First Chromospheric Activity and Doppler Imaging Study of PW And Using a New Doppler Imaging Code: SpotDIPy

• Published in: The Astrophysical journal Vol. 960; no. 1; pp. 60 - 75
• Main Authors: Bahar, Engin, Şenavcı, Hakan V., Işık, Emre, Hussain, Gaitee A. J., Kochukhov, Oleg, Montes, David, Xiang, Yue
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.01.2024; IOP Publishing
• Subjects: Astrophysics; Brightness distribution; Chromospheric activity; Cool stars; Doppler imaging; Image reconstruction; Indicators; K stars; Maximum entropy; Maximum entropy method; Photosphere; Rotating generators; Source code; Stars; Starspots; Stellar activity; Stellar flares; Stellar surfaces; Surface brightness; Surface spots; Titanium oxides
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.3847/1538-4357/ad055d

Measuring the coverage of dark spots on cool stars is important to understanding how stellar magnetic activity scales with the rotation rate and convection zone depth. In this respect, it is crucial to infer surface magnetic patterns on G and K stars, to reveal solar-like stellar dynamos in action. Molecular bands serve as invaluable indicators of cool spots on the surfaces of stars, as they play a crucial role in enabling accurate assessments of the extent of spot coverage across the stellar surface. Therefore, more reliable surface images can be obtained considering the inversion of atomic lines with molecular bands. In this context, we simultaneously carry out Doppler imaging (DI) using atomic lines as well as titanium oxide band profiles of PW And (K2 V) and also investigate chromospheric activity indicators for the first time in the literature, using high-resolution spectra. The surface spot distribution obtained from the inversion process represents both atomic line and TiO-band profiles quite accurately. The chromospheric emission is also correlated with photospheric spot coverage, except during a possible flare event during the observations. We detect frequent flare activity, using TESS photometry. We also introduce a new open-source, Python-based DI code SpotDIPy that allows performing surface reconstructions of single stars using the maximum entropy method. We test the code by comparing surface reconstruction simulations with the extensively used DoTS code. We show that the surface brightness distribution maps reconstructed via both codes using the same simulated data are consistent with each other.