A Deep Chandra Observation of the Oxygen-Rich Supernova Remnant 0540-69.3 in the Large Magellanic Cloud

📝 Abstract

Using our deep ~120 ks Chandra observation, we report on the results from our spatially-resolved X-ray spectral analysis of the “oxygen-rich” supernova remnant (SNR) 0540-69.3 in the Large Magellanic Cloud. We conclusively establish the nonthermal nature of the “arcs” in the east and west boundaries of the SNR, which confirms the cosmic-ray electron acceleration in the supernova shock (B ~ 20-140 microG). We report tentative evidence for Fe overabundance in the southern region close to the outer boundary of the SNR. While such a detection would be intriguing, the existence of Fe ejecta is not conclusive with the current data because of poor photon statistics and limited plasma models. If it is verified using deeper X-ray observations and improved plasma models, the presence of Fe ejecta, which was produced in the core of the supernova, near the SNR’s outer boundary would provide an intriguing opportunity to study the explosive nucleosynthesis and the ejecta mixing in this young core-collapse SNR. There is no evidence of X-ray counterparts for the optical O-rich ejecta in the central regions of the SNR.

💡 Analysis

Using our deep ~120 ks Chandra observation, we report on the results from our spatially-resolved X-ray spectral analysis of the “oxygen-rich” supernova remnant (SNR) 0540-69.3 in the Large Magellanic Cloud. We conclusively establish the nonthermal nature of the “arcs” in the east and west boundaries of the SNR, which confirms the cosmic-ray electron acceleration in the supernova shock (B ~ 20-140 microG). We report tentative evidence for Fe overabundance in the southern region close to the outer boundary of the SNR. While such a detection would be intriguing, the existence of Fe ejecta is not conclusive with the current data because of poor photon statistics and limited plasma models. If it is verified using deeper X-ray observations and improved plasma models, the presence of Fe ejecta, which was produced in the core of the supernova, near the SNR’s outer boundary would provide an intriguing opportunity to study the explosive nucleosynthesis and the ejecta mixing in this young core-collapse SNR. There is no evidence of X-ray counterparts for the optical O-rich ejecta in the central regions of the SNR.

📄 Content

arXiv:0912.5177v1 [astro-ph.HE] 28 Dec 2009 Accepted for the publication in the Astrophysical Journal A Deep Chandra Observation of the Oxygen-Rich Supernova Remnant 0540–69.3 in the Large Magellanic Cloud Sangwook Park Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA. 16802, USA park@astro.psu.edu John P. Hughes Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ. 08854-8019, USA Patrick O. Slane Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA. 02138, USA Koji Mori Department of Applied Physics, University of Miyazaki, 1-1 Gakuen Kibana-dai Nishi, Miyazaki, 889-2192, Japan and David N. Burrows Department of Astronomy and Astrophysics, 525 Davey Lab., Pennsylvania State University, University Park, PA. 16802, USA ABSTRACT Using our deep ∼120 ks Chandra observation, we report on the results from our spatially-resolved X-ray spectral analysis of the “oxygen-rich” supernova remnant (SNR) 0540-69.3 in the Large Magellanic Cloud. We conclusively establish the nonthermal na- ture of the “arcs” in the east and west boundaries of the SNR, which confirms the cosmic-ray electron acceleration in the supernova shock (B ∼20–140 µG). We report tentative evidence for Fe overabundance in the southern region close to the outer bound- ary of the SNR. While such a detection would be intriguing, the existence of Fe ejecta is not conclusive with the current data because of poor photon statistics and limited plasma models. If it is verified using deeper X-ray observations and improved plasma – 2 – models, the presence of Fe ejecta, which was produced in the core of the supernova, near the SNR’s outer boundary would provide an intriguing opportunity to study the explosive nucleosynthesis and the ejecta mixing in this young core-collapse SNR. There is no evidence of X-ray counterparts for the optical O-rich ejecta in the central regions of the SNR. Subject headings: ISM: abundances — ISM: individual (SNR 0540–69.3) — supernova remnants — X-rays: ISM 1. INTRODUCTION The supernova remnant (SNR) 0540–69.3 in the Large Magellanic Cloud (LMC) is well known for its bright central pulsar (PSR B0540–69.3) and its pulsar wind nebula (PWN) which show simi- lar characteristics to those of the Crab. The pulsar and PWN have been extensively studied at many wavelengths (e.g., Middleditch & Pennypacker 1985; Manchester et al. 1993a,b; Gotthelf & Wang 2000; Kaaret et al. 2001; Petre et al. 2007 and references therein). SNR 0540–69.3 is also one of the two known members of “oxygen-rich” SNRs in the LMC. In the optical band, early data of 0540– 69.3 showed a ring-like (∼4′′ in radius) [O III] feature around the pulsar/PWN, which is identified as the O-rich ejecta (Mathewson et al. 1980). The spatial and spectral structures of the optical fil- amentary features in this region were studied using the Hubble Space Telescope observations, which revealed the details of the ejecta and the synchrotron nebula (Morse et al. 2006). The filamentary features of the optical line emission were suggested to result from magnetic Rayleigh-Taylor instabil- ities due to the interaction between the expanding synchrotron nebula and the surrounding ejecta, just like those seen in the Crab (Morse et al. 2006). This central region was also thoroughly studied in infrared (IR) using the Spitzer Space Telescope observations (Williams et al. 2008). These ob- servations revealed that the central nebula of 0540–69.3 is analogous to that of the Crab, showing synchrotron emission from the PWN, a complex network of ejecta filaments, and newly formed dust. A progenitor mass of 20–25 M⊙was suggested based on the observed metal ejecta abun- dances (Williams et al. 2008). The enhanced optical and IR emission most likely originates from the interaction between the PWN and the freely-expanding metal-rich ejecta. Besides the central pulsar and PWN, the SNR shell produced by the interaction between the blast wave and the surrounding medium was detected in the radio band (Manchester et al. 1993b). The radio spectral index in the outer shell (α = 0.41, where Sν ∝ν−α) is steeper than that in the PWN (α = 0.25), which indicated that the shell emission is synchrotron radiation from the shock-accelerated electrons. The age of SNR 0540–69.3 has been estimated to be τ ∼760–1660 yr based on various methods such as the pulsar spin-down, the kinematics of the optical ejecta, and the overall dynamics of the ejecta evolutionary models (Seward et al. 1984; Kirshner et al. 1989; Reynolds 1985; Manchester et al. 1993a). Thermal emission from the SNR shell (∼1′ in diameter) has been detected in the X-ray band – 3 – (Hwang et al. 2001; van der Heyden et al. 2001). The overall SNR morphology of the nearly cir- cular shell with the bright W and faint E regions is consistent with that of the radio images. The bright W filaments are roughly coincident with the patchy [O III] emis

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