Short-Period Variability of b, a, and F Stars. III. a Survey of Delta Scuti Variable Stars

1969 ◽  
Vol 19 ◽  
pp. 79 ◽  
Author(s):  
Michel Breger
Keyword(s):  
Variable Stars ◽  
Period Variability ◽  
Short Period ◽  
Delta Scuti ◽  
F Stars

scholarly journals A Photometric Search for Circumstellar Shell Variability and Pre-Main Sequence Delta Scuti Variables

1971 ◽  
Vol 15 ◽  
pp. 85-89
Author(s):  
M. Breger ◽  
J. Hardorp
Keyword(s):  
Main Sequence ◽  
Color Variation ◽  
Sequence Band ◽  
Short Period ◽  
Circumstellar Shell ◽  
Delta Scuti ◽  
F Stars ◽  
Variability Study ◽  
Light Variability ◽  
Selective Extinction

AbstractA light variability study in NGC 2264 shows that about 25 % of the pre-main sequence A and F stars show irregular short-period variability and/or brightness changes since 1953. There exists a good correlation between this variability and (other) shell indicators. The scatter in the pre-main sequence band in the color-magnitude diagram can be partially explained by shells and an age spread between 1 and 3 × 106 years is indicated. W 90, a star below the main sequence, has brightened by half a magnitude to V = 12.5 since 1953. The corresponding color variation suggests a ratio of total to selective extinction of about 9.

scholarly journals Astrophysical Applications of Delta Scuti Stars

1995 ◽  
Vol 155 ◽  
pp. 70-80
Author(s):  
Michel Breger
Keyword(s):  
Main Sequence ◽  
Statistical Significance ◽  
Instability Strip ◽  
Short Period ◽  
Scuti Star ◽  
Systematic Behaviour ◽  
Delta Scuti ◽  
F Stars ◽  
Available Information ◽  
Scuti Stars

AbstractThe δ Scuti stars pulsate with a large number of low-order radial and nonradial p-modes. There also exists some evidence for the presence of g-modes.The pulsational variability outside the classical δ Scuti star instability strip (A1V - F0V on the main sequence) is examined. New measurements do not confirm the short-period variability of the hot B9p star ET And. However, a number of cool, early-F stars shows variability around one day: the γ Dor variables. An explanation involving nonradial g modes appears the most promising.An examination of available information on the multi-periodicity of δ Scuti stars shows no systematic behaviour in which pulsation modes axe excited to an observable level with luminosity and temperature. The asteroseismological potential of δ Scuti vaxiables is briefly examined.So far, the period changes of five luminous Pop. I δ Scuti variables have been studied. While stellar evolution predicts period increases, decreases have been observed and reported for all five stars. The statistical significance of this result and alternative explanations axe briefly examined.

scholarly journals Adaptive elliptical aperture photometry: A software package for high-cadence ground-based photometry

2019 ◽  
Vol 629 ◽  
pp. A21 ◽  
Author(s):  
Dominic M. Bowman ◽  
Daniel L. Holdsworth
Keyword(s):  
High Frequency ◽  
Software Package ◽  
Variable Stars ◽  
Light Curves ◽  
Series Data ◽  
Rapid Variability ◽  
Period Variability ◽  
Short Period ◽  
Ap Stars ◽  
High Cadence

Context. Modern space telescopes are currently providing high-precision light curves for a large fraction of the sky, such that many new variable stars are being discovered. However, some stars have periodic variability with periods on the order of minutes and require high-cadence photometry to probe the physical mechanisms responsible. A cadence of less than a minute is often required to remove Nyquist ambiguities and confirm rapid variability, which forces observers to obtain high-cadence ground-based photometry. Aims. We aim to provide a modern software package to reduce ground-based photometric time series data and deliver optimised (differential) light curves. To produce high-quality light curves, which maximise the amplitude signal-to-noise ratio of short-period variability in a Fourier spectrum, we require adaptive elliptical aperture photometry as this represents a significant advantage compared to aperture photometry using circular apertures of fixed radii. Methods. The methodology of our code and its advantages are demonstrated using high-cadence ground-based photometry from the South African Astronomical Observatory (SAAO) of a confirmed rapidly oscillating Ap (roAp) star. Furthermore, we employed our software package to search for rapid oscillations in three candidate roAp stars. Results. We demonstrate that our pipeline represents a significant improvement in the quality of light curves, and we make it available to the community for use with different instruments and observatories. We search for and demonstrate the lack of high-frequency roAp pulsations to a limit of ∼1 mmag using B data in the three Ap stars HD 158596, HD 166542, and HD 181810. Conclusions. We demonstrate the significant improvement in the extraction of short-period variability caused by high-frequency pulsation modes, and discuss the implication of null detections in three Ap stars.

scholarly journals PRELIMINARY RESULTS FOR SHORT-PERIOD VARIABILITY SURVEY (SPVS) : NEW FIELD VARIABLE STARS

2007 ◽  
Vol 22 (4) ◽  
pp. 141-149 ◽  
Author(s):  
Young-Beom Jeon ◽  
Ki-Hyung Nam ◽  
Yoon-Ho Park ◽  
Kyung-Hoon Lee
Keyword(s):  
Variable Stars ◽  
Field Variable ◽  
Preliminary Results ◽  
Period Variability ◽  
Short Period

scholarly journals Amplitudes and Frequencies of δ Scuti Stars: Systematics

1980 ◽  
Vol 5 ◽  
pp. 463-466 ◽  
Author(s):  
Michel Breger
Keyword(s):  
Main Sequence ◽  
Light Curves ◽  
Interior Structure ◽  
Minimum Requirement ◽  
Short Period ◽  
Delta Scuti ◽  
F Stars ◽  
Scuti Stars ◽  
Δ Scuti Stars

Delta Scuti stars are short-period pulsating A/F stars situated on or above the main sequence. They often pulsate with two more excited modes. The knowledge of the period lengths and period ratios is very important to deduce the nature of the pulsation modes, e.g. is the pulsation radial or nonradial? Furthermore, these values provide valuable information on the interior structure of these stars.The determination of the period ratios from the light curves is difficult, since only a few cycles can be covered during a night. The small amplitudes of about 0.01 mag in some variables also makes the multiperiod analysis difficult. While every star should be considered on its own merit, a rough estimate of about 5 nights per deduced period appears to be a minimum requirement. Even then different analyses can give different results. A recent example is the star 38 Cnc (=BT Cnc). An excellent set of observations by Guerrero, Mantegazza and Scardia (1979) gave three periods with nonradial period ratios and a good fit. Our subsequent analysis of the same data gave three radial periods with an even better fit!

scholarly journals CCD Photometry of Variable Stars in the Galactic Open Cluster NGC 7419

2002 ◽  
Vol 185 ◽  
pp. 150-151 ◽  
Author(s):  
Z. Kołaczkowski ◽  
A. Pigulski ◽  
G. Kopacki
Keyword(s):  
Time Scales ◽  
Open Cluster ◽  
Variable Stars ◽  
Be Stars ◽  
Ccd Photometry ◽  
Period Variability ◽  
Short Period ◽  
Young Open Cluster ◽  
Almost All ◽  
Different Time Scales

AbstractWe present results of a CCD variability search in the field of the young open cluster NGC 7419. This cluster contains a large number of Be stars and almost all of them turned out to be variable. They show mostly irregular variations on different time-scales with ranges up to 0.4 mag in the IC band. The most interesting result is the discovery of short-period variability in some of the Be stars.

scholarly journals A Search for Variable B Stars in the Northern Open Clusters

1995 ◽  
Vol 155 ◽  
pp. 293-294
Author(s):  
Andrzej Pigulski ◽  
Mikolaj Jerzykiewicz ◽  
Grzegorz Kopacki
Keyword(s):  
Ccd Camera ◽  
Variable Stars ◽  
Open Clusters ◽  
B Stars ◽  
Period Variability ◽  
Short Period ◽  
Central Regions ◽  
Period Variable

AbstractIn April 1994 we started a program of searching for variable B-type stars in young open clusters. The equipment consisted of a 60-cm reflecting telescope and a CCD camera with a Johnson’s B filter. Up to date we obtained nearly 1500 CCD frames of the central regions of four clusters: IC4996, NGC7235, NGC7510, and NGC654. In the range from B 0 to B 5, the photometric accuracy we achieve allows detection of short-period variability with amplitudes of about 5 mmag or greater. In this note we present the short-period variable stars we found in NGC 7235 and NGC 7510.

scholarly journals SuperWASP variable stars: classifying light curves using citizen science

2021 ◽  
Vol 502 (1) ◽  
pp. 1299-1311
Author(s):  
Heidi B Thiemann ◽  
Andrew J Norton ◽  
Hugh J Dickinson ◽  
Adam McMaster ◽  
Ulrich C Kolb
Keyword(s):  
Variable Stars ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Data Set ◽  
Resultant Data ◽  
Sky Survey ◽  
Short Period ◽  
Contact Binaries ◽  
Analysis Of Results

ABSTRACT We present the first analysis of results from the SuperWASP variable stars Zooniverse project, which is aiming to classify 1.6 million phase-folded light curves of candidate stellar variables observed by the SuperWASP all sky survey with periods detected in the SuperWASP periodicity catalogue. The resultant data set currently contains >1 million classifications corresponding to >500 000 object–period combinations, provided by citizen–scientist volunteers. Volunteer-classified light curves have ∼89 per cent accuracy for detached and semidetached eclipsing binaries, but only ∼9 per cent accuracy for rotationally modulated variables, based on known objects. We demonstrate that this Zooniverse project will be valuable for both population studies of individual variable types and the identification of stellar variables for follow-up. We present preliminary findings on various unique and extreme variables in this analysis, including long-period contact binaries and binaries near the short-period cut-off, and we identify 301 previously unknown binaries and pulsators. We are now in the process of developing a web portal to enable other researchers to access the outputs of the SuperWASP variable stars project.

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