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Calcium-rich gap transients: tidal detonations of white dwarfs?

Calcium-rich gap transients: tidal detonations of white dwarfs?
Calcium-rich gap transients: tidal detonations of white dwarfs?
We hypothesize that at least some of the recently discovered class of calcium-rich gap transients are tidal detonation events of white dwarfs (WDs) by black holes (BHs) or possibly neutron stars. We show that the properties of the calcium-rich gap transients agree well with the predictions of the tidal detonation model. Under the predictions of this model, we use a follow-up X-ray observation of one of these transients, SN 2012hn, to place weak upper limits on the detonator mass of this system that include all intermediate-mass BHs (IMBHs). As these transients are preferentially in the stellar haloes of galaxies, we discuss the possibility that these transients are tidal detonations of WDs caused by random flyby encounters with IMBHs in dwarf galaxies or globular clusters. This possibility has been already suggested in the literature but without connection to the calcium-rich gap transients. In order for the random flyby cross-section to be high enough, these events would have to be occurring inside these dense stellar associations. However, there is a lack of evidence for IMBHs in these systems, and recent observations have ruled out all but the very faintest dwarf galaxies and globular clusters for a few of these transients. Another possibility is that these are tidal detonations caused by three-body interactions, where a WD is perturbed towards the detonator in isolated multiple star systems. We highlight a number of ways this could occur, even in lower mass systems with stellar-mass BHs or neutron stars. Finally, we outline several new observational tests of this scenario, which are feasible with current instrumentation.
accretion, accretion discs, binaries: close, white dwarfs, galaxies: dwarf, galaxies: star clusters: general
0035-8711
4198-4206
Sell, P.H.
7c75071e-87fe-4e4e-bf4b-82d51df2c16d
Maccarone, T.J.
c2f1d87b-e2ef-4e33-b09f-a2861d917ea8
Kotak, R.
240df6f9-f459-47ea-9856-9664ccd9c98f
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Sand, D.J.
1d5b9338-c884-4586-bf6b-32902d9c3f3f
Sell, P.H.
7c75071e-87fe-4e4e-bf4b-82d51df2c16d
Maccarone, T.J.
c2f1d87b-e2ef-4e33-b09f-a2861d917ea8
Kotak, R.
240df6f9-f459-47ea-9856-9664ccd9c98f
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Sand, D.J.
1d5b9338-c884-4586-bf6b-32902d9c3f3f

Sell, P.H., Maccarone, T.J., Kotak, R., Knigge, C. and Sand, D.J. (2015) Calcium-rich gap transients: tidal detonations of white dwarfs? Monthly Notices of the Royal Astronomical Society, 450 (4), 4198-4206. (doi:10.1093/mnras/stv902).

Record type: Article

Abstract

We hypothesize that at least some of the recently discovered class of calcium-rich gap transients are tidal detonation events of white dwarfs (WDs) by black holes (BHs) or possibly neutron stars. We show that the properties of the calcium-rich gap transients agree well with the predictions of the tidal detonation model. Under the predictions of this model, we use a follow-up X-ray observation of one of these transients, SN 2012hn, to place weak upper limits on the detonator mass of this system that include all intermediate-mass BHs (IMBHs). As these transients are preferentially in the stellar haloes of galaxies, we discuss the possibility that these transients are tidal detonations of WDs caused by random flyby encounters with IMBHs in dwarf galaxies or globular clusters. This possibility has been already suggested in the literature but without connection to the calcium-rich gap transients. In order for the random flyby cross-section to be high enough, these events would have to be occurring inside these dense stellar associations. However, there is a lack of evidence for IMBHs in these systems, and recent observations have ruled out all but the very faintest dwarf galaxies and globular clusters for a few of these transients. Another possibility is that these are tidal detonations caused by three-body interactions, where a WD is perturbed towards the detonator in isolated multiple star systems. We highlight a number of ways this could occur, even in lower mass systems with stellar-mass BHs or neutron stars. Finally, we outline several new observational tests of this scenario, which are feasible with current instrumentation.

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Published date: 1 July 2015
Keywords: accretion, accretion discs, binaries: close, white dwarfs, galaxies: dwarf, galaxies: star clusters: general

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Local EPrints ID: 430099
URI: http://eprints.soton.ac.uk/id/eprint/430099
ISSN: 0035-8711
PURE UUID: 98416b49-447e-41f6-82e5-a67d25eea6bb

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Date deposited: 11 Apr 2019 16:30
Last modified: 21 Nov 2021 16:07

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Contributors

Author: P.H. Sell
Author: T.J. Maccarone
Author: R. Kotak
Author: C. Knigge
Author: D.J. Sand

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