G11.2−0.3: The Young Remnant of a Stripped-Envelope Supernova

Abstract

We present results of a 400-ks Chandra observation of the young shell supernova remnant (SNR) G11.2−0.3, containing a pulsar and pulsar-wind nebula (PWN). We measure a mean expansion rate for the shell since 2000 of 0.0277 ± 0.0018% yr −1 , implying an age between 1400 and 2400 yr, and making G11.2−0.3 one of the youngest core-collapse SNRs in the Galaxy. However, we find very high absorption (A V ∼ 16 m ± 2 m ), confirming near-IR determinations and ruling out a claimed association with the possible historical SN of 386 CE. The PWN shows strong jets and a faint torus within a larger, more diffuse region of radio emission and nonthermal X-rays. Central soft thermal X-ray emission is anticorrelated with the PWN; that, and more detailed morphological evidence, indicates that the reverse shock has already reheated all ejecta and compressed the PWN. The pulsar characteristic energy-loss timescale is well in excess of the remnant age, and we suggest that the bright jets have been produced since the recompression. The relatively pronounced shell and diffuse hard X-ray emission in the interior, enhanced at the inner edge of the shell, indicate that the immediate circumstellar medium into which G11.2−0.3 is expanding was quite anisotropic. We propose a possible origin for G11.2−0.3 in a stripped-envelope progenitor that had lost almost all its envelope mass, in an anisotropic wind or due to binary interaction, leaving a compact core whose fast winds swept previously lost mass into a dense irregular shell, and which exploded as a Type cIIb or Ibc supernova. Subject headings: ISM: individual objects (G11.2−0.3) -ISM: supernova remnants -X-rays: ISM

Comparing Neutron Star Kicks to Supernova Remnant Asymmetries

“…G11.2−0.3-G11.2−0.3 was first detected at X-ray wavelengths with Einstein HRI (Downes 1984) and was subsequently observed with ROSAT (Reynolds et al 1994) and with Chandra (Kaspi et al 2001;Roberts et al 2003;Lopez et al 2011;Borkowski et al 2016). The PWN and 65-ms period pulsar associated with G11.2−0.3 were discovered using ASCA observations (Vasisht et al 1996;Torii et al 1997), and Kaspi et al (2001) showed that the pulsar is only 8 from the geometric center of the SNR.…”

“…The PWN and 65-ms period pulsar associated with G11.2−0.3 were discovered using ASCA observations (Vasisht et al 1996;Torii et al 1997), and Kaspi et al (2001) showed that the pulsar is only 8 from the geometric center of the SNR. Borkowski et al (2016) used multiple epochs of Chandra observations to measure a shell expansion rate that implied an age of 1400-2400 years, making G11.2−0.3 one of the youngest identified CC SNRs in the Milky Way. Lopez et al (2011) performed a spatially-resolved spectroscopic analysis of 23 regions using Chandra data and found that the spectra were bestfit by a single absorbed, NEI component with absorbing columns of N H ≈ (2.1 − 2.9) × 10 22 cm −2 , temperatures of kT ≈ 0.6 − 1.4 keV, and ionization timescales of n e t ≈ (0.9 − 10) × 10 11 s cm −3 .…”

Expansion of Kes 73, A Shell Supernova Remnant Containing a Magnetar

“…The very good agreement found in expansion rates for the Epoch I -III and Epoch II -III image pairs suggests that the magnitude of this bias is much smaller than statistical errors. This source of systematic errors was examined by Borkowski et al (2016) in their studies of the significantly brighter SNR G11.2−0.3 that expands 20% faster than Kes 73. They found it less important than statistical errors, and this is also expected to hold for Kes 73.…”

“…We then smoothed this data cube with the multiscale partitioning method of Krishnamurthy et al (2010). We set the penalty parameter that controls smoothing to 0.015, the value that we found optimal for G11.2−0.3 (Borkowski et al 2016).…”

“…EXPANSION The time baseline between the 29 ks 2000 and 95 ks 2015 Chandra observations is almost 15 yr. In order to measure expansion, we use the method of Carlton et al (2011) and Borkowski et al (2016). First, we extracted a data cube from the merged 2015 observations, 1024 2 × 64 in size, and in the energy range from 0.8 to 8 keV.…”