Photometric variability of nitrogen-rich Wolf-Rayet stars in Magellanic Clouds with OGLE

¹ Universidad de Alcalá, Departamento de Física y Matemáticas, Grupo de Física Nuclear y de Partículas 28805 Alcalá de Henares Madrid, Spain
² Groupe d’Astrophysique des Hautes Energies, STAR, Université de Liège, Quartier Agora (B5c, Institut d’Astrophysique et de Géophysique), Allée du 6 Août 19c B-4000 Sart Tilman Liège, Belgium
³ Centro de Astrobiología, CSIC-INTA Torrejón de Ardoz Madrid, Spain
⁴ Astronomical Observatory, University of Warsaw Al. Ujazdowskie 4 00-478 Warszawa, Poland

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 3 June 2025
Accepted: 2 December 2025

Abstract

Aims. We present a comprehensive analysis of the photometric variability of (presumably single) nitrogen-rich Wolf-Rayet (WN) stars in the Magellanic Clouds, using long-term observations from the OGLE survey.

Methods. Our sample comprises 47 stars with no nearby Gaia counterparts. We characterize both overall and short-term variabilities, examining data dispersion and identifying periodicities. To validate our findings, we also compare the OGLE light curves with data from the MACHO and TESS missions.

Results. Variability is ubiquitous in our WR sample: about one third of stars display high variability, or four fifths if we include cases with moderate variations. The observed changes are found to be periodic in 11 cases, with timescales of 2–56 d. Such periodic variations originate in corotating wind structures, binary effects, or pulsations, thereby increasing the number of systems known to show these phenomena. Surprisingly, nine targets display (quasi-periodic) outbursts, making such changes a new type of WR variability. The variability shows a transient character, in about 30% of the sample, with changing amplitudes for periodic signals or for outbursts (they even sometimes completely disappear from view). Finally, we identified six long-period variables, four of which have been confirmed by at least two independent surveys.