PD-121203: Nonlinear phenomena in Cepheid variable stars (2016-2019)
PI: Emese Plachy
The role of nonlinear dynamics is one of the major questions in the field of stellar pulsations. The recent discovery of period doubling in the space-based measurements and chaos in hydrodynamical models of RR Lyrae stars opened up a new direction for nonlinear asteroseismology. Theoretical and observational evidences suggest that the pulsation of Cepheid variables is also governed by nonlinear dynamics. The aim of my research is to explore and study nonlinear phenomena in all types of Cepheids using large ground-based surveys and state of the art space-based measurements. This research will help us to better understand the dynamics of the pulsation, the interactions between different pulsation modes and the selection mechanisms behind them. The results may form the input basis of improved hydrodynamical calculations that can lead to the determination of physical properties of these variable stars. I plan to focus on four topics:
- - Nonlinear dynamical analysis of RV Tau stars, aimed at the detection of chaos and the determination of the fractal dimension of the underlying dynamics.
- - Systematic search for period doubling and other dynamical phenomena in BL Her- and W Vir-type stars by analysing ground-based surveys and the space photometric data of the extended mission of Kepler (K2).
- - Search for cycle to cycle variations in classical and anomalous Cepheids. Our knowledge is especially limited for the latter subgroup: my research could shed light on their formation and inner structure.
- - Study and characterize the Cepheid impostors that may mimic nonlinear phenomena.
Project no. 121203 has been implemented with the support provided from the National Research, Development and Innovation Fund of Hungary, financed under the PD_16 funding scheme.
Selected results and publications:
- Plachy, E.; Molnár, L.; Jurkovic, M. I.; Smolec, R.; Moskalik, P. A.; Pál, A.; Szabados, L.; Szabó, R.: First observations of W Virginis stars with K2: detection of period doubling, 2017, MNRAS, 465, 173
- Derekas, A.; Plachy, E.; Molnár, L.; Sódor, Á.; Benkõ, J. M.; Szabados, L.; Bognár, Zs.; Csák, B.; Szabó, Gy. M.; Szabó, R.; Pál, A. The Kepler Cepheid V1154 Cyg revisited: light curve modulation and detection of granulation, 2017, MNRAS, 464, 1553
- Plachy, E.: Cepheid investigations in the era of space photometric missions, 2017, Proceedings of the 2nd BRITE-Constellation Science Conference, Proc. Polish Astr. Soc., 5, 251
- Plachy, E.; Klagyivik, P.; Molnár, L.; Sódor, Á.; Szabó, R.: Extended Aperture Photometry of K2 RR Lyrae stars, 2017, Proceedings of the Joint TASC2-KASC9-SPACEINN-HELAS8 Conference, EpJ WoC, 160, 04009
- Plachy, E.; Klagyivik, P.; Molnár, L.; Szabó, R.: A modulated RRd star observed by K2, 2017, Proceedings of the Joint TASC2-KASC9-SPACEINN-HELAS8 Conference, EPJ WoC, 160, 04010
- Molnár, L., Pál, A., Plachy, E.: Cepheids with the eyes of photometric space telescopes, Proceedings of the 22nd Los Alamos Stellar Pulsation Conference, 2017, EpJ WoC, 152, 02004
- TASC3/KASC10 Workshop - TESSting Stellar Astrophysics, 2017. 07. 16-21., Birmingham (UK) - invited talk: "Cepheid and RR Lyrae studies with TESS: What Could 27 Days Give Us?"
- The RR Lyrae 2017 Conference - Revival of Classical Pulsators, 2017. 09. 17-21., Niepolomice (PL) - contributed talk: "K2 photometry of RR Lyrae stars"
Popular science articles, public lectures:
- Kepler watched a Cepheid star boil (phys.org, 2016. 09. 28)
- Forrongó cefeida, ahogy a Kepler látta (csillagaszat.hu, 2016. 09. 28.)