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Classical Cepheids as testbeds for stellar evolution and pulsation theories

project	SONATA BIS, 2018/30/E/ST9/00598
funding	Polish National Science Center, NCN
PI	Radosław Smolec
Co-Is	Vincent Hocde, post-doc (until Sep 2023)
	Rajeev Singh Rathour, PhD student (degree awarded in June, 2025)
	Oliwia Ziółkowska, PhD student
dates	04.2019 - 04.2026

Jump to project highlights, refereed publications, conference contributions, and presentations.

Project Highlights

• Photometric metallicity formulae for classical Cepheids

  Estimating the metallicity of classical Cepheids is of prime importance for studying metallicity effects on stellar evolution and the chemical evolution of galaxies, as well as on the period-luminosity relation used on the extragalactic distance scale. Our aim was to establish new empirical relations for estimating the iron content of classical Cepheids for short and long periods based on Fourier parameters from the V- and I-band light curves. The empirical relations in the V and I bands allowed us to derive the mean metallicity of a sample of MW, SMC, and LMC Cepheids that is in agreement with literature values. We also showed that these relations are precise enough to reconstruct the radial metallicity gradients within the Milky Way from OGLE data.

  More information: Hocde, V., Smolec, R., Moskalik, P., Ziółkowska, O., Singh Rathour, R. Metallicity estimation of MW, SMC and LMC classical Cepheids from the shape of the V- and I-band light curves; A&A, 671, A157 (2023);
  doi:10.1051/0004-6361/202245038.

  

  Left: metallicity distribution of the Milky Way. Right: estimated Cepheid metallicities versus the galactocentric distance for the Milky Way

  
  
• RSP - Radial Stellar Pulsation

  Modelling of large-amplitude nonlinear pulsation of classical pulsator is challenging, but now new open access tool, Radial Stellar Pulsation (RSP) is available as part of the Modules for Experiments in Stellar Astrophysics (MESA). RSP is based on nonlinear convective pulsation codes developed by R. Smolec as part of PhD thesis, see also Smolec & Moskalik (2008).

  More information: B. Paxton, R. Smolec, J. Schwab, A. Gautschy, et al. Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation, ApJ Suppl. Ser. (2019).
  doi:10.3847/1538-4365/ab2241.

  

  The Figure shows a comparison between observed and modelled amplitudes and amplitude ratios for fundamental mode (RRab) and first overtone (RRc) RR Lyrae stars.

  
  
• Pulsation Modelling of Y Oph

  Y Ophiuchi (Y Oph) is a classical Cepheid with a pulsation period of 17.12 days. This star is reported to be as dim as a Cepheid of about half its pulsation period and it exhibits a low radial velocity and light-curve amplitude. For these reasons, Y Oph is not used to calibrate period-luminosity (PL) relation and its distance remains uncertain.

  We find that all pulsation models at high effective temperatures are in remarkable agreement with the observations along the pulsation cycle. This result suggests that the low amplitude of Y Oph may be explained by proximal location to the blue edge of the instability strip (IS). We also find that a pulsational mass of about 7-8 solar masses is consistent with a non-canonical evolutionary model with moderate overshooting, PL relation and Gaia parallax. However, a much lower mass below 5 solar masses is required to match Baade-Wesselink (BW) distance measurements from the literature. We show that the combination of the impact of the CSE on the photometry, together with a projection factor of about 1.5, explains the discrepant distance and luminosity values obtained from BW methods.

  More information: Hocde, V., Smolec, R., Moskalik, P., Singh Rathour, R., Ziółkowska, O.; Pulsation modeling of the Cepheid Y Ophiuchi with RSP/MESA. Impact of the circumstellar envelope and a high projection factor on the Baade-Wesselink method; A&A, 683, A233 (2024);
  ADS, PDF, arXiv:2312.12046.

  

  The Figure shows HR diagram comparing parameters of MESA-RSP models of Y Oph (crosses) with evolutionary tracks computed with MESA for different stellar masses. These models assume an overshooting parameter f_ov = 0.02. The vertical blue strip corresponds to the measured value of the mean effective temperature for Y Oph, i.e. T_eff = 5800 ± 100K.

  
  
• New binary systems with classical Cepheids revealed from light travel time effect

  We conduct a systematic search for non-evolutionary period changes to look for Cepheids in likely binary configurations and quantify their incidence rates in the Magellanic Clouds. We collected over a decade's worth time series photometry from the publicly available Optical Gravitational Lensing Experiment (OGLE) with more than 7200 Cepheids altogether from the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC). Our sample contains both fundamental-mode and first-overtone mode Cepheids. Then we calculated the observed minus calculated (O-C) diagrams to reveal the light-travel time effect (LTTE).

  We found 52 candidate Cepheid binary systems in the LMC (30 fundamental and 22 first-overtone mode) and 145 in the SMC (85 fundamental and 60 first-overtone mode). The majority of the sample is characterized by orbital periods of 2000-4000 d and eccentricities of 0.2-0.5. Moreover, we report two candidates in each galaxy with the Cepheid likely existing with a giant companion. The incidence rate ratio for SMC to LMC calculated from our sample is in agreement with binary Cepheid population synthesis predictions.

  More information: Singh Rathour, R., et al.; Non-evolutionary effects on period change in Magellanic Cepheids. I. New binary systems revealed from light travel time effects; A&A, 686, A268 (2024);
  Full paper.

  

  The Figure shows exemplary O-C diagrams from our study.

  
  
• How robust are evolutionary tracks? Uncertainties quantified!

  Contemporary one-dimensional stellar evolution codes, like Modules for Experiments in Stellar Astrophysics (MESA), come with a large number of free parameters that allow us to model the physical processes in stellar interiors under many assumptions. The uncertainties that arise from this freedom are rarely discussed in the literature despite their impact on the evolution of the model.

  We have calculated a grid of evolutionary models with MESA, varying several controls, like solar mixture of heavy elements, mixing-length theory prescription, nuclear reaction rates, the scheme to determine convective boundaries, atmosphere model, and temporal and spatial resolution, and quantify their impact on age and location of the evolutionary track on the H-R diagram from the main sequence until the end of core helium burning.

  Our investigation was conducted for a full range of masses and metallicities expected for classical Cepheids. The uncertainties are signi cant, especially during core helium burning, reaching or exceeding the observational uncertainties of logT_eff and logL for detached eclipsing binary systems.

  More information: Ziolkowska, et al.; Toward a Comprehensive Grid of Cepheid Models with MESA I. Uncertainties of the Evolutionary Tracks of Intermediate-mass Stars; ApJ Suppl. Ser., 274, 30 (2024);
  Full paper.

  

  Median (solid line) along with 25th and 75th percentiles (colored regions) for the maximum recorded relative difference distributions for log age (top panels), logT_eff (middle panels), and logL (bottom panels) at progressing evolutionary phases (horizontal axis). The two colors correspond to models with (orange right-slanted lines) and without convective core overshooting (blue left-slanted lines).

  
  
• Precise Fourier parameters of Cepheid radial velocity curves

  We provide new precise Fourier parameters of Cepheid radial velocity (RV) curves determined from RV measurements available in the literature together with unpublished data. Our sample includes 178 fundamental-mode and 33 first-overtone pulsators. The pulsation period coverage and the precision obtained, in particular for Fourier phase ϕ₂₁, will be useful for studying the dynamics of Cepheid pulsations with the help of hydrodynamical models.

  More information: Hocde, V., et al.; Precise Fourier parameters of Cepheid radial velocity curves: Towards refining the Hertzsprung progression models; A&A, 689, A224 (2024);
  Full paper.

  

  The Figure shows low-order Fourier parameters for RV curves of fundamental-mode and first-overtone Cepheids.

  
  
• Non-evolutionary effects on period change rates in Magellanic Clouds Cepheids

  We provide a systematic and quantitative description of irregular period changes in Cepheids. Such a study is crucial for a complete understanding of period changes in Cepheids and is key to decoupling the evolutionary aspects from the non-evolutionary ones.

  In our investigation, 33.5±7% of analysed stars show irregular period changes. Considering the pulsation mode, irregular period changes were detected in 16.5±0.7% of the analysed fundamental mode stars and in 68.1±1.2% of the first overtone stars. The amplitude of variability in the O-C diagrams increases with the pulsation period, and at a given pulsation period, it is larger for first overtone stars. While the increase is linear for first overtone stars, for fundamental mode stars it becomes steeper as the pulsation period increases. Time scales of the observed variability range from a few hundred to a few thousand days.

  More information: Singh Rathour, R., et al.; Non-evolutionary effects on period change in Magellanic Cepheids. II. Empirical constraints on non-linear period changes; A&A, 695, A114 (2025);
  Full paper.

  

  The Figure shows exemplary O-C diagrams for LMC first overtone Cepheids with irregular period changes.

  
  
• Evolutionary and Pulsation Relations for Models with Core and Envelope Overshooting

  Evolutionary tracks for 2−8M_☉ models, covering a [Fe/H]=−1.0 (Z=0.0014) to [Fe/H]=+0.2 (Z=0.02) metallicity range are computed with Modules for Experiments in Stellar Astrophysics, MESA, to investigate evolutionary and pulsation properties of classical, fundamental mode Cepheids. We examine in detail the effects of convective overshooting from the Main Sequence core, as well as from the convective envelope on the Red Giant Branch.

  Period-Luminosity, Mass-Luminosity, Period-Radius and Period-Age relations are derived, both in analytical and tabular form. Their dependence on metallicity, crossing number and overshooting parameters are investigated.Considering metallicity effect of the Period-Luminosity relation, we find γ≈−0.20 mag dex⁻¹ , nearly independent on photometric pass band and in good agreement with recent observational studies.

  The full library of computed evolutionary models is available at Zenodo.

  More information: Smolec, R., et al.; Toward a Comprehensive Grid of Cepheid Models with MESA. III. Evolutionary and Pulsation Relations for Models with Core and Envelope Overshooting; ApJ Suppl. Ser., 284, 60 (2026);
  Full paper.

  

  Example of relations derived in the paper: Period-Radius relations for models without overshooting (top) and including overshooting (bottom), for Milky Way, LMC and SMC metallicities (in the left, middle, and right panels, respectively), confronted with observational determinations

  
  
• Self-Consistent Cepheid Pulsations in MESA!

  We present the first self-consistent integration of large-amplitude, nonlinear classical Cepheid pulsations directly within a MESA-star evolutionary run, demonstrating that the TDC formalism implemented in MESA-star and the MESA-RSP module are physically identical. Starting from a 6M_☉ blue-loop stellar evolution model, we demonstrate evolving the entire stellar model through pulsations as well as pausing the evolution, excising the core, and remeshing the envelope to match the grid used by MESA-RSP.

  This unified approach eliminates the reliance on separate postprocessing workflows and enables fully coupled evolution-pulsation simulations. This approach enables future studies of stellar pulsations with the inclusion of composition gradients, mass loss, or rotation.

  More information: Farag et al. (including Smolec, R.); Self-Consistent Nonlinear Classical Cepheid Pulsations during Stellar Evolution with MESA; ApJ, 1002, 172 (2026);
  Full paper.

  

  H-R diagram of the 6M_☉ MESA-star evolution model using TDC with and without the eddy-viscous damping, color coded by phase of evolution. An approximate location for the instability strip is shown as a gray region between the blue and red edges. In the bottom panel, we show a close-up of the Cepheid radial-pulsation growth (thin gray lines) to finite-amplitude pulsations (thick black line) in the H-R diagram overlaid on the evolution track.

  
  
• Rotation in fully diffusive approach does not lift Cepheid mass discrepancy

  We examine whether rotation can offer a plausible explanation for the mass discrepancy problem when it is included in the evolutionary code using the fully diffusive approximation for rotationally induced mixing processes. We find that rotation barely influences the appearance and luminosity levels of the blue loops. While luminosity increases with increasing initial rotation rate, the increase does not exceed 0.04 dex, a fraction of the increase resulting from including the main sequence core overshooting of 0.2H_p. As a consequence, rotation alone cannot resolve the mass discrepancy problem without simultaneously requiring significant MS core overshooting.

  These results are in contrast with those obtained with the Geneva code, which implements rotational mixing using the advective-diffusive scheme.

  The full library of computed evolutionary models with rotation is available at Zenodo.

  More information: Smolec, R., et al.; Toward a Comprehensive Grid of Cepheid Models with MESA. IV. Modest Effects of Rotation on Blue Loops; ApJ Suppl. Ser., in press (2026);
  Full paper at arXiv.

  

  Evolutionary tracks for 3, 4, 5, 6, 7, and 8M_☉ models with moderate MS core overshooting (f_H=0.01) for Z=0.014 (left), Z=0.006 (right), and different initial rotation rates coded by color: gray for non-rotating models, then blue for W₀=0.3, orange for W₀=0.5, and red for W₀=0.65. We also include 5M_☉, W₀=0.5 tracks computed with a twice as large MS core overshooting parameter (f_H=0.02, black dotted line) for comparison. The edges of the IS are plotted for reference.

  
  

Refereed Publications

• Smolec, R., Singh Rathour, R., Hocde, V.;Toward a Comprehensive Grid of Cepheid Models with MESA. IV. Modest Effects of Rotation on Blue Loops; ApJ Suppl. Ser., in press (2026); ADS, PDF, arXiv:2605.14128
• Salinas, R., Kalari, V., Hajdu, G., Prudil, Z., Saez-Carvajal, C., Narloch, W., Catelan, M., Howell, S. B., Bakowska, K., Chini, R., Galan, C., Gorski, M., Kaluszynski, M., Karczmarek, P., Kicia, M., Kiviaho, W., Kotysz, K., Marcadon, F., Mozdzierski, D., Netzel, H., Pietrzyński, G., Pych, W., Radziwonowicz, M., Romaniuk, P., Smolec, R., Wielgórski, P., Zgirski, B., Zuk, P.; Finding the elusive RR Lyrae companions via speckle imaging; A&A, in press (2026); ADS, PDF, arXiv:2603.28684
• Wielgorski, P., Pietrzynski, G., Gieren, W., Zgirski, B., Narloch, W., Hajdu, G., Storm, J., Nardetto, N., Kervella, P., Pilecki, B., Gorski, M., Smolec, R., Salinas, R., Graczyk, D., Hocde, V., Karczmarek, P., Taormina, M., Pych, W., Netzel, H., Chini, R., Hodapp, K., Kaluszynski, M., Pozo Nunez, F., Kotysz, K., Mozdzierski, D., Mikolajczyk, P., Kolaczek-Szymanski, P.;Period-Luminosity Relations, projection factor and radii of Anomalous Cepheids; A&A, in press (2026); ADS, PDF, arXiv:2603.28472
• Smolec, R., Ziolkowska, O., Singh Rathour, R., Hocde, V., Wielgorski, P.;Toward a Comprehensive Grid of Cepheid Models with MESA. III. Evolutionary and Pulsation Relations for Models with Core and Envelope Overshooting; ApJ Suppl. Ser., 284, 60 (2026); ADS, PDF, arXiv:2603.26111
• Hocde, V., Moskalik, P., Nardetto, N., Kervella, P., Pilecki, B., Smolec, R., Pietrzynski, G., Gieren, W., Hajdu, G., Gallenne, A., Bailleul, M.C., Bras, G., Wielgorski, P., Breuval, L., Merand, A., Rathour, R.S., Espinoza-Arancibia, F., Kiviaho, W., Apostolova, B., Sivkova, K.;Reconstruction of Cepheid radial velocity curves from the shape of the V-band light curves; A&A, 709, A151 (2026); ADS, PDF, arXiv:2603.11748
• Farag, E., Bellinger, E.P, Mocz, P., Kalici, S., Smolec, R., Kanbur, S., Bettwy, K., Lindsay, C.;Self-Consistent Nonlinear Classical Cepheid Pulsations during Stellar Evolution with MESA; ApJ, 1002, 172 (2026); ADS, PDF, arXiv:2603.15766
• Ziolkowska, O., Smolec, R., Thoul, A., Singh Rathour, R., Hocde, V.;Toward a Comprehensive Grid of Cepheid Models with MESA. II. Impact of Physical and Numerical Assumptions on Elemental Abundances; ApJ Suppl. Ser., 282, 45 (2026); ADS, PDF, arXiv:2602.08109
• Narloch, W., Hajdu, G., Pietrzynski, G., Wielgorski, P., Smolec, R., Gieren, W., Zgirski, B., Gorski, M., Karczmarek, P., Graczyk, D.;Period-luminosity relations for Galactic Type II Cepheids in the Sloan bands; A&A, 697, A30 (2025); ADS, PDF, arXiv:2503.10532
• Rathour, R.S., Smolec, R., Hajdu, G., Ziolkowska, O., Hocde, V., Soszynski, I., Udalski, A., Karczmarek, P.;Non-evolutionary effects on period change in Magellanic Cepheids: II. Empirical constraints on non-linear period changes; A&A, 695, A114 (2025); ADS, PDF, arXiv:2503.00661
• Das, S., Molnar, L, Szabo, R., Singh, H.P., Kanbur, S.M., Bhardwaj, A., Marconi, M., Smolec, R.; A theoretical framework for BL Her stars: IV. New period-luminosity relations in the Rubin-LSST filters; A&A, 695, A38 (2025); ADS, PDF, arXiv:2501.13937
• Das, S., Molnar, L, Kovacs, G.B., Smolec, R., Joyce, M., Kanbur, S.M., Szklenar, T., Bhardwaj, A., Singh, H.P., Marconi, M., Ripepi, V.;A theoretical framework for BL Her stars: III. A case study: Robust light curve optimization in the Large Magellanic Cloud; A&A, 694, A255 (2025); ADS, PDF, arXiv:2412.09287
• Hocde, V., Matter, A., Nardetto, N., Gallenne, A., Kervella, P., Merand, A., Pietrzynski, G., Gieren, W., Leftley, J., Robbe-Dubois, S., Lopez, B., Bailleul, M.C., Bras, G., Smolec, R., Wielgorski, P., Hajdu, G., Afanasiev, A.;Circumstellar emission of Cepheids across the instability strip: Mid-infrared observations with VLTI/MATISSE; A&A, 694, A101 (2025); ADS, PDF, arXiv:2501.00373
• Graczyk, D., Pietrzynski, G., Galan, C., Miller, N., Gieren, W., Zgirski, B., Hajdu, G., Kaluszynski, M., Chini, R., Gallenne, A., Gorski, M., Karczmarek, P., Kervella, P., Kicia, M., Maxted, P.F.L., Nardetto, N., Narloch, W., Pilecki, B., Pych, W., Rojas Garcia, G., Smolec, R., Suchomska, K., Taormina, M., Wielgorski, P.;Surface brightness-colour relations of dwarf stars from detached eclipsing binaries: II. Extension of the calibrating sample; A&A, 694, A65 (2025); ADS, PDF
• Netzel, H., Varga, V., Szabo, R., Smolec, R., Plachy, E.;Considering the incidence rate of RR Lyrae stars with non-radial modes; A&A, 692, A133 (2024); ADS, PDF, arXiv:2404.14373
• Ziolkowska, O., Smolec, R., Thoul, A., Farrell, E., Singh Rathour, R., Hocde, V.;Toward a Comprehensive Grid of Cepheid Models with MESA I. Uncertainties of the Evolutionary Tracks of Intermediate-mass Stars; ApJ Suppl. Ser., 274, 30 (2024); ADS, PDF, arXiv:2408.07136
• Hocde, V., Moskalik, P., Gorynya, N.A., Smolec, R., Singh Rathour, R., Ziolkowska, O.;Precise Fourier parameters of Cepheid radial velocity curves: Towards refining the Hertzsprung progression models; A&A, 689, A224 (2024); ADS, PDF, arXiv:2312.11407
• Rathour, R.S., Hajdu, G., Smolec, R., Karczmarek, P., Hocde, V., Ziolkowska, O., Soszynski, I., Udalski, A.;Non-evolutionary effects on period change in Magellanic Cepheids I. New binary systems revealed from light travel time effect; A&A, 686, A268 (2024); ADS, PDF, arXiv:2403.14039
• Prudil, Z., Smolec, R., Kunder, A., Koch-Hansen, A.J., Dekany, I.;The Galactic Bulge exploration II. Line-of-sight velocity templates for single mode RR Lyrae stars; A&A, 685, A153 (2024); ADS, PDF, arXiv:2404.05279
• Tylenda, R., Kaminski, T., Smolec, R.;Nova 1670 (CK Vulpeculae) was a merger of a red giant with a helium white dwarf; A&A, 685, A49 (2024); ADS, PDF, arXiv:2312.07433
• Das, S., Molnar, L., Kanbur, S., Joyce, M., Bhardwaj, A., Harinder Singh, P., Marconi, M., Ripepi, V., Smolec, R.;A theoretical framework for BL Her stars II. New period-luminosity relations in Gaia passbands; A&A, 684, A170 (2024); ADS, PDF, arXiv:2401.11869
• Hocde, V., Smolec, R., Moskalik, P., Singh Rathour, R., Ziółkowska, O.;Pulsation modeling of the Cepheid Y Ophiuchi with RSP/MESA. Impact of the circumstellar envelope and a high projection factor on the Baade-Wesselink method; A&A, 683, A233 (2024); ADS, PDF, arXiv:2312.12046
• Zwintz, K., et al. (incl. Smolec, R.); Catalogue of BRITE-Constellation targets. I. Fields 1 to 14 (November 2013-April 2016); A&A, 683, A49 (2024); ADS, PDF, arXiv:2311.18382
• Espinoza-Arancibia, F., Pilecki, B., Pietrzynski, G., Smolec, R., Kervella, P.; Empirical instability strip for classical Cepheids. I. The Large Magellanic Cloud galaxy; A&A, 682, A185 (2024); ADS, PDF, arXiv:2311.15849
• Gladkowski, M., Hajduk, M., Smolec, R., Szczerba, R., Soszynski, I.; Binary central stars of planetary nebulae in the Large Magellanic Cloud ; A&A, 682, A70 (2024); ADS, PDF, arXiv:2311.14556
• Karczmarek, P., Hajdu, G., Pietrzyński, G., Gieren, W., Narloch, W., Smolec, R., Wiktorowicz, G., Belczynski, K., Synthetic Population of Binary Cepheids. II. The Effect of Companion Light on the Extragalactic Distance Scale; ApJ, 950, 182 (2023); ADS, PDF, arXiv:2303.15664
• Hocde, V., Smolec, R., Moskalik, P., Ziółkowska, O., Singh Rathour, R. Metallicity estimation of MW, SMC and LMC classical Cepheids from the shape of the V- and I-band light curves; A&A, 671, A157 (2023); ADS, PDF, arXiv:2301.00229
• Nardetto, N., Gieren, W., Storm, J., Hocde, V., et al., HARPS-N high spectral resolution observations of Cepheids. II. The impact of the surface-brightness color relation on the Baade-Wesselink projection factor of η Aql; A&A, 671, A14 (2023); ADS, PDF, arXiv:2301.09468
• Smolec, R., Ziółkowska, O., Ochalik, M., Śniegowska, M., First Overtone Cepheids of the OGLE Magellanic Cloud Collection -- beyond radial modes; MNRAS, 519 4010 (2023); ADS, PDF, arXiv:2212.06732
• Jermyn, A.S., Bauer, E.B., Schwab, J., Farmer, R., Ball, W.H., Bellinger, E.P., Dotter, A., Joyce, M., Marchant, P., Mombarg, J.S.G., Wolf, W.M., Wong, T.L.S., Cinquegrana, G.C., Farrell, E., Smolec, R., Thoul, A., Cantiello, M., Herwig, F., Toloza, O., Bildsten, L., Townsend, R.H.D., Timmes, F.X. Modules for Experiments in Stellar Astrophysics (MESA): Time-Dependent Convection, Energy Conservation, Automatic Differentiation, and Infrastructure; MNRAS, 265, 15 (2023); ADS, PDF, arXiv:2208.03651
• Suchomska, K., Graczyk, D., Gałan, C., Ziółkowska, O., Smolec, R., Pietrzyński, G., Gieren, W., Villanova, S., Górski, M., Thompson, I.B., Wielgórski, P., Zgirski, B., Karczmarek, P., Pilecki, B., Taormina, M., Narloch, W., Hajdu, G., Lewis, M., Kałuszyński, M., Rojas Garcia, G. Evolved eclipsing binary systems in the Galactic bulge: Precise physical and orbital parameters of OGLE-BLG-ECL-305487 and OGLE-BLG-ECL-116218; A&A, 668, A30 (2022); ADS, PDF, arXiv:2210.12413
• Narloch, W., Pietrzyński, G., Gieren, W., Piatti, A.E., Karczmarek, P., Górski, M., Graczyk, D., Smolec, R., Hajdu, G., Suchomska, K., Zgirski, B., Wielgórski, P., Pilecki, B., Taormina, M., Kałuszyński, M., Pych, W., Rojas Garcia, G., Lewis, M.O., Metallicities and ages for star clusters and their surrounding fields in the Large Magellanic Cloud; A&A, 666, A80 (2022); ADS, PDF, arXiv:2207.13153
• Drevon, J., et al. including Hocde, V., Locating dust and molecules in the inner circumstellar environment of R Sculptoris with MATISSE; A&A, 665, A32 (2022); ADS, PDF, arXiv:2208.10845
• Netzel, H., Smolec, R., Modeling of multimode radially pulsating High-Amplitude delta Scuti stars from the OGLE Galactic bulge sample; MNRAS, 515, 4574 (2022); ADS, PDF, arXiv:2207.04210
• Netzel, H., Smolec, R., Asteroseismology of RR Lyrae stars with non-radial modes; MNRAS, 515, 3439 (2022); ADS, PDF, arXiv:2206.12853
• Karczmarek, P., Smolec, R., Hajdu, G., Pietrzyński, G., Gieren, W., Narloch, W., Wiktorowicz, G., Belczynski, K., Synthetic Population of Binary Cepheids. I. The Effect of Metallicity and Initial Parameter Distribution on Characteristics of Cepheids' Companions; ApJ, 930, 65 (2022); ADS, PDF, arXiv:2204.00661
• Chiavassa, A., et al. including Hocde, V., The extended atmosphere and circumstellar environment of the cool evolved star VX Sagittarii as seen by MATISSE; A&A, 658, A185 (2022); ADS, PDF, arXiv:2112.10695
• Wielgórski, P., Pietrzyński, G., Pilecki, B., Gieren, W., Zgirski, B., Górski, M., Hajdu, G., Narloch, W., Karczmarek, P., Smolec, R., Kervella, P., Storm, J., Gallenne, A., Breuval, L., Lewis, M., Kałuszyński, M., Graczyk, D., Pych, W., Suchomska, K., Taormina, M., Rojas Garcia, G., Kotek, A., Chini, R., Pozo Nunez, F., Noroozi, S., Sobrino Figaredo, C., Haas, M., Hodapp, K., Mikołajczyk, P., Kotysz, K., MoĹşdzierski, D., Kołaczek-Szymański, P., An absolute calibration of the near-infrared Period-Luminosity Relations of Type II Cepheids in the Milky Way and in the Large Magellanic Cloud; ApJ, 927, 89 (2022); ADS, PDF, arXiv:2112.12122
• Molnar, L. et al., with Smolec, R., First results on RR Lyrae stars with the TESS space telescope: untangling the connections between mode content, colors and distances; ApJ Suppl. Ser., 258, 8 (2022); ADS, PDF, arXiv:2109.07329
• Rathour, R.S., Smolec, R., Netzel, H., Frequency analysis of OGLE-IV photometry for classical Cepheids in Galactic fields: non-radial modes and modulations; MNRAS, 505, 5412 (2021); ADS, PDF, arXiv:2106.02872
• Plachy, E., et al., including Smolec, R.; TESS Observations of Cepheid Stars: First Light Results ; ApJ Suppl. Ser., 253, 11 (2021); ADS, PDF, arXiv:2012.09709
• Das, S., Kanbur, S., Smolec, R., Bhardwaj, A., Singh, H.P., Rejkuba, M.; A theoretical framework of BL Her stars. I. Effect of metallicity and convection parameters on period-luminosity and period-radius relations; MNRAS, 501, 875 (2021); ADS, PDF, arXiv:2011.11626
• Graczyk, D., Pietrzynski, G., Thompson, I.B., Gieren, W., Zgirski, B., Villanova, S., Gorski, M., Wielgorski, P., Karczmarek, P., Narloch, W., Pilecki, B., Taormina, M., Smolec, R., Suchomska, K., Gallenne, A., Nardetto, N., Storm, J., Kudritzki, R.-P., Kaluszynski, M., Pych, W.; A distance determination to the Small Magellanic Cloud with an accuracy of better than 2 percent based on late-type eclipsing binary stars; ApJ, 904, 13 (2020); ADS, PDF, arXiv:2010.08754
• Soszyński, I., Smolec, R., Udalski, A., Szymański, M.K., Pietrukowicz, P., Skowron, D.M., Skowron, J., Mroz, P., Poleski, R., Kozłowski, S., Iwanek, P., Wrona, M., Gromadzki, M., Ulaczyk, K., Rybicki, K.; OGLE-GAL-ACEP-091 - The First Known Multi-Mode Anomalous Cepheid; ApJ Lett., 901, L25 (2020); ADS, PDF, arXiv:2009.06642
• Savino, A., Koch, A., Prudil, Z., Kunder, A., Smolec, R.; he age of the Milky Way inner stellar spheroid from RR Lyrae population synthesis; A&A, 641, A96 (2020); ADS, PDF, arXiv:2006.12507
• Paxton, B., Smolec, R., Gautschy, A., Bildsten, L., Cantiello, M., Dotter, A., Farmer, R., Goldberg, J.A., Jermyn, A.S., Kanbur, S.M., Marchant, P., Schwab, J., Thoul, A., Townsend, R.H.D., Wolf, W.M., Zhang, M., Timmes, F.X.; Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation; ApJ Suppl Ser, 243, 10 (2019); ADS, PDF, arXiv:1903.01426

Conference Publications

• Rathour, R.S., Smolec, R. Hajdu, G., Karczmarek, P., Hocde, V., Ziółkowska, O., Soszynski, I., Udalski, A.; Non-evolutionary effects on period change in Magellanic Cepheids, in Contributions of the Astronomical Observatory Skalnate Pleso (2025), 55, 431; KOPAL Conference: Binary and multiple Stars in the Era of Big Sky Surveys, Litomyšl, Sep 9-13, 2024, www
• Hocde, V., Smolec, R., Moskalik, P.; Why Y Oph is off? Pulsation modeling of the Cepheid Y Ophiuchi with MESA/RSP, in Proceedings of the annual meeting of the French Society of Astronomy & Astrophysics (2024), 77; Annual meeting of the French Society of Astronomy and Astrophysics, Marseille, Jun 4-7, 2024
• Rathour, R.S., Smolec, R. Hajdu, G., Karczmarek, P., Hocde, V., Ziółkowska, O., Soszynski, I., Udalski, A.; Insights from O-C Study of 7200+ Magellanic Cepheids from the OGLE Survey: Census of Irregular Period Changes and Binary Cepheids Candidates, in Proc. of the Polish Astron. Society (2024), 13, 157; XLI Polish Astronomical Society Meeting, Torun, Sep 11-15, 2023, www
• Smolec, R., Ziółkowska, O., Rathour, R.S., Hocde, V.; MESA Stellar Evolutionary Tracks for Medium Mass Stars - Preliminary Results, in Proc. of the Polish Astron. Society (2024), 13, 209; XLI Polish Astronomical Society Meeting, Torun, Sep 11-15, 2023, www
• Rathour, R.S., Smolec, R., Netzel, H.; Non-radial Modes and Modulation in Galactic Cepheids from OGLE-IV Survey, in Proc. of the Polish Astron. Society (2022), 12, 202; XL Polish Astronomical Society Meeting, Szczecin, Sep 13-17, 2021, www
• Rathour, R.S., Smolec, R.; Period Doubling Effect in Blazkho Modulated RRc Star from OGLE-IV Survey?, in Proc. of the Polish Astron. Society (2022), 12, 209; XL Polish Astronomical Society Meeting, Szczecin, Sep 13-17, 2021, www
• Ziółkowska, O., Suchomska, K., Galan, C., Smolec, R.; Estimating mass-loss rate in low-mass, evolved eclipsing binaries, in Proc. of the Polish Astron. Society (2022), 12, 213; XL Polish Astronomical Society Meeting, Szczecin, Sep 13-17, 2021, www
• Smolec, R.; Low-amplitude periodicities and modulations in classical pulsators, in Astron. Soc. of the Pacific Conf. Ser. (2020), 529, 287; RRL/Cep 2019 - Frontiers of Classical Pulsators: Theory and Observations, Cloudcroft, Oct 13-18, 2019; www

Selected Conference Presentations

• 2025, Pune, India, Stellar Variability: Taking the Pulse of the Universe, 24-28 Nov; www
  → Challenges in evolution and pulsation of Cepheids through the MESA eyepiece; invited talk
  
• 2025, Warszawa, Poland, 42th Meeting of the Polish Astronomical Society, 8-12 Sep; www
  → OGLE-ing Period Changes in Classical Cepheids: Binary Clues and Irregular Blues; contributed talk by R. Rathour
  
• 2024, Marrakesh, Morocco, The RRL/Cep-2024: Frontiers of Classical Pulsators - Theory and Observations, 24-30 Nov; www
  → Looking Beyond the Regular: Census of Non-Evolutionary Effects on Period Change from O-C Study of 7200+ Magellanic Cepheids ; contributed talk by R. Rathour
  → Toward a Comprehensive Grid of Cepheid Models with MESA: Uncertainties of the Evolutionary Tracks ; contributed talk by O. Ziolkowska
  → Towards Consistent Set of Evolutionary and Pulsation Models with MESA; poster
  
• 2024, Litomyšl, Czech Republic, KOPAL Conference: Binary and multiple Stars in the Era of Big Sky Surveys, 9-13 Sep; www
  → Non-evolutionary effects on Period change in Magellanic Cepheids I. New binary systems revealed from Light Travel Time Effect; contributed talk by R. Rathour
  
• 2024, Paris, France, Galactic and Extragalactic Distances for the Hubble constant Araucaria Collaboration Meeting 2024, 2-6 Sep; www
  → A new library of consistent evolutionary and pulsation models for classical Cepheids; contributed talk by R. Smolec
  
• 2024, Porto, Portugal, 8th TESS/15th Kepler Asteroseismic Science Consortium Workshop, 15-19 Jul; www
  → Census of Non-evolutionary effects on period change from O-C study of 7000+ Magellanic Cepheids ; contributed talk by R. Rathour
  → Toward a comprehensive grid of Cepheid models with MESA I. Uncertainties of the evolutionary tracks ; poster
  
• 2024, Marseille, France, Annual Meeting of the French Society of Astronomy and Astrophysics, 4-7 Jun; www
  → Why Y Oph is off? Pulsation modeling of the Cepheid Y Ophiuchi with MESA/RSP; contributed talk by V. Hocde
  
• 2023, Torun, Poland, 41st Meeting of the Polish Astronomical Society, 11-15 Sep; www
  → Insights from O-C study of 7000+ Magellanic Cepheids from OGLE survey: Census of irregular period changes and binary Cepheids candidates; contributed talk by R. Rathour
  → Stellar evolutionary tracks for medium mass stars - effects of microphysics, core and envelope overshooting and mass loss; poster by O. Ziolkowska et al.
  
• 2023, Krakow, Polska, EAS 2023 Annual Meeting, 10-14 Jul; www
  → Insights from O-C study of 7000+ Magellanic Cepheids from OGLE survey: Census of irregular period changes and binary Cepheids candidates; contributed talk by R. Rathour
  → Stellar evolutionary tracks for medium mass stars - effects of microphysics, core and envelope overshooting and mass loss; poster
  
• 2023, Milazzo, Italy, PLATO Stellar Science Conference 2023, 26-30 Jun; www
  → Stellar evolutionary tracks for medium mass stars - effects of microphysics, core and envelope overshooting and mass loss; poster by R. Smolec et al.
  
• 2023, Budapest, Hungary, IAU Symposium 376: , 17-21 Apr; www
  → Metallicity Estimations of MW, SMC, and LMC Classical Cepheids from the Shape of the V- and I-band Light Curves; contributed talk by V. Hocde
  
• 2022, La Palma, Spain, The RRL/Cep-2022: Large-scale surveys as bridges between spectroscopy and photometry, 26-30 Sep; www
  → Empirical relation for metallicity determination of classical Cepheids; contributed talk by V. Hocde
  → Quantifying the uncertainties of MESA evolutionary tracks for medium mass stars till end of core helium burning ; contributed talk by O. Ziolkowska
  → Looking beyond the regular: Study of irregular period changes in Magellanic Cepheids; poster
  → Non-radial modes and modulation in Galactic Cepheids from OGLE-IV survey; poster
  
• 2021, Sopot, Poland, Physics behind the primary distance indicators - Araucaria Collaboration Meeting 2021, 13-17 Sep; www
  → Evolution of classical Cepheids: challenges and prospects; contributed talk by R. Smolec
  → Circumstellar envelopes of Cepheids and the calibration of distances in the Universe; contributed talk by V. Hocde
  
• 2021, Szczecin, Poland, 40th Meeting of the Polish Astronomical Society, 13-17 Sep; www
  → Candidate for period-doubling effect in Blazkho modulated RRc candidate from OGLE-IV survey; poster by R. Rathour et al.
  → Search for non-radial mode and modulation phenomenon in galactic cepheids from OGLE-IV survey; poster by R. Rathour et al.
  → Estimating mass-loss rate in low-mass, evolved eclipsing binaries; poster by O. Ziolkowska et al.
  
• 2019, Cloudcroft, USA, RRL/Cep 2019 - Frontiers of Classical Pulsators: Theory and Observations, 13-18 Oct; www
  → Classical pulsators: beyond radial modes - observations and theory; invited talk
  

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