The instability strip and pulsation features of post-AGB star models

Aikawa, Toshiki

doi:10.1051/0004-6361/200912991

Cited by 11 publications

(12 citation statements)

References 33 publications

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“…Pulsation periods and amplitudes, together with the determined temperatures, can potentially be used with stellar pulsational models to determine the masses and luminosities of these evolved objects (Fokin et al 2001;Aikawa 2010). These derived values can be compared to theoretical massluminosity relationships derived for post-AGB stars (Vassiliadis & Wood 1994;Blöcker 1995).…”

Section: Discussionmentioning

confidence: 99%

Variability in Proto-Planetary Nebulae. Iv. Light Curve Analysis of Four Oxygen-Rich, F Spectral Type Objects

Hrivnak¹,

Lu²,

Nault³

2015

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We present new light curves covering 14-19 years of observations of four bright proto-planetary nebulae (PPNs), all oxygen-rich and of F spectral type. They each display cyclical light curves with significant variations in amplitude. All four were previously known to vary in light. Our data were combined with published data and searched for periodicity. The results are as follows: IRAS 19475+3119 (HD 331319; 41.0 days), 17436+5003 (HD 161796; 45.2 days), 19386+0155 (101.8 days), and 18095+2704 (113.3 days). The two longer periods are in agreement with previous studies while the two shorter periods each reveal for the first time a dominant period over these long observing intervals. Multiple periods were also found for each object. The secondary periods were all close to the dominant periods, with P 2 /P 1 ranging from 0.86 to 1.06. The variations in color reveal maximum variations in T eff of 400-770 K. These variations are due to pulsations in these post-asymptotic giant branch objects. Maximum seasonal light variations are all less than 0.23 mag (V), consistent for their temperatures and periods with the results of Hrivnak et al. for 12 C-rich PPNs. For all of these PPNs, there is an inverse relationship between period and temperature; however, there is a suggestion that the period-temperature relationship may be somewhat steeper for the O-rich than for the C-rich PPNs.

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Section: Discussionmentioning

confidence: 99%

Variability in Proto-Planetary Nebulae. Iv. Light Curve Analysis of Four Oxygen-Rich, F Spectral Type Objects

Hrivnak¹,

Lu²,

Nault³

2015

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“…The matter of an AGB star is lost through two processes: firstly, carbon and oxygen produced during the nucleosynthesis join the degenerate C-O core (which changes the character of energy release), secondly, the matter is lost owing to wind from the surface of the star. As a result, the AGB star loses from 50% to 85% of its initial mass [12]. Due to the matter loss, an optically thick envelope is formed around the star, and the star becomes difficult to observe in the optical range.…”

Section: Introductionmentioning

confidence: 99%

“…At some point in the AGB star lifetime its mass loss rate suddenly increases dramatically. One of the reasons for the large mass loss rate increase can be the pulsating instability of supergiants, which is inherent, according to [12], to the stars on this evolutionary stage in a fairly wide range of fundamental parameters. Two physical phenomena: the synthesis of heavy metals and the pulsation activity characteristic of stars on the AGB stage and after it, determine the main interest in these objects.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopy of Supergiants with Infrared Excess: Results of 1998–2018

Клочкова

2019

Astrophys. Bull.

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The results of our second stage of the detailed spectroscopy of peculiar supergiants identified with galactic infrared sources, performed at the 6-meter BTA telescope are summarized. The main aspect of the program is a search for the evolutionary variations in the chemical composition of stars, past the AGB stage and the TDU, as well as an analysis of spectral manifestations of kinematic processes in their extended, often unstable, atmospheres and in the envelopes. The most significant result is detection of the s-process element excesses in seven single post-AGB stars, which confirms the theory of evolution of this type of stars. In three of these stars we for the first time discovered the ejection of the s-process heavy metals to the circumstellar envelopes. A Li excess was found in the atmospheres of peculiar supergiants V2324 Cyg and V4334 Sgr. The results of investigation of the kinematical parameters of atmospheres and envelopes will clarify the equilibrium of matter produced by stars in the AGB and post-AGB stages and delivered to the interstellar medium.

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“…There is no published evidence that BD+39°4926 has a variable brightness. However, the cooler HD46703 lies in a high-luminosity extension of the RRLyrae pulsational instability strip; it is a semiregular variable with a range of ∼0.3mag and a main period of about 29days Hrivnak et al 2008;Aikawa 2010).…”

Section: Introductionmentioning

confidence: 99%

A Luminous Yellow Post-Agb Star in the Galactic Globular Cluster M79*

Bond

Ciardullo

Siegel

2016

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We report the discovery of a luminous F-type post-asymptotic-giant-branch (PAGB) star in the Galactic globular cluster (GC) M79 (NGC1904). At visual apparent and absolute magnitudes of V 12.20 = and M 3.46 V = -, this "yellow" PAGB star is by a small margin the visually brightest star known in any GC. It was identified using CCD observations in the uBVI photometric system, which is optimized to detect stars with large Balmer discontinuities, indicative of very low surface gravities. Follow-up observations with the SMARTS 1.3 and 1.5 m telescopes show that the star is not variable in light or radial velocity, and that its velocity is consistent with cluster membership. Near-and mid-infrared observations with 2MASS and WISE show no evidence for circumstellar dust. We argue that a sharp upper limit to the luminosity function exists for yellow PAGB stars in old populations, making them excellent candidates for PopulationII standard candles, which are four magnitudes brighter than RRLyrae variables. Their luminosities are consistent with the stars being in a PAGB evolutionary phase, with core masses of M 0.53  . We also detected four very hot stars lying above the horizontal branch ("AGB-manqué" stars); along with the PAGB star, they are the brightest objects in M79 in the near-ultraviolet. In the Appendix, we give periods and light curves for five variables in M79: three RRLyrae stars, a TypeII Cepheid, and a semiregular variable.

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The instability strip and pulsation features of post-AGB star models

Cited by 11 publications

References 33 publications

Variability in Proto-Planetary Nebulae. Iv. Light Curve Analysis of Four Oxygen-Rich, F Spectral Type Objects

Variability in Proto-Planetary Nebulae. Iv. Light Curve Analysis of Four Oxygen-Rich, F Spectral Type Objects

Spectroscopy of Supergiants with Infrared Excess: Results of 1998–2018

A Luminous Yellow Post-Agb Star in the Galactic Globular Cluster M79*

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