Faint calcium-rich transient from the double-detonation of a $0.6M_{\odot }$ carbon-oxygen white dwarf star

Abstract

We have computed a three-dimensional hydrodynamic simulation of the merger between a massive ($0.4M_{\odot }$) helium white dwarf (He WD) and a low-mass ($0.6M_{\odot }$) carbon-oxygen white dwarf (CO WD). Despite the low mass of the primary, the merger triggers a thermonuclear explosion as a result of a double detonation, producing a faint transient and leaving no remnant behind. This type of event could also take place during common-envelope mergers whenever the companion is a CO WD and the core of the giant star has a sufficiently large He mass. The spectra show strong Ca lines throughout the first few weeks after the explosion. The explosion only yields $<0.01M_{\odot }$ of ${}^{56}$Ni, resulting in a low-luminosity SN Ia-like lightcurve that resembles the Ca-rich transients within this broad class of objects, with a peak magnitude of $M_{\mathrm{bol}}\approx -15.7$mag and a rather slow decline rate of $\Delta m_{15}^{\mathrm{bol}}\approx 1.5$mag. Both, its lightcurve-shape and spectral appearance, resemble the appearance of Ca-rich transients, suggesting such mergers as a possible progenitor scenario for this class of events.

Submitted to A&A letters, posted on ArXiv after positive referee report. 7 pages, 4 figures

Cited by in corpus (1)

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