Features of the Behavior of Magnetic Chemically Peculiar Stars on the Main Sequence I

2021 ◽  
Vol 76 (4) ◽  
pp. 435-449
Author(s):  
Yu. V. Glagolevskij
Keyword(s):  
Main Sequence ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Chemically Peculiar Stars

scholarly journals 29. Stellar Spectra

1982 ◽  
Vol 18 (1) ◽  
pp. 343-360 ◽  
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 ◽  
Ap 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.

scholarly journals Discovery of Secular Evolution of the Atmospheric Abundances of Ap Stars

2014 ◽  
Vol 9 (S307) ◽  
pp. 365-366
Author(s):  
J. D. Bailey ◽  
J. D. Landstreet ◽  
S. Bagnulo
Keyword(s):  
Main Sequence ◽  
Chemical Abundance ◽  
Mixing Processes ◽  
Chemical Tracers ◽  
Secular Evolution ◽  
Abundance Patterns ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Chemically Peculiar Stars ◽  
Ap Stars

AbstractThe stars of the middle main-sequence have relatively quiescent outer layers, and unusual chemical abundance patterns may develop in their atmospheres, revealing the action of such subsurface phenomena as gravitational settling and radiatively driven levitation of trace elements, and their competition with mixing processes such as turbulent diffusion. We report the discovery of the time evolution of such chemical tracers through the main-sequence lifetime of magnetic chemically peculiar stars.

scholarly journals HST/STIS analysis of the first main sequence pulsar CU Virginis

2019 ◽  
Vol 625 ◽  
pp. A34 ◽  
Author(s):  
J. Krtička ◽  
Z. Mikulášek ◽  
G. W. Henry ◽  
J. Janík ◽  
O. Kochukhov ◽  
...  
Keyword(s):  
Radio Emission ◽  
Main Sequence ◽  
Flux Distribution ◽  
Mass Loss Rate ◽  
Rotational Period ◽  
Uv Spectrum ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Chemically Peculiar Stars

Context. CU Vir has been the first main sequence star that showed regular radio pulses that persist for decades, resembling the radio lighthouse of pulsars and interpreted as auroral radio emission similar to that found in planets. The star belongs to a rare group of magnetic chemically peculiar stars with variable rotational period. Aims. We study the ultraviolet (UV) spectrum of CU Vir obtained using STIS spectrograph onboard the Hubble Space Telescope (HST) to search for the source of radio emission and to test the model of the rotational period evolution. Methods. We used our own far-UV and visual photometric observations supplemented with the archival data to improve the parameters of the quasisinusoidal long-term variations of the rotational period. We predict the flux variations of CU Vir from surface abundance maps and compare these variations with UV flux distribution. We searched for wind, auroral, and interstellar lines in the spectra. Results. The UV and visual light curves display the same long-term period variations supporting their common origin. New updated abundance maps provide better agreement with the observed flux distribution. The upper limit of the wind mass-loss rate is about 10−12 M⊙ yr−1. We do not find any auroral lines. We find rotationally modulated variability of interstellar lines, which is most likely of instrumental origin. Conclusions. Our analysis supports the flux redistribution from far-UV to near-UV and visual domains originating in surface abundance spots as the main cause of the flux variability in chemically peculiar stars. Therefore, UV and optical variations are related and the structures leading to these variations are rigidly confined to the stellar surface. The radio emission of CU Vir is most likely powered by a very weak presumably purely metallic wind, which leaves no imprint in spectra.

scholarly journals Time Resolved Photometric and Spectroscopic Analysis of Chemically Peculiar Stars

2014 ◽  
Vol 9 (S307) ◽  
pp. 218-219 ◽  
Author(s):  
Santosh Joshi ◽  
Gireesh C. Joshi ◽  
Y. C. Joshi ◽  
Rahul Aggrawal
Keyword(s):  
Time Series ◽  
Main Sequence ◽  
Spectroscopic Analysis ◽  
Time Resolved ◽  
Photometric Variability ◽  
Chemically Peculiar ◽  
Photometric Observations ◽  
Peculiar Stars ◽  
The Family ◽  
Chemically Peculiar Stars

AbstractHere we present the report on the “Nainital–Cape survey” research project aiming to search for and study the pulsational variability of main-sequence chemically peculiar (CP) stars. For this study, the time-series photometric observations of the sample stars were carried out at the 1.04 m ARIES telescope (India), while the high-resolution spectroscopic and spectro-polarimetric observations were carried out at the the 6.0 m Russian telescope. Under this project, we have recently found clear evidence of photometric variability in the Am star HD 73045, which is likely to be pulsating in nature with a period of about 36 min, hence adding a new member to the family of the δ Scuti pulsating variables that have peculiar abundances.

scholarly journals Interpreting the Spectra of Chemically Peculiar Stars

1995 ◽  
Vol 10 ◽  
pp. 582-584
Author(s):  
Thierry Lanz
Keyword(s):  
Main Sequence ◽  
Chemical Elements ◽  
Line Strength ◽  
Atomic Data ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Chemically Peculiar Stars ◽  
Chemical Anomalies ◽  
Ap Stars ◽  
Absorption Features

Similarly to many astrophysical studies, a spectroscopic analysis of chemically peculiar (CP) stars requires extensive, accurate sets of atomic data. Our purpose is to show here that the CP stars can also serve as a laboratory for checking the accuracy of the atomic data. Despite additional challenges toward modeling the atmospheres of the CP stars, they have a definite advantage as laboratories for atomic physics: their strong chemical anomalies make some spectral features especially prominent in their spectra, which can be better checked against theoretical predictions. This statement may be applied to both to stars exhibiting large over- or under- abundances. We discuss several examples how CP stars can be used along this idea.We will focus here on the chemically peculiar stars of the upper main-sequence, which encompass the classical Am and Ap stars. Chemical anomalies are widespread on the main sequence for spectral types B. to F. These stars mostly show weak helium lines, and abnormally strong lines from iron-peak and heavier (e.g. the lanthanides) elements. A classical characteristics of Am stars in their weak Ca lines, while Ap stars may exhibit either strong Si or Hg lines. CP stars can be grouped according to the most obvious line strength anomalies, which are related to the effective temperature and to the presence or the absence of a magnetic field. In magnetic CP stars, the chemical elements are not uniformly distributed over the stellar surface, but they seem to be concentrated (or depleted) in rings or polar caps following the magnetic geometry. Magnetic CP stars have also broad absorption features in their ultraviolet and visible spectra that can used photometric peculiarity criteria. Using the new extensive photoionization data from the Opacity Project (OP), the UV absorption features can be identified and the UV spectrum can be well reproduced.

scholarly journals The Kepler view of magnetic chemically peculiar stars

2018 ◽  
Vol 619 ◽  
pp. A98 ◽  
Author(s):  
S. Hümmerich ◽  
Z. Mikulášek ◽  
E. Paunzen ◽  
K. Bernhard ◽  
J. Janík ◽  
...  
Keyword(s):  
Light Curve ◽  
Main Sequence ◽  
Complex Surface ◽  
Atomic Diffusion ◽  
Stellar Rotation ◽  
Photometric Variability ◽  
Chemically Peculiar ◽  
Final Sample ◽  
Peculiar Stars ◽  
Chemically Peculiar Stars

Context. Magnetic chemically peculiar (mCP) stars exhibit complex atmospheres that allow the investigation of such diverse phenomena as atomic diffusion, magnetic fields, and stellar rotation. The advent of space-based photometry provides the opportunity for the first precise characterizations of the photometric variability properties of these stars, which might advance our understanding of the processes involved and the atmospheric structures of mCP stars. Aims. We carried out a search for new mCP stars in the Kepler field with the ultimate aim of investigating their photometric variability properties using Kepler data. As an aside, we describe criteria for selecting mCP star candidates based on light curve properties, and assess the accuracy of the spectral classifications provided by the MKCLASS code. Methods. As only very few known mCP stars are situated in the Kepler field, we had to depend largely on alternative (non-spectroscopic) means of identifying suitable candidates that rely mostly on light curve properties; in particular we relied on monoperiodic variability and light curve stability. Newly acquired and archival spectra were used to confirm most of our mCP star candidates. Linear ephemeris parameters and effective amplitudes were derived from detrended Kepler data. Results. Our final sample consists of 41 spectroscopically confirmed mCP stars of which 39 are new discoveries, 5 candidate mCP stars, and 7 stars in which no chemical peculiarities could be established. Our targets populate the whole age range from zero-age main sequence to terminal-age main sequence and are distributed in the mass interval from 1.5 M⊙ to 4 M⊙. About 25% of the mCP stars show a hitherto unobserved wealth of detail in their light curves indicative of complex surface structures. We identified light curve stability as a primary criterion for identifying mCP star candidates among early-type stars in large photometric surveys, and prove the reliability of the spectral classifications provided by the MKCLASS code.

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