al, 2010; Hrivnak et al2015; 2018) to Π ≈ 200 day (Arkhipova et al Ikonnikova et al, 2018). Moreover, the pulsating variable AI CMi with period Π ≈ 310 day seems to be the early post-AGB star (Arkhipova et al, 2017). A common feature of post-AGB stars is a lack of strict repetition in light variations, so that observational estimates of the period are often highly uncertain.The post-AGB stars are on the late stage of stellar evolution so that comparison of observations with results of evolutionary computations is often accompanied with difficulties arising from uncertainties of the theory (e.g., the mass loss rate on the AGB stage).…”

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confidence: 99%

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Evolution and Pulsations of Population I Post-AGB Stars

Fadeyev

2019

Astron. Lett.

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Evolutionary calculations of population I stars with initial masses M 0 = 1M ⊙ , 1.5M ⊙ and 2M ⊙ were carried out up to the stage of the proto-planetary nebula. Selected models of post-AGB evolutionary sequences with effective temperatures 3.6 × 10 3 K T eff 2 × 10 4 K were used as initial conditions in calculations of self-escited stellar oscillations. For the first time the sequences of hydrodynamic models of radially pulsating post-AGB stars were computed using the self-consistent solution of the equations of radiation hydrodynamics and time-dependent convection. Within this range of effective temperatures the post-AGB stars are the fundamental mode pulsators with period decreasing as the star evolves from Π ≈ 300 day to several days. Period fluctuations are due to nonlinear effects and are most prominent at effective temperatures T eff < 5000 K. The amplitude of bolometric light variations is ∆M bol ≈ 1 at T eff 6000 K and rapidly decreases with increasing T eff . The theoretical dependence of the pulsation period as a function of effective temperature obtained in the study can be used as a criterion for the evolutionary status of pulsating variables suspected to be post-AGB stars. 1 introduction The red giant evolutionary stage of stars with solar composition and the zero-age main sequence mass M 0 9M ⊙ is completed due to the strong stellar wind and the loss of the major fraction of the hydrogen envelope. The star leaves the asymptotic giant branch (AGB) and crosses the Hertzsprung-Russel diagram (HRD) at nearly constant luminosity towards the region of planetary nebula cores with effective temperatures T eff ∼ 10 5 K. An idea that the planetary nebulae originate from red giants was suggested by Shklovsky (1956) and was later confirmed by evolutionary computations (PaczyńskiFormation of the opaque gas-dust envelope surrounding the star on the tip of the AGB substantially restricts abilities of optical observations, so that the evolutionary transition to the post-AGB stage still remains unclear. The strong stellar wind on the tip of the AGB seems to be due to nonlinear stellar pulsations that lead to dynamical instability of the outer stellar layers (Tuchman et al., 1978). Therefore, large infrared (IR) excesses detected in post-AGB stars (Volk, Kwok, 1989; Hrivnak et al., 1989; 1994; Ikonnikova et al., 2018) indicate existence of circumstellar dust grains condensed during the preceding evolutionary stage with high mass loss rates. The photometric variability due to stellar pulsations is a typical property of post-AGB stars. The period of light variations ranges from several dozen days (Arkhipova et al., 2010; Hrivnak et al.2015; 2018) to Π ≈ 200 day (Arkhipova et al. Ikonnikova et al., 2018). Moreover, the pulsating variable AI CMi with period Π ≈ 310 day seems to be the early post-AGB star (Arkhipova et al., 2017). A common feature of post-AGB stars is a lack of strict repetition in light variations, so that observational estimates of the period are often highly uncertain.The post-AGB stars are on the late...

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

Evolution and Pulsations of Population I Post-AGB Stars

Fadeyev

2019

Astron. Lett.

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An infrared study of Galactic OH/IR stars – III. Variability properties of the Arecibo sample

Jiménez-Esteban

Engels

Aguado

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We present the results of a near-infrared (NIR) monitoring program carried out between 1999 and 2005 to determine the variability properties of the ‘Arecibo sample of OH/IR stars’. The sample consists of 385 IRAS-selected Asymptotic Giant Branch (AGB) candidates, for which their O-rich chemistry has been proven by the detection of 1612 MHz OH maser emission. The monitoring data was complemented by data collected from public optical and NIR surveys. We fitted the light curves obtained in the optical and NIR bands with a model using an asymmetric cosine function, and derived a period for 345 sources (∼90 per cent of the sample). Based on their variability properties, most of the Arecibo sources are classified as long-period large-amplitude variable stars (LPLAV), 4 per cent as (candidate) post-AGB stars, and 3 per cent remain unclassified although they are likely post-AGB stars or highly obscured AGB stars. The period distribution of the LPLAVs peaks at ∼400 days, with periods between 300 and 800 days for most of the sources, and has a long tail up to ∼2100 days. Typically, the amplitudes are between 1 and 3 mag in the NIR and between 2 and 6 mag in the optical. We find correlations between periods and amplitudes, with larger amplitudes associated to longer periods, as well as between the period and the infrared colours, with the longer periods linked to the redder sources. Among the post-AGB stars, the light curve of IRAS 19566+3423 was exceptional, showing a large systematic increase (> 0.4 mag yr−1) in K-band brightness over 7 years.

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