Short-period variability of B, A and F stars. II. Photometry of new delta Scuti stars.

1969 ◽  
Vol 74 ◽  
pp. 166 ◽  
Author(s):  
M. Breger
Keyword(s):  
Period Variability ◽  
Short Period ◽  
Delta Scuti ◽  
F Stars ◽  
Scuti Stars

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 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 The Delta Scuti Network: Steps Towards Successful Asteroseismology of Delta Scuti Stars

2002 ◽  
Vol 185 ◽  
pp. 598-599
Author(s):  
W. Zima ◽  
M. Breger ◽  
K. Bischof ◽  
F. Rodler ◽  
A. Stankov ◽  
...  
Keyword(s):  
High Precision ◽  
Main Sequence ◽  
Scientific Research ◽  
Mode Identification ◽  
Short Period ◽  
Delta Scuti ◽  
The Moment ◽  
Identification Techniques ◽  
Scuti Stars ◽  
Nonradial Oscillations

AbstractThe Delta Scuti Network (DSN) is a collaboration of astronomers all around the globe who study and observe short-period variables. The field of scientific research includes high-precision photometric and Spectroscopic global campaigns, mode identification techniques, and asteroseismological pulsation modeling. We present results for three stars that are receiving the most attention at the moment: 4 CVn, BI CMi, and 44 Tau. Our results demonstrate that a large number of simultaneously excited nonradial oscillations in stars on and above the main sequence can be detected by conventional means.

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 High- and Low-Degree Modes in Delta Scuti Stars: 1- and 2-D Fourier Analyses Of τ Peg

1993 ◽  
Vol 137 ◽  
pp. 743-745 ◽  
Author(s):  
Edward J. Kennelly ◽  
Jaymie M. Matthews ◽  
Gordon A.H. Walker
Keyword(s):  
Radial Velocity ◽  
Time Evolution ◽  
Main Sequence ◽  
Velocity Measurements ◽  
Low Degree ◽  
Delta Scuti ◽  
Stellar Seismology ◽  
F Stars ◽  
High Degree ◽  
Scuti Stars

Stellar seismology of δ Scuti stars offers the best prospect for determining the interior properties of normal non-magnetic A-F stars on or near the main sequence. The discovery of rich eigenfrequency spectra in the light variations of several δ Scuti stars (e.g., θ2 Tau: Breger et al. 1989; GX Peg: Michel et al. 1990) should make this possible for low-degree modes (l ≤ 4). However, due to cancellation effects, modes of higher l cannot be studied through photometry or radial velocity measurements.The detection of rapid line-profile variations among rapidly rotating δ Scuti stars (e.g., Walker et al. 1987; Kennelly et al. 1992) has extended our sensitivity to much higher modes. These variations are consistent with moderate- to high-degree modes, where |m| ~ l. (In the simplest case, they could be pure sectorial modes with |m| = l and pulsation amplitudes strongly confined to the stellar equator.) To use these data effectively, we need an objective way to identify the modes and their time evolution.

scholarly journals Delta Scuti stars in the Praesepe cluster observed by the MOST satellite

2012 ◽  
Vol 333 (2) ◽  
pp. 131-137 ◽  
Author(s):  
M. Breger ◽  
M. Hareter ◽  
M. Endl ◽  
R. Kuschnig ◽  
W.W. Weiss ◽  
...  
Keyword(s):  
Delta Scuti ◽  
Scuti Stars

scholarly journals XCOV13 and Asteroseismology of Delta Scuti Stars

1998 ◽  
Vol 7 (2) ◽  
Author(s):  
Michel Breger
Keyword(s):  
Delta Scuti ◽  
Scuti Stars
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