Large-scale Evolution of Seconds-long Relativistic Jets from Black Hole–Neutron Star Mergers

Journal Article · 30 August 2023 · The Astrophysical Journal. Letters

DOI: https://doi.org/10.3847/2041-8213/aceeff · OSTI ID:2281673

Gottlieb, Ore  ^[1]; Issa, Danat  ^[1]; Jacquemin-Ide, Jonatan  ^[1]; Liska, Matthew  ^[2]; Foucart, Francois  ^[3]; Tchekhovskoy, Alexander  ^[1]; Metzger, Brian D.  ^[4]; Quataert, Eliot  ^[5]; Perna, Rosalba  ^[6]; Kasen, Daniel  ^[7]; Duez, Matthew D.  ^[8]; Kidder, Lawrence E.  ^[9]; Pfeiffer, Harald P.  ^[10]; Scheel, Mark A.  ^[11]

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1. Northwestern Univ., Evanston, IL (United States)
2. Harvard Univ., Cambridge, MA (United States)
3. Univ. of New Hampshire, Durham, NH (United States)
4. Columbia Univ., New York, NY (United States); Flatiron Institute, New York, NY (United States)
5. Princeton Univ., NJ (United States)
6. Flatiron Institute, New York, NY (United States); Stony Brook Univ., NY (United States)
7. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
8. Washington State Univ., Pullman, WA (United States)
9. Cornell Univ., Ithaca, NY (United States)
10. Max Planck Institute for Gravitational Physics, Potsdam (Germany). Albert Einstein Institute
11. California Institute of Technology (CalTech), Pasadena, CA (United States). Walter Burke Institute for Theoretical Physics

We present the first numerical simulations that track the evolution of a black hole–neutron star (BH–NS) merger from premerger to r ≳ 10¹¹ cm. The disk that forms after a merger of mass ratio q = 2 ejects massive disk winds (3–5 × 10^–2M_⊙). We introduce various postmerger magnetic configurations and find that initial poloidal fields lead to jet launching shortly after the merger. The jet maintains a constant power due to the constancy of the large-scale BH magnetic flux until the disk becomes magnetically arrested (MAD), where the jet power falls off as L_j ~ t^–2. All jets inevitably exhibit either excessive luminosity due to rapid MAD activation when the accretion rate is high or excessive duration due to delayed MAD activation compared to typical short gamma-ray bursts (sGRBs). This provides a natural explanation for long sGRBs such as GRB 211211A but also raises a fundamental challenge to our understanding of jet formation in binary mergers. One possible implication is the necessity of higher binary mass ratios or moderate BH spins to launch typical sGRB jets. For postmerger disks with a toroidal magnetic field, dynamo processes delay jet launching such that the jets break out of the disk winds after several seconds. We show for the first time that sGRB jets with initial magnetization σ0 > 100 retain significant magnetization (σ $$\gg$$ 1) at r > 10¹⁰ cm, emphasizing the importance of magnetic processes in the prompt emission. The jet–wind interaction leads to a power-law angular energy distribution by inflating an energetic cocoon whose emission is studied in a companion paper.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)
• Sponsoring Organization: National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); USDOE Office of Science (SC), High Energy Physics (HEP); USDOE Office of Science (SC), Nuclear Physics (NP)
• Grant/Contract Number: AC02-05CH11231; AC05-00OR22725
• OSTI ID: 2281673
• Journal Information: The Astrophysical Journal. Letters, Journal Name: The Astrophysical Journal. Letters Journal Issue: 1 Vol. 954; ISSN 2041-8205
• Publisher: IOP PublishingCopyright Statement
• Country of Publication: United States
• Language: English