Kick Paper

One of the coalescing binary black holes discovered by LIGO (GW151226 or “Boxing Day”) is consistent with a scenario where the more massive black hole is spinning, with its spin misaligned with the orbital angular momentum. If true, some event or process must have imparted this misalignment. In one way the binary might have formed, this misalignment would arise when the biggest star ends its life and forms a black hole, via a “natal kick” imparted to the newborn BH. These natal kicks are known to be imparted to newborn black holes; some observations suggest they may also be imparted to BHs.

In a new paper, my collaborators and I tried to constrain the strength of these natal kicks, based on GW151226. Working under the assumption they formed from isolated pairs of stars, we found strong natal BH kicks were required.

For experts: We show how current gravitational wave observations provide new insight into how black holes form in stellar collapse. This paper is the first study to attempt to extract information about concrete astrophysical properties of supernova explosions from gravitational wave observations. It provides an easily-understoond and -generalized framework to enable the interpretation of future events. With just one event, our results begin to challenge standard supernova theory and black-hole binary formation models.

For more information, see the links below:

• ROS, Gerosa, Wysocki, “Inferences about supernova physics from gravitational-wave measurements: GW151226 spin misalignment as an indicator of strong black-hole natal kicks” (PRL 119, 011101) , summarized in Physics
• LIGO’s GW151226 paper