Evolutionary Status of the Ap Stars HD 110066 and HD 153882

In this paper some thoughts and problems are presented from the viewpoint that the evolution of stars may play a key role in generating magnetic fields which, in turn, may affect the mixing of nuclearly processed elements from the stellar interior to the surface. The relevant parameter is stellar rotation which, upon interaction with convective turbulence driven by thermal instabilities, leads to the generation of magnetic fields. A possible connection to Bidelman's hypothesis on the evolutionary status of Ap stars is also discussed in the context of a post-core-helium-flash hypothesis.

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Fundamental parameters and evolutionary status of the magnetic chemically peculiar stars HD 188041 (V1291 Aquilae), HD 111133 (EP Virginis), and HD 204411: spectroscopy versus interferometry

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1858 ◽

2019 ◽

Vol 488 (2) ◽

pp. 2343-2356 ◽

Cited By ~ 3

Author(s):

A Romanovskaya ◽

T Ryabchikova ◽

D Shulyak ◽

K Perraut ◽

G Valyavin ◽

...

Keyword(s):

Chemical Composition ◽

Measurement Errors ◽

Chemical Elements ◽

Model Fitting ◽

Evolutionary Status ◽

Fundamental Parameters ◽

Chemically Peculiar ◽

Peculiar Stars ◽

Chemically Peculiar Stars ◽

Ap Stars

ABSTRACT The determination of fundamental parameters of stars is one of the main tasks of astrophysics. For magnetic chemically peculiar stars, this problem is complicated by the anomalous chemical composition of their atmospheres, which requires special analysis methods. We present the results of the effective temperature, surface gravity, abundance, and radius determinations for three CP stars HD 188041, HD 111133, and HD 204411. Our analysis is based on a self-consistent model fitting of high-resolution spectra and spectrophotometric observations over a wide wavelength range, taking into account the anomalous chemical composition of atmospheres and the inhomogeneous vertical distribution for three chemical elements: Ca, Cr, and Fe. For two stars, HD 188041 and HD 204411, we also performed interferometric observations that provided us with the direct estimates of stellar radii. Comparison of the radii determined from the analysis of spectroscopic/spectrophotometric observations with direct measurements of the radii by interferometry methods for seven CP stars shows that the radii agree within the limits of measurement errors, which proves indirect spectroscopic analysis capable of proving reliable determinations of the fundamental parameters of fainter Ap stars that are not possible to study with modern interferometric facilities.

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Magnetic Ap Stars: Evolutionary Status and Abundance Anomalies

Evolution of Stars: The Photospheric Abundance Connection ◽

10.1007/978-94-011-3416-3_14 ◽

1991 ◽

pp. 149-160 ◽

Cited By ~ 7

Author(s):

T. A. Ryabchikova

Keyword(s):

Evolutionary Status ◽

Abundance Anomalies ◽

Ap Stars

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Magnetic Ap Stars: Evolutionary Status and Abundance Anomalies

Symposium - International Astronomical Union ◽

10.1017/s0074180900227332 ◽

1991 ◽

Vol 145 ◽

pp. 149-160 ◽

Cited By ~ 3

Author(s):

T. A. Ryabchikova

Keyword(s):

Magnetic Field ◽

Diffusion Theory ◽

Point Of View ◽

Evolutionary Status ◽

Chemical Abundance ◽

General Properties ◽

Radiative Diffusion ◽

Abundance Anomalies ◽

Ap Stars

Some general properties and evolutionary status of magnetic Ap stars are briefly considered. Chemical abundance anomalies are discussed from the point of view of current theories presumably the radiative diffusion theory in the presence of magnetic field.

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The Photometric Properties of the Ap Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100080684 ◽

1976 ◽

Vol 32 ◽

pp. 365-377 ◽

Cited By ~ 2

Author(s):

B. Hauck

Keyword(s):

Physical Properties ◽

Ap Stars

The Ap stars are numerous - the photometric systems tool It would be very tedious to review in detail all that which is in the literature concerning the photometry of the Ap stars. In my opinion it is necessary to examine the problem of the photometric properties of the Ap stars by considering first of all the possibility of deriving some physical properties for the Ap stars, or of detecting new ones. My talk today is prepared in this spirit. The classification by means of photoelectric photometric systems is at the present time very well established for many systems, such as UBV, uvbyβ, Vilnius, Geneva and DDO systems. Details and methods of classification can be found in Golay (1974) or in the proceedings of the Albany Colloquium edited by Philip and Hayes (1975).

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Variation of Heavy Element Lines in the Ap Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100080623 ◽

1976 ◽

Vol 32 ◽

pp. 311-320 ◽

Cited By ~ 1

Author(s):

I.A. Aslanov ◽

Yu. S. Rustamov ◽

M. Kowalski

Keyword(s):

Heavy Element ◽

Ap Stars

SummaryLines of U II were found in the spectrograms of the Ap stars HR 465, 17 Com A and HD 224801. Pm II lines were found in HR 465. These lines vary in intensity in HR 465 with a period of 6h41m, in 17 Com A of 71m, and in HD 224801 of 6h.

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Peculiarity Parameters

International Astronomical Union Colloquium ◽

10.1017/s0252921100080581 ◽

1976 ◽

Vol 32 ◽

pp. 233-254

Author(s):

H. M. Maitzen

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Theoretical Work ◽

Observational Evidence ◽

Rotator Model ◽

Peculiar Behaviour ◽

Field Spectrum ◽

Oblique Rotator ◽

Ap Stars ◽

The Way

Ap stars are peculiar in many aspects. During this century astronomers have been trying to collect data about these and have found a confusing variety of peculiar behaviour even from star to star that Struve stated in 1942 that at least we know that these phenomena are not supernatural. A real push to start deeper theoretical work on Ap stars was given by an additional observational evidence, namely the discovery of magnetic fields on these stars by Babcock (1947). This originated the concept that magnetic fields are the cause for spectroscopic and photometric peculiarities. Great leaps for the astronomical mankind were the Oblique Rotator model by Stibbs (1950) and Deutsch (1954), which by the way provided mathematical tools for the later handling pulsar geometries, anti the discovery of phase coincidence of the extrema of magnetic field, spectrum and photometric variations (e.g. Jarzebowski, 1960).

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Nuclear Processes Related to the Ap Stars and the Heaviest Chemical Elements

International Astronomical Union Colloquium ◽

10.1017/s0252921100080520 ◽

1976 ◽

Vol 32 ◽

pp. 169-182

Author(s):

B. Kuchowicz

Keyword(s):

Nuclear Physics ◽

Nuclear Reactions ◽

Chemical Elements ◽

Fission Products ◽

Abundance Pattern ◽

Isotopic Shifts ◽

Processed Material ◽

R Process ◽

Ap Stars ◽

Nuclear Processes

SummaryIsotopic shifts in the lines of the heavy elements in Ap stars, and the characteristic abundance pattern of these elements point to the fact that we are observing mainly the products of rapid neutron capture. The peculiar A stars may be treated as the show windows for the products of a recent r-process in their neighbourhood. This process can be located either in Supernovae exploding in a binary system in which the present Ap stars were secondaries, or in Supernovae exploding in young clusters. Secondary processes, e.g. spontaneous fission or nuclear reactions with highly abundant fission products, may occur further with the r-processed material in the surface of the Ap stars. The role of these stars to the theory of nucleosynthesis and to nuclear physics is emphasized.

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On The Radii of Ap Stars

International Astronomical Union Colloquium ◽

10.1017/s025292110008043x ◽

1976 ◽

Vol 32 ◽

pp. 49-55 ◽

Cited By ~ 1

Author(s):

F.A. Catalano ◽

G. Strazzulla

Keyword(s):

Observational Data ◽

Line Width ◽

Main Sequence ◽

Main Sequence Stars ◽

Ap Stars

SummaryFrom the analysis of the observational data of about 100 Ap stars, the radii have been computed under the assumption that Ap are main sequence stars. Radii range from 1.4 to 4.9 solar units. These values are all compatible with the Deutsch's period versus line-width relation.

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Gaia DR2 data and the evolutionary status of eight high-velocity hot post-AGB candidates

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psaa097 ◽

2020 ◽

Vol 72 (6) ◽

Author(s):

Mudumba Parthasarathy ◽

Tadafumi Matsuno ◽

Wako Aoki

Keyword(s):

Effective Temperature ◽

High Velocity ◽

Circumstellar Dust ◽

Evolutionary Status ◽

Agb Stars ◽

Horizontal Branch ◽

Dust Shells ◽

The Past ◽

Gaia Dr2 ◽

Branch Star

Abstract From Gaia DR2 data of eight high-velocity hot post-AGB candidates, LS 3593, LSE 148, LS 5107, HD 172324, HD 214539, LS IV −12 111, LS III +52 24, and LS 3099, we found that six of them have accurate parallaxes which made it possible to derive their distances, absolute visual magnitudes (MV) and luminosity (log L/L⊙). All the stars except LS 5107 have an accurate effective temperature (Teff) in the literature. Some of these stars are metal poor, and some of them do not have circumstellar dust shells. In the past, the distances of some stars were estimated to be 6 kpc, which we find to be incorrect. The accurate Gaia DR2 parallaxes show that they are relatively nearby, post-AGB stars. When compared with post-AGB evolutionary tracks we find their initial masses to be in the range 1 M⊙ to 2 M⊙. We find the luminosity of LSE 148 to be significantly lower than that of post-AGB stars, suggesting that this is a post-horizontal-branch star or post-early-AGB star. LS 3593 and LS 5107 are new high-velocity hot post-AGB stars from Gaia DR2.

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