Trust, Otto ; Jurua, Edward ; De Cat, Peter ; Joshi, Santosh

Invited talk presented at 1-day BINA Meeting "Evaluation and future prospects of the Indo-Belgian collaboration", Brussels, Belgium on 2023-10-10

Abstract: Pulsation, spot-induced rotational modulation, chemical peculiarity, and the Rossby wave phenomena are all interesting aspects of A- and F-type main sequence stars. Understanding the relationships between these features was (is) our primary focus. We used Nainital-Cape survey photometric data, high-precision photometric data from Kepler, K2, and TESS, and high-resolution spectroscopic and spectropolarimetric observations with HERMES (Mercator), MRES (TNT), NES (BTA), MSS (BTA), and HESP (HCT). Rotation and spot properties were well determined for a subsample using hump and spike features in their Fourier transforms (a manifestation of Rossby waves). To establish their chemical uniqueness, atmospheric parameters and chemical abundances (LTE) were examined for a subsample. NLTE abundances for a good number of elements were also determined for HD 180347. Based on space-based photometric data, we discovered that a number of stars in our sample that yielded null findings with ground-based photometric observations turned out to be variable (pulsational and rotational). Spots in A- and F-type stars are weak, indicating that magnetic fields are modest. Magnetic field measurements on HD 73619 indicated minimal field strengths. A number of spectral lines respond strongly to NLTE effects, and taking NLTE into account increases the accuracy of the obtained abundances. We are currently conducting NLTE analysis on our subsample with high-resolution spectra. In addition, we are investigating the new binary, pulsational, and rotational variables in our sample.