Limits on a population of collisional-triples as progenitors of Type-Ia supernovae. (arXiv:1905.00032v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Hallakoun_N/0/1/0/all/0/1">Na'ama Hallakoun</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Maoz_D/0/1/0/all/0/1">Dan Maoz</a>
The progenitor systems of Type-Ia supernovae (SNe Ia) are yet unknown. The
collisional-triple SN Ia progenitor model posits that SNe Ia result from
head-on collisions of binary white dwarfs (WDs), driven by dynamical
perturbations by the tertiary stars in mild-hierarchical triple systems. To
reproduce the Galactic SN Ia rate, some 30-55 per cent of all WDs would need to
be in triple systems of a specific architecture. We test this scenario by
searching the Gaia DR2 database for the postulated progenitor triples. Within a
volume out to 120 pc, we search around Gaia-resolved double WDs with projected
separations up to 300 au, for physical tertiary companions at projected
separations out to 9000 au. At 120 pc, Gaia can detect faint low-mass
tertiaries down to the bottom of the main sequence and to the coolest WDs.
Around 27 double WDs, we identify zero tertiaries at such separations, setting
a 95 per cent confidence upper limit of 11 per cent on the fraction of binary
WDs that are part of mild hierarchical triples of the kind required by the
model. As only a fraction (likely ~10 per cent) of all WDs are in <300 au WD
binaries, the potential collisional-triple progenitor population appears to be
at least an order of magnitude (and likely several) smaller than required by
the model.
The progenitor systems of Type-Ia supernovae (SNe Ia) are yet unknown. The
collisional-triple SN Ia progenitor model posits that SNe Ia result from
head-on collisions of binary white dwarfs (WDs), driven by dynamical
perturbations by the tertiary stars in mild-hierarchical triple systems. To
reproduce the Galactic SN Ia rate, some 30-55 per cent of all WDs would need to
be in triple systems of a specific architecture. We test this scenario by
searching the Gaia DR2 database for the postulated progenitor triples. Within a
volume out to 120 pc, we search around Gaia-resolved double WDs with projected
separations up to 300 au, for physical tertiary companions at projected
separations out to 9000 au. At 120 pc, Gaia can detect faint low-mass
tertiaries down to the bottom of the main sequence and to the coolest WDs.
Around 27 double WDs, we identify zero tertiaries at such separations, setting
a 95 per cent confidence upper limit of 11 per cent on the fraction of binary
WDs that are part of mild hierarchical triples of the kind required by the
model. As only a fraction (likely ~10 per cent) of all WDs are in <300 au WD
binaries, the potential collisional-triple progenitor population appears to be
at least an order of magnitude (and likely several) smaller than required by
the model.
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