A black hole X-ray binary at ~100 Hz: multiwavelength timing of MAXIJ1820+070 with HiPERCAM and NICER

: J A Paice, P Gandhi, T Shahbaz, P Uttley, Z Arzoumanian, P A Charles, V S Dhillon, K C Gendreau, S P Littlefair, J Malzac, S Markoff, T R Marsh, R Misra, D M Russell, A Veledina

Publisher: OXFORD UNIV PRESS

: 2019

: Monthly Notices of the Royal Astronomical Society: Letters

: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

: MON NOT R ASTRON SOC

: 490

: 1

: L62

: L66

: 5

: 0035-8711

: 1745-3933

DOI: https://doi.org/10.1093/mnrasl/slz148(external)

: https://research.utu.fi/converis/portal/detail/Publication/46524942(external)

We report on simultaneous sub-second optical and X-ray timing observations of the low-mass X-ray binary black hole candidate MAXI J1820+070. The bright 2018 outburst rise allowed simultaneous photometry in five optical bands (ugrizs) with HiPERCAM/GTC (Optical) at frame rates over 100 Hz, together with NICER/ISS observations (X-rays). Intense (factor of 2) red flaring activity in the optical is seen over a broad range of time-scales down to similar to 10 ms. Cross-correlating the bands reveals a prominent anticorrelation on time-scales of similar to seconds, and a narrow sub-second correlation at a lag of approximate to+165 ms (optical lagging X-rays). This lag increases with optical wavelength, and is approximately constant over Fourier frequencies of similar to 0.3-10 Hz. These features are consistent with an origin in the inner accretion flow and jet base within similar to 5000 Gravitational radii. An additional similar to+5 s lag feature may be ascribable to disc reprocessing. MAXI J1820+070 is the third black hole transient to display a clear similar to 0.1 s optical lag, which may be common feature in such objects. The sub-second lag variation with wavelength is novel, and may allow constraints on internal shock jet stratification models.

slz148.pdf