Exploring The Connection Between Chromospheric Activity And Starspots In Late-Type Active Stars: Implications For Dynamo Evolution
ŞENAVCI H. V. (Yürütücü), YILMAZ M., ÖZAVCI İ., BAHAR E.
TÜBİTAK Uluslararası İkili İşbirliği Projesi, 2544 - Japon Bilimi Destekleme Kurumu (JSPS) ile İkili İşbirliği Programı, 2026 - 2028
- Proje Türü: TÜBİTAK Uluslararası İkili İşbirliği Projesi
- Destek Programı: 2544 - Japon Bilimi Destekleme Kurumu (JSPS) ile İkili İşbirliği Programı
- Başlama Tarihi: Mayıs 2026
- Bitiş Tarihi: Mayıs 2028
Proje Özeti
This project aims to systematically investigate the physical connection between the chromospheric activity indicator Hα and the photospheric spot filling factor (fs) in late-type active stars. Stellar magnetic activity arises from multi-component processes manifesting in different atmospheric layers, including spots, plages, filaments, prominences, and flares. Deciphering the interactions among these structures is critical for understanding the operation of stellar dynamos and for assessing the habitability of exoplanets. Previous studies have reported both correlations and anti-correlations between fs and Hα variability, leaving a significant ambiguity in the literature. The originality of this project lies in addressing this gap through a sample-based analysis of ten active stars with diverse spectral types and rotation rates, supported by simultaneous spectroscopic and photometric observations.
The observational strategy combines high-resolution spectroscopic data obtained at Japanese observatories with simultaneous multi-color photometry from facilities in Türkiye and Japan, alongside space-based photometry and an extensive archive of high-quality spectra. This design ensures comprehensive rotational and temporal coverage, enabling a systematic investigation of the spatial and temporal relationships between surface spot distributions and chromospheric activity. Spot distributions will be derived using Doppler Imaging (DI) and Light Curve Inversion (LCI), while chromospheric diagnostics will be based on equivalent widths, narrow-band indices, and bolometric-normalized Hα fluxes. This dual approach will produce phase-resolved measurements of fs(ϕ) and Hα(ϕ), allowing correlations and potential phase lags to be quantified with statistical rigor.
The resulting trends will be examined as a function of Rossby number and interpreted in the context of modeling rotation–magnetism–activity relations and evaluating Hα–spot area couplings under solar analogies. This approach will reveal under which conditions strong, weak, or anti-correlated behaviors emerge, how correlation strength and phase lag vary with Rossby number, and to what extent plages, filaments, flares, prominences, and CME-like events contribute to the observed Hα variability. These findings will not only provide observational constraints on stellar dynamo processes but also improve the modeling of magnetic activity-induced jitter, thereby enhancing the reliability of exoplanet detection.
Beyond its direct scientific outcomes, the project offers an innovative methodological framework. By integrating DI, LCI, and Hα variability into a unified analysis, the project will set a reference for large-scale stellar surveys such as TESS, PLATO, and LAMOST, demonstrating the applicability of this methodology to broader stellar samples. Furthermore, the project will deliver open-source software modules and standardized data-reduction protocols, while all observational data and derived products will be archived in standard formats and made available to the wider research community. Thus, both the scientific results and the methodological advancements will contribute to the long-term development of stellar astrophysics.
The success of the project relies on the close collaboration between Turkish and Japanese teams. The Turkish group will lead DI and LCI analyses and contribute to modeling the rotation–magnetism–activity connection, while the Japanese group will provide high-resolution spectroscopy, flare diagnostics, and chromospheric activity analyses. The collaboration is reinforced by harmonized data-reduction protocols and coordinated observing campaigns, ensuring synergy between the partners. Knowledge exchange will be sustained through mutual visits, short workshops, and regular online meetings. The project is expected to yield at least three international journal publications, contribute directly to one MSc and one PhD thesis, and deliver presentations at major international conferences. In doing so, it will foster not only significant scientific advances but also the training of early-career researchers and the long-term building of international research capacity.