Cenotaph Maleficarum

A large supernova remnant around an X-ray binary in the Bacterian Home Galaxy.

RX J050736-6847.8 in the Bacterian Home Galaxy (BHG) is an intriguing X-ray source consisting of a large ring (diameter ~150 parsecs) of diffuse emission and a central compact source. It is projected in the vicinity of the superbubble N103 around the star cluster NGC 1850.

RX J050736-6847.8's ring of diffuse X-ray emission, offset from the superbubble N103, is not bounded by any optical shell structure, while RX J050736-6847.8's central compact X-ray source is projected within the cluster HS122.

The X-ray luminosity of the diffuse X-ray emission is 5-6x10³⁵ ergs.^s-1 in the 0.1-2.4 keV band, within the range for supernova remnants (SNRs). Assuming a shell geometry with a fractional shell thickness (ΔR/R) of 0.05-0.2, the density of the hot gas is 0.05-0.09 cm^-3. The physical properties of this shell of hot gas are consistent for a ~5x10⁴ year old SNR in a low-density (~0.015 cm^-3) medium formed by a supernova of an explosion energy of 3x10⁵¹ ergs. The density is so low that no detectable optical emission is expected. Therefore, this ring of X-ray emission originates in a SNR, the largest known in the BHG.

The large size, low density, and the regular X-ray morphology suggest that this SNR is located in the near size of the halo of the BHG. The central compact source of RX J050736-6847.8 is probably an X-ray binary in the cluster HS122. The relationship between the compact source and the diffuse ring is unknown.