scholarly journals Frequency analysis of δ Scuti stars towards the Galactic bulge

2021 ◽  
Author(s):  
H Netzel ◽  
P Pietrukowicz ◽  
I Soszyński ◽  
M Wrona
Keyword(s):  
Frequency Analysis ◽  
Gravitational Lensing ◽  
Fundamental Mode ◽  
Statistical Properties ◽  
Galactic Bulge ◽  
Homogeneous Sample ◽  
Theoretical Predictions ◽  
Scuti Stars ◽  
Δ Scuti Stars

Abstract We have performed a frequency analysis of 10,092 δ Scuti-type stars detected in the fourth phase of the Optical Gravitational Lensing Experiment (OGLE) towards the Galactic bulge, which is the most numerous homogeneous sample of δ Scuti stars observed so far. The main goal was to search for stars pulsating in at least two radial modes simultaneously. We have found 3083 candidates for such stars, which is the largest set obtained to date. Among them, 2655 stars pulsate in two radial modes, 414 stars pulsate in three radial modes, and 14 stars pulsate in four radial modes at the same time. We report the identification of 221 δ Scuti stars pulsating in the fundamental mode, first overtone, and third overtone simultaneously. We show the most populated Petersen and Bailey diagrams and discuss statistical properties of the identified frequencies based on this numerous sample. Additionally, we present theoretical predictions of period ratios for δ Scuti stars pulsating in overtones from the fourth to the seventh.

scholarly journals Non-Adiabatic Seismic Study of The Thin Convective Envelope of δ Scuti Stars

2004 ◽  
Vol 193 ◽  
pp. 470-473
Author(s):  
M.-A. Dupret ◽  
A. Grigahcène ◽  
R. Garrido ◽  
J. Montalban ◽  
M. Gabriel ◽  
...  
Keyword(s):  
Instability Strip ◽  
Full Spectrum ◽  
Convective Envelope ◽  
Theoretical Predictions ◽  
Mode Stability ◽  
Different Color ◽  
Mixing Length Theory ◽  
Scuti Stars ◽  
Δ Scuti Stars ◽  
Phase Differences

AbstractFor δ Sct stars, the theoretical predictions of a non-adiabatic pulsation code are very dependent on the characteristics of the thin convective envelope of the models (Balona & Evers 1999). The treatment of the non-adiabatic interaction between convection and pulsation also has a significant impact on the results, particularly near the red edge of the instability strip. The non-adiabatic theoretical predictions can be tested upon observations by comparing them to the amplitude ratios and phase differences as observed in different color passbands (Dupret et al. 2003). In the first part of this paper, we compare the results obtained by adopting different treatments of convection in the interior and atmosphere models: mixing-length theory (MLT) and full spectrum of turbulence (FST) (Canuto et al. 1996, CGM). In the second part, we examine the problem of the interaction between convection and pulsation and compare the mode stability obtained with and without including time-dependent convection in our non-adiabatic code.

The MACHO Project Sample of Galactic Bulge High‐Amplitude δ Scuti Stars: Pulsation Behavior and Stellar Properties

2000 ◽  
Vol 536 (2) ◽  
pp. 798-815 ◽  
Author(s):  
C. Alcock ◽  
R. A. Allsman ◽  
D. R. Alves ◽  
T. S. Axelrod ◽  
A. C. Becker ◽  
...  
Keyword(s):  
High Amplitude ◽  
Galactic Bulge ◽  
Stellar Properties ◽  
Scuti Stars ◽  
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 STATISTICAL PROPERTIES OF GALACTIC δ SCUTI STARS: REVISITED

2013 ◽  
Vol 145 (5) ◽  
pp. 132 ◽  
Author(s):  
S.-W. Chang ◽  
P. Protopapas ◽  
D.-W. Kim ◽  
Y.-I. Byun
Keyword(s):  
Statistical Properties ◽  
Scuti Stars ◽  
Δ Scuti Stars

scholarly journals Blazhko effect in the Galactic bulge fundamental mode RR Lyrae stars – II. Modulation shapes, amplitudes, and periods

2020 ◽  
Vol 494 (1) ◽  
pp. 1237-1249
Author(s):  
M Skarka ◽  
Z Prudil ◽  
J Jurcsik
Keyword(s):  
Gravitational Lensing ◽  
Fundamental Mode ◽  
Pulsation Period ◽  
Galactic Bulge ◽  
Rr Lyrae Stars ◽  
Modulation Period ◽  
Rr Lyrae ◽  
Blazhko Effect ◽  
Two Parameters ◽  
Lyrae Stars

ABSTRACT The number of stars observed by the Optical Gravitational Lensing Experiment (OGLE) project in the Galactic bulge offers an invaluable chance to study RR Lyrae stars in a statistical manner. We used data of 3141 fundamental-mode RR Lyrae stars showing the Blazhko effect observed in OGLE-IV to investigate a possible connection between modulation amplitudes and periods, light curve, and pulsation characteristics. We found that there is no simple monotonic correlation between any combination of two parameters concerning the Blazhko and pulsation amplitudes, periods, and the shape of the light curves. There are only systematic limits. There is a bottom limit of the modulation period with respect to the pulsation period. We also found that the possible range of modulation amplitudes decreases with increasing pulsation period, which could point towards that the Blazhko effect is suppressed in cooler, larger, more luminous, and less metal abundant bulge RR Lyrae stars. Our investigation revealed that the distribution of the modulation periods can be described with two populations of stars with the mean modulation periods of 48 and 186  d. There is a certain region with a low density of the modulated stars, which we call the Blazhko valley, in the pulsation period–modulation period plane. Based on the similarity of the modulation envelopes, basically every star can be assigned to one of six morphological classes. The double modulation was found in 25 per cent of the studied stars. Only 6.3 per cent of modulated stars belong to the Oosterhoff group II.

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 The census of non-radial pulsation in first-overtone RR Lyrae stars of the OGLE Galactic bulge collection

2019 ◽  
Vol 487 (4) ◽  
pp. 5584-5592 ◽  
Author(s):  
H Netzel ◽  
R Smolec
Keyword(s):  
Gravitational Lensing ◽  
Incidence Rates ◽  
Statistical Properties ◽  
Radial Pulsation ◽  
Galactic Bulge ◽  
Frequency Spectra ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Low Amplitude ◽  
Lyrae Stars

ABSTRACT We analysed photometry for the up-to-date collection of the first-overtone RR Lyrae stars (RRc; 11 415 stars) and double-mode RR Lyrae stars (RRd; 148 stars) towards the Galactic bulge from the Optical Gravitational Lensing Experiment (OGLE). We analysed frequency spectra of these stars in search for additional, low-amplitude signals, beyond the radial modes. We focused on stars from two groups: RR0.61 and RR0.68. In the first group, additional low-amplitude signals have periods shorter than the first-overtone period; period ratios fall in the 0.60–0.64 range. In the second group, additional low-amplitude signals have periods longer than the first-overtone period; period ratios tightly cluster around 0.68. Altogether we have detected 960 and 147 RR Lyrae stars that belong to RR0.61 and RR0.68 groups, respectively, which yield the incidence rates of 8.3 and 1.3 per cent of the considered sample. We discuss statistical properties of RR Lyrae stars with additional periodicities. For RR0.61 group we provide strong arguments that additional periodicities are connected to non-radial pulsation modes of degrees ℓ = 8 and ℓ = 9, as proposed by Dziembowski. We have also detected two double-periodic variables, with two close periodicities, similar to RR Lyrae variable V37 in NGC 6362. Properties of these peculiar variables, which may form a new group of double-mode pulsators, are discussed.

scholarly journals The Luminosities of δ Scuti Stars

2002 ◽  
Vol 185 ◽  
pp. 116-117
Author(s):  
D.H. McNamara
Keyword(s):  
Fundamental Mode ◽  
Globular Clusters ◽  
Main Sequence ◽  
Light Curves ◽  
Instability Strip ◽  
Period Range ◽  
Blue Straggler ◽  
Scuti Stars ◽  
Δ Scuti Stars ◽  
Nonradial Pulsation

The δ Scuti stars are variables found in the instability strip above the zero-age main sequence. Radial and nonradial pulsation modes have been detected in these stars. The large-amplitude variables with asymmetric light curves are radial pulsators. The pulsation periods are found to be in the period range of 0.03 – 0.25 days. Generally, the light amplitudes are small (total range < 0.3 mag), but some fundamental-mode variables reach 0.70 mag. The majority of the variables have light amplitudes <0.10 mag. Population II δ Scuti variables are frequently called SX Phe stars. Many of these variables have been found in globular clusters, where they populate the blue-straggler domain of the color-magnitude diagrams.

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