scholarly journals Fractal analysis applied to light curves of δ Scuti stars★

2018 ◽  
Author(s):  
S de Franciscis ◽  
J Pascual-Granado ◽  
J C Suárez ◽  
A García Hernández ◽  
R Garrido
Keyword(s):  
Fractal Analysis ◽  
Light Curves ◽  
Scuti Stars ◽  
Δ Scuti Stars

scholarly journals Bulge δ Scuti stars in the MACHO database

1997 ◽  
Vol 189 ◽  
pp. 293-298
Author(s):  
D. Minniti ◽  
C. Alcock ◽  
D.R. Alves ◽  
T.S. Axelrod ◽  
A.C. Becker ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
High Amplitude ◽  
Light Curves ◽  
Evolutionary Status ◽  
Absolute Magnitudes ◽  
Scuti Stars ◽  
Δ Scuti Stars

We describe the search for δ Scuti stars in the MACHO database of bulge fields. Concentrating on a sample of high amplitude δ Scutis, we examine the light curves and pulsation modes. We also discuss their spatial distribution and evolutionary status using mean colors and absolute magnitudes.

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 Oscillation Patterns of SX Phœnicis Variables in Globular Clusters

2000 ◽  
Vol 176 ◽  
pp. 497-498
Author(s):  
J. O. Petersen ◽  
M. Quaade ◽  
M. I. Andersen ◽  
L. M. Freyhammer
Keyword(s):  
Life History ◽  
Globular Clusters ◽  
Open Clusters ◽  
Light Curves ◽  
Standard Field ◽  
Blue Straggler ◽  
Scuti Stars ◽  
Δ Scuti Stars

AbstractBased on new analyses of light curves of SX Phœnicis variables in globular clusters and on results taken from the literature, an overview of oscillation patterns in this subgroup of δ Scuti variables is given. Belonging to the Blue Straggler stars, they are expected to have a more complicated life history than “normal” δ Scuti stars in the field or in open clusters. The overall picture is that the patterns found in this SX Phe group seem to be similar to the patterns that are well established for standard field δ Set stars.

scholarly journals Accretion and pulsation of IU Per based on INTEGRAL and ground base photometry

2012 ◽  
Vol 8 (S290) ◽  
pp. 377-378
Author(s):  
Emil Kundra ◽  
Ladislav Hric ◽  
Rudolf Gális
Keyword(s):  
Primary Component ◽  
Light Curves ◽  
Optical Monitoring ◽  
Short Term ◽  
Period Analysis ◽  
Massive Component ◽  
Monitoring Camera ◽  
Pulsation Activity ◽  
Scuti Stars ◽  
Δ Scuti Stars

AbstractIU Persei (IU Per) is an eclipsing semi detached (SD) binary with pulsating component (oscillating eclipsing Algol - oEA). Using our ground base photometry in Johnson's B and V filters and INTEGRAL/OMC (Optical Monitoring Camera) data in V filter we introduce the model of this system. We determined the (O - C) diagram behavior. Moreover, the short term variations of the light curve were detected. Whats more, we obtained residua, by comparison of observational and synthetic light curves (LC), of which the detailed period analysis enabled to characterize and localize their source, that can be explained as the pulsation activity of the primary component. The secondary, less massive component, is beyond the instability belt on H-R diagram and fulfills its Roche lobe. The accreting primary component pulsates in modes typical for the δ Scuti stars.

scholarly journals The pulsation properties of λ bootis stars I. the southern TESS sample

2020 ◽  
Vol 495 (2) ◽  
pp. 1888-1912
Author(s):  
S J Murphy ◽  
E Paunzen ◽  
T R Bedding ◽  
P Walczak ◽  
D Huber
Keyword(s):  
Stellar Evolution ◽  
Fundamental Mode ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Mode Identification ◽  
Regular Sequences ◽  
Stellar Ages ◽  
Scuti Stars ◽  
Δ Scuti Stars ◽  
Gaia Dr2

ABSTRACT We analyse TESS light curves for 70 southern λ Boo stars to identify binaries and to determine which of them pulsate as δ Scuti stars. We find two heartbeat stars and two eclipsing binaries among the sample. We calculate that 81 per cent of λ Boo stars pulsate as δ Sct variables, which is about twice that of normal stars over the same parameter space. We determine the temperatures and luminosities of the λ Boo stars from photometry and Gaia DR2 parallaxes. A subset of 40 λ Boo stars have 2-min TESS data, reliable temperatures and luminosities, and δ Sct pulsation. We use Petersen diagrams (period ratios), échelle diagrams, and the period–luminosity relation to identify the fundamental mode in 20 of those 40 stars and conclude that a further 8 stars are not pulsating in this mode. For the remaining 12, the fundamental mode cannot be unambiguously identified. Further mode identification is possible for 12 of the fundamental mode pulsators that have regular sequences of pulsation overtones in their échelle diagrams. We use stellar evolution models to determine statistically that the λ Boo stars are only superficially metal weak. Simple pulsation models also better fit the observations at a metallicity of Z = 0.01 than at Z = 0.001. The TESS observations reveal the great potential of asteroseismology on λ Boo stars, for determining precise stellar ages and shedding light on the origin(s) of the λ Boo phenomenon.

scholarly journals Frequency analysis of multiperiodic δ Scuti stars

1993 ◽  
Vol 139 ◽  
pp. 149-149 ◽  
Author(s):  
L. Mantegazza ◽  
E. Poretti ◽  
F.M. Zerbi
Keyword(s):  
Light Curve ◽  
Frequency Analysis ◽  
Curve Analysis ◽  
Light Curves ◽  
Light Curve Analysis ◽  
Preliminary Results ◽  
Long Time ◽  
Scuti Star ◽  
Scuti Stars ◽  
Δ Scuti Stars

We report some of the recent results of our studies on δ Scuti star pulsation which are based on observations made at Merate and La Silla Observatories, sometimes in two site campaigns. Our recent experiences on X Caeli and 44 Tauri have shown that quite complicate light curves can be resolved even with observations obtained from one site only, if compact and accurate datasets are collected on sufficiently long time baselines (Mantegazza and Poretti, 1992; Poretti et al., 1992). Here we report the preliminary results of the light curve analysis of three more stars surveyed for more than 120 hours each: BI CMi, HD 18878 and HD 224639.BI CMi has been observed in a two-site campaign in January-February 1991, the observations being collected during 17 nights. The frequency analysis of the light curve allowed us to identify unambiguously 4 pulsation modes at 8.247, 8.863, 8.514 and 7.424 c/d with semi-amplitudes of 22, 19, 5 and 5 mmag respectively.

scholarly journals Unveiling the power spectra of δ Scuti stars with TESS

2020 ◽  
Vol 638 ◽  
pp. A59 ◽  
Author(s):  
S. Barceló Forteza ◽  
A. Moya ◽  
D. Barrado ◽  
E. Solano ◽  
S. Martín-Ruiz ◽  
...  
Keyword(s):  
Power Spectra ◽  
Light Curves ◽  
Space Telescopes ◽  
Stellar Objects ◽  
Long Duration ◽  
Solar Type ◽  
Seismic Index ◽  
Scuti Stars ◽  
Δ Scuti Stars ◽  
High Cadence

Thanks to high-precision photometric data legacy from space telescopes like CoRoT and Kepler, the scientific community could detect and characterize the power spectra of hundreds of thousands of stars. Using the scaling relations, it is possible to estimate masses and radii for solar-type pulsators. However, these stars are not the only kind of stellar objects that follow these rules: δ Scuti stars seem to be characterized with seismic indexes such as the large separation (Δν). Thanks to long-duration high-cadence TESS light curves, we analysed more than two thousand of this kind of classical pulsators. In that way, we propose the frequency at maximum power (νmax) as a proper seismic index since it is directly related with the intrinsic temperature, mass and radius of the star. This parameter seems not to be affected by rotation, inclination, extinction or resonances, with the exception of the evolution of the stellar parameters. Furthermore, we can constrain rotation and inclination using the departure of temperature produced by the gravity-darkening effect. This is especially feasible for fast rotators as most of δ Scuti stars seem to be.

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 Analysis of γ Doradus and δ Scuti stars observed by Kepler

2013 ◽  
Vol 9 (S301) ◽  
pp. 387-388 ◽  
Author(s):  
Paul A. Bradley ◽  
Joyce A. Guzik ◽  
Lillian F. Miles ◽  
Jason Jackiewicz ◽  
Katrien Uytterhoeven ◽  
...  
Keyword(s):  
Fourier Transforms ◽  
Contamination Factor ◽  
Light Curves ◽  
Scuti Stars ◽  
Δ Scuti Stars

AbstractThe Kepler spacecraft observed over 2000 faint stars that were part of our Guest Observer proposals. The stars were selected from the Kepler Input Catalog (KIC) to be in or near the γ Doradus or δ Scuti instability strips (8300 K > Teff > 6200 K and 3.6 < log g < 4.7). The Kepler magnitude was <16 and the contamination factor was < 10−2. The goal was to extend the search for “hybrid” δ Sct-γ Dor pulsators to fainter magnitudes. By inspecting the light curves and Fourier transforms, we find 42 δ Sct candidate stars, 299 γ Dor candidates, and 36 “hybrid” candidate stars showing both types of variations.

scholarly journals Ultra-precise analysis of the light curves of CoRoT and Kepler δ Scuti stars

2017 ◽  
Vol 152 ◽  
pp. 03012
Author(s):  
Javier Pascual-Granado ◽  
Juan Carlos Suárez ◽  
Rafael Garrido
Keyword(s):  
Light Curves ◽  
Precise Analysis ◽  
Scuti Stars ◽  
Δ Scuti Stars
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