Swift UVOT observations of the 2015 outburst of V404 Cygni
Swift UVOT observations of the 2015 outburst of V404 Cygni
The black-hole binary, V404 Cyg, went into outburst in June 2015, after 26 years of X-ray quiescence. We observed the outburst with the Neil Gehrels Swift observatory. We present the optical/UV observations taken with the Swift Ultra-Violet Optical Telescope, and compare them with the X-ray observations obtained with the Swift X-ray telescope. We find that dust extinction, affecting the optical/UV, does not correlate with absorption due to neutral hydrogen, which affects the X-ray emission. We suggest that there is a small inhomogeneous high density absorber, containing a negligible amount of dust, close to the black hole. Overall, temporal variations in the optical/UV emission trace those in the X-ray band, with a time-lag of (0 - 30)s, with the optical/UV generally lagging the X-rays. The amplitude of the variations is correlated with flux in both bands, but less significantly in the optical/UV. The variability in the light curves may be produced by a complex combination of processes. Some of the variability observed only in the X-ray may be due to the presence of a local, inhomogeneous and dust-free absorber. While variability visible in both the X-ray and optical/UV bands may instead be driven by the accretion flow: the X-rays are produced in the inner accretion disc, some of which are reprocessed to the optical/UV; and/or the X-ray and optical/UV emission is produced within the jet.
astro-ph.HE
4843-4857
Oates, S. R.
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Motta, S.
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Beardmore, A. P.
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Gandhi, P.
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Kuin, N. P. M.
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Pasquale, M. De
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Altamirano, D.
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Breeveld, A. A.
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Castro-Tirado, A. J.
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Knigge, C.
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Steeghs, Danny
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October 2019
Oates, S. R.
ad6dac21-5a31-4119-a643-849046998b86
Motta, S.
461dbdce-0b15-4702-8baf-85b26197ae36
Beardmore, A. P.
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Gandhi, P.
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Kuin, N. P. M.
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Pasquale, M. De
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Altamirano, D.
d5ccdb09-0b71-4303-9538-05b467be075b
Breeveld, A. A.
b8bbf6f0-4a64-43e6-a6d7-128e5d77f127
Castro-Tirado, A. J.
e86b7d0a-8fd6-41cd-a261-4999ba488179
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Steeghs, Danny
f631b06c-3e33-4daa-8959-c41f188e9c38
Oates, S. R., Motta, S., Beardmore, A. P., Gandhi, P., Kuin, N. P. M., Pasquale, M. De, Altamirano, D., Breeveld, A. A., Castro-Tirado, A. J., Knigge, C. and Steeghs, Danny
(2019)
Swift UVOT observations of the 2015 outburst of V404 Cygni.
Monthly Notices of the Royal Astronomical Society, 488 (4), .
(doi:10.1093/mnras/stz1998).
Abstract
The black-hole binary, V404 Cyg, went into outburst in June 2015, after 26 years of X-ray quiescence. We observed the outburst with the Neil Gehrels Swift observatory. We present the optical/UV observations taken with the Swift Ultra-Violet Optical Telescope, and compare them with the X-ray observations obtained with the Swift X-ray telescope. We find that dust extinction, affecting the optical/UV, does not correlate with absorption due to neutral hydrogen, which affects the X-ray emission. We suggest that there is a small inhomogeneous high density absorber, containing a negligible amount of dust, close to the black hole. Overall, temporal variations in the optical/UV emission trace those in the X-ray band, with a time-lag of (0 - 30)s, with the optical/UV generally lagging the X-rays. The amplitude of the variations is correlated with flux in both bands, but less significantly in the optical/UV. The variability in the light curves may be produced by a complex combination of processes. Some of the variability observed only in the X-ray may be due to the presence of a local, inhomogeneous and dust-free absorber. While variability visible in both the X-ray and optical/UV bands may instead be driven by the accretion flow: the X-rays are produced in the inner accretion disc, some of which are reprocessed to the optical/UV; and/or the X-ray and optical/UV emission is produced within the jet.
Text
stz1998
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Submitted date: 10 September 2018
Accepted/In Press date: 16 July 2019
e-pub ahead of print date: 25 July 2019
Published date: October 2019
Keywords:
astro-ph.HE
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Local EPrints ID: 423531
URI: http://eprints.soton.ac.uk/id/eprint/423531
ISSN: 1365-2966
PURE UUID: c938ca09-1920-4ecb-920b-e829569011a6
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Date deposited: 25 Sep 2018 16:30
Last modified: 16 Mar 2024 04:20
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Contributors
Author:
S. R. Oates
Author:
S. Motta
Author:
A. P. Beardmore
Author:
N. P. M. Kuin
Author:
M. De Pasquale
Author:
A. A. Breeveld
Author:
A. J. Castro-Tirado
Author:
Danny Steeghs
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