Remarks on Difference of Properties of Am and Ap Stars

10.1017/s0252921100080684 ◽

1976 ◽

Vol 32 ◽

pp. 365-377 ◽

Cited By ~ 2

Author(s):

B. Hauck

Keyword(s):

Physical Properties ◽

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).

Variation of Heavy Element Lines in the Ap Stars

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 ◽

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.

Peculiarity Parameters

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).

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

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.

On The Radii of Ap Stars

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 ◽

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.

Broadband Linear Polarization in Ap Stars

10.1017/s0252921100020662 ◽

1993 ◽

Vol 138 ◽

pp. 305-309

Author(s):

Marco Landolfi ◽

Egidio Landi Degl’Innocenti ◽

Maurizio Landi Degl’Innocenti ◽

Jean-Louis Leroy ◽

Stefano Bagnulo

Keyword(s):

Magnetic Field ◽

Circular Polarization ◽

Linear Polarization ◽

Rotation Axis ◽

Spectral Lines ◽

Line Of Sight ◽

Long Time ◽

Rotating Star ◽

Ap Stars ◽

The Magnetic Field

AbstractBroadband linear polarization in the spectra of Ap stars is believed to be due to differential saturation between σ and π Zeeman components in spectral lines. This mechanism has been known for a long time to be the main agent of a similar phenomenon observed in sunspots. Since this phenomenon has been carefully calibrated in the solar case, it can be confidently used to deduce the magnetic field of Ap stars.Given the magnetic configuration of a rotating star, it is possible to deduce the broadband polarization at any phase. Calculations performed for the oblique dipole model show that the resulting polarization diagrams are very sensitive to the values of i (the angle between the rotation axis and the line of sight) and β (the angle between the rotation and magnetic axes). The dependence on i and β is such that the four-fold ambiguity typical of the circular polarization observations ((i,β), (β,i), (π-i,π-β), (π-β,π-i)) can be removed.

Multiplicity of rapidly oscillating Ap stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201118538 ◽

2012 ◽

Vol 545 ◽

pp. A38 ◽

Cited By ~ 10

Author(s):

M. Schöller ◽

S. Correia ◽

S. Hubrig ◽

D. W. Kurtz

Keyword(s):

An evolutionary study of magnetic Ap stars in 4 northern open clusters

EAS Publications Series ◽

10.1051/eas:2005139 ◽

2005 ◽

Vol 17 ◽

pp. 349-352

Author(s):

J. Silvester ◽

G.A. Wade ◽

D.A. Hanes

Keyword(s):

Open Clusters ◽

Evolutionary Study ◽

29. Stellar Spectra

Transactions of the International Astronomical Union ◽

10.1017/s0251107x00004739 ◽

1982 ◽

Vol 18 (1) ◽

pp. 343-360 ◽

Cited By ~ 1

Author(s):

W.K. Bonsack

Keyword(s):

Stellar Evolution ◽

Working Group ◽

Main Sequence ◽

Symbiotic Stars ◽

Be Stars ◽

Stellar Spectra ◽

Chemically Peculiar ◽

Peculiar Stars ◽

Chemically Peculiar Stars ◽

During the interval covered by this report, Commission 29 has sponsored or cosponsored the following IAU meetings: Symposium 98 on “Be Stars,” Munich, FRG, April 1981; Colloquium 59, “Effects of Mass-Loss on Stellar Evolution,” Trieste, Italy, September 1980; and Colloquim 70, “The Nature of Symbiotic Stars,” Haute-Provence, France, August 1981. In addition, Commission 29, through its Working Group on Ap Stars, collaborated in the organization of the 23rd Liege International Astrophysical Symposium on Upper Main-Sequence Chemically Peculiar Stars. Several IAU symposia and colloquia proposed for 1982 and 1983 are also cosponsored by Commission 29.

A New Opacity-Sampling Model Atmosphere Program for Arbitrary Abundances

10.1017/s0252921100020327 ◽

1993 ◽

Vol 138 ◽

pp. 87-97 ◽

Cited By ~ 18

Author(s):

Robert L. Kurucz

Keyword(s):

Distribution Function ◽

Energy Level ◽

Lower Energy ◽

Van Der Waals ◽

Model Atmosphere ◽

Function Model ◽

Elemental Abundances ◽

Lower Energy Level ◽

Molecular Lines ◽

AbstractI have developed a new version of my model atmosphere program called ATLAS12. It recognizes more than 1000 species, each in up to 10 isotopic forms, including all ions of the elements up through Zn and the first 5 ions of heavier elements up through Es. The elemental abundances are treated as variable with depth. ATLAS12 has 6 input files of line data containing 58,000,000 atomic and molecular lines. For each line the wavelength, identification, lower energy level, gf, radiative, Stark, and van der Waals damping constants are packed into 16 bytes. At each wavelength point in a frequency integration the profiles of all the significant nearby lines are computed and summed. The program and line files will be distributed in the fall of 1992.There are no significant differences at A0 between an opacity-sampled model computed with ATLAS12 and opacity-distribution-function model computed with ATLAS9. ATLAS12 allows arbitrary abundances but is slower. The new program can be used to produce improved models for Am and Ap stars that include the effects of millions of lines.