1. Lightkurve Collaboration et al., 2018 ascl:1812.013. 2. Hippke M., et al., 2019, AJ, 158, 143. 3. Günther M. N., Daylan T., 2021, ApJSS, 254, 13. 4. Southworth J., 2013, A&A, 557, A119. 5. Claret A., 2004, A&A, 428.1001C. 6. Zucker S., Mazeh T., 1994, ApJ, 420, 806. 7. Konacki M., et al., 2010, ApJ, 719, 1293. 8. Miller N. J., et al., 2020, MNRAS, 497, 2899. 9. Hełminiak et al., 2009, MNRAS,400.969H. Modeling Codes: We performed two runs using the following codes for LC modeling: ●ALLESFITTER (Günther & Daylan, 2021, 2019) ●JKTEBOP (Southworth 2013) Limb-darkening Laws: Initial values estimated using JKTLD based on Claret (2004) and used the following two laws for the two runs: ●Quadratic law in ALLESFITTER ●Logarithmic law in JKTEBOP Error Estimation: Two runs used different error estimation algorithms: ●MCMC with ALLESFITTER ●MC with JKTEBOP RV Modeling: We used to TODCOR algorithm (Zucker & Mazeh 1994) to extract the radial velocities and modelled them in V2FIT (Konacki et al. 2010). Photometric observations: Photometric observations from TESS covering the continuous observing zone i.e. 25 sectors. Fig. on the top-right shows lightcurves (LC) from sector 1 to 62 (1, 2, 4-12, 27-32, 34-39, 61 & 62). We used Lightkurve package (Lightkurve Collaboration et al., 2011) to extract the lightcurves with customize aperture and removed the scattered background light. We used Biweight method from WOTAN (Hippke et al., 2019) for detrending. Spectroscopic observations: Spectroscopic observations were taken with HARPS, FEROS, and CORALIE, under the CRÉME project and from the ESO archive, as well as with UCLES from Hełminiak et al. (2009). Long-term Stability of Solutions in Benchmark Stars: UX Mensae Ganesh Pawar∗1, Krzysztof Hełminiak1, Ayush Moharana1, and Tilaksingh Pawar1 1Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences, Toruń, Poland Eclipsing binaries (EBs) provide a direct determination of fundamental parameters, and detached eclipsing binaries (DEBs) offer highly accurate and precise stellar parameters. DEBs with accurate and precise fundamental parameters serve as ideal benchmark systems for testing stellar models and data analysis algorithms of PLATO. In this project we have utilized space-based photometry data from the Transiting Exoplanet Survey Satellite (TESS), observing the system UX Men for 25 sectors and time-series high-resolution spectroscopic data from the CRÉME project. We are analyzing the stability of lightcurve solutions and investigating factors influencing error rates. The primary goal is to determine the conditions for a DEB to be considered a reliable benchmark in stellar parameter determination. Ra/a →Radius of Primary Rb/a →Radius of Secondary (Ra+Rb)/a→ Sum of Radii i →Inclination of the Orbit k →Ratio of Radii J →Surface Brightness Ratio L3 →Third Light Ratio e → Eccentricity ω → Argument of Periastron M1→Mass of Primary M2→Mass of Secondary ●Errors cannot be solely estimated from single sector observation. We need to accommodate variations over sectors to obtain proper errors for a benchmark system. ●The cause of these variation is uncertain, it can be from instrumental or numerical origin and/or stellar activity. ●We plan to do a stability check on photometric estimation of effective temperatures (using Miller et al. 2020) compared to spectroscopic estimates (disentangling + spectral analysis). ●A detailed inspection will be conducted to investigate the probable cause of variations. Abstract: Analysis: Observations: Parameters: Results & Future Work: Parameters Ra/a Rb/a Inc. (i) k J L3 (Ra+Rb)/a e cos ω e sin ω M1 M2 0.092746 0.087309 89.6287 0.9414 0.9722 0.0208 0.1801 0.0198 0.0202 1.23 1.195 +1σ 0.000092 0.000583 0.007785 0.001047 0.001192 0.008153 0.000081 0.002137 0.007855 0.00149 0.00167 -1σ 0.00008 0.000487 0.00734 0.000866 0.001277 0.008918 0.000076 0.002331 0.008529 0.00149 0.00167 About the author: Ganesh Pawar is a 1st year PhD student at the Nicolaus Copernicus A