Re-classification of ROTSE-I 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.

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

International Astronomical Union Colloquium ◽

10.1017/s0252921100058450 ◽

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.

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Reclassification of ROTSE-I δ Scuti Stars with Multiband Photometry and Fourier Decomposition

The Astronomical Journal ◽

10.1086/423908 ◽

2004 ◽

Vol 128 (4) ◽

pp. 1847-1856 ◽

Cited By ~ 16

Author(s):

H. Jin ◽

S.-L. Kim ◽

C.-U. Lee ◽

D.-J. Lee ◽

K.-S. Kim

Keyword(s):

Fourier Decomposition ◽

Scuti Stars ◽

Δ Scuti Stars

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Double Mode Pulsating Stars and Opacity Changes

International Astronomical Union Colloquium ◽

10.1017/s0252921100011568 ◽

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.

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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa499 ◽

2020 ◽

Vol 493 (3) ◽

pp. 4186-4208 ◽

Cited By ~ 6

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.

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

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316006050 ◽

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.

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Automated Classification of Variable Stars for ASAS Data

International Astronomical Union Colloquium ◽

10.1017/s0252921100015876 ◽

2002 ◽

Vol 185 ◽

pp. 160-161

Author(s):

Laurent Eyer ◽

Cullen Blake

Keyword(s):

Time Series ◽

Light Curve ◽

Large Fraction ◽

Variable Stars ◽

Red Giants ◽

Automated Classification ◽

Fourier Decomposition ◽

Large Numbers ◽

Remarkable Relation

AbstractWith the advent of surveys generating multi-epoch photometry and their discoveries of large numbers of variable stars, the classification of the obtained time series has to be automated. We have developed a classification algorithm for the periodic variable stars using a Bayesian classifier on a Fourier decomposition of the light curve. This algorithm is applied to ASAS (AII Sky Automated Survey, Pojmanski, 2000). In ASAS 85% of the variables are red giants. A remarkable relation between their period and amplitude is found for a large fraction of those stars.

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Luminosity of δ Scuti Stars After Hipparcos Satellite

Highlights of Astronomy ◽

10.1017/s1539299600022231 ◽

1998 ◽

Vol 11 (1) ◽

pp. 567-567

Author(s):

E. Antonello ◽

L. Mantegazza ◽

E. Poretti

Keyword(s):

Globular Clusters ◽

Rotational Velocity ◽

High Amplitude ◽

Empirical Dependence ◽

Trigonometric Parallaxes ◽

Nearby Stars ◽

Observational Errors ◽

Absolute Magnitudes ◽

Scuti Stars ◽

Δ Scuti Stars

The absolute magnitudes of δ Scuti stars derived from parallaxes measured by the Hipparcos satellite were compared with the previous estimates based on photometric uvby² indices, and significant differences were found which are related to photometric effects of metallicity and rotational velocity. A reliable calibration of Mv in terms of the photometric indices shall include an estimate of these effects. It is important also to take into account the possible presence of unresolved close companions in order to fully exploit the accuracy of Mv of nearby stars derived from the trigonometric parallaxes. The Mv of few bright SX Phe stars support the period-luminosity relation obtained with ground based observations of globular clusters, while it does not seem to confirm the empirical dependence of this relation on the metallicity. Some high amplitude δ Scuti stars with intermediate or normal metallicity and small and uncertain parallax have apparently a very low luminosity. Simulations of Mv determinations from observed parallaxes based on the discussion of observational errors by Lutz and Kelker (1973) have shown that the low luminosity could be an effect related to these errors.

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

International Astronomical Union Colloquium ◽

10.1017/s0252921100011167 ◽

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.

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