期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 471, 期 1, 页码 373-382出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stx1555
关键词
accretion, accretion disc; black hole physics; binaries: general; stars: individual: V404 Cygni; X-rays: binaries
资金
- Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan [25120007]
- RFBR grant [15-02-06178]
- United States National Science Foundation under Grant Division of Mathematical Sciences [1127914]
- Grants-in-Aid for Scientific Research [17J10039, 16K17672, 17J08772] Funding Source: KAKEN
- Division Of Mathematical Sciences
- Direct For Mathematical & Physical Scien [1127914] Funding Source: National Science Foundation
We present optical multicolour photometry of V404 Cyg during the outburst from 2015 December to 2016 January together with the simultaneous X-ray data. This outburst occurred less than sixmonths after the previous outburst in 2015 June-July. These two outbursts in 2015 were of a slow-rise and rapid-decay type and showed large-amplitude (similar to 2mag) and short-term (similar to 10 min-3 h) optical variations even at low luminosity (0.01-0.1L(Edd)). We found correlated optical and X-ray variations in two similar to 1 h time intervals and obtained a Bayesian estimate of an X-ray delay against the optical emission, which is similar to 30-50 s, during those two intervals. In addition, the relationship between the optical and X-ray luminosities was L-opt alpha L-X(0.25-0.29) at that time. These features cannot be easily explained by the conventional picture of transient black hole binaries, such as canonical disc reprocessing and synchrotron emission related to a jet. We suggest that the disc was truncated during those intervals and that the X-ray delays represent the required time for the propagation of mass accretion flow to the inner optically thin region with a speed comparable to the free-fall velocity.
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