scholarly journals Double Mode Pulsating Stars and Opacity Changes

1989 ◽  
Vol 111 ◽  
pp. 248-248
Author(s):  
G.K. Andreasen
Keyword(s):  
Physical Properties ◽  
Variable Stars ◽  
Period Ratio ◽  
Pulsating Stars ◽  
Temperature Range ◽  
Ratio Data ◽  
Mass Calibration ◽  
Scuti Stars ◽  
Δ Scuti Stars

AbstractThe basic physical properties of double mode Cepheids and double mode δ Scuti stars are still highly controversial. Based on results of very recent opacity calculations a detailed consistent, possible solution of the problem of the nature of double mode variable stars has been developed. Extensive studies have been performed to establish the rules governing the morphology of the period ratio diagrams. An ideal reproduction of the period ratio data for both stellar types are obtained assuming an increase of the Cox-Steward opacity by a factor of about 2.5 in the temperature range from 1.5 X 105K to 8.0 X 105K. Consequences for the mass calibration of Petersen diagrams are evaluated.

scholarly journals Do the Pre-Main Sequence δ Scuti Stars Really Exist?

2002 ◽  
Vol 185 ◽  
pp. 346-347
Author(s):  
J.H. Peña ◽  
R. Peniche ◽  
J.C. Plascencia ◽  
M.A. Hobart ◽  
C. de la Cruz ◽  
...  
Keyword(s):  
Main Sequence ◽  
Variable Stars ◽  
Current Status ◽  
Excellent Review ◽  
Scuti Stars ◽  
Δ Scuti Stars

Recently, new views of the current status of δ Scuti stars have been developed by Rodríguez & Breger (2001) who carried out an excellent review, listing 8 pre-main-sequence (PMS) δ Scuti candidates and examined the possibility of the existence of PMS δ Scuti variable stars. Here we discuss the nature of 4 stars from their list: 2 said to be members of NGC 2264 and 2 of NGC 6823.

scholarly journals A fractal analysis application of the pre-whitening technique to δ Scuti stars time series

2019 ◽  
Vol 487 (3) ◽  
pp. 4457-4463 ◽  
Author(s):  
S de Franciscis ◽  
J Pascual-Granado ◽  
J C Suárez ◽  
A García Hernández ◽  
R Garrido ◽  
...  
Keyword(s):  
Time Series ◽  
Power Spectra ◽  
Coarse Graining ◽  
Light Curves ◽  
Pulsating Stars ◽  
Oscillation Modes ◽  
Analysis Application ◽  
New Criterion ◽  
Scuti Stars ◽  
Δ Scuti Stars

ABSTRACT Fractal fingerprints have been found recently in the light curves of several δ Scuti stars observed by Convection Rotation and planetary Transits(CoRoT) satellite. This sole fact might pose a problem for the detection of pulsation frequencies using classical pre-whitening techniques, but it is also a potentially rich source for information about physical mechanisms associated with stellar variability. Assuming that a light curve is composed of a superposition of oscillation modes with a fractal background noise, in this work we applied the Coarse Graining Spectral Analysis (CGSA), a fast Fourier transform (FFT)-based algorithm, which can discriminate in a time series the stochastic fractal power spectra from the harmonic one. We have found that the fractal background component is determining the frequency content extracted using classical pre-whitening techniques in the light curves of δ Scuti stars. This might be crucial to understand the amount of frequencies excited in these kinds of pulsating stars. Additionally, CGSA resulted to be relevant in order to extract the oscillation modes, this points to a new criterion to stop the pre-whitening cascade based on the percentage of fractal component in the residuals.

scholarly journals Re-classification of ROTSE-I δ Scuti stars

2004 ◽  
Vol 193 ◽  
pp. 279-282
Author(s):  
H. Jin ◽  
S.-L. Kim ◽  
C.-U. Lee ◽  
D.-J. Lee ◽  
K.-S. Kim
Keyword(s):  
Decomposition Analysis ◽  
Variable Stars ◽  
Fourier Decomposition ◽  
Eclipsing Variable Stars ◽  
Scuti Stars ◽  
Δ Scuti Stars

AbstractWe present new multiband photometric results for ROTSE-I δ Sct stars and the Fourier decomposition analysis. Our result shows that most of the stars classified as ROTSE-I δ Sct stars seem to be W UMa type eclipsing variable stars.

scholarly journals Finding binaries from phase modulation of pulsating stars with Kepler – VI. Orbits for 10 new binaries with mischaracterized primaries

2020 ◽  
Vol 493 (4) ◽  
pp. 5382-5388
Author(s):  
Simon J Murphy ◽  
Nicholas H Barbara ◽  
Daniel Hey ◽  
Timothy R Bedding ◽  
Ben D Fulcher
Keyword(s):  
Phase Modulation ◽  
White Dwarfs ◽  
Binary Systems ◽  
Main Sequence ◽  
Classification Algorithm ◽  
Orbital Parameters ◽  
Pulsating Stars ◽  
Stellar Properties ◽  
Scuti Stars ◽  
Δ Scuti Stars

ABSTRACT Measuring phase modulation in pulsating stars has proven to be a highly successful way of finding binary systems. The class of pulsating main-sequence A and F variables, known as δ Scuti stars consists of particularly good targets for this, and the Kepler sample of these has been almost fully exploited. However, some Keplerδ Scuti stars have incorrect temperatures in stellar properties catalogues, and were missed in previous analyses. We used an automated pulsation classification algorithm to find 93 new δ Scuti pulsators among tens of thousands of F-type stars, which we then searched for phase modulation attributable to binarity. We discovered 10 new binary systems and calculated their orbital parameters, which we compared with those of binaries previously discovered in the same way. The results suggest that some of the new companions may be white dwarfs.

scholarly journals Delta Scuti Stars in Open Clusters: w2 and w20 in NGC 2264 and h501 and h906 in α Per

2000 ◽  
Vol 176 ◽  
pp. 465-466
Author(s):  
J. H. Peña ◽  
R. Peniche ◽  
F. Cervantes ◽  
R. M. García ◽  
J. P. Sareyan
Keyword(s):  
Chemical Composition ◽  
Effective Temperature ◽  
Variable Stars ◽  
Open Clusters ◽  
Early Type ◽  
Early Type Stars ◽  
Delta Scuti ◽  
Scuti Stars ◽  
Δ Scuti Stars

There are many advantages to studying variable stars in open clusters; the parameters that determine the evolution of the stars, such as chemical composition and age, can be considered to be the same for all the stars in the cluster. These data, along with the mass, effective temperature and superficial gravity, allow us to better determine the physics which explain the pulsation mechanisms. In the present paper the variable stars h501 and h906 in α Per and w2 and w20 in NGC 2264 are studied. In particular, the reasons why δ Scuti stars coexist with early type stars in NGC 2264 is examined.

scholarly journals Theoretical properties of regularities in the oscillation spectra of A-F main-sequence stars

2013 ◽  
Vol 9 (S301) ◽  
pp. 89-92 ◽  
Author(s):  
Juan Carlos Suárez ◽  
Antonio García Hernández ◽  
Andrés Moya ◽  
Carlos Rodrigo ◽  
Enrique Solano ◽  
...  
Keyword(s):  
Main Sequence ◽  
Low Frequency ◽  
Average Density ◽  
Stellar Structure ◽  
Main Sequence Stars ◽  
Mode Identification ◽  
Pulsating Stars ◽  
The Mean ◽  
Scuti Stars ◽  
Δ Scuti Stars

AbstractWe study the theoretical properties of the regular spacings found in the oscillation spectra of δ Scuti stars. A linear relation between the large separation and the mean density is predicted to be found in the low-frequency domain (i.e. radial orders spanning from 1 to 8, approximately) of the main-sequence δ Scuti stars' oscillation spectrum. This implies an independent direct measure of the average density of δ Scuti stars, analogous to that of the Sun, and places tight constraints on the mode identification and hence on the stellar internal structure and dynamics, and allows a determination the radii of planets orbiting around δ Scuti stars with unprecedented precision. This opens the way for studying the evolution of regular patterns in pulsating stars, and its relation to stellar structure and evolution.

Seismology of δ Scuti Stars: Problems and Prospects

2002 ◽  
Vol 185 ◽  
pp. 306-318
Author(s):  
M.J. Goupil ◽  
S. Talon
Keyword(s):  
Main Sequence ◽  
Instability Strip ◽  
Pulsating Stars ◽  
Current State ◽  
Cno Cycle ◽  
The Mean ◽  
Scuti Stars ◽  
High Temperature Sensitivity ◽  
Δ Scuti Stars ◽  
Mean Molecular Weight

The current state of seismology of δ Scuti stars is reviewed with particular emphasis on seismic signatures of the extension of their mixed central region and of rotation. We refer also to Goupil et al. (2000) and more generally to Breger & Montgomery (2000) for more details.δ Scuti stars are population I pulsating stars with spectral type A-early F, located on or near the main sequence. They are found in the lower part of the classical instability strip in a HR diagram (Fig. 1). Masses range from ∼ 1.5M⊙ to ∼ 2.5M⊙ and δ Scuti stars are either in a stage of H-core or H-shell burning. On the main sequence, the high temperature sensitivity of the dominant CNO cycle causes a large convective core to develop, which later shrinks leaving behind a gradient ∇μ in the mean molecular weight.

scholarly journals The Pulsation of some δ Scuti Stars with Unusual Light Curves

1989 ◽  
Vol 111 ◽  
pp. 249-249
Author(s):  
E. Antonello ◽  
E. Poretti
Keyword(s):  
Light Curve ◽  
Large Amplitude ◽  
Model Atmosphere ◽  
Anomalous Behavior ◽  
Zone Model ◽  
Curve Shape ◽  
Pulsating Stars ◽  
Diffusion Phenomena ◽  
Scuti Stars ◽  
Δ Scuti Stars

AbstractAmong the δ Scuti stars with large amplitude there are a few stars with unusual light curve shape and multiperiodicity. These stars are V1719 Cyg, V798 Cyg, V974 Oph and δ Scuti. The Fourier phase difference for the main pulsation mode is very different from that typical of the other large amplitude δ Scuti, SX Phe and RR Lyrae stars. The period ratio is generally high, ≧0.80. Two of the stars (δ Scuti and V1719 Cyg) have known spectral type or Stromgren indices, and these indicate high metallicity which should be related to the δ Delphini type (evolved Am/Fm stars). Some tests with the one-zone model show that the unusual light curve shape could be related to a poor He content in the envelope, while the application of model atmosphere grids shows that the anomalous behavior of the metallicity photometric index of V1719 Cyg is simply due to the high metal abundance of its atmosphere. The conclusion is that diffusion phenomena such as the He settling and the metal enhancement should be able to explain all the observed characteristics of these pulsating stars.

scholarly journals The ASAS-SN catalogue of variable stars VI: an all-sky sample of δ Scuti stars

2020 ◽  
Vol 493 (3) ◽  
pp. 4186-4208 ◽  
Author(s):  
T Jayasinghe ◽  
K Z Stanek ◽  
C S Kochanek ◽  
P J Vallely ◽  
B J Shappee ◽  
...  
Keyword(s):  
Fundamental Mode ◽  
Variable Stars ◽  
Scale Height ◽  
Eclipsing Binaries ◽  
Image Subtraction ◽  
Orbital Periods ◽  
Many Sources ◽  
Scuti Stars ◽  
Δ Scuti Stars ◽  
Gaia Dr2

ABSTRACT We characterize an all-sky catalogue of ∼8400 δ Scuti variables in ASAS-SN, which includes ∼3300 new discoveries. Using distances from Gaia DR2, we derive period–luminosity relationships for both the fundamental mode and overtone pulsators in the WJK, V, Gaia DR2 G, J, H, Ks, and W1 bands. We find that the overtone pulsators have a dominant overtone mode, with many sources pulsating in the second overtone or higher order modes. The fundamental mode pulsators have metallicity-dependent periods, with log10(P) ∼ −1.1 for $\rm [Fe/H]\lt -0.3$ and log10(P) ∼ −0.9 for $\rm [Fe/H]\gt 0$, which leads to a period-dependent scale height. Stars with $P\gt 0.100\, \rm d$ are predominantly located close to the Galactic disc ($\rm |\mathit{ Z}|\lt 0.5\, kpc$). The median period at a scale height of $Z\sim 0\, \rm kpc$ also increases with the Galactocentric radius R, from log10(P) ∼ −0.94 for sources with $R\gt 9\, \rm kpc$ to log10(P) ∼ −0.85 for sources with $R\lt 7\, \rm kpc$, which is indicative of a radial metallicity gradient. To illustrate potential applications of this all-sky catalogue, we obtained 30 min cadence, image subtraction TESS light curves for a sample of 10 fundamental mode and 10 overtone δ Scuti stars discovered by ASAS-SN. From this sample, we identified two new δ Scuti eclipsing binaries, ASASSN-V J071855.62−434247.3 and ASASSN-V J170344.20−615941.2 with short orbital periods of Porb = 2.6096 and 2.5347 d, respectively.

scholarly journals How to separate the low amplitude δ Scuti variation from the instrumental ones in CoRoT data?

2015 ◽  
Vol 11 (A29B) ◽  
pp. 529-531
Author(s):  
József M. Benkő ◽  
Margit Paparó
Keyword(s):  
Real Data ◽  
High Amplitude ◽  
Variable Stars ◽  
South Atlantic ◽  
Frequency Range ◽  
South Atlantic Anomaly ◽  
Fourier Spectra ◽  
Low Amplitude ◽  
Scuti Stars ◽  
Δ Scuti Stars

AbstractRich regular frequency patterns were found in the Fourier spectra of low-amplitude δ Scuti stars observed by CoRoT satellite (see Paparó et al. in prep.). The CoRoT observations are, however, influenced by the disturbing effect of the South Atlantic Anomaly. The effect is marginal for high amplitude variable stars but it could be critical in the case of low amplitude variables, especially if the frequency range of the intrinsic variation overlaps the interval of the instrumental frequencies. Some tests were carried out both on synthetic and real data for distinguishing technical and stars' frequencies.

Sign in / Sign up

Export Citation Format

Share Document