Spectral Study of the WNL Star FSZ35 in the M33 Galaxy

TL;DR

This study analyzes the spectral and physical properties of the hydrogen-rich WN8 star FSZ35 in M33, revealing its stability, nebular features, and possible runaway status through spectral classification and radiative transfer modeling.

Contribution

It provides the first detailed spectral classification and physical parameter determination of FSZ35 using CMFGEN, and compares its properties to similar stars, highlighting its stability and potential runaway nature.

Findings

FSZ35 is classified as a hydrogen-rich WN8 star.

The star exhibits a stable spectrum and photometry over time.

FSZ35 has a compact nebula with faint [OIII] emission.

Abstract

We study and analyse low-resolution spectra of the unordinary late WN star FSZ35 in M33. We classify the object as a hydrogen-rich WN8 star. Using the radiative transfer code CMFGEN, we determine the physical parameters of this object and compare them to the parameters of other WN8 stars including the LBV star Romano's star during the minimum of brightness. Unlike Romano's star, the object is fairly stable both spectrally and photometrically, that may be attributed to its more advanced evolutionary stage or lower luminosity. FSZ35 is shown to possess a compact nebula producing faint but detectable [OIII]emission. Location of this object at a large distance (about 100 pc) from the nearest association suggests the object may be one more example of a massive runaway star.