M87* plasma and an X-ray binary reveal new structure across wavelengths
The first spatially resolved spectral-index map of M87* points to optically thick plasma inside the 1.3-millimetre ring and thin plasma outside it. In the first X-ray polarimetry observation of 4U 1822-37, hard-band polarisation exceeded twice the soft-band level. NASA's new 34-metre dish at Goldstone began work by tracking Chandra, expanding the ground network used to maintain links with distant missions.
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The M87* map separates the two sides of the ring
Researchers brought 2018 images of M87* at 3.5 and 1.3 millimetres to a common 30-microarcsecond beam and divided them pixel by pixel. In the first spatially resolved spectral-index map, the index stays near plus 1 inside the 1.3-millimetre ring and crosses zero at roughly 30 microarcseconds, where the 3.5-millimetre ring lies. The pattern points to optically thick plasma inside and thin plasma outside. The observations at the two frequencies were close in date but not simultaneous; typical index uncertainty is about 0.2 and rises to about 0.5 at the map's edge.[1]
The hard band of 4U 1822-37 is more strongly polarised
The first Imaging X-ray Polarimetry Explorer observation of 4U 1822-37 covered 44 orbital cycles with simultaneous Swift-XRT data. Polarisation averaged 5.6 per cent from 2 to 5 kiloelectronvolts and 11.6 per cent from 5 to 8, a difference above 3 sigma. During eclipse by the companion star, soft-band polarisation fell to a level consistent with zero while the hard band rose to 21.3 per cent. The authors interpret the split as soft and hard photons leaving regions of different extent, with the high polarisation linked to scattering.[2]
Goldstone's new dish began work with Chandra
Deep Space Station 23, a 34-metre dish at Goldstone, began operations on 3 August by tracking the Chandra X-ray Observatory. It is Goldstone's fifth antenna and the fifth of six dishes in an enhancement programme that will bring the network to 13 antennas of that size across California, Spain and Australia. Its beam-waveguide design routes signals underground to equipment rooms, allowing one dish to serve missions on several radio bands and simplifying maintenance compared with older antennas. The new unit expands the ground infrastructure that keeps data-producing space instruments connected.[3]
