Gamma-ray astronomy

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Radio and X-ray detections of GX 339-4 in quiescence using MeerKAT and Swift

Monthly Notices of the Royal Astronomical Society: Letters Oxford University Press 493:1 (2020) L132-L137

Authors:

E Tremou, S Corbel, Rp Fender, Pa Woudt, Jca Miller-Jones, Sara Motta, I Heywood, Robert Armstrong, P Groot, A Horesh, Aj Van Der Horst, E Koerding, Kunal Mooley, A Rowlinson, Ramj Wijers

Abstract:

The radio-X-ray correlation that characterizes accreting black holes at all mass scales - from stellar mass black holes in binary systems to supermassive black holes powering active galactic nuclei - is one of the most important pieces of observational evidence supporting the existence of a connection between the accretion process and the generation of collimated outflows - or jets - in accreting systems. Although recent studies suggest that the correlation extends down to low luminosities, only a handful of stellar mass black holes have been clearly detected, and in general only upper limits (especially at radio wavelengths) can be obtained during quiescence. We recently obtained detections of the black hole X-ray binary (XRB) GX 339-4 in quiescence using the Meer Karoo Array Telescope (MeerKAT) radio telescope and Swift X-ray Telescope instrument on board the Neil Gehrels Swift Observatory, probing the lower end of the radio-X-ray correlation. We present the properties of accretion and of the connected generation of jets in the poorly studied low-accretion rate regime for this canonical black hole XRB system.

Radio & X-ray detections of GX 339--4 in quiescence using MeerKAT and Swift

(2020)

Authors:

E Tremou, S Corbel, RP Fender, PA Woudt, JCA Miller-Jones, SE Motta, I Heywood, RP Armstrong, P Groot, A Horesh, AJ van der Horst, E Koerding, KP Mooley, A Rowlinson, RAMJ Wijers

A spectroscopic, photometric, polarimetric and radio study of the eclipsing polar UZ Fornacis: the first simultaneous SALT and MeerKAT observations

(2020)

Authors:

Zwidofhelangani N Khangale, Stephen B Potter, Patrick A Woudt, David AH Buckley, Andrey N Semena, Enrico J Kotze, Danièl N Groenewald, Dante M Hewitt, Margaretha L Pretorius, Rob P Fender, Paul Groot, Steven Bloemen, Marc Klein-Wolt, Elmar Körding, Rudolf Le Poole, Vanessa A McBride, Lee Townsend, Kerry Paterson, Danielle LA Pieterse, Paul M Vreeswijk

FPGA architecture to search for accelerated pulsars with SKA

Institute of Electrical and Electronics Engineers (IEEE) 00 (2020) 1-5

Authors:

P Thiagaraj, B Stappers, A Ghalame, L Levin, A Karastergiou, J Roy, M Mickaliger, M Keith

MKT J170456.2-482100: the first transient discovered by MeerKAT

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 491:1 (2020) 560-575

Authors:

Ln Driessen, I McDonald, Dah Buckley, M Caleb, Ej Kotze, Sb Potter, Km Rajwade, A Rowlinson, Bw Stappers, E Tremou, Pa Woudt, Rp Fender, R Armstrong, P Groot, I Heywood, A Horesh, Aj van der Horst, E Koerding, Va McBride, Jca Miller-Jones, Kp Mooley, Ramj Wijers

Abstract:

© 2019 The Author(s) We report the discovery of the first transient with MeerKAT, MKT J170456.2−482100, discovered in ThunderKAT images of the low-mass X-ray binary GX339−4. MKT J170456.2−482100 is variable in the radio, reaching a maximum flux density of 0.71 ± 0.11 mJy on 2019 October 12, and is undetected in 15 out of 48 ThunderKAT epochs. MKT J170456.2−482100 is coincident with the chromospherically active K-type sub-giant TYC 8332-2529-1, and ∼ 18 yr of archival optical photometry of the star shows that it varies with a period of 21.25 ± 0.04 d. The shape and phase of the optical light curve changes over time, and we detect both X-ray and UV emission at the position of MKT J170456.2−482100, which may indicate that TYC 8332-2529-1 has large star spots. Spectroscopic analysis shows that TYC 8332-2529-1 is in a binary, and has a line-of-sight radial velocity amplitude of 43 km s−1. We also observe a spectral feature in antiphase with the K-type sub-giant, with a line-of-sight radial velocity amplitude of ∼ 12 ± 10 km s−1, whose origins cannot currently be explained. Further observations and investigation are required to determine the nature of the MKT J170456.2−482100 system.