The detection of heavy metals in the circumstellar envelopes of post-AGB stars

Клочкова, В. Г.; Панчук, В. Е.

doi:10.1134/s1063772916030082

Cited by 9 publications

(13 citation statements)

References 48 publications

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“…This expansion of the task required conducting for each program object of multiple observations with high spectral resolution in a broad wavelength range. The main results we have obtained from the spectroscopic data at the 6-m telescope are summarized in a number of recent publications [2,3,4]. Let us briefly note the most important of them.…”

Section: Introductionmentioning

confidence: 99%

On the Evolutionary State of High-Latitude Variable V534 Lyr

2018

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Based on the high resolution spectral monitoring conducted at the 6-m BTA telescope, we study the optical spectrum of the high-latitude variable V534 Lyr. Heliocentric radial velocities V r corresponding to the positions of all metal absorption components, as well as the Na I D and Hα lines were measured during all the observational dates. The analysis of the velocity field examining the lines of various nature revealed a low-amplitude variability of V r based on the lines with a high excitation potential, which are formed in deep layers of the stellar atmosphere, and allowed to estimate the systemic velocity of V sys ≈ −125 km s −1 (V lsr ≈ −105 km s −1 ). The distance estimate of d ≈ 6 kpc for the star leads us to its absolute magnitude of M V ≈ −5. m 3, what corresponds to the MK spectral classification. The previously undetected for this star spectral phenomenon was revealed: at certain times a splitting of the profiles of low-excited absorptions is observed, reaching ∆V r = 20-50 km s −1 . A combination of the parameters: reduced metallicity [Met/H] ⊙ = −0.28, increased nitrogen abundance [N/Fe] = +1.10, large spatial velocity, high luminosity, a strong variability of the emission-absorption profiles of H I lines, splitting of metal absorptions at different times of observations and the variability of the velocity field in the atmosphere allow us to classify V534 Lyr as a pulsating star near the HB and belonging to the thick disk of our Galaxy.

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Section: Introductionmentioning

confidence: 99%

On the Evolutionary State of High-Latitude Variable V534 Lyr

2018

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“…For example, as part of the PPN spectroscopy program, we studied the optical spectrum of IRAS 23304+6147 in detail [29] (Galactic coordinates l/b≈ 113 • /0 • ). This remote object belongs to a small subgroup of PPN with atmospheres enriched in s-process products [13]. In the current context, it is important that an interstellar component of the Na I (1) lines with the velocity Vr(IS) =−61.6 km/s was identified in the optical spectrum of IRAS 23304+6147 [16], similar to the case of RAFGL 5081.…”

Section: Discussion Of the Resultsmentioning

confidence: 84%

“…In particular, the analysis of the extensive collection of high-quality echelle spectra of post-AGB stars enabled the detection of previously unknown features in the spectra of selected post-AGB stars with atmospheres enriched in carbon and heavy s-process metals and circumstellar envelopes containing carbon molecules: splitting (or asymmetric) strong absorption lines [2,13]. Using published IR and radio spectroscopic data, it was shown that the individual components of the split absorptions are formed in the structured circumstellar envelopes of post-AGB stars [2].…”

Section: Discussion Of the Resultsmentioning

confidence: 99%

Non-stationary wind in the system of the infrared source RAFGL 5081

Клочкова¹,

Ченцов²,

Панчук³

et al. 2017

Astron. Rep.

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For the first time, based on long-term spectral monitoring with high spectral resolution, the optical spectrum of the weak central star of the IR source RAFGL 5081 has been studied. The spectral type of this star is close to G5÷8 II, and its effective temperature is Teff≈5400 K. An unusual spectral phenomenon was discovered: splitting of the profiles of broad, stationary absorption lines of medium and low intensity. The heliocentric radial velocities Vr of all components of metal absorption lines, the Na I D lines, and the Hα line were measured for all the observation epochs. The constancy of the absorption lines rules out the possibility that the line splitting is due to binarity. The radial velocities of the wind components in the profiles of the Na I D and Hα lines reach −250 and −600 km/s, respectively. These profiles have narrow components, whose number, depth, and position vary with time. The time variability and multicomponent structure of the profiles of the Na I D and Hα lines indicates inhomogeneity and instability of the circumstellar envelope of RAFGL 5081. The presence of components with velocity Vr(IS) =65 km/s in the Na I (1) lines provides evidence that RAFGL 5081 is located behind the Perseus arm, i.e, no closer than 2 kpc. It is noted that RAFGL 5081 is associated with the reflection nebula GN 02.44.7.

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“…The absence of the expected excess of heavy metals with respect to iron is a fact known for post-AGB supergiants. The deficiency of the s-process elements in the atmospheres of post-AGB stars is observed much more often than their excess [25,[49][50][51]. The presence or absence of an excess of the s-process elements is associated with the initial mass of a star and the mass loss rate at the AGB stage, which determine the evolution of an individual star and the mass of the stellar core [6].…”

Section: Heavy Metalsmentioning

confidence: 99%

“…The deficiency of heavy metals in the atmosphere of the star under study could have been be predicted due to the belonging of IRAS 19386+0155 to O-rich sources, as an excess of s-process elements is usually associated with a carbon excess in the atmosphere of a star having a carbon-rich envelope [25]. The estimated excess of europium [X/Fe] ⊙ =0.50 synthesized mainly in the rapid neutron capture reactions (the r-process) is typical of the atmospheres of post-AGB stars (see examples in papers [18,50,51]).…”

Section: Heavy Metalsmentioning

confidence: 99%

Optical Spectrum of Distant OH/IR Star V1648 Aql (IRAS 19386+0155)

Клочкова

Tavolzhanskaya

2019

Astrophys. Bull.

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An optical spectrum of the star V1648 Aql (= IRAS 19386+0155) was obtained at the 6-meter telescope with a spectral resolution of R≥ 60 000. Heliocentric radial velocity measured from numerous metallic absorptions is equal to V r =10.18±0.05 km s −1 (V LSR =18.1 km s −1 ). We determined the atmospheric, circumstellar, and interstellar components in the profile of the Na I D lines at V r =9.2, −3.4, and −12.8 km s −1 respectively. The averaged over twenty identified DIBs velocity V r (DIBs)=−12.5 ± 0.2 km s −1 coincides with the interstellar Na I component. Weak emissions with an intensity of about 10% of the local continuum level were detected in the spectrum; they are identified as low-excitation metal lines. Their averaged position, V r =8.44±0.28 km s −1 , may point to the presence of a weak velocity gradient in the upper layers of the stellar atmosphere. Based on the spectroscopic data and taking into account the interstellar and circumstellar reddening, we estimated the star's luminosity M V ≈ −5 m and also obtained the lower estimate of distance d≥ 1.8 kpc. Using the model atmosphere method, we determined the fundamental parameters and chemical abundances in the atmosphere approving the status of a post-AGB star for V1648 Aql.

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The detection of heavy metals in the circumstellar envelopes of post-AGB stars

Cited by 9 publications

References 48 publications

On the Evolutionary State of High-Latitude Variable V534 Lyr

On the Evolutionary State of High-Latitude Variable V534 Lyr

Non-stationary wind in the system of the infrared source RAFGL 5081

Optical Spectrum of Distant OH/IR Star V1648 Aql (IRAS 19386+0155)

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