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On the formation of GW190814

Lu, Wenbin and Beniamini, Paz and Bonnerot, Clément (2020) On the formation of GW190814. . (Unpublished) https://resolver.caltech.edu/CaltechAUTHORS:20201012-142717744

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Abstract

The LIGO-Virgo collaboration recently reported a puzzling event, GW190814, with component masses of 23 and 2.6_⊙. Motivated by the relatively small rate of such a coalescence and the fact that the mass of the secondary is close to the total mass of known binary neutron star (bNS) systems, we propose that GW190814 was a second-generation merger from a hierarchical triple system, i.e., the remnant from the bNS coalescence was able to merge again with the 23 M_⊙ black hole (BH) tertiary. We show that this occurs at a sufficiently high probability provided that the semimajor axis of the outer orbit is less than a few AU at the time of bNS coalescence. It remains to be explored whether the conditions for the formation of such tight triple systems are commonly realized in the Universe, especially in low metallicity (less than 0.1 solar) environments. Our model provides a number of predictions. (1) The spin of the secondary in GW190814-like systems is 0.6 to 0.7. (2) The component mass distribution from a large sample of LIGO sources should have a narrow peak between 2.5 and ~3.5 M_⊙, whereas the range between ~3.5 and ~5 M_⊙ stays empty (provided that stellar evolution does not generate such BHs in the "mass gap"). (3) About 90% (10%) of GW190814-like events have an eccentricity of e ≳ 2 x 10⁻³ (≳0.1) near gravitational wave frequency of 10 mHz. (4) A significant fraction (≳10%) of bNS mergers should have signatures of a massive tertiary at a distance of a few AU in the gravitational waveform. (5) There are 10⁵ undetected radio-quiet bNS systems with a massive BH tertiary in the Milky Way.


Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription
http://arxiv.org/abs/2009.10082arXivDiscussion Paper
ORCID:
AuthorORCID
Lu, Wenbin0000-0002-1568-7461
Beniamini, Paz0000-0001-7833-1043
Bonnerot, Clément0000-0001-9970-2843
Additional Information:WL thank Shri Kulkarni for his encouragement throughout this project and many insightful suggestions.We thank Tony Piro for suggesting looking into low-GW-frequency observations of the predicted signals. We thank Brian Metzger, Bin Liu, Imre Bartos, Kyle Kremer, Jim Fuller, Ylva Goetberg, Pawan Kumar for many useful discussions and comments. We acknowledge the detailed explanations of their earlier work on AGN-assisted mergers by Imre Bartos and Yang Yang. WL was supported by the David and Ellen Lee Fellowship at Caltech. The research of PB and CB was funded by the Gordon and Betty Moore Foundation through Grant GBMF5076. Data Availability: The data underlying this article will be shared on reasonable request to the corresponding author.
Group:TAPIR
Funders:
Funding AgencyGrant Number
David and Ellen Lee Postdoctoral ScholarshipUNSPECIFIED
Gordon and Betty Moore FoundationGBMF5076
Subject Keywords:gravitational waves ; compact objects ; black hole mergers ; neutron star mergers
Record Number:CaltechAUTHORS:20201012-142717744
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20201012-142717744
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105990
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:12 Oct 2020 21:41
Last Modified:12 Oct 2020 21:41

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