Examinando por Autor "Williams, D. R. A."

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Observations of a radio-bright, X-ray obscured GRS 1915+105
(Oxford Academics: Oxford University Press, 2021-02-24) Motta, Sara E.; Kajava, J. J. E.; Giustini, M.; Williams, D. R. A.; Del Santo, M.; Fender, R.; Green, D. A.; Heywood, I.; Rhodes, L.; Segreto, A.; Sivakoff, G.; Woudt, P. A.; Science and Technology Facilities Council (STFC); Agencia Estatal de Investigación (AEI); Comunidad de Madrid; Istituto Nazionale di Astrofisica (INAF); European Commission (EC); Motta, S. E. [0000-0002-6154-5843]; Kajava, J. J. E. [0000-0002-3010-8333]; Williams, D. R. A. [0000-0001-7361-0246]; Del Santo, M. [0000-0002-1793-1050]; Green, D. A. [0000-0003-3189-9998]; Woudt, P. A. [0000-0002-6896-1655]
The Galactic black hole transient GRS 1915+105 is famous for its markedly variable X-ray and radio behaviour, and for being the archetypal galactic source of relativistic jets. It entered an X-ray outburst in 1992 and has been active ever since. Since 2018 GRS 1915+105 has declined into an extended low-flux X-ray plateau, occasionally interrupted by multiwavelength flares. Here, we report the radio and X-ray properties of GRS 1915+105 collected in this new phase, and compare the recent data to historic observations. We find that while the X-ray emission remained unprecedentedly low for most of the time following the decline in 2018, the radio emission shows a clear mode change half way through the extended X-ray plateau in 2019 June: from low flux (∼3 mJy) and limited variability, to marked flaring with fluxes two orders of magnitude larger. GRS 1915+105 appears to have entered a low-luminosity canonical hard state, and then transitioned to an unusual accretion phase, characterized by heavy X-ray absorption/obscuration. Hence, we argue that a local absorber hides from the observer the accretion processes feeding the variable jet responsible for the radio flaring. The radio–X-ray correlation suggests that the current low X-ray flux state may be a signature of a super-Eddington state akin to the X-ray binaries SS433 or V404 Cyg.