A1 Journal article – refereed

X-ray dips and a complex UV/X-ray cross-correlation function in the black hole candidate MAXI J1820+070




List of Authors: Kajava J.J.E., Motta S.E., Sanna A., Veledina A., Del Santo M., Segreto A.

Publisher: OXFORD UNIV PRESS

Publication year: 2019

Journal: Monthly Notices of the Royal Astronomical Society: Letters

Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Journal acronym: MON NOT R ASTRON SOC

Volume number: 488

Issue number: 1

Number of pages: 6

ISSN: 0035-8711

DOI: http://dx.doi.org/10.1093/mnrasl/slz089


Abstract
MAXI J1820+070, a black hole candidate first detected in early 2018 March, was observed by XMM-Newton during the outburst rise. In this letter we report on the spectral and timing analysis of the XMM-Newton X-ray and UV data, as well as contemporaneous X-ray data from the Swift satellite. The X-ray spectrum is well described by a hard thermal Comptonization continuum. The XMM-Newton X-ray light curve shows a pronounced dipping interval, and spectral analysis indicates that it is caused by a moderately ionized partial covering absorber. The XMM-Newton/OM U-filter data do not reveal any signs of the 17 h orbital modulation that was seen later on during the outburst decay. The UV/X-ray cross-correlation function shows a complex shape, with a peak at positive lags of about 4 s and a precognition dip at negative lags, which is absent during the X-ray dipping episode. Such shape could arise if the UV emission comes partially from synchrotron self-Compton emission near the black hole, as well as from reprocessing of the X-rays in the colder accretion disc further out.

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Last updated on 2021-24-06 at 11:47