# LMC X-1: A New Spectral Analysis of the O-star in the binary and surrounding nebula

## TL;DR

This study presents new spectroscopic and imaging observations of the LMC X-1 O star and its nebula, revealing a wind bow shock structure and providing insights into the system's dynamics and possible origins.

## Contribution

It introduces a new spectrum extraction technique and identifies a wind bow shock structure, linking it to the black hole progenitor and potential non-thermal radio emission.

## Key findings

- Updated spatial velocity of the O star (~21 km/s)
- Detection of a bow shock-like nebula structure
- Possible non-thermal radio emission from the nebula

## Abstract

We provide new observations of the LMC X-1 O star and its extended nebula structure using spectroscopic data from VLT/UVES as well as H$\alpha$ imaging from the Wide Field Imager on the Max Planck Gesellschaft / European Southern Observatory 2.2m telescope and ATCA imaging of the 2.1 GHz radio continuum. This nebula is one of the few known to be energized by an X-ray binary. We use a new spectrum extraction technique that is superior to other methods to obtain both radial velocities and fluxes. This provides an updated spatial velocity of $\simeq 21.0~\pm~4.8$ km s$^{-1}$ for the O star. The slit encompasses both the photo-ionized and shock-ionized regions of the nebula. The imaging shows a clear arc-like structure reminiscent of a wind bow shock in between the ionization cone and shock-ionized nebula. The observed structure can be fit well by the parabolic shape of a wind bow shock. If an interpretation of a wind bow shock system is valid, we investigate the N159-O1 star cluster as a potential parent of the system, suggesting a progenitor mass of $\sim 60$ M$_{\odot}$ for the black hole. We further note that the radio emission could be non-thermal emission from the wind bow shock, or synchrotron emission associated with the jet inflated nebula. For both wind and jet-powered origins, this would represent one of the first radio detections of such a structure.