期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 488, 期 1, 页码 1356-1365出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stz1793
关键词
accretion, accretion discs; stars: black holes; stars: individual: V404 Cyg; stars: winds, outflows; X-rays: binaries
资金
- Leverhulme Trust through the Visiting Professorship Grant [VP2-2015-046]
- Spanish Ministry of Economy, Industry, and Competitiveness (MINECO) [AYA2017-83216-P]
- Ramon y Cajal programme [RYC-2015-18148, RYC-2015-17854]
- Advanced Fellowship from the Severo Ochoa excellence programme [SEV-2015-0548]
- State Research Agency (AEI) of the Spanish Ministry of Science, Innovation and Universities (MCIU)
- European Regional Development Fund (FEDER) [AYA2017-83383-P]
- Leverhulme Trust through an Emeritus Fellowship
- ERC under the European Union's Horizon 2020 research and innovation programme [715051]
We study the optical evolution of the 2015 outburst in V404 Cyg, with emphasis on the peculiar nebular phase and subsequent decay to quiescence. From the decay time-scale of the Balmer emission associated with the nebula, we measure an outflow mass M-wind similar or equal to 4 x 10(-6) M-circle dot. Remarkably, this is similar to 100 times larger than the accreted mass and similar to 10 per cent of the total mass stored in the disc. The wind efficiency must therefore be significantly larger than previous estimates for black hole transients, suggesting that radiation pressure (in addition to other mechanisms such as Compton-heating) plays a key role in V404 Cyg. In addition, we compare the evolution of the 2015 and 1989 outbursts and find not only clear similarities (namely a large luminosity drop similar to 10 d after the X-ray trigger, followed by a brief nebular phase) but also remarkable differences in decay time-scales and long-term evolution of the H alpha profile. In particular, we see evidence for a rapid disc contraction in 2015, consistent with a burst of mass transfer. This could be driven by the response of the companion to hard X-ray illumination, most notably during the last gigantic (super-Eddington) flare on 2015 June 25. We argue that irradiation and consequential disc wind are key factors to understand the different outburst histories in 1989 and 2015. In the latter case, radiation pressure may be responsible for the abrupt end of the outburst through depleting inner parts of the disc, thus quenching accretion and X-ray irradiation. We also present a refined orbital period and updated ephemeris.
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