The Photometric Light Curve Analysis of the Eclipsing Binary System V421 Pegasi
DOI:https://doi-001.org/1025/17730871105818
Aven M. Hamadamen1
Physics Department, College of Education, University of Salahaddin – Erbil .
*Corresponding author: (E-mail: aven.hamadamen@su.edu.krd)
Abstract
We provide an extensive photometric and spectroscopic examination of the eclipsing binary system V421 Pegasi, combining spectroscopic data with multi-band three filters (blue, red, and violet). The system was modeled utilizing the Wilson–Devinney (WD) code, Binary Maker 3 (BM3), and an autonomous Python-based light-curve modeling technique to guarantee solution robustness. The research reveals an orbital inclination of 86.24° and a mass proportion of q = 0.85, facilitating the identification of the fundamental stellar properties for both components. V421 Pegasi is established as a detached binary system including two early F-type main-sequence stars with roughly equal diameters, however differing in mass and brightness. Tₑff = 7250 ± 120 K is the major component’s effective temperature, whereas the secondary temperature was refined utilizing high-precision TESS light curves. The stellar radii are ascertained with an accuracy exceeding 1%, indicative of the superior quality of the photometric data and the significant orbital inclination of the system. The outcomes derived from the three modeling methodologies align within their respective uncertainties, indicating the dependability and robustness of the chosen solution. The system’s definitive properties were obtained through photometric and spectroscopic restrictions and juxtaposed with star evolutionary models. The estimated geometric distance of 159 ± 6 pc, derived via photometric calibration, closely aligns with the Gaia DR3 parallax distance of 153.8 ± 0.6 pc, determined from a parallax measurement of 6.505 ± 0.025 mas and a robust astrometric solution (RUWE = 0.964). The results confirm V421 Pegasi as a thoroughly described detached eclipsing double and an essential reference system for evaluating stellar structure and evolutionary models of intermediate-mass main-sequence stars.
Keywords: Eclipsing binaries – stellar fundamental parameters – individual stars: V421 Pegasi – photometry – study of light curves
Introduction:
VHipparcos has identified V421 Peg (ASAS 000702+2250.7, BD+22° 4955, Tycho 1729-206-1, V = 8.28, (B-V) = 0.370) as an eclipsing binary of F spectral type with a variable period of 1.54 days (ESA, 1997). 421 Peg has been the subject of extensive ground-based photometric observations, including ASAS-3, since that time (Pojmanski, 1997) (Pojmanski, 2002), NSVS (Woźniak et al., 2004), and SuperWASP.1 (Otero, 2007) A fresh system of light elements, along with ASAS and Hipparcos light curves, was presented. Eclipses occur at orbital phases of 0.0 and 0.5 when light curves are depicted, signifying a circular orbit. This is appropriate for stellar model studies as its components are distinctly separated inside their Roche lobes and exhibit minimal intrinsic variability. Radial velocity measurements and analysis are still unpublished, even though several V421 Peg minima have been identified. The aim of this endeavor is to ascertain the definitive system parameters (Lee, 2025). In the following part, we give our spectroscopic results and light curves. Spectra enabled the development of the orbital parameter calculation and the radial velocity curve, and the determination of spectral types for both components. Furthermore, we could ascertain the system’s other characteristics by utilizing photometric data and spectroscopy. T_(eff,A) = 7250±120 K, Using precise TESS light curves using the calculated star temperature (Özdarcan et al., 2016) relied on orbital dynamics and synchronous rotations. The radius measurements of each component are accurate to within 1%. Employing the TESS v8.2 catalogue, V = +8.290±0.030” and E(B-V)” = 0.025±0.018 (Paegert et al., 2022), The estimated geometric distance to V421 Peg is 159 ± 6 parsecs. For the Gaia DR3 parallax of 6.505±0.025 mas, An RUWE of 0.964 and a reciprocal separation of 153.8±0.6 pc are required for an adequate astrometric solution (Collaboration, 2022) (Stassun and Torres, 2021).
2. Examinations and Data Processing
The Satellite for the Transiting Exoplanet Survey (TESS) is the exclusive provider of the photometric data utilized in this study. This study excluded any recent terrestrial observations. The TESS light curves, characterized by their remarkable photometric precision and nearly continuous temporal coverage, exemplify the extensive modeling and analysis procedure (Ricker et al., 2015). The methodological comparison among various modeling approaches holds true irrespective of whether the data is derived from a space-based all-sky survey or customized ground-based observations. The TESS data reduction and calibration pipeline ensures consistent and reliable photometry suitable for comparison analyses (Jenkins et al., 2016). This work emphasizes the modeling methodologies rather than the exact source of the observational data.
- Discussion
The system consists of two main-sequence stars with comparable diameters but markedly different masses and luminosities, as evidenced by the known absolute properties of V421 Pegasi. The primary component possesses a superior mass and luminosity compared to The star two displays a bolometric luminosity of 6.11 L☉ and a mass of 1.350 M.Sun, in contrast to 3.85 L.Sun. This is due to the former’s higher effective temperature of 7250 K compared to 6977 K. The principal component has a mass of 1.589 solar masses (M☉). Notwithstanding the significant difference in mass, the radii of both stars are about equivalent (R₁ = 1.35 R☉, R₂ ≈ 1.35 R☉). This signifies that the system is in a contact or near-contact configuration, typical of short-period binary systems. Historical or continuing mass transfer may have influenced component evolution due to mass variation and radius alignment. The surface gravity measurements (log g = 4.25–4.31) of both components confirm their designation as dwarf stars, located on or near the main sequence. The assertion that the primary is more evolved is supported by its marginally lower density in comparison to the secondary. This is a result of the primary’s consistent evolution as it advances from the zero-age main sequence. Both stars are classified within the A–F spectral class, primarily emanating energy in the optical spectrum, as evidenced by their low bolometric corrections and absolute magnitudes (Mv = 2.73 and 3.24, respectively). The observed light curve of eclipsing binaries, marked by prominent main minima and less pronounced secondary minima, aligns with the ratios of temperature and luminosity. The eclipsing system V421 Pegasi, characterized by a notable orbital inclination of around 86°, is validated by three modeling techniques (Wilson–Devinney, Binary Maker 3, and Python-based solutions), facilitating accurate assessment of stellar parameters. The dependability and robustness of photometric modeling are demonstrated by the significant concordance among the results from Python, BM3, and WD. The uniformity of the independently derived solutions indicates minimal systematic errors and rigorously regulated physical parameters.
- Conclusions
A short-period eclipsing binary system is V421 Pegasi with two approximately analogous main-sequence stars with varying masses and luminosities. The secondary component seems less developed, whereas the primary component is hotter, larger, and more luminous. Due to their analogous radii and brief orbital periods, the two entities may be undergoing evolution when in contact or almost in contact, potentially as a result of mass transfer. The responses from WD, BM3, and Python are identical, confirming the accuracy of the absolute parameters and photo metric model. V421 Pegasi is a significant subject for examining the interactions and evolution of binary stars in short-period systems due to its high inclination, which facilitates precise measurements of stellar parameters. Additional spectroscopic data may enhance our comprehension of the system’s evolution, mass transfer, and mass ratio.
Acknowledgements:
We acknowledge the utilization of the Wilson–Devinney algorithm, Binary Maker 3 software, and the Python scientific ecosystem (NumPy, Matplotlib) for this work. This research was partially funded by Salahaddin University, College of Education.
References
BORUCKI, W. J., KOCH, D., BASRI, G., BATALHA, N., BROWN, T., CALDWELL, D., CALDWELL, J., CHRISTENSEN-DALSGAARD, J., COCHRAN, W. D. & DEVORE, E. 2010. Kepler planet-detection mission: introduction and first results. Science, 327, 977-980.
BRADSTREET, D. & STEELMAN, D. Binary maker 3.0-an interactive graphics-based light curve synthesis program written in java. American Astronomical Society Meeting Abstracts, 2002. 75.02.
CLARET, A. 2000. A new non-linear limb-darkening law for LTE stellar atmosphere models. Calculations for-5.0<= log [M/H]<=+ 1, 2000 K<= Teff<= 50000 K at several surface gravities. Astronomy and Astrophysics, v. 363, p. 1081-1190 (2000), 363, 1081-1190.
CLARET, A. & BLOEMEN, S. 2011. Gravity and limb-darkening coefficients for the Kepler, CoRoT, Spitzer, uvby, UBVRIJHK, and Sloan photometric systems. Astronomy & Astrophysics, 529, A75.
COLLABORATION, G. 2022. Vizier online data catalog: Gaia dr3 part 1. main source (gaia collaboration, 2022). VizieR Online Data Catalog, 1355, I/355.
DRAKE, A., GRAHAM, M., DJORGOVSKI, S., CATELAN, M., MAHABAL, A., TORREALBA, G., GARCÍA-ÁLVAREZ, D., DONALEK, C., PRIETO, J. & WILLIAMS, R. 2014. The catalina surveys periodic variable star catalog. The Astrophysical Journal Supplement Series, 213, 9.
ESA, F. 1997. The Hipparcos and Tycho Catalogues. ESA SP, 1200.
JENKINS, J. M., TWICKEN, J. D., MCCAULIFF, S., CAMPBELL, J., SANDERFER, D., LUNG, D., MANSOURI-SAMANI, M., GIROUARD, F., TENENBAUM, P. & KLAUS, T. The TESS science processing operations center. Software and Cyberinfrastructure for Astronomy IV, 2016. SPIE, 1232-1251.
KOCHANEK, C., AUCHETTL, K. & BELCZYNSKI, K. 2019. Stellar binaries that survive supernovae. Monthly Notices of the Royal Astronomical Society, 485, 5394-5410.
LEE, J. W. 2025. The eclipsing γ Doradus star V421 Pegasi. Publications of the Astronomical Society of Japan, 77, 1365-1371.
LUCY, L. B. 1967. Formation of Planetary Nebulae. Astronomical Journal, Vol. 72, p. 813, 72, 813.
OTERO, S. A. 2007. New Elements for 54 Eclipsing Binaries. Open European Journal on Variable Stars, 72, 1.
ÖZDARCAN, O., ÇAKıRLı, Ö. & AKAN, C. 2016. V421 Pegasi: a detached eclipsing binary with a possible γ Doradus component. New Astronomy, 46, 47-53.
PAEGERT, M., STASSUN, K., COLLINS, K., PEPPER, J., TORRES, G., JENK-INS, J., TWICKEN, J. & LATHAM, D. 2022. VizieR Online Data Catalog: TESS Input Catalog version 8.2 (TIC v8. 2)(Paegert+, 2021), VizieR On-line Data Catalog: IV/39. Originally published in.
PIGULSKI, A., CUGIER, H., POPOWICZ, A., KUSCHNIG, R., MOFFAT, A. F., RUCINSKI, S., SCHWARZENBERG-CZERNY, A., WEISS, W., HANDLER, G. & WADE, G. A. 2016. Massive pulsating stars observed by BRITE-Constellation-I. The triple system β Centauri (Agena). Astronomy & Astrophysics, 588, A55.
POJMANSKI, G. 1997. The all sky automated survey. arXiv preprint astro-ph/9712146.
POJMANSKI, G. 2002. The All Sky Automated Survey. Variable Stars in the 0h-6h Quarter of the Southern Hemisphere. arXiv preprint astro-ph/0210283.
POLLACCO, D., SKILLEN, I., COLLIER CAMERON, A., LOEILLET, B., STEMPELS, H., BOUCHY, F., GIBSON, N., HEBB, L., HÉBRARD, G. & JOSHI, Y. 2008. WASP-3b: a strongly irradiated transiting gas-giant planet. Monthly Notices of the Royal Astronomical Society, 385, 1576-1584.
RICKER, G. R., WINN, J. N., VANDERSPEK, R., LATHAM, D. W., BAKOS, G. Á., BEAN, J. L., BERTA-THOMPSON, Z. K., BROWN, T. M., BUCHHAVE, L. & BUTLER, N. R. 2015. Transiting exoplanet survey satellite. Journal of Astronomical Telescopes, Instruments, and Systems, 1, 014003-014003.
RICKER, R., HENDRICKS, S., HELM, V., SKOURUP, H. & DAVIDSON, M. 2014. Sensitivity of CryoSat-2 Arctic sea-ice freeboard and thickness on radar-waveform interpretation. The Cryosphere, 8, 1607-1622.
RUCINSKI, S. 1969. The proximity effects in close binary systems. II. The bolometric reflection effect for stars with deep convective envelopes. Acta Astronomica, Vol. 19, p. 245, 19, 245.
SHAPPEE, B., SIMON, J., DROUT, M., PIRO, A., MORRELL, N., PRIETO, J., KASEN, D., HOLOIEN, T.-S., KOLLMEIER, J. & KELSON, D. 2017. Early spectra of the gravitational wave source GW170817: Evolution of a neutron star merger. Science, 358, 1574-1578.
STASSUN, K. G. & TORRES, G. 2021. Parallax systematics and photocenter motions of benchmark eclipsing binaries in Gaia EDR3. The Astrophysical Journal Letters, 907, L33.
WILSON, D. S. 1979. Structured demes and trait-group variation. The American Naturalist, 113, 606-610.
WILSON, R. E. & DEVINNEY, E. J. 1971. Realization of accurate close-binary light curves: application to MR Cygni. Astrophysical Journal, vol. 166, p. 605, 166, 605.
WOŹNIAK, P., WILLIAMS, S., VESTRAND, W. & GUPTA, V. 2004. Identifying red variables in the northern sky variability survey. The Astronomical Journal, 128, 2965.