Short-Period Variability of b, a, and F Stars.IV. Variability in the Lower Hertzsprung Gap

1969 ◽  
Vol 19 ◽  
pp. 99 ◽  
Author(s):  
Michel Breger
Keyword(s):  
Period Variability ◽  
Short Period ◽  
Hertzsprung Gap

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 Insights from Pulsating Nova Envelopes

2002 ◽  
Vol 185 ◽  
pp. 580-583
Author(s):  
K. Schenker
Keyword(s):  
Mass Loss ◽  
Point Of View ◽  
X Ray ◽  
Classical Novae ◽  
Decline Phase ◽  
Period Variability ◽  
Short Period ◽  
Running Wave ◽  
Nova Outburst ◽  
Radial Pulsations

AbstractBased on a linear and non-linear study of radial pulsations in the envelopes of classical novae (Schenker, 1999), I discuss the results both from the point of view of pulsation theory as well as their consequences for current nova models. Starting from initially static envelope structures at various stages during the decline of a nova outburst, strong ‘running-wave’ instabilities have been found that rapidly grow into shocks. Improved analytical concepts give a new direction to the interpretation of such highly non-adiabatic radial pulsations. For direct observational confirmation, a search for short period variability in the UV and soft X-ray is suggested during the very late decline phase. Speculative consequences for mass-loss scenarios in novae due to these instabilities will need some more work in the future.

scholarly journals Discovery of a Magnetic White Dwarf with Unusual Short-period Variability

2018 ◽  
Vol 2 (1) ◽  
pp. 27 ◽  
Author(s):  
Aleks Scholz ◽  
Joe Llama ◽  
Koraljka Muzic ◽  
Sarah Faller ◽  
Dirk Froebrich ◽  
...  
Keyword(s):  
White Dwarf ◽  
Period Variability ◽  
Short Period
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