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Statistical examination of the correlations among active regions, flares, coronal mass ejections and interplanetary shocks
(Elsevier Sci Ltd, 2025) Çavuş, Hüseyin; Çoban, Gani Çağlar; Wang, Haimin; Raheem, Abd-ur; Wang, Jason T. L.; Asgari-Targhi, Mahboubeh
In this study, the statistical relationship among active region (AR)-associated flares and coronal mass ejections (CMEs) and the interplanetary shock waves (IPS) caused by CMEs have been investigated for the years between 2011 and 2021. The study aims to contribute to the efforts of investigating the Sun-Earth connection by statistically examining the relationship between the magnetic properties of AR groups and the eruptive events associated with these groups. Though the significance of AR group structure on flare strength is commonly known, one of our study’s results is that it also has a substantial effect on CME energies and IPS varieties. A further intriguing result of our investigation is the evident correlation between flare intensity and CME energy levels connected with these flares. Furthermore, it has been revealed that there is an association between the speeds of IPS-producing CMEs, the intensity of associated flares, and the complexity of corresponding AR groups.
Absolute parameters of young stars: NO Puppis
(Cambridge Univ Press, 2025) Erdem, Ahmet; Bakış, Volkan; Southworth, John; Rhodes, Michael; Kahraman Alicavus, Filiz; Budding, Edwin; Blackford, Mark G.; Kahraman Aliçavuş, Filiz
The southern early-type, young, eccentric-orbit eclipsing binary NO Puppis forms the A component of the multiple star Gaia DR3 5528147999779517568. The B component is an astrometric binary now at a separation of about 8.1 arcsec. There may be other fainter stars in this interesting but complex stellar system. We have combined several lines of evidence, including TESS data from four sectors, new ground-based BVR photometry, HARPS (ESO) and HERCULES (UCMJO) high-resolution spectra and astrometry of NO Pup. We derive a revised set of absolute parameters with increased precision. Alternative optimal curve-fitting programs were used in the analysis, allowing a wider view of modelling and parameter uncertainties. The main parameters are as follows: 𝑀𝐴⁢𝑎 =3.58 ±0.11, 𝑀𝐴⁢𝑏 =1.68 ±0.09 (M⊙); 𝑅𝐴⁢𝑎 =2.17 ±0.03, 𝑅𝐴⁢𝑏 =1.51 ±0.06 (R⊙), and 𝑇e⁢Aa =13 300 ±500, 𝑇e⁢Ab =7 400 ±500 (K). We estimate approximate masses of the wide companions, Ba and Bb, as 𝑀𝐵⁢𝑎 =2.0 and 𝑀𝐵⁢𝑏 =1.8 (M⊙). The close binary’s orbital separation is 𝑎 =8.51 ±0.05 (R⊙); its age is approximately 20 Myr and distance 172 ±1 pc. The close binary’s secondary (Ab) appears to be the source of low amplitude 𝛿 Scuti-type oscillations, although the form of these oscillations is irregular and unrepetitive. Analysis of the 𝜆 6678 He I profile of the primary show synchronism of the mean bodily and orbital rotations. The retention of significant orbital eccentricity, in view of the closeness of the A-system components, is unexpected and poses challenges for the explanation that we discuss.
BSN. IV. The First Multiband Light Curve Study of Five W UMa-type Contact Binary Systems
(Iop Publishing Ltd, 2025) Poro, Atila; Michel, Raul; Coliac, Jean-Francois; Nastaran, Maryam; Fernandez Lajus, Eduardo; Javier Tamayo, Francisco; Aceves, Hector; Aliçavuş, Fahri
In this work, we present a detailed investigation of five contact binary systems of the W Ursae Majoris (W UMa) type. Multiband photometric observations were conducted using ground-based telescopes in both the northern and southern hemispheres, yielding new times of minima. O − C diagram analysis reveals that two systems exhibit parabolic trends, indicating a gradual long-term decrease in their orbital periods. The light curves were modeled using version 1.0 of the BSN application, with one system requiring the inclusion of a cool starspot to achieve a satisfactory fit. We examined empirical relationships between orbital period and fundamental parameters, identifying the period–semimajor axis (P–a) relation as the most robust correlation, which was used to estimate absolute parameters. To statistically assess thermal equilibrium, we analyzed temperature differences between components and found that 90% of systems exhibit less than 9.4% contrast. Two target systems with extremely low mass ratios were identified, and their orbital stability was evaluated. Based on the effective temperatures and component masses, two systems were classified as W-subtype and three as A-subtype. The evolutionary status of the binaries was assessed through their locations in mass–radius, mass–luminosity, and other empirical diagrams, and initial component masses as well as total mass loss were also estimated.
BSN-III: The First Multiband Photometric Study on the Eight Total Eclipse Contact Binary Stars
(Iop Publishing Ltd, 2025) Poro, Atila; Li, Kai; Michel, Raul; Wang, Li-Heng; Aliçavus, Fahri; Alizadeh, Ghazal; Altamirano-Devora, Liliana
This study continues our in-depth investigation of total-eclipse W Ursae Majoris-type contact binaries by analyzing eight new systems, complementing our previous work. Multiband BVRcIc photometric data were acquired through ground-based observations at an observatory in Mexico, from which new times of minima were determined. Our analysis of orbital period variations using the O - C method revealed that one system shows no long-term variation, four systems exhibit a secular decrease in their orbital periods, and two systems exhibit a secular increase, suggesting mass transfer between the components. Notably, one system displays a cyclic variation with an amplitude of 0.00865 days and a period of 10.49 yr, which we attribute to the light travel time effect induced by a tertiary companion, possibly a brown dwarf. We modeled the light curves using the PHysics Of Eclipsing BinariEs Python code. Six of the target systems required the inclusion of a cold starspot on one of the system's stars due to the asymmetry observed in the maxima of their light curves. Absolute parameters were estimated using the Gaia DR3 parallax method. Using the components' effective temperatures and masses, we classified five of the systems as W-subtype and three as A-subtype. The stellar evolution was illustrated through the mass-radius and mass-luminosity diagrams. Furthermore, we investigated the dynamical stability of two systems with extremely low mass ratios.
Viscous fluid with neutrino in f(R,Φ,X) gravity
(Iop Publishing Ltd, 2025) Eraslan, Erkan; Doğru, Melis Ulu; Taşer, Doğukan; Aydın, Hüseyin
In this study, we investigate the Kantowski-Sachs space-time within the framework of f(R,Φ,X) gravity, incorporating a general fluid distribution with neutrino contributions. The field equations are constructed using a hybrid f(R,Φ,X) function that combines features of the Starobinsky-like model and k-essence functions with canonical scalar fields. Analytical solutions are obtained, showing that the fluid can exhibit bulk viscous behavior with neutrino contributions. The model’s kinematical properties and energy conditions are investigated. NEC, WEC and DEC are satisfied, while SEC is violated, indicating scenarios where gravity repels matter, enabling exotic configurations. These results provide insights into the early universe’s dynamics and the role of viscous fluids and neutrinos in modified gravity theories.
BSN. V. The First Detailed Light Curve Modeling of Eight Totally Eclipsing Contact Binary Stars Using Ground-based and TESS Observations
(Iop Publishing Ltd, 2025) Poro, Atila; Michel, Raul; Javier Tamayo, Francisco; Hedayatjoo, Mahya; Aceves, Hector; Aliçavuş, Fahri
This study broadens our comprehensive investigation of total-eclipse W Ursae Majoris-type contact binaries by analyzing eight additional systems, continuing our previous research. Multiband BV RcIc photometric data were obtained at an observatory in Mexico, from which new times of minima were determined. All target systems also had available space-based Transiting Exoplanet Survey Satellite time-series data. Orbital period variations were studied for eight target systems, showing either linear or parabolic trends. The target systems exhibiting parabolic trends demonstrated a sustained decrease in their orbital periods over time. We modeled the light curves utilizing the PHOEBE Python code in combination with the BSN application. We revisited the relationship between orbital period and the temperature of the hotter component in contact binary systems using an empirical approach. Our analysis identified a clear break at P = 0.27 day, separating the systems into two distinct groups for orbital periods shorter than 0.6 day. Following the determination of stellar extinction, absolute parameters for seven systems were estimated employing parallax measurements from Gaia DR3. Based on the components' effective temperatures and masses, the systems were classified into A- and W-subtypes. Their evolutionary states were illustrated using mass-radius and mass-luminosity diagrams.
Spectroscopic and photometric investigation of some potentially chemically peculiar δ Scuti stars
(Oxford Univ Press, 2025) Kahraman Aliçavuş, Filiz; Aliçavuş, Fahri; Özkardeş, Burcu; Çelik, Eda
Investigating chemically peculiar pulsating stars is crucial for understanding the pulsation driving mechanism in detail. To reveal the true peculiarity properties of stars, detailed spectroscopic analysis is essential. Therefore, in this study, we focused on delta Scuti stars previously identified as chemically peculiar but which needed comprehensive updated spectroscopic analysis to uncover their chemical abundance structure. We selected 10 targets which have publicly available high-resolution spectroscopic and photometric data. Performing spectral analyses, we determined the spectral classification, atmospheric parameters, and detailed chemical abundance distributions of the selected stars. The pulsation properties were also analyzed using TESS data, and pulsation modes for the highest amplitude pulsation frequencies were derived. We estimated the masses and ages of the targets using the evolutionary tracks and isochrones. As a result of our study, we show that only three targets exhibit chemical peculiarity: AU Scl and FG Eri as metallic A (Am) stars, and HZ Vel as a lambda Bootis. However, others were found to be chemically normal stars. This study show us the importance of chemical abundance analysis in the classification of chemical peculiar stars.
Characterizing the variability of a sample of massive stars in eclipsing binaries
(Slovak Academy Sciences Astronomical Inst, 2025) Eze, C. I.; Handler, G.; Kahraman Aliçavuş, Filiz; Pawar, T.; Miszuda, A.
Massive stars exhibit a perplexing mismatch between their inferred masses from different observational techniques, posing a significant challenge to our understanding of stellar evolution and structure. This discrepancy is believed to be caused by the underestimation of the convective core masses. The efficiency of such measurement is usually impaired by a lot of processes at work in the interior of the stars such as convective core overshooting and interior rotation. By integrating the precision of asteroseismology which provides insights into the internal structure and dynamics of stars, with the detailed observational constraints offered by eclipsing binary systems, this study aims to precisely characterize a sample of massive stars in eclipsing binaries to infer their properties and evolutionary state. In this paper, the sample, observed photometrically with TESS and spectroscopically with SALT HRS, CHIRON, HERMES and a spectrograph at Skalnate Pleso Observatory between 2021 and 2024, are analyzed. The orbital elements as well as the basic stellar parameters of the targets in the sample are fitted to derive the geometry of their orbits as well as their absolute parameters. The asteroseismic properties of the targets are also obtained, which unravel their core dynamics and profiles. This is a precursor work that provides detailed characterization of the targets in the sample for future theoretical modeling.
Interrelated main-sequence MLR, MRR, MTR relations from planet hosting stars
(Slovak Academy Sciences Astronomical Inst, 2025) Bakış, Volkan; Eker, Z.; Soydugan, Faruk; Bilir, S.
In this study, we investigated the interrelated mass-luminosity, mass-radius, and mass-temperature relations of planet-hosting stars. The sample, which is chosen to be main-sequence systems, is divided into two metallicity regimes: one regime is below the average of all samples (z=0.017) and the other above it. Suitable figures represent the comparisons of each distinct metallicity regime.
Pulsating and Nonpulsating Components of Detached Eclipsing Binaries in the δ Scuti Instability Strip
(Iop Publishing Ltd, 2025) Kahraman Aliçavuç, Filiz; Aliçavuş, Fahri; Çelik Orhan, Zeynep; Çelik, Eda; Catanzaro, Giovanni; Giarrusso, Marina
Pulsating detached eclipsing binary systems are crucial for studying the internal structure of oscillating stars. These systems are advantageous because binary effects on pulsations are minimal, allowing for more accurate determinations of fundamental stellar parameters such as mass and radius. They serve as unique laboratories for detailed investigations of pulsating stars. In this study, we focused on four detached eclipsing binaries exhibiting δ Scuti−type oscillations: HD 117476, 205 Dra, HY Vir, and V1031 Ori. Our preliminary investigation showed that all binary components of these targets lie within the δ Scuti instability strip. Therefore, we aimed to determine which components are pulsating and which are not and to explore the differences between them. To achieve this, we analyzed TESS photometric data and high-resolution spectra of the targets. Radial velocity (RV) variations were measured, and atmospheric parameters for each component were derived using spectral disentangling or synthetic composite spectra. We also modeled the binary light and RV curves to determine the fundamental physical parameters of the components. Furthermore, we examined pulsation properties using three different approaches to identify the pulsating components. The evolutionary status of the targets was also assessed. Our analysis revealed that, in each system, only one component exhibits δ Scuti−type pulsations, while the others are nonpulsating. Interestingly, we found that the key difference between pulsating and nonpulsating components within the same binary is metallicity: the metal-rich components were found to be nonpulsators, supporting theoretical studies on the effect of metallicity on δ Scuti−type pulsations.
BSN. II. The First Light Curve Study of Eight Total Eclipsing Contact Binary Stars with Shallow Fillout Factors
(Iop Publishing Ltd, 2025) Poro, Atila; Li, Kai; Michel, Raul; Wang, Li-Heng; Aliçavuş, Fahri; Najera, Morgan Rhai; Santillan-Ortega, Priscila
This study provides the first comprehensive analysis of eight total-eclipse W Ursae Majoris-type contact binary systems. Ground-based photometric multiband observations were conducted at a Mexican observatory, and new times of minima were extracted. The O-C analysis reveals that four of our target binaries exhibit a long-term increase in their orbital periods, while the others show a long-term decrease in their orbital periods. We analyzed the light curves using the PHOEBE Python code and BSN application. Among the target systems, two required the inclusion of a cold starspot on one of the components to achieve an adequate fit. The light curve analysis revealed that the target systems exhibit a shallow fillout factor. Absolute parameters were estimated using the Gaia DR3 parallax and astrophysics equations. Considering the effective temperatures and component masses, each system was classified as either the A- or W-subtype. The stellar evolution of the systems was represented through the mass-radius and mass-luminosity diagrams. Additionally, we calculated the initial masses of the companion stars and the total mass lost for each target system.
A Combined TESS and Ground-based Study of Transit Timing Variations in HAT-P-16, TOI-1516 and TOI-2046 Systems
(Iop Publishing Ltd, 2025) Sonbaş, E.; Kaplan, K.; Tanrıver, M.; Keskin, A.; Dhuga, K.; Bulut, Ahmet; Göğüş, E.
We present new results for the hot Jupiters HAT-P-16b, TOI-1516b, and TOI-2046b, based on photometric observations collected using both space- and ground-based facilities. Ground-based data were collected in the 2020–2024 time span with the 0.6 m telescope (ADYU60) located at the Adiyaman University Application and Research Center (Adiyaman, Türkiye) and the 1.0 m telescope at the Türkiye National Observatory (TUG, Türkiye). Through a combination of fits to our ground-based data, the midtransit times data from TESS, and additional data taken from the literature, we present an updated linear ephemeris for each system. Transit timing variations (TTVs) were analyzed using linear, orbital decay, and apsidal precession models. The resulting BIC(ΔBIC) values indicate that the orbital decay model is statistically favored for HAT-P-16b and TOI-1516b, while the constant period model is preferred for TOI-2046b. False alarm probabilities (FAPs) were computed to assess the significance of any periodic signals. TOI-1516b displays a strong TTV signal with a FAP (of 0.0001) well below the 0.01 threshold, suggesting a likely dynamical origin that warrants further investigation. The higher FAP value (0.0055) for HAT-P-16b suggests that the case of a possible presence of an additional body in the system is less convincing. In contrast, the much higher FAP value (0.0196) for TOI-2046b implies that there are no statistically significant TTVs.
Zonklayan Çift Sistemler
(Türk Astronomi Derneği, 2020) Soydugan, Esin
Bu çalışmada zonklayan bileşenli çift sistemlerde yapılan zonklama çalışmalarının bilime kazandırdıkları ve çift sistemlerde zonklama çalışmalarının neden önemli olduğu üzerinde durulmuştur. Çanakkale Onsekiz Mart Üniversitesi Gözlemevi'nde sıcak bileşeninde ilk defa $\delta$ Scuti türü ışık değişimi belirlenen bir örten çift sistem IO UMa'nın sıcak bileşenin zonklama doğasını ortaya koymak için zonklayan bileşenin zonklama parametreleri, frekans ve mod değerleri belirlenmiştir. Örnek sistem IO UMa'nın sıcak zonklayan bileşeninin dört frekans değeriyle zonklama yaptığı ve genlik oranları ve evre farklarına göre belirlenen \textit{l} değerine göre çapsal olmayan zonklama gösterdiği bulunmuştur. Yer tabanlı yapılan gözlemler sonucunda elde edilen zonklama parametreleriyle, uydu verileriyle elde edilen zonklama parametrelerinin karşılaştırılması yapılmıştır. Kepler uydusunun zonklama çalışmalarına katkıları üzerinde de durulmuştur.
YY Gem Aktif Çiftinin Çoklu Dalgaboyu Çalışması
(Türk Astronomi Derneği, 2020) Erkan, Naci
Bu çalışmada YY Gem aktif çiftinin 1988 yılında yapılan çoklu dalgaboyu kampanya gözlem sonuçları incelenmiş, elde edilen optik ışık eğrileri modellenip, diğer dalgaboyundaki gözlem sonuçlarıyla karşılaştırılmıştır.
A comprehensive investigation of PtNPs/PEI N-GQDs nanocomposite: DFT modeling, anticancer activity, and biosensing applications
(Springer, 2025) Altınok Güneş, Buket; Kırlangıç, Ömer Faruk; Kılıç, Murat; Ketenoğlu, Didem; Aslan, Ayşenur; Kabaş, Sultan Yağmur; Kabaş, Afşar; Kaya, İsmet; Yıldız, Mustafa
This research focuses on the synthesis and characterization of a novel nanocomposite, PtNPs/PEI N-GQDs, utilizing FTIR, UV-Vis, SEM, TEM, XPS, and XRD techniques. The study investigates the cytotoxic, apoptotic, and antiangiogenic effects of the nanocomposite on OVCAR-3 cells, aiming to understand the interplay between nanomaterials and cancer. Additionally, the electrochemical properties of PtNPs/PEI N-GQDs-modified glassy carbon electrodes (GCE) are explored, emphasizing analyses of HOMO-LUMO energy levels and band gap energy. Density Functional Theory (DFT) analysis results further support these findings by providing insights into the electronic structure and energetics of the nanocomposite. The nanocomposite exhibits promising electrochemical behavior, demonstrating high capacitance and sensitivity in glucose detection through cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Selectivity towards glucose among interfering bioanalytes is highlighted, showcasing potential applications in tumor monitoring and diagnosis. Furthermore, the nanocomposite displays significant toxicity against cancer cells, inducing apoptosis and cell cycle arrest. Antiangiogenic effects are also observed, suggesting potential therapeutic benefits. Overall, these findings underscore the multifunctional properties of the synthesized nanocomposite, offering insights into its potential for cancer therapy and biosensor applications for glucose detection in bodily fluids.
Tailoring the physical properties of ultrasonically spray pyrolyzed SnS thin films with silver doping
(Springer, 2025) Güneş, İbrahim; Sarıca, Emrah; Bilgin, Vildan; Küçükarslan, Ayşe
In this study, the effects of silver (Ag) doping on the structural, morphological, optical, and electrical properties of tin monosulfide (SnS) thin films were investigated. The films, undoped and doped with 3%, 6%, and 9% Ag, were deposited using the ultrasonic spray pyrolysis (USP) technique at a substrate temperature of 350 degrees C. X-ray diffraction (XRD) analysis confirmed a pi-SnS (cubic) structure with (400) preferred orientation for undoped and <= 6% Ag-doped films, while 9% doping induced amorphization due to severe lattice distortions. Morphological analyses revealed smooth, void-free surfaces, with average roughness increasing from 5.8 nm (undoped) to 19.6 nm (9% doping). Optical measurements showed that the band gap widened from 1.84 eV (undoped) to 2.47 eV (9% Ag-doped), and Urbach energy increased from 190 meV to 600 meV. Hall effect measurements confirmed p-type conductivity for all films. Resistivity ranged from 4.34 x 10(5) Omega cm to 9.48 x 10(5) Omega cm, carrier concentration varied between 2.7 x 10(12) cm(-3) and 5.6 x 10(12) cm(-3), while mobility decreased from 3.3 x 10(1) cm(2)/Vs to 2.0 x 10(1) cm(2)/Vs with increasing Ag doping. These findings demonstrate that Ag doping significantly influences the structural and optoelectronic behavior of SnS thin films, making them promising candidates for thin-film solar cells and optoelectronic applications.
First photometric investigation of V517 Cam combined with ground-based and TESS data
(Elsevier, 2025) Alan, Neslihan; Aliçavuş, Fahri; Alpsoy, Mehmet
The observations of eclipsing binary systems are of great importance in astrophysics, as they allow direct measurements of fundamental stellar parameters. By analysing high-quality space-based observations with ground-based photometric data, it becomes possible to detect these fundamental parameters with greater precision using multicolour photometry. Here, we report the first photometric analysis results of the V517 Cam eclipsing binary system by combining the Transiting Exoplanet Survey Satellite ( TESS ) light curve and new CCD observations in BVRI filters, obtained with a 60 cm robotic telescope (T60) at the T & Uuml;B & Idot;TAK National Observatory. By means of photometric analyses, the masses and radii of the primary and secondary stars were carefully determined to be M1 = 1.47 +/- 0.06 M ae, M2 = 0.79 +/- 0.05 M ae, and R1 = 1.43 +/- 0.03 R ae, R2 = 0.75 +/- 0.04 R ae, respectively. Furthermore, the distance to V517 Cam was calculated to be 284 +/- 20 pc. The overall age of the system is estimated to be around 63 +/- 15 Myr. At this age, the primary component stands near the onset of its main-sequence evolution, near the ZAMS, whereas the secondary component remains in the pre-main- sequence evolutionary phase. To better understand the evolutionary status and nature of V517 Cam, the mass ratio and temperature values, obtained with relatively low sensitivity by photometric measurements, need to be confirmed by spectral analysis.
Charge-Transfer Processes within the Isolated Tetramer Models of the Reaction Center Rhodobacter sphaeroides
(Amer Chemical Soc, 2025) Geçit, Fehime Hayal; Aksu, Hüseyin
Over the last two decades, advancements in structural resolution and spectral characterization have significantly enhanced our understanding of photosynthesis. However, the complexity of photosystem (PS) supercomplexes still presents challenges. In the Rhodobacter sphaeroides reaction center (RSRC), the charge separation process begins with a charge-transfer (CT) step at the special pair (P), a dimer of bacteriochlorophyll a (BChl), which acts as the donor, and continues with electron transport through the active pigments. Our computational study explores CT rectification in RSRC. We find that the CT rate is faster in the A branch compared with the B branch, which can be attributed to the orientation of the pigments near P and the influence of the surrounding protein complex on the dielectric constant. The calculated rate constants are derived using Fermi's golden rule, with a first-principles approach that employs an optimally tuned screened range-separated hybrid functional within a polarizable continuum model (SRSH-PCM).
Understanding Primary Charge Separation and Revealing Fermi's Golden Rule in the Heliobacterium Modesticaldum Reaction Center
(Amer Chemical Soc, 2025) Ertürk, Murat; Güneş, Zühra; Aksu, Hüseyin
We investigate the spectroscopic properties and charge transfer (CT) processes in the homodimeric reaction center of Heliobacterium modesticaldum (HbRC), for which we report the first-principles calculation of Fermi's golden rule (FGR) for the first time in the literature. HbRC is the simplest known analogue to other photosystems and consists of the SPP molecule, the adjacent Acc, and key amino acid residues (His537 and Gln458), along with two water molecules. We identify intrapair CT processes within the SPP molecule, which acts as the donor for the simplified model used in this study. We also examine the SPP+Acc- CT processes, where we demonstrate, in agreement with experimental findings, symmetric hole-electron delocalization across both Acc monomers. The calculated forward CT states are lower in energy than the bright states, facilitating electron transfer through a downhill CT reaction pathway. To explore the influence of surrounding molecular pigments on the electronic structure and FGR rate, we use augmented models incorporating nonsymmetrized molecular orientations. Most FGR rates are found to be on the order of picoseconds (ps). All electronic parameters are derived using an optimally tuned screened range-separated hybrid functional within a polarizable continuum model (SRSH-PCM), considering different dielectric constants.
BSN-I: the first in-depth photometric study of seven total-eclipse contact binary systems
(Oxford Univ Press, 2025) Poro, A.; Li, K.; Paki, E.; Baudart, S.; Michel, R.; Wang, L.; Lajus, E. Fernandez; Aliçavuş, Fahri
This is the first in-depth study of seven total-eclipse W Ursae Majoris-type contact binary systems using photometric light curves. The ground-based observations were conducted with four observatories in the Northern and Southern hemispheres. We also used the Transiting Exoplanet Survey Satellite for four target systems. We presented the analysis of orbital period variations of six systems and found that they display parabolic variations. The material transfer rates between the stars of the systems were calculated. Also, the results show that four systems have a long-term increase, while two have a long-term decrease in their orbital periods. We analysed light curves using the PHysics Of Eclipsing BinariEs python code and the Markov chain Monte Carlo algorithm to estimate different parameters of target systems and their uncertainties. Six of the target systems required the addition of a cold or hot star-spot. We estimated absolute parameters using the empirical relationship between the orbital period and the semimajor axis (P-a). According to each component's effective temperature and mass, it was recognized that the studied systems are W subtype. We examined the dynamic stability of two targets, which were low mass ratio contact binary systems. We also showed the evolution of stars in the M-R and M-L diagrams. Finally, we showed that the hotter stars in contact systems have a temperature difference of less than approximate to 400 K compared to the Gaia Data Release 3 temperature report.

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