Archive abstract

Abstract of the proposal for the experiment EM148

VLBI imaging has confirmed the unusual double-lobed structure of 41.95+57.5, unlike the more typical shell-like M82 SNR.The lobe separation historically was increasing at a rate of 0.24mas/yr, yielding an upper limit to the age of ~100 years. 41.95+575 has decreased in flux density at ~8.8%/yr since L-Band monitoring began in the early 1970s, indicating a birth 1.4GHz flux density of ~170Jy , with a luminosity approaching that of radio after-glows of long-duration gamma-ray bursts, suggesting that 41.95+57.5 may be a late stage GRB radio afterglow.

Global VLBI confirms the double-lobed structure continues to fade, however the evolving structure now appears more ring-like within the previous lobe-structure, and L-Band monitoring from 1993 onwards shows flux decreasing ~6.4% / yr. In addition, e-MERLIN imaging in 2014 shows the 1.5-6.2GHz spectral index has flattened to ~-0.5 from -0.8, suggesting an emerging flatter spectrum central nebula is beginning to appear, consistent with some form of flat spectrum Pulsar Wind Nebula.

We propose Western EVN+e-MERLIN continuum 6cm imaging to detect this putative central nebula
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