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.

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 Photometry of Chemically Peculiar Stars with Automatic Photoelectric Telescopes

1993 ◽  
Vol 138 ◽  
pp. 644-649 ◽  
Author(s):  
Saul J. Adelman ◽  
Diane M. Pyper
Keyword(s):  
Light Curve ◽  
Main Sequence ◽  
Las Vegas ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Chemically Peculiar Stars ◽  
The University ◽  
Villanova University ◽  
Initial Results ◽  
The Phoenix

AbstractThe College of Charleston The Citadel, the University of Nevada, Las Vegas and Villanova University constitute the Four College Automatic Photoelectric Telescope Consortium which has a 0.75-m telescope on Mt. Hopkins, Arizona. It has been in regular operation for two years. Prior to this time we obtained some differential UBV observations with the Phoenix 10” APT of the Fairborn Observatory. We are coordinating observations of CP stars of the upper main sequence. Some initial results include evidence for significant changes in the light curve of 56 Ari, the constancy of the HgMn stars 53 Tau and HR 4072, an improved period for HD 244801, and new observations in the broad minimum of HD 9996.

scholarly journals Distribution of Elements Inside Stars

2019 ◽  
pp. 52-59
Author(s):  
G. Alecian
Keyword(s):  
Chemical Composition ◽  
Stellar Evolution ◽  
Main Sequence ◽  
Stellar Atmospheres ◽  
Atomic Diffusion ◽  
The Core ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Distribution Of Elements ◽  
Chemically Peculiar Stars

The chemical composition measured in stellar atmospheres is not necessarily the same as in deeper layers (outside the core). Indeed, for a significant fraction of main-sequence G to B types stars the discrepancies between superficial and internal abundances go from a few percent (for the coldest of these stars) to huge factors (for hot chemically peculiar stars). This is due to atomic diffusion process, which may produces elements segregation at some stages of the stellar evolution.

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 First detection of bromine and antimony in hot stars

2018 ◽  
Vol 614 ◽  
pp. A96 ◽  
Author(s):  
K. Werner ◽  
T. Rauch ◽  
M. Knörzer ◽  
J. W. Kruk
Keyword(s):  
Model Atmosphere ◽  
Atomic Diffusion ◽  
Laboratory Measurements ◽  
Solar Abundance ◽  
Hot Stars ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Resonance Doublet ◽  
Chemically Peculiar Stars ◽  
Far Ultraviolet

Bromine (Z = 35) and antimony (Z = 51) are extremely difficult to detect in stars. In very few instances, weak and mostly uncertain identifications of Br I, Br II, and Sb II in relatively cool, chemically peculiar stars were successful. Adopted solar abundance values rely on meteoritic determinations. Here, we announce the first identification of these species in far-ultraviolet spectra of hot stars (with effective temperatures of 49 500–70 000 K), namely in helium-rich (spectral type DO) white dwarfs. We identify the Br VI resonance line at 945.96 Å. A previous claim of Br detection based on this line is incorrect because its wavelength position is inaccurate by about 7 Å in atomic databases. Taking advantage of precise laboratory measurements, we identify this line as well as two other, subordinate Br VI lines. Antimony is detected by the Sb V resonance doublet at 1104.23/1225.98 Å as well as two subordinate Sb VI lines. A model-atmosphere analysis reveals strongly oversolar Br and Sb abundances that are caused by radiative-levitation dominated atomic diffusion.

scholarly journals The nature of the photometric variability of HgMn stars: a test of simulated light curves of φ Phe against the TESS data

2019 ◽  
Vol 492 (2) ◽  
pp. 1834-1840 ◽  
Author(s):  
Milan Prvák ◽  
Jiří Krtička ◽  
Heidi Korhonen
Keyword(s):  
Light Curves ◽  
Heavy Elements ◽  
High Resolution Spectroscopy ◽  
Inhomogeneous Surface ◽  
Surface Distribution ◽  
Photometric Variability ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Chemically Peculiar Stars ◽  
Light Variability

ABSTRACT The inhomogeneous surface distribution of heavy elements is known to cause periodic light variability of magnetic chemically peculiar stars. It is unclear to what extent the same paradigm applies to mercury–manganese (HgMn) stars. We aim to model the photometric variability of the HgMn star φ Phe using abundance maps obtained from high-resolution spectroscopy and to study how this variability evolves with time. We compute a grid of atlas12 model atmospheres and the corresponding synspec synthetic spectra. Interpolating within this grid and integrating the specific intensity over the visible stellar surface at different rotational phases, we obtain theoretical light curves of the star. We predict the variability of φ Phe in the ultraviolet and in the visible spectral regions with amplitude of the order of millimagnitudes, mainly caused by absorption in lines of yttrium, chromium, and titanium. We also show how this variability is affected by changes of the distribution of the heavy elements over time. The main characteristics of the predicted light variability of φ Phe correspond roughly to the variability of the star observed with the Transiting Exoplanet Survey Satellite (TESS).

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