Supernovae producing unbound binaries and triples

Abstract

The fraction of stars which are in binaries or triples at the time of stellar death and the fraction of these systems which survive the supernova (SN) explosion are crucial constraints for evolution models and predictions for gravitational wave source populations. These fractions are also subject to direct observational determination. Here we search 10 supernova remnants (SNR) containing compact objects with proper motions for unbound binaries or triples using Gaia EDR3 and new statistical methods and tests for false positives. We confirm the one known example of an unbound binary, HD 37424 in G180.0−01.7, and find no other examples. Combining this with our previous searches for bound and unbound binaries, and assuming no bias in favour of finding interacting binaries, we find that 72.0 per cent (52.2 per cent-86.4 per cent, 90 per cent confidence) of SN producing neutron stars are not binaries at the time of explosion, 13.9 per cent (5.4 per cent-27.2 per cent) produce bound binaries and 12.5 per cent (2.8 per cent-31.3 per cent) produce unbound binaries. With a strong bias in favour of finding interacting binaries, the medians shift to 76.0 per cent were not binaries at death, 9.5 per cent leave bound and 13.2 per cent leave unbound binaries. Of explosions that do not leave binaries, $<18.9{{\ \rm per\ cent}}$ can be fully unbound triples. These limits are conservatively for M > 5 M⊙ companions, although the mass limits for some individual systems are significantly stronger. At birth, the progenitor of PSR J0538+2817 was probably a 13-19 M⊙ star, and at the time of explosion it was probably a Roche limited, partially stripped star transferring mass to HD 37424 and then producing a Type IIL or IIb supernova.

The Peculiar Ejecta Rings in the O-Rich Supernova Remnant Puppis A: Evidence of a Binary Interaction?

“…There have in fact been at least two recent efforts to search for a binary companion in Pup A using the newly available data from the Gaia Early Data Release 3. Lux et al (2021) and Kochanek (2021) extracted proper motions for stars near the center of Pup A and found no evidence of an unbound binary companion. Indeed, using statistical searches for surviving binaries in additional SNRs, Kochanek (2021) estimated that nearly 70% of core-collapse SNe are unlikely to be binary systems at the time of explosion, with the remaining fraction divided nearly evenly between bound and unbound systems.…”

“…Lux et al (2021) and Kochanek (2021) extracted proper motions for stars near the center of Pup A and found no evidence of an unbound binary companion. Indeed, using statistical searches for surviving binaries in additional SNRs, Kochanek (2021) estimated that nearly 70% of core-collapse SNe are unlikely to be binary systems at the time of explosion, with the remaining fraction divided nearly evenly between bound and unbound systems. The CCO in Pup A has no known optical counterpart, so a surviving neutron star nondegenerate binary can also be ruled out.…”

Where are the magnetar binary companions? Candidates from a comparison with binary population synthesis predictions

“…The kick of Bray & Eldridge ( 2016 ) and Bray & Eldridge ( 2018 ), ho we ver, gi ves a substantially larger value of 0.23. For an observational comparison, we refer to Kochanek ( 2021 ), who performed a Gaia search for unbound companions to 10 supernova remnants. Combining these results with a previous search for surviving bound companions in supernova remnants, they find that 0.036-0.197 (90 per cent confidence, excluding triple systems) of core-collapse neutron stars are born in primaries that remain bound post-supernova.…”

Where are the magnetar binary companions? Candidates from a comparison with binary population synthesis predictions

“…The kick of Bray & Eldridge (2016, however, gives a substantially larger value of 0.23. For an observational comparison, we refer to Kochanek (2021) who performed a Gaia search for unbound companions to 10 supernova remnants. Combining these results with a previous search for surviving bound companions in supernova remnants, they find that 0.036-0.197 (90 per cent confidence, excluding triple systems) of core-collapse neutron stars are born in primaries which remain bound post supernova.…”