Properties of the three-dimensional structure in the central region of the supernova remnant SNR 0540−69.3★

Abstract

We present and discuss new visual wavelength-range observations of the inner regions of the supernova remnant SNR 0540-69.3 that is located in the Large Magellanic Cloud (LMC). These observations provide us with more spatial and spectral information than were previously available for this object. We use these data to create a detailed three-dimensional model of the remnant, assuming linear expansion of the ejecta. With the observations and the model we study the general three-dimensional structure of the remnant, and the influence of an active region in the remnant -a "blob" -that we address in previous papers. We used the fibrefed integral-field spectrograph VIMOS at the Very Large Telescope of the European Southern Observatory. The observations provide us with three-dimensional data in [O iii] λ5007 and [S ii] λλ6717, 6731 at an 0. ′′ 33×0. ′′ 33 spatial sampling and a velocity resolution of about 35 km s −1 . We decomposed the two, partially overlapping, sulphur lines and used them to calculate electron densities across the remnant at high signal-to-noise ratio. In our study we recover results of previous studies, but we are more importantly able to obtain more detailed information than before. Our analysis reveals a structure that stretches from the position of the "blob", and into the plane of the sky at a position angle of PA ≃ 60 • . Assuming a remnant age of 1000 years and the usual LMC distance, the structure has an inclination angle of about 65 • to the line of sight. The position angle is close to the symmetry axis with present and past activity in the visual and the X-ray wavelength ranges. We speculate that the pulsar is positioned along this activity axis, where it has a velocity along the line of sight of a few hundred km s −1 . The "blob" is most likely a region of shock activity, as it is mainly bright in [S ii]; future observations of [O ii] λλ3726, 3729 would be useful to test whether the S/O abundance ratio is higher than average for that location in the remnant. The striking resemblance in Xrays between the pulsar wind nebula (PWN) of SNR 0540-69.3 and the Crab, in combination with our findings in this paper, suggests that the symmetry axis is part of a torus in the PWN. This is in agreement with the original suggestion by Gotthelf & Wang.

Clumps and rings of ejecta in SNR 0540-69.3 as seen in 3D

“…In addition to the small-scale asymmetries in the form of rings and clumps, the inner ejecta of SNR 0540 show a global asymmetry in the sense that the redshifted ejecta have higher fluxes and higher velocities than the blueshifted side. This has been noted in previous observations (Kirshner et al 1989;Serafimovich et al 2005;Morse et al 2006;Sandin et al 2013) and is likely caused by asymmetries in the explosion and/or the energy input from the pulsar. Net motion of the progenitor relative to the local ISM may also play a role in explaining this asymmetry, as originally discussed by Kirshner et al (1989).…”

“…For the [S II] emission, we take the ratio I([S II] λ6731)/I([S II] λ6716) = 1.0, which is close to the average number of Serafimovich et al (2005) and Sandin et al (2013). We will investigate possible spatial variations of this line ratio in future work.…”

“…The [O III] λ5007 and [S II] λλ6717, 6731 emission from the inner region have previously been studied in 3D using VLT/VIMOS observations, which revealed ringlike structures (Sandin et al 2013). Here we present new information about the 3D structure of the ejecta using observations from VLT/MUSE and X-shooter.…”

CSI in Supernova Remnants

“…The structure of Sk−69 202's CSM is almost identical to the CSM of Sher 25, a Galactic B1.5 I supergiant (Brandner, Chu, Eisenhauer, et al 1997). Interestingly, the second youngest CCSNR in the LMC, 0540−69.3, also shows a [N II] ring around the SN that corresponds to a CSM similar to that around Sk−69 202 or Sher 25 (Caraveo, Mignani, & Bignami 1998;Sandin, Lundqvist, Lundqvist, et al 2013).…”

Core-Collapse Supernova Remnants and Interactions with Their Surroundings

“…The elongation was initially thought (Gotthelf & Wang 2000) to be a jet, but high-resolution optical imaging (Morse et al 2006) showed a diffuse "breakout" instead of a collimated jet in this region. More recent analysis (Sandin et al 2013) has suggested that this elongation may actually be a torus around the pulsar, similar to the X-ray torus around the Crab (Figure 1.5), with a jet pointing to the southwest.…”