Modelling hystereses observed during dwarf-nova outbursts
Modelling hystereses observed during dwarf-nova outbursts
Context. Although the disc instability model is widely accepted as the explanation for dwarf nova outbursts, it is still necessary to compare its predictions to observations because many of the constraints on angular momentum transport in accretion discs are derived from the application of this model to real systems. Aims. We test the predictions of the model concerning the multicolour time evolution of outbursts for two well-observed systems, SS Cyg and VW Hyi. Methods. We calculate the multicolour evolution of dwarf nova outbursts using the disc instability model and taking into account the contribution from the irradiated secondary, the white dwarf and the hot spot. Results. Observations definitely show the existence of a hysteresis in the optical colour-magnitude diagram during the evolution of dwarf nova outbursts. We find that the disc instability model naturally explains the existence and the orientation of this hysteresis. For the specific cases of SS Cyg and VW Hyi, the colour and magnitude ranges covered during the evolution of the system are in reasonable agreement with observations. However, the observed colours are bluer than observed near the peak of the outbursts, as in steady systems, and the amplitude of the hysteresis cycle is smaller than observed. The predicted colours significantly depend on the assumptions made for calculating the disc spectrum during rise, and on the magnitude of the secondary irradiation for the decaying part of the outburst. Conclusions. Improvements in the spectral disc models are strongly needed if the system evolution in the UV is to be addressed.
astro-ph.HE, astro-ph.SR
Hameury, J. -M.
de96fab6-6fd4-40c0-badd-c7356db1ce07
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Lasota, J. -P.
47fcca7a-1082-415e-94e0-df546c4f49fc
Hambsch, F. -J.
8067539d-8ad0-42cc-80db-5942f58de570
James, R.
b2bf9dc8-4cb2-41cf-b77c-6b042856f60f
3 April 2020
Hameury, J. -M.
de96fab6-6fd4-40c0-badd-c7356db1ce07
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Lasota, J. -P.
47fcca7a-1082-415e-94e0-df546c4f49fc
Hambsch, F. -J.
8067539d-8ad0-42cc-80db-5942f58de570
James, R.
b2bf9dc8-4cb2-41cf-b77c-6b042856f60f
Hameury, J. -M., Knigge, C., Lasota, J. -P., Hambsch, F. -J. and James, R.
(2020)
Modelling hystereses observed during dwarf-nova outbursts.
Astronomy & Astrophysics, 636, [A1].
(doi:10.1051/0004-6361/202037631).
Abstract
Context. Although the disc instability model is widely accepted as the explanation for dwarf nova outbursts, it is still necessary to compare its predictions to observations because many of the constraints on angular momentum transport in accretion discs are derived from the application of this model to real systems. Aims. We test the predictions of the model concerning the multicolour time evolution of outbursts for two well-observed systems, SS Cyg and VW Hyi. Methods. We calculate the multicolour evolution of dwarf nova outbursts using the disc instability model and taking into account the contribution from the irradiated secondary, the white dwarf and the hot spot. Results. Observations definitely show the existence of a hysteresis in the optical colour-magnitude diagram during the evolution of dwarf nova outbursts. We find that the disc instability model naturally explains the existence and the orientation of this hysteresis. For the specific cases of SS Cyg and VW Hyi, the colour and magnitude ranges covered during the evolution of the system are in reasonable agreement with observations. However, the observed colours are bluer than observed near the peak of the outbursts, as in steady systems, and the amplitude of the hysteresis cycle is smaller than observed. The predicted colours significantly depend on the assumptions made for calculating the disc spectrum during rise, and on the magnitude of the secondary irradiation for the decaying part of the outburst. Conclusions. Improvements in the spectral disc models are strongly needed if the system evolution in the UV is to be addressed.
Text
2003.03056v1
- Accepted Manuscript
More information
Accepted/In Press date: 6 March 2020
e-pub ahead of print date: 3 April 2020
Published date: 3 April 2020
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Funding Information:
Acknowledgements. We acknowledge with thanks the variable star observations from the AAVSO International Database contributed by observers worldwide and used in this research. This work was supported by a National Science Centre, Poland grant 2015/19/B/ST9/01099. JPL was supported by a grant from the French Space Agency CNES. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www. cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/ consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.
Publisher Copyright:
© 2020. J.-M. Hameury et al.
Keywords:
astro-ph.HE, astro-ph.SR
Identifiers
Local EPrints ID: 438848
URI: http://eprints.soton.ac.uk/id/eprint/438848
ISSN: 0004-6361
PURE UUID: 2e8cc6a1-16f4-48a7-a113-dda5019396c3
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Date deposited: 25 Mar 2020 17:31
Last modified: 16 Mar 2024 07:06
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Author:
J. -M. Hameury
Author:
J. -P. Lasota
Author:
F. -J. Hambsch
Author:
R. James
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