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

Kajava, J. J. E.Univ Turku, Finnish Ctr Astron ESO FINCH, FI-20014 Turku, Finland. (author)

20190924
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.

Motta, S. E.Univ Oxford, Dept Phys, Astrophys, Denys Wilkinson Bldg,Keble Rd, Oxford OX1 3RH, England. (author)
Sanna, A.Univ Cagliari, Dipartimento Fis, SP Monserrato Sestu Km 0-7, I-09042 Monserrato, Italy. (author)
Veledina, AlexandraStockholms universitet,KTH,Nordic Institute for Theoretical Physics NORDITA,Univ Turku, Dept Phys & Astron, FI-20014 Turku, Finland.;Stockholm Univ, Roslagstultsbacken 23, SE-10691 Stockholm, Sweden.;Russian Acad Sci, Space Res Inst, Profsoyuznaya Str 84-32, Moscow 117997, Russia.,Nordiska institutet för teoretisk fysik (Nordita),University of Turku, Finland; Space Research Institute of the Russian Academy of Sciences, Russia(Swepub:su)avele (author)
Del Santo, M.IASF Palermo, Ist Nazl Astrofis, Via U La Malfa 153, I-90146 Palermo, Italy. (author)
Segreto, A.IASF Palermo, Ist Nazl Astrofis, Via U La Malfa 153, I-90146 Palermo, Italy. (author)
Univ Turku, Finnish Ctr Astron ESO FINCH, FI-20014 Turku, Finland.Univ Oxford, Dept Phys, Astrophys, Denys Wilkinson Bldg,Keble Rd, Oxford OX1 3RH, England. (creator_code:org_t)

In:Monthly notices of the Royal Astronomical Society: OXFORD UNIV PRESS488:1, s. L18-L230035-87111365-29661745-39251745-3933

By the author/editor: Kajava, J. J. E.; Motta, S. E.; Sanna, A.; Veledina, Alexan ...; Del Santo, M.; Segreto, A.

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NATURAL SCIENCES: NATURAL SCIENCES; and Physical Science ...; and Astronomy Astrop ...

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