Breakthrough Listen

Abstract:

We present radio [1.3 GHz MeerKAT, 4–8 GHz Karl G. Jansky Very Large Array (VLA), and 15.5 GHz Arcminute Microkelvin Imager Large Array (AMI-LA)] and X-ray (Swift and MAXI) data from the 2019 outburst of the candidate Black Hole X-ray Binary (BHXB) EXO 1846−031. We compute a Hardness–Intensity diagram, which shows the characteristic q-shaped hysteresis of BHXBs in outburst. EXO 1846−031 was monitored weekly with MeerKAT and approximately daily with AMI-LA. The VLA observations provide sub-arcsecond-resolution images at key points in the outburst, showing moving radio components. The radio and X-ray light curves broadly follow each other, showing a peak on ∼MJD 58702, followed by a short decline before a second peak between ∼MJD 58731–58739. We estimate the minimum energy of these radio flares from equipartition, calculating values of Emin ∼ 4 × 1041 and 5 × 1042 erg, respectively. The exact date of the return to ‘quiescence’ is missed in the X-ray and radio observations, but we suggest that it likely occurred between MJD 58887 and 58905. From the Swift X-ray flux on MJD 58905 and assuming the soft-to-hard transition happened at 0.3–3 per cent Eddington, we calculate a distance range of 2.4–7.5 kpc. We computed the radio:X-ray plane for EXO 1846−031 in the ‘hard’ state, showing that it is most likely a ‘radio-quiet’ BH, preferentially at 4.5 kpc. Using this distance and a jet inclination angle of θ = 73◦, the VLA data place limits on the intrinsic jet speed of βint = 0.29c, indicating subluminal jet motion.

Abstract:

Abstract Swarm is the first European Space Agency (ESA) constellation mission for Earth Observation. Three identical Swarm satellites were launched into near-polar orbits on 22 November 2013. Each satellite hosts a range of instruments, including a Langmuir probe, GPS receivers, and magnetometers, from which the ionospheric plasma can be sampled and current systems inferred. In March 2018, the CASSIOPE/e-POP mission was formally integrated into the Swarm mission through ESA’s Earthnet Third Party Mission Programme. Collectively the instruments on the Swarm satellites enable detailed studies of ionospheric plasma, together with the variability of this plasma in space and in time. This allows the driving processes to be determined and understood. The purpose of this paper is to review ionospheric results from the first seven years of the Swarm mission and to discuss scientific challenges for future work in this field.