Multiple variability time-scales of the early nitrogen-rich Wolf-Rayet star WR7

TL;DR

This study analyzes the optical variability of Wolf-Rayet star WR7, revealing multi-periodic behavior with a dominant 2.64-day period, likely caused by pulsations and wind structures, with implications for understanding massive star variability.

Contribution

First detailed multi-scale variability analysis of WR7 combining TESS photometry and spectroscopy, suggesting pulsations and wind effects as variability mechanisms.

Findings

Detected a dominant 2.6433-day period in WR7.

Identified multi-scale variability including short and long-term periods.

No strong evidence for a stellar or compact companion.

Abstract

We present the analysis of the optical variability of the early, nitrogen-rich Wolf-Rayet (WR) star WR7. The analysis of multi-sector Transiting Exoplanet Survey Satellite (TESS) light curves and high-resolution spectroscopic observations confirm multi-periodic variability that is modulated on time-scales of years. We detect a dominant period of $2.6433 \pm 0.0005$ d in the TESS sectors 33 and 34 light curves in addition to the previously reported high-frequency features from sector 7. We discuss the plausible mechanisms that may be responsible for such variability in WR7, including pulsations, binarity, co-rotating interacting regions (CIRs) and clumpy winds. Given the lack of strong evidence for the presence of a stellar or compact companion, we suggest that WR7 may pulsate in quasi-coherent modes in addition to wind variability likely caused by CIRs on top of stochastic low-frequency variability. WR7 is certainly a worthy target for future monitoring in both spectroscopy and photometry to sample both the short ($\lesssim 1$ d) and long ($\gtrsim 1000$ d) variability time scales.