scholarly journals New and improved rotational periods of magnetic CP stars from ASAS-3, KELT, and MASCARA data

2020 ◽  
Vol 493 (3) ◽  
pp. 3293-3330 ◽  
Author(s):  
Klaus Bernhard ◽  
Stefan Hümmerich ◽  
Ernst Paunzen
Keyword(s):  
Binary Systems ◽  
Time Series Data ◽  
Eclipsing Binaries ◽  
Atomic Diffusion ◽  
Close Binary ◽  
Series Data ◽  
Rotational Period ◽  
Stellar Rotation ◽  
Apparent Lack ◽  
Final Sample

ABSTRACT Magnetic chemically peculiar (mCP) stars allow the investigation of such diverse phenomena as atomic diffusion, magnetic fields, and stellar rotation. The aim of the present investigation is to enhance our knowledge of the rotational properties of mCP stars by increasing the sample of objects with accurately determined rotational periods. To this end, archival photometric time-series data from the ASAS-3, KELT, and MASCARA surveys were employed to improve existing rotational period information and derive rotational periods for mCP stars hitherto not known to be photometric variables. Our final sample consists of 294 mCP stars, a considerable amount of which (more than 40 per cent) are presented here as photometric variables for the first time. In addition, we identified 24 mCP star candidates that show light variability in agreement with rotational modulation but lack spectroscopic confirmation. The rotational period distribution of our sample agrees well with the literature. Most stars are between 100 Myr and 1 Gyr old, with an apparent lack of very young stars. No objects were found on the zero-age main sequence; several stars seem to have evolved to the subgiant stage, albeit well before the first dredge-up. We identified four eclipsing binaries (HD 244391, HD 247441, HD 248784, and HD 252519), which potentially host an mCP star. This is of great interest because mCP stars are very rarely found in close binary systems, particularly eclipsing ones. Using archival spectra, we find strong evidence that the HD 252519 system indeed harbours an mCP star component.

scholarly journals Stellar Chromospheric Variability

Universe ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 440
Author(s):  
Richard de de Grijs ◽  
Devika Kamath
Keyword(s):  
Large Scale ◽  
Binary Systems ◽  
Magnetic Activity ◽  
Close Binary ◽  
Physical Parameters ◽  
Stellar Rotation ◽  
Chromospheric Activity ◽  
Recent Developments ◽  
Hα Emission ◽  
Activity Cycles

Cool stars with convective envelopes of spectral types F and later tend to exhibit magnetic activity throughout their atmospheres. The presence of strong and variable magnetic fields is evidenced by photospheric starspots, chromospheric plages and coronal flares, as well as by strong Ca ii H+K and Hα emission, combined with the presence of ultraviolet resonance lines. We review the drivers of stellar chromospheric activity and the resulting physical parameters implied by the observational diagnostics. At a basic level, we explore the importance of stellar dynamos and their activity cycles for a range of stellar types across the Hertzsprung–Russell diagram. We focus, in particular, on recent developments pertaining to stellar rotation properties, including the putative Vaughan–Preston gap. We also pay specific attention to magnetic variability associated with close binary systems, including RS Canum Venaticorum, BY Draconis, W Ursae Majoris and Algol binaries. At the present time, large-scale photometric and spectroscopic surveys are becoming generally available, thus leading to a resurgence of research into chromospheric activity. This opens up promising prospects to gain a much improved understanding of chromospheric physics and its wide-ranging impact.

scholarly journals Close Binary Systems in Globular Clusters: A Preliminary Report

1980 ◽  
Vol 88 ◽  
pp. 561-565 ◽  
Author(s):  
R. F. Webbink
Keyword(s):  
Globular Cluster ◽  
Preliminary Report ◽  
Globular Clusters ◽  
Binary Systems ◽  
Cataclysmic Variables ◽  
Eclipsing Binaries ◽  
Close Binary ◽  
Promising Candidate ◽  
Eclipsing Binary ◽  
Ursa Minor

A brief survey of known eclipsing binaries and cataclysmic variables in globular cluster fields is presented. None of the 47 known or suspected eclipsing variables is a promising candidate, although a very few remain possible members. V101 in M5 is a good candidate for membership, among 5 known or suspected dwarf novae. Three novae have been discovered in globular cluster fields, of which two are almost certainly members. Attention is also called to the eclipsing binary V80, a system which appears to contain an RRc variable, in the dwarf spheroidal galaxy in Ursa Minor.

scholarly journals Investigating stellar surface rotation using observations of starspots

2011 ◽  
Vol 7 (S286) ◽  
pp. 268-278
Author(s):  
Heidi Korhonen
Keyword(s):  
Differential Rotation ◽  
Binary Systems ◽  
Solar Surface ◽  
Magnetic Activity ◽  
Stellar Surface ◽  
Close Binary ◽  
Line Profiles ◽  
Stellar Rotation ◽  
Rotation Rates ◽  
Cool Stars

AbstractRapid rotation enhances the dynamo operating in stars, and thus also introduces significantly stronger magnetic activity than is seen in slower rotators. Many young cool stars still have the rapid, primordial rotation rates induced by the interstellar molecular cloud from which they were formed. Also older stars in close binary systems are often rapid rotators. These types of stars can show strong magnetic activity and large starspots. In the case of large starspots which cause observable changes in the brightness of the star, and even in the shapes of the spectral line profiles, one can get information on the rotation of the star. At times even information on the spot rotation at different stellar latitudes can be obtained, similarly to the solar surface differential rotation measurements using magnetic features as tracers. Here, I will review investigations of stellar rotation based on starspots. I will discuss what we can obtain from ground-based photometry and how that improves with the uninterrupted, high precision, observations from space. The emphasis will be on how starspots, and even stellar surface differential rotation, can be studied using high resolution spectra.

scholarly journals Eclipsing Spectroscopic Binaries in the SMC

2005 ◽  
Vol 13 ◽  
pp. 455-455 ◽  
Author(s):  
Ron W. Hilditch ◽  
Tim J. Harries ◽  
Ian D. Howarth
Keyword(s):  
Binary Stars ◽  
Binary Systems ◽  
Binary Star ◽  
Theoretical Models ◽  
Eclipsing Binaries ◽  
Spectroscopic Binaries ◽  
Close Binary ◽  
Exchange Processes ◽  
The Mean ◽  
Close Binary Star

The OGLE survey of the SMC has discovered ~1500 eclipsing binaries thereby providing an excellent platform to study the evolution of close binary systems through case A and case B mass-exchange processes. The complementary spectroscopic radial-velocity studies of these binaries are now in progress and are revealing many interesting systems which challenge current theoretical models of close binary star evolution. These studies also provide excellent direct determinations of distances to these binary stars leading to an improved understanding of the mean distance to the SMC and its 3-D structure. Comparisons between these binary-star distances and other methods of determining the mean distance to the SMC will also be made.

scholarly journals MULTICOLOR STUDY OF V1009 PER, A CLOSE BINARY SYSTEM AT THE BEGINNING OF THE OVERCONTACT PHASE, AND OF CRTS J031642.2+332639, A NEW BINARY SYSTEM IN THE SAME FIELD

2019 ◽  
Vol 55 (1) ◽  
pp. 65-72
Author(s):  
Raúl Michel ◽  
Francesco Acerbi ◽  
Carlo Barani ◽  
Massimiliano Martignoni
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Binary Systems ◽  
General Pattern ◽  
Close Binary System ◽  
Eclipsing Binaries ◽  
Close Binary ◽  
Mass Ratio ◽  
Period Variations ◽  
Contact Binaries

The first multicolor observations and light curve solutions of the eclipsing binary systems V1009 Per and CRTS J031642.2+332639 are presented. Using the 2005 version of the Wilson-Devinney code, both systems are found to be W UMa contact binaries. V1009 Per has a mass ratio of q = 0.362±0.002 and a shallow fill out parameter of f = 11.8 ± 0.6% while CRTS J031642.2+332639 has a mass ratio of q = 2.507±0.006 and a fill out of f = 13.6±0.4%. High orbital inclinations, i = 85◦.9 for V1009 Per and i = 83◦.2 for CRTS J031642.2+332639, imply that both systems are total eclipsing binaries and that the photometric parameters here obtained are reliable. Based on 16 times of minimum the orbital period variations of V1009 Per are discussed. The absolute dimensions of the systems are estimated and, from the log M − log L diagram, it is found that both components of the systems follow the general pattern of the W subtype W Ursae Majoris systems.

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 The Period Distribution of Close Binary Systems

1980 ◽  
Vol 88 ◽  
pp. 23-26
Author(s):  
L. Mantegazza ◽  
P. Paolicchi ◽  
P. Farinella ◽  
F. Luzny
Keyword(s):  
Spectral Type ◽  
Binary Systems ◽  
Eclipsing Binaries ◽  
Close Binary ◽  
Selection Effects ◽  
Late Type ◽  
Close Binary Systems ◽  
Period Distribution ◽  
Spectroscopic Binary

The analysis of the period distribution of eclipsing and spectroscopic binary systems shows the presence of some secundary maxima, which cannot depend on selection effects. These secundary maxima are mainly due to late type stars, as can be seen from the distribution curves for eclipsing binaries of various spectral types. The average separation of the components (in units of the sum of stellar radii) increases with the spectral type from 0 types to late B types, remaining almost constant for later spectral types.

Some Results of the Spectroscopic Study of Four Close Binary Systems of Early Spectral Types

1965 ◽  
Vol 5 ◽  
pp. 120-130
Author(s):  
T. S. Galkina
Keyword(s):  
Spectroscopic Study ◽  
Spectral Type ◽  
Spectroscopic Investigation ◽  
Binary Systems ◽  
Quantitative Information ◽  
Close Binary ◽  
Physical Parameters ◽  
Absorption And Emission ◽  
Close Binary Systems ◽  
Quantitative Estimates

It is necessary to have quantitative estimates of the intensity of lines (both absorption and emission) to obtain the physical parameters of the atmosphere of components.Some years ago at the Crimean observatory we began the spectroscopic investigation of close binary systems of the early spectral type with components WR, Of, O, B to try and obtain more quantitative information from the study of the spectra of the components.

Quasi-Periodic Oscillations in Dwarf Novae

1979 ◽  
Vol 46 ◽  
pp. 77-88
Author(s):  
Edward L. Robinson
Keyword(s):  
Binary Systems ◽  
Outer Edge ◽  
Light Curves ◽  
Close Binary ◽  
Bright Spot ◽  
Dwarf Novae ◽  
Periodic Oscillations ◽  
High Frequencies ◽  
Short Period ◽  
Typical Time

Three distinct kinds of rapid variations have been detected in the light curves of dwarf novae: rapid flickering, short period coherent oscillations, and quasi-periodic oscillations. The rapid flickering is seen in the light curves of most, if not all, dwarf novae, and is especially apparent during minimum light between eruptions. The flickering has a typical time scale of a few minutes or less and a typical amplitude of about .1 mag. The flickering is completely random and unpredictable; the power spectrum of flickering shows only a slow decrease from low to high frequencies. The observations of U Gem by Warner and Nather (1971) showed conclusively that most of the flickering is produced by variations in the luminosity of the bright spot near the outer edge of the accretion disk around the white dwarf in these close binary systems.

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