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Optical/X-ray correlations during the V404 Cygni June 2015 outburst

Optical/X-ray correlations during the V404 Cygni June 2015 outburst
Optical/X-ray correlations during the V404 Cygni June 2015 outburst

Context. We present a multiwavelength analysis of the simultaneous optical and X-ray light curves of the microquasar V404 Cyg during the June 2015 outburst. Aims. We have performed a comprehensive analysis of all the INTEGRAL/IBIS, JEM-X, and OMC observations during the brightest epoch of the outburst, along with complementary NuSTAR, AAVSO, and VSNET data, to examine the timing relationship between the simultaneous optical and X-ray light curves, in order to understand the emission mechanisms and physical locations. Methods. We have identified all optical flares that have simultaneous X-ray observations, and performed a cross-correlation analysis to estimate the time delays between the optical and soft and hard X-ray emission. We also compared the evolution of the optical and X-ray emission with the hardness ratios. Results. We have identified several types of behaviour during the outburst. On many occasions, the optical flares occur simultaneously with X-ray flares, but at other times, positive and negative time delays between the optical and X-ray emission are measured. Conclusions. We conclude that the observed optical variability is driven by different physical mechanisms, including reprocessing of X-rays in the accretion disc and/or the companion star, interaction of the jet ejections with surrounding material or with previously ejected blobs, and synchrotron emission from the jet.

Accretion, accretion disks, Stars: black holes, X-rays: binaries
0004-6361
Alfonso-Garzón, J.
7995e2d4-7675-4825-9516-b88d5d0bb2ce
Sánchez-Fernández, C.
8671413a-270a-4942-aacf-c819129cb01d
Charles, P. A.
0429b380-0754-4dc1-8def-885c7fa6a086
Mas-Hesse, J. M.
46b66c16-ab4b-442d-b109-69aaa0dd51d0
Gandhi, P.
5bc3b5af-42b0-4dd8-8f1f-f74048d4d4a9
Kimura, M.
eec0f994-5e97-4616-b39f-706b56c00fa0
Domingo, A.
b5805000-ba7b-4fd8-ad5d-3ce3301e5d41
Rodriguez, J.
0c2b2628-3eb1-405f-abf7-ed3ed9562e4e
Chenevez, J.
21f50a66-a919-4f31-9688-02f760e4fe09
Alfonso-Garzón, J.
7995e2d4-7675-4825-9516-b88d5d0bb2ce
Sánchez-Fernández, C.
8671413a-270a-4942-aacf-c819129cb01d
Charles, P. A.
0429b380-0754-4dc1-8def-885c7fa6a086
Mas-Hesse, J. M.
46b66c16-ab4b-442d-b109-69aaa0dd51d0
Gandhi, P.
5bc3b5af-42b0-4dd8-8f1f-f74048d4d4a9
Kimura, M.
eec0f994-5e97-4616-b39f-706b56c00fa0
Domingo, A.
b5805000-ba7b-4fd8-ad5d-3ce3301e5d41
Rodriguez, J.
0c2b2628-3eb1-405f-abf7-ed3ed9562e4e
Chenevez, J.
21f50a66-a919-4f31-9688-02f760e4fe09

Alfonso-Garzón, J., Sánchez-Fernández, C., Charles, P. A., Mas-Hesse, J. M., Gandhi, P., Kimura, M., Domingo, A., Rodriguez, J. and Chenevez, J. (2018) Optical/X-ray correlations during the V404 Cygni June 2015 outburst. Astronomy & Astrophysics, 620, [A110]. (doi:10.1051/0004-6361/201834102).

Record type: Article

Abstract

Context. We present a multiwavelength analysis of the simultaneous optical and X-ray light curves of the microquasar V404 Cyg during the June 2015 outburst. Aims. We have performed a comprehensive analysis of all the INTEGRAL/IBIS, JEM-X, and OMC observations during the brightest epoch of the outburst, along with complementary NuSTAR, AAVSO, and VSNET data, to examine the timing relationship between the simultaneous optical and X-ray light curves, in order to understand the emission mechanisms and physical locations. Methods. We have identified all optical flares that have simultaneous X-ray observations, and performed a cross-correlation analysis to estimate the time delays between the optical and soft and hard X-ray emission. We also compared the evolution of the optical and X-ray emission with the hardness ratios. Results. We have identified several types of behaviour during the outburst. On many occasions, the optical flares occur simultaneously with X-ray flares, but at other times, positive and negative time delays between the optical and X-ray emission are measured. Conclusions. We conclude that the observed optical variability is driven by different physical mechanisms, including reprocessing of X-rays in the accretion disc and/or the companion star, interaction of the jet ejections with surrounding material or with previously ejected blobs, and synchrotron emission from the jet.

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More information

Accepted/In Press date: 7 October 2018
e-pub ahead of print date: 7 December 2018
Published date: December 2018
Keywords: Accretion, accretion disks, Stars: black holes, X-rays: binaries

Identifiers

Local EPrints ID: 428584
URI: http://eprints.soton.ac.uk/id/eprint/428584
ISSN: 0004-6361
PURE UUID: a59c3954-6151-459d-af51-8c2434900f87
ORCID for P. Gandhi: ORCID iD orcid.org/0000-0003-3105-2615

Catalogue record

Date deposited: 01 Mar 2019 17:30
Last modified: 10 Dec 2019 01:33

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Contributors

Author: J. Alfonso-Garzón
Author: C. Sánchez-Fernández
Author: P. A. Charles
Author: J. M. Mas-Hesse
Author: P. Gandhi ORCID iD
Author: M. Kimura
Author: A. Domingo
Author: J. Rodriguez
Author: J. Chenevez

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