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Furiously fast and red : sub-second optical flaring in V404 Cyg during the 2015 outburst peak
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Marsh, Tom (2016) Furiously fast and red : sub-second optical flaring in V404 Cyg during the 2015 outburst peak. Monthly Notices of the Royal Astronomical Society, 459 (1). pp. 554-572. doi:10.1093/mnras/stw571 ISSN 0035-8711.
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Official URL: http://dx.doi.org/10.1093/mnras/stw571
Abstract
We present observations of rapid (sub-second) optical flux variability in V404 Cyg during its 2015 June outburst. Simultaneous three-band observations with the ULTRACAM fast imager on four nights show steep power spectra dominated by slow variations on ˜100-1000 s time-scales. Near the peak of the outburst on June 26, a dramatic change occurs and additional, persistent sub-second optical flaring appears close in time to giant radio and X-ray flaring. The flares reach peak optical luminosities of ˜ few × 1036 erg s-1. Some are unresolved down to a time resolution of 24 ms. Whereas the fast flares are stronger in the red, the slow variations are bluer when brighter. The redder slopes, emitted power and characteristic time-scales of the fast flares can be explained as optically thin synchrotron emission from a compact jet arising on size scales ˜140-500 Gravitational radii (with a possible additional contribution by a thermal particle distribution). The origin of the slower variations is unclear. The optical continuum spectral slopes are strongly affected by dereddening uncertainties and contamination by strong Hα emission, but the variations of these slopes follow relatively stable loci as a function of flux. Cross-correlating the slow variations between the different bands shows asymmetries on all nights consistent with a small red skew (i.e. red lag). X-ray reprocessing and non-thermal emission could both contribute to these. These data reveal a complex mix of components over five decades in time-scale during the outburst.
Item Type: | Journal Article | ||||||||||
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Subjects: | Q Science > QB Astronomy | ||||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||||
Library of Congress Subject Headings (LCSH): | Accretion (Astrophysics), Black holes (Astronomy), Double stars | ||||||||||
Journal or Publication Title: | Monthly Notices of the Royal Astronomical Society | ||||||||||
Publisher: | Oxford University Press | ||||||||||
ISSN: | 0035-8711 | ||||||||||
Official Date: | 11 June 2016 | ||||||||||
Dates: |
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Volume: | 459 | ||||||||||
Number: | 1 | ||||||||||
Page Range: | pp. 554-572 | ||||||||||
DOI: | 10.1093/mnras/stw571 | ||||||||||
Status: | Peer Reviewed | ||||||||||
Publication Status: | Published | ||||||||||
Access rights to Published version: | Open Access (Creative Commons) | ||||||||||
Date of first compliant deposit: | 24 October 2016 | ||||||||||
Date of first compliant Open Access: | 24 October 2016 | ||||||||||
Funder: | Science and Technology Facilities Council (Great Britain) (STFC), UK-India Education Research Initiative (UKIERI), Royal Society (Great Britain), Spain. Ministerio de Economía y Competitividad [Ministry of Economy and Competitiveness] (MINECO), Consejo Nacional de Ciencia y Tecnología (Mexico) [Mexican Council for Science and Technology] (CONACYT), University of Southampton. School of Physics and Astronomy, Spain. Ministerio de Educación, Cultura y Deporte, Seventh Framework Programme (European Commission) (FP7) | ||||||||||
Grant number: | ST/J003697/1, PP/D002370/1, ST/L000733/1 (SFTC), UGC 2014-15/02 (UKIERI), AYA2013-42627 (MINECO), PR2015-00397 (Ministerio de Educación), 2012-322259 (FP7) |
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