Deep Chandra Observations of the Pulsar Wind Nebula Created by PSR B0355+54

Abstract

We report on Chandra X-ray Observatory (CXO) observations of the pulsar wind nebula (PWN) associated with PSR B0355+54 (eight observations with a 395 ks total exposure, performed over an 8 month period). We investigated the spatial and spectral properties of the emission coincident with the pulsar, compact nebula (CN), and extended tail. We find that the CN morphology can be interpreted in a way that suggests a small angle between the pulsar spin axis and our line-of-sight, as inferred from the radio data. On larger scales, emission from the 7 (≈ 2 pc) tail is clearly seen. We also found hints of two faint extensions nearly orthogonal to the direction of the pulsar's proper motion. The spectrum extracted at the pulsar position can be described with an absorbed power-law + blackbody model. The nonthermal component can be attributed to magnetospheric emission, while the thermal component can be attributed to emission from either a hot spot (e.g., a polar cap) or the entire neutron star surface. Surprisingly, the spectrum of the tail shows only a slight hint of cooling with increasing distance from the pulsar. This implies either a low magnetic field with fast flow speed, or particle re-acceleration within the tail. We estimate physical properties of the PWN and compare the morphologies of the CN and the extended tail with those of other bow shock PWNe observed with long CXO exposures.

Pulsar-Wind Nebulae and Magnetar Outflows: Observations at Radio, X-Ray, and Gamma-Ray Wavelengths

“…The stem is split into two structures that apparently originate from the pulsar and slightly diverge from each other further away. Klingler et al (2016b) speculate that these structures could be pulsar's jets swept back by the ram pressure, which could also explain the brightening along the cap's axis. Overall, the "mushroom" morphology suggests a small angle between the pulsar's spin axis and our line of sight, in agreement with the lack of γ-ray pulsations.…”

“…Observations with Chandra and XMM-Newton revealed the presence of a PWN (dubbed the Mushroom by consisting of a compact "cap" and a dimmer "stem", with a hint of extended emission visible up to ∼ 7 (2 pc) southwest of the pulsar (McGowan et al 2006). A series of 8 Chandra observations, performed over an 8-month period in 2012-2013 (total exposure of 395 ks) revealed the detailed structure of the B0355+54 PWN (see Figure 32) and allowed us to measure the spectra of its elements (Klingler et al 2016b). In particular, they showed a "filled" morphology of the cap, in contrast with the "hollow" morphologies of the Geminga PWN and the CN of the J1509-5850 PWN.…”

“…The deep observation also allowed Klingler et al (2016b) to detect two additional very faint, extended features (dubbed "whiskers") on either side of the compact nebula, likely another example of a misaligned outflow.…”

Escape of high-energy particles from bow-shock pulsar wind nebulae

“…The ram pressure balance between the pulsar wind and the supersonic ISM flow (in the reference frame of the PSR itself) leads to the formation of a cometary nebula known as bow-shock pulsar wind nebula (BSPWN) (Wilkin 1996;Bucciantini & Bandiera 2001;Bucciantini 2002). These nebulae have been observed in H α emission, due to neutral Hydrogen of the ISM interacting through chargeexchange with the ionized component of the ISM itself, shocked in the outer bow-shock (Kulkarni & Hester 1988;Cordes, Romani & Lundgren 1993;Bell et al 1995;van Kerkwijk & Kulkarni 2001;Jones, Stappers & Gaensler 2002;Brownsberger & Romani 2014;Romani, Slane & Green 2017), and in non-thermal radio/X-rays associated with the shocked pulsar wind, flowing backward into long tails (Arzoumanian et al 2004;Kargaltsev et al 2017Kargaltsev et al , 2008Gaensler et al 2004;Yusef-Zadeh & Gaensler 2005;Li, Lu & Li 2005;Gaensler 2005;Chatterjee et al 2005;Ng et al 2009;Hales et al 2009;Ng et al 2010;De Luca et al 2011;Marelli et al 2013;Jakobsen et al 2014;Posselt et al 2017;Klingler et al 2016;Ng et al 2012). E-mail: niccolo@arcetri.astro.it Modeling of BSPWNe have progressed in the last decades from simple classical axisymmetric hydrodynamics (Bucciantini 2002) to relativistic MHD (Bucciantini, Amato & Del Zanna 2005) and full and/or simplified 3D (Vigelius et al 2007;Bucciantini 2018;Barkov & Lyutikov 2018).…”

On the origin of jet-like features in bow shock pulsar wind nebulae

“…It is thus expected that the vast majority of them is found directly interacting with the interstellar medium (ISM). Bow shock pulsar wind nebulae (BSPWNe) form due to the confinement of the pulsar wind by the incoming (in the frame of the pulsar) ISM material, and indeed many of such systems have been observed in the past: some of them in optical H α (Kulkarni & Hester 1988;Cordes, Romani & Lundgren 1993;Bell et al 1995;van Kerkwijk & Kulkarni 2001;Jones, Stappers & Gaensler 2002;Brownsberger & Romani 2014;Romani, Slane & Green 2017), others in nonthermal X-ray and radio (Arzoumanian et al 2004;Kargaltsev et al 2017Kargaltsev et al , 2008Gaensler et al 2004;Yusef-Zadeh & Gaensler 2005;Li, Lu & Li 2005;Gaensler 2005;Chatterjee et al 2005;Ng et al 2009;Hales et al 2009;Ng et al 2010;De Luca et al 2011;Marelli et al 2013;Jakobsen et al 2014;Posselt et al 2017;Klingler et al 2016;Ng et al 2012), in the UV (Rangelov et al 2016) and IR (Wang et al 2013). There are even cases of BSPWNe where the pulsar is moving through the E-mail: barbara@arcetri.astro.it parent supernova shell (Frail et al 1996;Swartz et al 2015;Temim et al 2015).…”