The Mouse Pulsar Wind Nebula

TL;DR

This paper presents detailed X-ray, radio, and infrared observations of the Mouse pulsar wind nebula powered by pulsar J1747-2958, revealing its structure, spectrum, and electron cooling processes, and providing insights into its magnetic field and flow dynamics.

Contribution

It offers the first combined multiwavelength analysis of the Mouse PWN, including spatially-resolved spectroscopy and modeling of electron cooling and magnetic field properties.

Findings

The PWN exhibits a spectral steepening along the X-ray tail.

The tail's integrated spectrum fits a single power-law with photon index 2.09.

Multiwavelength data suggest synchrotron cooling and a broken power-law spectrum.

Abstract

The young energetic pulsar J1747-2958 ($\tau=26$ kyr, $\dot{E}=2.5\times 10^{36}$ erg s$^{-1}$) powers the Mouse pulsar wind nebula (PWN), famous for its spectacular tail spanning 45$"$ in X-rays and 12$'$ in radio ($d\sim5$ kpc). We present the results of Chandra observations of the PWN and the analysis of archival lower-frequency data. The Chandra HRC image reveals a point-like source at the pulsar position, $\approx$1$'$ behind the bow shock apex of the PWN. The flattened appearance of the compact nebula is consistent with an equatorial outflow deformed by the ram pressure, implying that the angle between the pulsar's spin axis and line of sight is $\sim70^\circ$ (in agreement with the radio and $\gamma$-ray pulse profiles). The spatially-resolved spectroscopy with Chandra ACIS shows that the power-law (PL) spectrum steepens from $\Gamma=1.65\pm0.02$ to $3.0\pm0.1$ over the 45$'$ extent of the X-ray tail. However, the tail's X-ray spectrum integrated over its 45$"$ length fits a single absorbed PL with $\Gamma=2.09\pm0.03$. We also found the Mouse PWN in 150 MHz GMRT data, and a possible counterpart in 24 ${\rm \mu}$m Spitzer data. The multiwavelength data suggest that, at low frequencies, the spectrum of the X-ray-emitting tail region can be described by a broken PL with at least one turnover between radio and X-rays. This is consistent with synchrotron cooling of electrons injected at the termination shock (with an SED slope of 2.2) in an equipartition magnetic field $B\sim200$ ${\rm \mu G}$ and a bulk flow speed $v\sim4000$ km s$^{-1}$.