Scuti Type Research Articles

KIC 8840638: A Newly Discovered Eclipsing Binary with δ Scuti–Type Oscillations

In this paper, we analyze the light variation of KIC 8840638 using high-precision time-series data from the Kepler mission. The analysis reveals that this target is a new detached eclipsing binary system with a δ Scuti component, rather than a single δ Scuti star as previously known. The frequency analysis of short-cadence data reveals 95 significant frequencies, most of which lie in a frequency range of 23−32 day−1. Among them, seven independent frequencies are detected in the typical frequency range of δ Scuti stars, and they are identified as pressure modes. In addition, a possible large separation value of Δν = 36.5 ± 0.1 μHz is also detected with the Fourier transform (FT) and autocorrelation function (AC) analysis. The orbital frequency f orb (= 0.320008 day−1) and its harmonics are also detected directly in the frequency spectrum. The binary modelings derived from PHOEBE indicate that this binary system is in detached configurations with a mass ratio of q=0.33−0.04+0.06 , an inclination angle of 40.19−2.84+3.96 ​​​​​°. The derived parameters and binary evolutionary model suggest that the primary star is an object on the verge of leaving the main sequence with a temperature of ∼7600 K, while the secondary appears to be a cool component entering the giant branch with a temperature ∼3100 K lower than the primary. Moreover, this system may have undergone a mass ratio reversal, where the more massive star is the gainer component and the less massive one is the donor star.

Fundamental Parameters of a Binary System Consisting of a Red Dwarf and a Compact Star

TIC 157365951 has been classified as a δ Scuti type by the International Variable Star Index. Through the spectra from Large Sky Area Multi-Object Fiber Spectroscopic Telescope and its light curve, we further discovered that it is a binary system. This binary system comprises a red-dwarf star and a compact star. Through the spectral energy distribution fitting, we determined the mass of the red dwarf star as M 1 = 0.31 ± 0.01M ⊙ and its radius as R 1 = 0.414 ± 0.004R ⊙. By fitting the double-peaked Hα emission, we derived the mass ratio of q = 1.76 ± 0.04, indicating a compact star mass of M 2 = 0.54 ± 0.01M ⊙. Using Phoebe to model the light curve and radial velocity curve for the detached binary system, we obtained a red dwarf star mass of M 1 = 0.29 ± 0.02M ⊙, a radius of R 1 = 0.39 ± 0.04R ⊙, and a Roche–lobe filling factor of f = 0.995 ± 0.129, which is close to the f = 1 expected for a semidetached system. The Phoebe model gives a compact star mass M 2 = 0.53 ± 0.05M ⊙. Constraining the system to be semidetached gives M 1 = 0.34 ± 0.02M ⊙, R 1 = 0.41 ± 0.01R ⊙, and M 2 = 0.62 ± 0.03M ⊙. The consistency of the models is encouraging. The value of the Roche–lobe filling factor suggests that there might be ongoing mass transfer. The compact star mass is as massive as a typical white dwarf.

Variability and stellar pulsation incidence in Am and Fm stars using TESS and Gaia data

Aims. We aim to study chemically peculiar Am and Fm stars, distinguished by their unique abundance patterns, which are crucial for studying mixing processes in intermediate-mass stars. These stars provide a window into the atomic diffusion in their stellar envelopes, the evolution-dependent changes in mixing, and the resulting effects on pulsation mechanisms. Methods. This study examines the pulsation characteristics of the Am and Fm star group. Our analysis encompasses 1276 stars (available as catalogues on GitHub), utilising data from TESS and Gaia and focussing on stars from the Renson catalogue. Results. In our sample, 51% of stars (649) display no variability, and are thus categorised as constant stars. Among those that remain, 25% (318 stars) are pulsating Am, Fm, and ρ Puppis stars, including 20% (261 stars) that are exclusively Am and Fm stars. Additionally, 17% of stars (210) show variability indicative of binarity and/or rotational modulation and 7% (93 stars) are eclipsing binaries. Of the pulsating stars, 10% (32 stars) are γ Doradus type, 54% (172 stars) δ Scuti type, and 36% (114 stars) are hybrids, underlining a diverse pulsational behaviour of Am and Fm stars. Conclusions. Our findings indicate that pulsating stars predominantly occupy positions near the red edge of the classical instability strip, allowing us to ascertain the incidence of pulsations in this stellar population.

Characterization of the δ Scuti eclipsing binary KIC 4851217 and its tertiary companion as well as detection of tidally tilted pulsations

Abstract Stellar theory enables us to understand the properties of stars at different stages of their evolution, and contributes to other fields of astrophysics such as galactic and exoplanet studies. Assessing the accuracy of stellar theories necessitates high precision, model-independent measurements of the properties of real stars, such as those obtainable for the components of double lined eclipsing binaries (DLEBs), while asteroseismology offers probing power of the stellar interior if one or both components pulsate. KIC 4851217 is a DLEB containing two late A-type stars and exhibits pulsations of the δ Scuti type. By analysing high resolution HERMES and moderate resolution ISIS spectra, jointly with Kepler and TESS light curves, we measured the masses, radii and effective temperatures of the components to precisions of ∼0.5, ∼1.1 and ∼1 per cent, respectively. We additionally report the discovery and characterisation of a tertiary M-dwarf companion. Models of the system’s spectral energy distribution agree with an age of 0.82 Gyr, with the more massive and larger secondary component near the end of the main sequence lifetime. An examination of the pulsating component’s pulsation frequencies reveals 39 pulsation multiplets that are split by the orbital frequency. For most of these, it is evident that the pulsation axes have been tilted into the orbital plane. This makes KIC 4851217 a tidally tilted pulsator (TTP). This precisely characterized δ Scuti DLEB is an ideal candidate for advancing intermediate-mass stellar theory, contributing to our understanding of hierarchichal systems as well as to the topic of TTPs.

Maxima Times of Pulsating Variables Obtained in 2023-2024

We present 17 times of maxima of 10 delta Scuti type pulsating variables obtained with the IST40 telescope of the Istanbul University Observatory between May 2023 - May 2024.

DISCOVERY AND CATALOGING OF A NEW DELTA SCUTI STAR IN PERSEUS

In this work, we present the discovery and cataloguing of a new variable star in Perseus. After its photometric study, it was concluded that we were facing a new  Scuti type variable star which, although it was included in the ZTF catalogue of periodic variables as suspected, was not adequately characterised. For our study, we used data from other sources, such as the aforementioned ZTF or ASAS-SN, and our own data. Finally, it was included in the AAVSO’s The International Variable Star Index with the name GSC 03319-01926.

Seçilmiş Zonklayan Değişenlerin IST40 Teleskobuyla Elde Edilmiş Maksimum Zamanları

We present 21 times of maxima of 10 $\delta$ Scuti type pulsating variables obtained from Istanbul University Observatory between 2020-2023.

Discovery of a substellar companion in the TESS light curve of the δ Scuti/γ Doradus hybrid pulsator HD 31221

Context. Close-in, sub-stellar companions to δ Scuti type stars present a highly suitable testbed for examining how planetary-mass objects can influence stellar pulsations. Aims. We aim to constrain the mass of HD 31221 b, probe its atmosphere, and demonstrate how it affects the pulsational pattern of its host, HD 31221. Methods. We made use of the available data from the short-cadence Transiting Exoplanet Survey Satellite (TESS). We modeled the nine observed transits and the out-of-phase variations, including Doppler beaming, ellipsoidal variations, and the reflection effect. We also incorporated ground-based photometry from the MuSCAT2 imager installed at the 1.52 m Telescopio Carlos Sanchez in the Teide Observatory, Spain, as well as speckle interferometry from the Southern Astrophysical Research telescope. Results. We found HD 31221 b to have an orbital period of 4.66631 ± 0.00011 days, with a radius of 1.32 ± 0.14 RJ and a mass of 11.5 ± 10.3 MJ (from the ellipsoidal effect), making it consistent with either a brown dwarf or a giant planet. As HD 31221 is a rapid rotator (v sin I⋆ = 175.31 ± 1.74 km s−1), we deduced the spin-orbit misalignment to be λ = −121.6 ± 14.4° and I⋆ = 55.9 ± 11.3°. The phase curve is dominated by the reflection effect, with a geometric albedo of 1.58 ± 0.50. We also found evidence that HD 31221 is a δ Scuti/γ Doradus hybrid pulsator. There are three cases for which the 3rd, 85th, and 221st orbital harmonics almost exactly coincide with peaks in the Fourier spectrum of the star, hinting at tidally perturbed stellar oscillations. Conclusions. HD 31221 b is the third substellar object that is found to be disrupting the pulsations of its host, following HAT-P-2 and WASP-33. Additional photometric observations by CHEOPS and/or PLATO can be used to further constrain its mass and provide a more in-depth analysis of its atmosphere.

Detection of δ Scuti Pulsators in the Eclipsing Binaries Observed by TESS

Based on 2 minute cadence TESS data from sectors 1–50, we report the results of the systematic extraction of δ Scuti–type pulsations in the 6431 eclipsing binaries with orbital periods shorter than 13 days. A total number of 242 pulsators were found in those systems, including 143 new discoveries. We examined their pulsation properties based on the H-R diagram and the relationships between the dominant pulsation period P dom, orbital period P orb, and effective temperature T eff. As a consequence, 216 targets are likely δ Scuti stars (123 new), 11 likely γ Doradus–δ Scuti hybrid stars (8 new), 5 likely β Cephei stars (4 new), 4 likely δ Scuti–γ Doradus hybrid stars (3 new), 3 likely Maia stars (3 new), 2 likely pulsating red giants (1 new), and a new unclassified star. As for the six new δ Scuti pulsators in eclipsing binaries with P orb < 0.65 days, we found that three of them significantly exceed the upper limits of the P dom/P orb ratio. This may indicate that P dom and P orb are uncorrelated for them. Finally, we statistically analyzed the dominant pulsation periods of the 216 δ Scuti stars in eclipsing binaries. Those stars concentrate around 225 μHz and the proportion of stars in the high-frequency region is significantly higher than that of single stars, which could be ascribed to the mass-transfer process.

Comprehensive analysis of southern eclipsing systems with pulsating components: The cases of HM Pup, V632 Sco, and TT Vel

This work presents an extensive analysis of the properties of three southern semi-detached eclipsing binaries hosting a pulsating component, namely HM Pup, V632 Sco, and TT Vel. Systematic multi-filtered photometric observations were obtained using telescopes located in Australia and Chile mostly between 2018 and 2021. These observations were combined with data from the Transiting Exoplanet Survey Satellite (TESS) mission for a detailed analysis of pulsations. Spectral types and radial velocities were determined from spectra obtained with the Australian National University’s 2.3 m telescope and Wide Field Spectrograph. The data are modelled and the absolute parameters of all components are derived. The light curve residuals are further analysed using Fourier transformation techniques for the determination of the pulsation frequencies. Using theoretical models, the most probable modes of the principal oscillations are also identified. Eclipse-timing variation analysis is also carried out for all systems and the most likely mechanisms modulating the orbital period are proposed. The physical properties of these systems are compared with other similar cases and the locations of their components are plotted in the Mass-Radius (M−R) and Hertzsprung-Russell diagrams. Finally, the pulsational properties of the oscillating components are compared with currently known systems of this type within the orbital-pulsation period and log g-pulsation period diagrams. These systems are confirmed as oscillating eclipsing Algol-type systems (oEA stars), as the primary components are pulsating stars of δ Scuti type, with evidence of mass flow from the evolved secondary components present in their Na I D spectra.

DISCOVERY OF FOUR DELTA SCUTI STARS

Four stars, namely TYC 1615-03493-1, TYC 3672-00435-1, GSC 3672-0481, and TYC 5130-00273-1, are announced as new variables for the first time. The stars were observed as by-product and by applying standard photometry techniques, their light curves were obtained and analyzed using Fourier transformation methods. The results of the analyses showed that all of them are delta Scuti type pulsators, they exhibit multi-periodic oscillations and their dominant pulsation frequencies are derived.

A search for variable stars in the four open star clusters

We present a CCD photometric survey for the search of variable stars in four open clusters namely Berkeley 69, King 5, King 7, and Berkeley 20. The time series observations were carried out for 1 and/or 2 nights for each of the clusters in the year 1998, which have led to identify nineteen variable stars in these clusters. Out of these 19 variable stars, five stars show delta Scuti like variability and two stars show W UMa type variability. In other stars, we could not find the periods and hence the type of variability due to the lack of sufficient data. The periods of delta Scuti type stars are found to be in the range of 0.13 to 0.21 days, whereas the two stars in the cluster Berkeley 20, which showed W UMa type variability have orbital periods of 0.396 and 0.418 days, respectively. Using the Gaia data, the basic parameters of the clusters Berkeley 69, King 7 and King 5 are also revised. The age and reddening are estimated to be 0.79 \pm 0.09 Gyr and 0.68 \pm 0.03 mag for Berkeley 69, 0.79 \pm 0.09 Gyr and 1.22 \pm 0.03mag for the cluster King 7 and 1.59 \pm 0.19 Gyr and 0.63 \pm 0.02 mag for the cluster King 5, respectively. Signature of mass segregation is found in the clusters King 7 and King 5.

HD 99458: First time ever Ap-type star as a δ Scuti pulsator in a short period eclipsing binary?

We present the discovery of a unique object, a chemically peculiar Ap-type star showing $\delta$ Scuti pulsations which is bound in an eclipsing binary system with an orbital period shorter than 3 days. HD 99458 is, therefore, a complex astrophysical laboratory opening doors for studying various, often contradictory, physical phenomena at the same time. It is the first Ap star ever discovered in an eclipsing binary. The orbital period of 2.722 days is the second shortest among all known chemically peculiar (CP2) binary stars. Pulsations of $\delta$ Scuti type are also extremely rare among CP2 stars and no unambiguously proven candidate has been reported. HD 99458 was formerly thought to be a star hosting an exoplanet, but we definitely reject this hypothesis by using photometric observations from the K2 mission and new radial velocity measurements. The companion is a low-mass red dwarf star ($M_{2}=0.45(2)$ M$_{\odot}$) on an inclined orbit ($i=73.2(6)$ degrees) that shows only grazing eclipses. The rotation and orbital periods are synchronized, while the rotation and orbital axes are misaligned. HD 99458 is an interesting system deserving of more intense investigations.

Eclipse mapping of Algol-type systems with oscillating δ Scuti type components

The oscillating Algol-type (oEA) stars are the former secondaries of evolved, semi-detached eclipsing binaries which are (still) undergoing mass transfer and form a newly detected class of pulsators close to the main sequence. Their unique feature consists of mass accretion onto the atmosphere of the pulsating star. Mass accretion affects the mass, radius, density as well as the star’s evolution. Such stars are therefore very attractive targets for asteroseismic studies. A new tool for mode identification of pulsating components in eclipsing binaries consists in using the event of primary eclipse as a spatial filter to resolve the pulsations across the stellar surface of the pulsator. During an eclipse, depending on the spatial structure of modes represented by the wave numbers (l,m), different shapes of the pulsation amplitude and phase variations can be observed. A comparison between the modelled and the observed amplitudes and phases then provides the correct mode identification. The method needs a geometrical model, the pulsation frequencies and the light curves as input. The geometrical model can be obtained from a simultaneous modelling of the light and radial velocity curves. The pulsation frequencies are obtained from subtracting a binary model from the original light curves followed by a frequency analysis of the residuals. We will identify and illustrate systems where observations with a fast CCD camera equipping the 3.6-m DOT telescope could deliver the data needed for the application of the eclipse mapping method.

STEREO observations of hybrid stars V775 Tau and V483 Tau

In this study, pulsational and physical characteristics of two $\delta$ Scuti stars, V775 Tau and V483 Tau, are analysed by using four-year high-precision photometric data of STEREO satellite. Thus, it is aimed to gain new insights into behaviours of these pulsators and evolution of $\delta$ Scuti, $\gamma$ Dor and Am type stars. The data are taken between 2007--2011 and examined with the help of the Lomb-Scargle method. The detection precision in the four-year combined data is around $10^{-5}$ c/d in frequency and $10^{-5}$ mag in amplitude. It is revealed that V775 Tau exhibits weak pulsation characteristic which is interpreted as the existence of the interaction between the helium loss in the partial ionization zone and pulsation intensities. It is also considered that the absence of strong pulsations is also related to the evolution status of the star. Further, its periodogram shows low-frequency peaks. If these oscillations are g-modes, V775 Tau can be thought to be one of the rare stars that show all $\gamma$ Dor, $\delta$ Scuti and Am type variations. V483 Tau is comparatively more luminous, hotter and has higher rotational velocity. Therefore, although it shares the same region with V775 Tau in the H-R diagram, it is not considered to be an Am star. Yet, it exactly overlaps with the $\gamma\,$ Dor stars. These clues as well as g-modes detected in its periodogram indicate that V483\,Tau is a hybrid star. Finally, both V775 Tau and V483 Tau display period changes whose rates are between $10^{-3}$ and $10^{-4}$ $yr^{-1}$. Considering the $\delta$ Scuti nature, it may be speculated that these changes are non-evolutionary.

Variability Analysis of δ Scuti Candidate Stars

The Hipparcos catalog contains stars suspected to be δ Scuti variables for which extensive ground-based observations and characterization of variability are necessary. Our aim was to characterize variability of 13 candidates to δ Scuti type stars. We obtained 24 215 CCD images and analyzed stellar light curves using the Period04 program. Twelve δ Scuti candidate stars have been characterized as pulsating with frequencies intrinsic to δ Scuti stars: HIP 2923, HIP 5526, HIP 5659, HIP 11090, HIP 17585, HIP 74155, HIP 101473, HIP 106219, HIP 107786, HIP 113487, HIP 115093, and HIP 115856. Five of them (HIP 2923, HIP 5526, HIP 11090, HIP 115856, and HIP 106219) may be hybrid δ Scuti-γ Doradus pulsators. One more candidate, HIP 106223, is a variable star with longer periods of pulsations which are intrinsic to γ Doradus.

Stellar Variability at the Main-sequence Turnoff of the Intermediate-age LMC Cluster NGC 1846*

Abstract Intermediate-age (IA) star clusters in the Large Magellanic Cloud (LMC) present extended main-sequence turn-offs (MSTO) that have been attributed to either multiple stellar populations or an effect of stellar rotation. Recently it has been proposed that these extended main sequences can also be produced by ill-characterized stellar variability. Here we present Gemini-S/Gemini Multi-Object Spectrometer (GMOS) time series observations of the IA cluster NGC 1846. Using differential image analysis, we identified 73 new variable stars, with 55 of those being of the Delta Scuti type, that is, pulsating variables close the MSTO for the cluster age. Considering completeness and background contamination effects, we estimate the number of δ Sct belonging to the cluster between 40 and 60 members, although this number is based on the detection of a single δ Sct within the cluster half-light radius. This amount of variable stars at the MSTO level will not produce significant broadening of the MSTO, albeit higher-resolution imaging will be needed to rule out variable stars as a major contributor to the extended MSTO phenomenon. Though modest, this amount of δ Sct makes NGC 1846 the star cluster with the highest number of these variables ever discovered. Lastly, our results present a cautionary tale about the adequacy of shallow variability surveys in the LMC (like OGLE) to derive properties of its δ Sct population.

Asteroseismology ofKeplerAlgol-type oscillating eclipsing binaries

Context. This research paper contains light curve modelling, spectroscopy and detailed asteroseismic studies for four out of five in total semidetached eclipsing binaries with a delta Scuti component, that have been detected to date through Kepler mission, namely KIC 06669809, KIC 10581918, KIC 10619109 and KIC 11175495. Aims. The goal is to study the pulsational characteristics of the oscillating stars of the systems as well as to estimate their absolute parameters and enrich the so far poor sample of this kind of systems. Methods. Ground based spectroscopic observations provide the means to estimate the spectral types of the primary components and to model the light curves with higher certainty. The photometric data are analysed using eclipsing binary modeling techniques, while Fourier analysis is applied on their residuals in order to reveal the pulsation frequency modes. Results. The results of analyses show that the primaries are pulsating stars of delta Scuti type and that all systems belong to the group of Algol type binaries with an oscillating star, namely oEA stars. The primaries of KIC 06669809, KIC 10581918, and KIC 10619109 pulsate in three, two, and five frequencies, respectively and in more than 200 other detected as combinations. The delta Scuti star of KIC 11175495 is the youngest and the fastest pulsator in binary systems that has ever been found and it oscillates in three main non radial frequencies, while other 153 are also found as depended ones. Moreover, a comparison of their properties with other systems of the same type as well as with theoretical models of pulsating stars are also presented and discussed.

An astrometric and spectroscopic study of the δ Scuti variable HD 21190 and its wide companion CPD −83° 64B

Although pulsations of $\delta$ Scuti type are not expected among Ap stars from a theoretical point of view, previous observations of the known $\delta$ Scuti star HD21190 indicated a spectral classification F2 III SrEuSi:, making it the most evolved Ap star known. Our atmospheric chemical analysis based on recent HARPS observations confirms the presence of chemical peculiarities in HD21190. This star is also the only target known to host a magnetic field along with its $\delta$ Scuti pulsation properties. Using an astrometric analysis, we show that HD21190 forms a physical binary system with the companion CPD -83$^{\circ}$ 64B. The presented astrometric and spectroscopic study of the binary components is important to understand the complex interplay between stellar pulsations, magnetic fields, and chemical composition.

KIC 8262223: A Post-mass Transfer Eclipsing Binary Consisting of a Delta Scuti Pulsator and a Helium White Dwarf Precursor

Abstract KIC 8262223 is an eclipsing binary with a short orbital period (P = 1.61 day). The Kepler light curves are of Algol-type and display deep and partial eclipses, ellipsoidal variations, and pulsations of δ Scuti type. We analyzed the Kepler photometric data, complemented by phase-resolved spectra from the R-C Spectrograph on the 4 meter Mayall telescope at the Kitt Peak National Observatory and determined the fundamental parameters of this system. The low-mass and oversized secondary ( , ) is the remnant of the donor star that transferred most of its mass to the gainer, and now the primary star. The current primary star is thus not a normal δ Scuti star but the result of mass accretion from a lower mass progenitor. We discuss the possible evolutionary history and demonstrate with the MESA evolution code that this system and several other systems discussed in prior literature can be understood as the result of non-conservative binary evolution for the formation of EL CVn-type binaries. The pulsations of the primary star can be explained as radial and non-radial pressure modes. The equilibrium models from single star evolutionary tracks can match the observed mass and radius ( , ) but the predicted unstable modes associated with these models differ somewhat from those observed. We discuss the need for better theoretical understanding of such post-mass transfer δ Scuti pulsators.