Evolutionary Map of the Universe: Detection and Analysis of the Shell Surrounding the Runaway Wolf-Rayet Star WR16

Fuente: arXiv

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Bibliographic Details
Main Authors:	Bradley, A. C., Filipović, M. D., Smeaton, Z. J., Sano, H., Fukui, Y., Bordiu, C., Cichowolski, S., Tothill, N. F. H., Alsaberi, R. Z. E., Bufano, F., Dai, S., Gordon, Y. A., Hopkins, A. M., Jarrett, T. H., Koribalski, B. S., Lazarević, S., Riseley, C. J., Rowell, G., Sasaki, M., Urošević, D., Vernstrom, T.
Format:	Preprint
Published:	2025
Subjects:	Solar and Stellar Astrophysics Astrophysics of Galaxies
Online Access:	Acceder al recurso
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author	Bradley, A. C. Filipović, M. D. Smeaton, Z. J. Sano, H. Fukui, Y. Bordiu, C. Cichowolski, S. Tothill, N. F. H. Alsaberi, R. Z. E. Bufano, F. Dai, S. Gordon, Y. A. Hopkins, A. M. Jarrett, T. H. Koribalski, B. S. Lazarević, S. Riseley, C. J. Rowell, G. Sasaki, M. Urošević, D. Vernstrom, T.
author_facet	Bradley, A. C. Filipović, M. D. Smeaton, Z. J. Sano, H. Fukui, Y. Bordiu, C. Cichowolski, S. Tothill, N. F. H. Alsaberi, R. Z. E. Bufano, F. Dai, S. Gordon, Y. A. Hopkins, A. M. Jarrett, T. H. Koribalski, B. S. Lazarević, S. Riseley, C. J. Rowell, G. Sasaki, M. Urošević, D. Vernstrom, T.
contents	We present the first radio--continuum detection of the circumstellar shell around the well-known WN8 type Wolf-Rayet star WR16 at 943.5\,MHz using the \ac{ASKAP} \ac{EMU} survey. At this frequency, the shell has a measured flux density of 72.2$\pm$7.2\,mJy. Using previous \ac{ATCA} measurements at 2.4, 4.8, and 8.64~GHz, as well as the \ac{EMU} observations of the star itself, we determine a spectral index of $α\,=\,+0.74\pm0.02$, indicating thermal emission. We propose that the shell and star both exhibit thermal emission, supported by the its appearance in near-infrared and H$α$ observations. The latest \textit{Gaia} parallax is used to determine a distance of 2.28$\pm$0.09\,kpc. This star is well-known for its surrounding circular nebulosity, and using the distance and an angular diameter of 8\farcm42, we determine the shell size to be 5.57$\pm$0.22~pc. We use the \textit{Gaia} \acp{PM} of WR16 to determine peculiar velocities of the star as $V_α(pec) =$ --45.3$\pm$5.4\,\kms\ and $V_δ(pec) =$ 22.8$\pm$4.7\,\kms, which indicates that the star is moving in a north-west direction, and translates to a peculiar tangential velocity to be 50.7$\pm$6.9\,\kms. We also use these \acp{PM} to determine the shell's origin, estimate an age of $\sim 9500\pm 1300$\,yr, and determine its average expansion velocity to be $280\pm40$\,\kms. This average expansion velocity suggests that the previous transitional phase is a \ac{LBV} phase, rather than a \ac{RSG} phase. We also use the measured flux at 943.5~MHz to determine a mass-loss rate of $1.753\times 10^{-5}~M_\odot~$yr$^{-1}$, and use this to determine a lower-limit on ionising photons of $N_{UV} > 1.406\times 10^{47}~$s$^{-1}$.
format	Preprint
id	arxiv_https___arxiv_org_abs_2506_23588
institution	arXiv
publishDate	2025
record_format	arxiv
spellingShingle	Evolutionary Map of the Universe: Detection and Analysis of the Shell Surrounding the Runaway Wolf-Rayet Star WR16 Bradley, A. C. Filipović, M. D. Smeaton, Z. J. Sano, H. Fukui, Y. Bordiu, C. Cichowolski, S. Tothill, N. F. H. Alsaberi, R. Z. E. Bufano, F. Dai, S. Gordon, Y. A. Hopkins, A. M. Jarrett, T. H. Koribalski, B. S. Lazarević, S. Riseley, C. J. Rowell, G. Sasaki, M. Urošević, D. Vernstrom, T. Solar and Stellar Astrophysics Astrophysics of Galaxies We present the first radio--continuum detection of the circumstellar shell around the well-known WN8 type Wolf-Rayet star WR16 at 943.5\,MHz using the \ac{ASKAP} \ac{EMU} survey. At this frequency, the shell has a measured flux density of 72.2$\pm$7.2\,mJy. Using previous \ac{ATCA} measurements at 2.4, 4.8, and 8.64~GHz, as well as the \ac{EMU} observations of the star itself, we determine a spectral index of $α\,=\,+0.74\pm0.02$, indicating thermal emission. We propose that the shell and star both exhibit thermal emission, supported by the its appearance in near-infrared and H$α$ observations. The latest \textit{Gaia} parallax is used to determine a distance of 2.28$\pm$0.09\,kpc. This star is well-known for its surrounding circular nebulosity, and using the distance and an angular diameter of 8\farcm42, we determine the shell size to be 5.57$\pm$0.22~pc. We use the \textit{Gaia} \acp{PM} of WR16 to determine peculiar velocities of the star as $V_α(pec) =$ --45.3$\pm$5.4\,\kms\ and $V_δ(pec) =$ 22.8$\pm$4.7\,\kms, which indicates that the star is moving in a north-west direction, and translates to a peculiar tangential velocity to be 50.7$\pm$6.9\,\kms. We also use these \acp{PM} to determine the shell's origin, estimate an age of $\sim 9500\pm 1300$\,yr, and determine its average expansion velocity to be $280\pm40$\,\kms. This average expansion velocity suggests that the previous transitional phase is a \ac{LBV} phase, rather than a \ac{RSG} phase. We also use the measured flux at 943.5~MHz to determine a mass-loss rate of $1.753\times 10^{-5}~M_\odot~$yr$^{-1}$, and use this to determine a lower-limit on ionising photons of $N_{UV} > 1.406\times 10^{47}~$s$^{-1}$.
title	Evolutionary Map of the Universe: Detection and Analysis of the Shell Surrounding the Runaway Wolf-Rayet Star WR16
topic	Solar and Stellar Astrophysics Astrophysics of Galaxies
url	https://arxiv.org/abs/2506.23588