arXiv subjects

Ehsan Paki

Publications and source records attributed to Ehsan Paki.

9 recordsLinked to original sources

arXiv2026

Detailed Investigation of a W UMa Contact Binary with an Ultralow Mass Ratio and a Third-Body as a Potential Merger Candidate

The lower limit of the mass ratio in contact binaries remains uncertain, with observations suggesting systems exist below theoretical predictions. The stability of such very low mass ratio systems is still debated. Based on our review of systems within the mass ratio cutoff range, we reanalyzed TYC 3801-1529-1 and found it to have the lowest known mass ratio, $q = 0.024_{-(1)}^{+(2)}$, among analyzed contact binaries. The reanalysis of this target was carried out using the BSN application and the MCMC method. We then compared our light curve solution obtained from TESS observations with the results of a previous study. We studied the period variations of this system and identified a cyclic trend over the past six years. After the third-body contribution has been removed, the system's period variations can be described either by a linear trend with a negative slope or by a quadratic trend with a downward curvature. These results indicate that it is still not possible to definitively determine whether the orbital period is increasing or decreasing, underscoring the importance of future observations. By considering the challenges of detecting the faint secondary in extremely low mass ratio systems, we estimated the absolute parameters of the target. Based on our analysis, the secondary component of the binary is likely a brown dwarf, while the third body appears to be a low-mass M-type dwarf. According to our analysis, TYC 3801-1529-1 is dynamically unstable and thus represents a remarkable candidate for a binary merger.

astro-ph.SR↗

arXiv2025

The BSN Application-I: Photometric Light Curve Solutions of Contact Binary Systems

Light curve analysis of W UMa-type contact binary systems using MCMC or MC methods can be time-consuming, primarily because the repeated generation of synthetic light curves tends to be relatively slow during the fitting process. Although various approaches have been proposed to address this issue, their implementation is often challenging due to complexity or uncertain performance. In this study, we introduce the BSN application, whose name is taken from the BSN project. The application is designed for analyzing contact binary system light curves, supporting photometric data, and employing an MCMC algorithm for efficient parameter estimation. The BSN application generates synthetic light curves more than 40 times faster than PHOEBE during the MCMC fitting process. The BSN application enhances light curve analysis with an expanded feature set and a more intuitive interface while maintaining compliance with established scientific standards. In addition, we present the first light curve analyses of four contact binary systems based on the TESS data, utilizing the BSN application version 1.0. We also conducted a light curve analysis using the PHOEBE Python code and compared the resulting outputs. Two of the target systems exhibited asymmetries in the maxima of their light curves, which were appropriately modeled by introducing a cold starspot on one of the components. The estimated mass ratios of these total-eclipse systems place them within the category of low mass ratio contact binary stars. The estimation of the absolute parameters for the selected systems was carried out using the $P-a$ empirical relationship. Based on the effective temperatures and masses of the components, three of the target systems were classified as A-subtype, while TIC 434222993 was identified as a W-subtype system.

astro-ph.SR↗

arXiv2024

Reanalyzing the Light Curves and Absolute Parameters of Twenty Contact Binary Stars Using TESS Data

Reanalyzing contact binaries with space-based photometric data and investigating possible parameter changes can yield accurate samples for theoretical studies. We investigated light curve solutions and fundamental parameters for twenty contact binary systems. The most recent Transiting Exoplanet Survey Satellite (TESS) data is used to analyze. The target systems in the investigation have an orbital period of less than 0.58 days. Light curve solutions were performed using the PHysics Of Eclipsing BinariEs (PHOEBE) Python code version 2.4.9. The results show that systems had various mass ratios from q=0.149 to q=3.915, fillout factors from f=0.072 to f=0.566, and inclinations from i=52.8deg to i=87.3deg. The effective temperature of the stars was less than 7016 K, which was expected given the features of most contact binary stars. Twelve of the target systems' light curves were asymmetrical in the maxima, showing the O'Connell effect, and a starspot was required for light curve solutions. The estimation of the absolute parameters of the binary systems was presented using the a-P empirical relationship and discussed. The orbital angular momentum (J_0) of the systems was calculated. The positions of the systems were also depicted on the M-L, M-R, q-L_ratio, M_tot-J_0, and T-M diagrams.

astro-ph.SR↗

arXiv2024

Global Parameters of Eight W UMa-type Binary Systems

Multiband photometric investigations for eight binary systems of the W Ursae Majoris (W UMa)-type are presented. Six systems are presented for the first time to analyze their light curves. All the analyzed systems have a temperature below 5000 K and an orbital period of less than 0.28 days. We extracted primary and secondary minima from the ground-based observations of these systems. According to a few observations reported in the literature, linear fits were considered in the O-C diagrams, and new ephemerides were presented. Light curve solutions were performed using the PHysics Of Eclipsing BinariEs (PHOEBE) code. The results of the mass ratio and fillout factor indicate that the systems are contact binary stars. Six of them showed the O'Connell effect, and a cold starspot on each companion was required for light curve solutions. Their absolute parameters were estimated and evaluated by two other methods. In this study, the empirical relationship between the orbital period and semi-major axis was updated using a sample consisting of 414 contact binary systems and the Monte Carlo Markov Chain (MCMC) approach. Also, using Machine Learning (ML) and the Artificial Neural Network (ANN) model, the relationship between $P-T_1-M_1$ was updated for a better estimation of the mass of the primary star.

astro-ph.SR↗

arXiv2023

Two-dimensional Parameter Relationships for W UMa-type Systems Revisited

Reviewing the empirical and theoretical parameter relationships between various parameters is a good way to understand more about contact binary systems. In this investigation, two-dimensional (2D) relationships for P-M_V(system), P-L_1,2, M_1,2-L_1,2, and q-L_ratio were revisited. The sample used is related to 118 contact binary systems with an orbital period shorter than 0.6 days whose absolute parameters were estimated based on the Gaia Data Release 3 (DR3) parallax. We reviewed previous studies on 2D relationships and updated six parameter relationships. Therefore, Markov chain Monte Carlo (MCMC) and Machine Learning (ML) methods were used, and the outcomes were compared. We selected 22 contact binary systems from eight previous studies for comparison, which had light curve solutions using spectroscopic data. The results show that the systems are in good agreement with the results of this study.

astro-ph.SR↗

arXiv2023

The First Photometric Study of the Binary System CSS J003106.8+313347

We performed the first photometric study of the CSS J003106.8+313347 W Ursae Majoris (W UMa)-type system based on ground-based observations. We extracted times of minima from our observations and proposed a linear ephemeris based on the increasing incline of the orbital period using a Markov chain Monte Carlo (MCMC) approach. The PHOEBE Python code and the MCMC approach were used for the light curve analysis. This system did not need starspots for the light curve analysis. Mass ratio, fillout factor, and inclination were obtained as 0.699, 0.322, and 60.6deg respectively. We also estimated the absolute parameters of the system using the Gaia DR3 parallax method. Therefore, the masses, radii, and luminosities have been determined to be M1=1.675, M2=1.171, R1=1.292, R2=1.097, L1=1.348, and L2=1.221. The orbital angular momentum (J0) of the CSS J003106.8+313347 illustrates that this system is located in a region of contact binaries. The positions of the primary and secondary components on the Hertzsprung-Russell (HR) diagram are depicted.

astro-ph.SR↗

arXiv2022

The Photometric Study of Six W UMa Systems and Investigation of the Mass-Radius Relations for Contact Binary Stars

We present the photometric analysis of six short-period systems (EI Oct, V336 TrA, NX Boo, V356 Boo, PS Boo, and V2282 Cyg). This is the first photometric analysis of these systems except for V336 TrA. Observations were conducted for 27 nights at three observatories in the northern and southern hemispheres. We calculated a new ephemeris for each of the systems using our minimum times and additional literature. The Markov Chain Monte Carlo (MCMC) approach was used to determine the eclipse timing variation trends of the systems. We found a likely orbital growth for V336 TrA and PS Boo; four other systems show a linear trend in orbital period changes, which is most likely due to the accumulation of measurement errors in their linear ephemeris parameters. The light curve analysis was performed using the Physics of Eclipsing Binaries (PHOEBE) 2.3.59 version code with the MCMC approach. The absolute parameters of the systems were calculated by using the Gaia Early Data Release 3 (EDR3) parallax. The positions of the systems were also depicted on the Hertzsprung-Russell (H-R) and $logJ_0-logM$ diagrams. According to a sample, we were able to present relations for the mass-radius (M-R) relationships of contact binary systems. There is also a strong relationship between the mass ratio and the radius ratio in the W UMa systems for which we also provided a new relation. We compared the M-R updated relationships in this study with seven systems in other studies obtained using the spectroscopic method. In addition, we estimated some of the absolute parameters for 1734 EW systems, based on the new relationships.

astro-ph.SR↗

arXiv2021

Refined Ephemeris for Four Hot Jupiters using Ground-Based and TESS Observations

WASP-12 b, WASP-33 b, WASP-36 b, and WASP-46 b are four transiting planetary systems which we have studied. These systems' light curves were derived from observations made by the Transiting Light Exoplanet Survey Satellite (TESS) and some ground-based telescopes. We used Exofast-v1 to model these light curves and calculate mid-transit times. Also, we plotted TTV diagrams for them using derived mid-transit times and those available within the literature. O-C analysis of these timings enables us to refine the linear ephemeris of four systems. We measured WASP-12's tidal quality factor based on adding TESS data as Q*'=(2.13+-0.29)*10^5. According to the analysis, the orbital period of the WASP-46 b system is increasing. The WASP-36 b and WASP-33 b systems have not shown any obvious quadratic trend in their TTV diagrams. The increase in their period is most likely due to inaccurate liner ephemeris that has increased over time. So, more observations are needed to evaluate whether or not there is an orbital decay in the WASP-36 b and WASP-33 b systems.

astro-ph.EP↗

arXiv2021

Observational and Theoretical Studies of 27 $δ$ Scuti Stars with Investigation of the Period-Luminosity Relation

The multi-color CCD photometric study of 27 Delta Scuti stars is presented. By using approximately three years of photometric observations, we obtained the times of maxima and magnitude changes during the observation time interval for each star. The ephemerides of our Delta Scuti stars were calculated based on the Markov Chain Monte Carlo (MCMC) method using the observed times of maxima and the period of the stars' oscillations. We used the Gaia EDR3 parallaxes to calculate the luminosities and also the absolute magnitudes of these Delta Scuti stars. The fundamental physical parameters of all the stars in our sample such as masses and radii were estimated. We determined the pulsation modes of the stars based on the pulsation constants. Moreover, the period-luminosity (P-L) relation of Delta Scuti stars was investigated and discussed. Then, by using a machine learning classification, new P-L relations for fundamental and overtone modes are presented.

astro-ph.SR↗