A Black Hole X-ray Binary at $sim$100 Hz: Multiwavelength Timing of MAXI J1820+070 with HiPERCAM and NICER. (arXiv:1910.04174v1 [astro-ph.HE])

A Black Hole X-ray Binary at $sim$100 Hz: Multiwavelength Timing of MAXI J1820+070 with HiPERCAM and NICER. (arXiv:1910.04174v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Paice_J/0/1/0/all/0/1">J. A. Paice</a> (Uni. Southampton, IUCAA), <a href="http://arxiv.org/find/astro-ph/1/au:+Gandhi_P/0/1/0/all/0/1">P. Gandhi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shahbaz_T/0/1/0/all/0/1">T. Shahbaz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Uttley_P/0/1/0/all/0/1">P. Uttley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Arzoumanian_Z/0/1/0/all/0/1">Z. Arzoumanian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Charles_P/0/1/0/all/0/1">P. A. Charles</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dhillon_V/0/1/0/all/0/1">V. S. Dhillon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gendreau_K/0/1/0/all/0/1">K. C. Gendreau</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Littlefair_S/0/1/0/all/0/1">S. P. Littlefair</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Malzac_J/0/1/0/all/0/1">J. Malzac</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Markoff_S/0/1/0/all/0/1">S. Markoff</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marsh_T/0/1/0/all/0/1">T. R. Marsh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Misra_R/0/1/0/all/0/1">R. Misra</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Russell_D/0/1/0/all/0/1">D. M. Russell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Veledina_A/0/1/0/all/0/1">A. Veledina</a>

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 ($ugriz_s$)
with HiPERCAM/GTC (Optical) at frame rates over 100 Hz, together with NICER/ISS
observations (X-rays). Intense (factor of two) red flaring activity in the
optical is seen over a broad range of timescales down to $sim$10 ms.
Cross-correlating the bands reveals a prominent anti-correlation on timescales
of $sim$seconds, and a narrow sub-second correlation at a lag of $approx$+165
ms (optical lagging X-rays). This lag increases with optical wavelength, and is
approximately constant over Fourier frequencies of $sim$0.3-10 Hz. These
features are consistent with an origin in the inner accretion flow and jet base
within $sim$5000 Gravitational radii. An additional $sim$+5 s lag feature may
be ascribable to disc reprocessing. MAXI J1820+070 is the third black hole
transient to display a clear $sim$0.1s 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.

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 ($ugriz_s$)
with HiPERCAM/GTC (Optical) at frame rates over 100 Hz, together with NICER/ISS
observations (X-rays). Intense (factor of two) red flaring activity in the
optical is seen over a broad range of timescales down to $sim$10 ms.
Cross-correlating the bands reveals a prominent anti-correlation on timescales
of $sim$seconds, and a narrow sub-second correlation at a lag of $approx$+165
ms (optical lagging X-rays). This lag increases with optical wavelength, and is
approximately constant over Fourier frequencies of $sim$0.3-10 Hz. These
features are consistent with an origin in the inner accretion flow and jet base
within $sim$5000 Gravitational radii. An additional $sim$+5 s lag feature may
be ascribable to disc reprocessing. MAXI J1820+070 is the third black hole
transient to display a clear $sim$0.1s 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.

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