7770 20260108161002.0 10.1093/mnras/staf1247 DOI SCART-2026-0040 Dileep, Athul Chemical abundances and Doppler imaging of the Ap Si/He-wk star HD 100357 2025 We present the results of time-resolved photometry, abundance analysis, and Doppler imaging of an Ap star, HD 100357. The TESS photometry revealed rotational modulation with a period of 1.6279247 d. Upon inspecting the residuals after removing the rotational period and its harmonics, we found additional frequencies around 15.8054 d⁻1, which we later confirmed with ground-based observations as originating from a nearby star. Using high-resolution spectroscopy, we identified HD 100357 as an Ap Si/He-wk star exhibiting rotational modulation caused by surface abundance spots. The stellar parameters of HD 100357 were determined as T_eff = 11 850 K, logg = 4.57, υsini = 60 kms^{-1}, and an inclination angle i = 72 deg. The detailed abundance analysis revealed strongly overabundant stratified silicon, an overabundance of iron-peak elements and rare earth elements combined with remarkably deficient helium. Mapping of Fe and Cr abundances revealed the existence of ring-shaped regions with a lower concentration of the elements. Their geometry might reflect the orientation of the hypothetical magnetic field of the star, oriented ∼90 deg to the rotational axis. HD 100357, with its strong chemical peculiarities and indications of possible magnetic fields, represents an interesting candidate for follow-up spectropolarimetric observations aimed at investigating its magnetic field topology and stellar activity. NO Line: profiles Stars: abundances Stars: chemically peculiar Stars: individual: HD100357 Stars: rotation Stars: starspots Solar and Stellar Astrophysics Joshi, Santosh Alexeeva, Sofya Kochukhov, Oleg Semenko, Eugene De Cat, Peter Zúñiga-Fernández, Sebastián Trust, Otto Pollard, Karen Crause, Lisa Barkaoui, Khalid Gillon, Michaël Jehin, Emmanuel Rathore, Neeraj Monthly Notices of the Royal Astronomical Society 542 2025 2 747--761 peter.decat@ksb-orb.be 4163602 http://publi2-as.oma.be/record/7770/files/Dileep2025_MNRAS542_747.pdf 4337 http://publi2-as.oma.be/record/7770/files/Dileep2025_MNRAS542_747.gif?subformat=icon icon 6774 http://publi2-as.oma.be/record/7770/files/Dileep2025_MNRAS542_747.jpg?subformat=icon-180 icon-180 published in REFERD