A newly-identified emission-line region around P Cygni

Abstract

We present a high-resolution ($R\simeq 20,000$) near-infrared (9,100-13,500 $\tilde{A}$) long-slit spectrum of P Cygni obtained with the newly commissioned WINERED spectrograph in Japan. In the obtained spectrum, we have found that the velocity profiles of the [Fe II] emission lines are resolved into two peaks at a velocity of $\simeq 220$ km s${}^{-1}$ with a moderate dip in between and with additional sub-peaks at $\simeq \pm 100$~km~s${}^{-1}$. The sub-peak component is confirmed with the long-slit echellogram to originate in the known shell with a radius of $\simeq 10^{\prime \prime }$, which was originally created by the outburst in 1600 AD. On the other hand, the $\simeq 220$ km s${}^{-1}$ component, which dominates the [Fe II] flux from P Cygni, is found to be concentrated closer to the central star with an apparent spatial extent of $\simeq 3^{\prime \prime }$. The extent is much larger than the compact ($<0^{\prime \prime }.1$) regions traced with hydrogen, helium, and metal permitted lines. The velocity, estimated mass, and dynamical time of the extended emission-line region suggest that the region is an outer part of the stellar wind region. We suggest that the newly-identified emission-line region may trace a reverse shock due to the stellar wind overtaking the outburst shell.

16 pages, 8 figures, accepted in MNRAS