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Flares, wind and nebulae: the 2015 December mini-outburst of V404 Cygni

Muñoz-Darias, T.; Casares, J.; Mata Sánchez, D.; Fender, R.P.; Armas Padilla, M.; Mooley, K.; Hardy, L.; Charles, P.A.; Ponti, G.; Motta, S.E.; Dhillon, V.S.; Gandhi, P.; Jiménez-Ibarra, F.; Butterley, T.; Carey, S.; Grainge, K.J.B.; Hickish, J.; Littlefair, S.P.; Perrott, Y.C.; Razavi-Ghods, N.; Rumsey, C.; Scaife, A.M.M.; Scott, P.F.; Titterington, D.J.; Wilson, R.W.

Flares, wind and nebulae: the 2015 December mini-outburst of V404 Cygni Thumbnail


T. Muñoz-Darias

J. Casares

D. Mata Sánchez

R.P. Fender

M. Armas Padilla

K. Mooley

L. Hardy

P.A. Charles

G. Ponti

S.E. Motta

V.S. Dhillon

P. Gandhi

F. Jiménez-Ibarra

S. Carey

K.J.B. Grainge

J. Hickish

S.P. Littlefair

Y.C. Perrott

N. Razavi-Ghods

C. Rumsey

A.M.M. Scaife

P.F. Scott

D.J. Titterington

R.W. Wilson


After more than 26 years in quiescence, the black hole transient V404 Cyg went into a luminous outburst in 2015 June, and additional activity was detected in late December of the same year. Here, we present an optical spectroscopic follow-up of the December mini-outburst, together with X-ray, optical and radio monitoring that spanned more than a month. Strong flares with gradually increasing intensity are detected in the three spectral ranges during the ∼10 d following the Swift trigger. Our optical spectra reveal the presence of a fast outflowing wind, as implied by the detection of a P-Cyg profile (He I–5876 Å) with a terminal velocity of ∼2500 km s−1 . Nebular-like spectra – with an Hα equivalent width of ∼500 Å – are also observed. All these features are similar to those seen during the main 2015 June outburst. Thus, the fast optical wind simultaneous with the radio jet is most likely present in every V404 Cyg outburst. Finally, we report on the detection of a strong radio flare in late 2016 January, when X-ray and optical monitoring had stopped due to Sun constraints.


Muñoz-Darias, T., Casares, J., Mata Sánchez, D., Fender, R., Armas Padilla, M., Mooley, K., …Wilson, R. (2017). Flares, wind and nebulae: the 2015 December mini-outburst of V404 Cygni. Monthly Notices of the Royal Astronomical Society: Letters, 465(1), L124-L128.

Journal Article Type Article
Acceptance Date Oct 21, 2016
Online Publication Date Oct 27, 2016
Publication Date Feb 11, 2017
Deposit Date Jul 6, 2017
Publicly Available Date Jul 6, 2017
Journal Monthly Notices of the Royal Astronomical Society: Letters
Electronic ISSN 1745-3933
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 465
Issue 1
Pages L124-L128


Published Journal Article (653 Kb)

Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society letters. ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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