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

P. H. Sell*, T. J. Maccarone, R. Kotak, C. Knigge, D. J. Sand

*Corresponding author for this work

Research output: Contribution to journalArticle

22 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)4198-4206
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Volume450
Issue number4
Early online date20 May 2015
DOIs
Publication statusPublished - 11 Jul 2015

Keywords

  • Accretion
  • Accretion discs
  • Binaries: close
  • Galaxies: dwarf
  • Galaxies: star clusters: general
  • White dwarfs

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

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