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EX draconis: using eclipses to separate outside-in and inside-out outbursts

EX draconis: using eclipses to separate outside-in and inside-out outbursts
EX draconis: using eclipses to separate outside-in and inside-out outbursts
We present a study of the eclipses in the accreting white dwarf EX draconis (EX Dra) during TESS Cycles 14 and 15. During both of the two outbursts present in this data set, the eclipses undergo a hysteretic loop in eclipse-depth/out-of-eclipse-flux space. In each case, the direction in which the loops are executed strongly suggests an outburst that is triggered near the inner edge of the accretion disc and propagates outwards. This in turn suggests that the outbursts in EX Dra are ‘inside out’ outbursts; events predicted by previous hydrodynamic studies of dwarf nova accretion discs and confirmed spectroscopically in a number of other accreting white dwarf systems. We therefore propose that the direction of the loop executed in eclipse-depth/out-of-eclipse flux space be used as a test to phenomenologically distinguish between ‘inside out’ and ‘outside in’ outbursts in other eclipsing dwarf novae; a reliable and purely photometric test to differentiate between these phenomena.
accretion, accretion discs, eclipses, novae, cataclysmic variables, stars: Individual: EX Dra
0035-8711
4656-4664
Court, J M C
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Scaringi, S
88701970-a1b9-41fe-bf55-886716ee3374
Littlefield, C
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Castro segura, N
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Long, K S
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Maccarone, T
c2f1d87b-e2ef-4e33-b09f-a2861d917ea8
Altamirano, D
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Degenaar, N
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Wijnands, R
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Shahbaz, T
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Zhan, Z
f23d16a6-80f8-453d-9df3-07a570e02dc9
Court, J M C
6e39b3e2-c269-49eb-9e06-cc47981117f1
Scaringi, S
88701970-a1b9-41fe-bf55-886716ee3374
Littlefield, C
5844d5fc-231e-44dd-ab6f-ace3c7f92db7
Castro segura, N
5bd44a1e-55d4-4c68-85bf-a0b651bcd0a3
Long, K S
839b3509-5ef3-4126-97fa-912e3357d8ef
Maccarone, T
c2f1d87b-e2ef-4e33-b09f-a2861d917ea8
Altamirano, D
d5ccdb09-0b71-4303-9538-05b467be075b
Degenaar, N
54149051-d74e-4e43-a7cd-501ec4023511
Wijnands, R
382893ee-0e03-45e3-9321-db8b9fc74914
Shahbaz, T
17cdfe98-d466-40b1-9810-86262df89777
Zhan, Z
f23d16a6-80f8-453d-9df3-07a570e02dc9

Court, J M C, Scaringi, S, Littlefield, C, Castro segura, N, Long, K S, Maccarone, T, Altamirano, D, Degenaar, N, Wijnands, R, Shahbaz, T and Zhan, Z (2020) EX draconis: using eclipses to separate outside-in and inside-out outbursts. Monthly Notices of the Royal Astronomical Society, 494 (4), 4656-4664. (doi:10.1093/mnras/staa1042).

Record type: Article

Abstract

We present a study of the eclipses in the accreting white dwarf EX draconis (EX Dra) during TESS Cycles 14 and 15. During both of the two outbursts present in this data set, the eclipses undergo a hysteretic loop in eclipse-depth/out-of-eclipse-flux space. In each case, the direction in which the loops are executed strongly suggests an outburst that is triggered near the inner edge of the accretion disc and propagates outwards. This in turn suggests that the outbursts in EX Dra are ‘inside out’ outbursts; events predicted by previous hydrodynamic studies of dwarf nova accretion discs and confirmed spectroscopically in a number of other accreting white dwarf systems. We therefore propose that the direction of the loop executed in eclipse-depth/out-of-eclipse flux space be used as a test to phenomenologically distinguish between ‘inside out’ and ‘outside in’ outbursts in other eclipsing dwarf novae; a reliable and purely photometric test to differentiate between these phenomena.

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2004.06802 - Accepted Manuscript
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Accepted/In Press date: 9 April 2020
e-pub ahead of print date: 24 April 2020
Published date: 1 June 2020
Keywords: accretion, accretion discs, eclipses, novae, cataclysmic variables, stars: Individual: EX Dra

Identifiers

Local EPrints ID: 442345
URI: http://eprints.soton.ac.uk/id/eprint/442345
ISSN: 0035-8711
PURE UUID: 54e9af92-8a57-4a8d-9f75-60c7d0ac5157
ORCID for D Altamirano: ORCID iD orcid.org/0000-0002-3422-0074

Catalogue record

Date deposited: 14 Jul 2020 16:30
Last modified: 26 Nov 2021 03:02

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Contributors

Author: J M C Court
Author: S Scaringi
Author: C Littlefield
Author: N Castro segura
Author: K S Long
Author: T Maccarone
Author: D Altamirano ORCID iD
Author: N Degenaar
Author: R Wijnands
Author: T Shahbaz
Author: Z Zhan

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