The Nonthermal Emission Following GW170817 is Consistent with a Conical Radially Stratified Outflow with Initial Lorentz Factor ≲10
We show that the nonthermal radio to X-ray emission following the neutron star merger GW170817 is consistent with synchrotron emission from a collisionless shock driven into the interstellar medium (ISM) by a conical radially stratified outflow observed ≈0.25 rad off-axis, with a power-law mass depe...
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IOP Publishing
2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/ade150 |
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| author | Gilad Sadeh Eli Waxman |
| author_facet | Gilad Sadeh Eli Waxman |
| author_sort | Gilad Sadeh |
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| description | We show that the nonthermal radio to X-ray emission following the neutron star merger GW170817 is consistent with synchrotron emission from a collisionless shock driven into the interstellar medium (ISM) by a conical radially stratified outflow observed ≈0.25 rad off-axis, with a power-law mass dependence on momentum, M (> γβ ) ∝ ( γβ ) ^−4 , maximum Lorenz factor γ = 10, opening (half-)angle ≈0.15 rad, and total energy of ≈5 × 10 ^50 erg. The temporal dependence of the flux during its rising phase is determined by the radial stratification structure, which determines the rate at which outflow energy is deposited in the ISM. This is in contrast with highly relativistic, γ ≈ 100, structured jet models, where the angular jet structure determines the time dependence through the gradual “unveiling” by deceleration of larger angular sections of the jet (which are initially “hidden” by relativistic beaming), typically leading to a predicted flux decline after the peak that is faster than observed. Our model predicts a dependence on the observing angle, which is different than that predicted by highly relativistic jet models. Particularly, similar merger events observed closer to the symmetry axis are predicted to show a similarly extended duration of flux increase with time. Our analysis demonstrates that the data do not require a highly relativistic γ ≈ 100 component, but the presence of such a component with opening angle ≪0.15 rad and energy ≪5 × 10 ^50 erg cannot be excluded. |
| format | Article |
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| institution | Kabale University |
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| language | English |
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| spelling | doaj-art-7565e968a7064aadb95ecb073c87fd2f2025-08-20T03:33:17ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01987217810.3847/1538-4357/ade150The Nonthermal Emission Following GW170817 is Consistent with a Conical Radially Stratified Outflow with Initial Lorentz Factor ≲10Gilad Sadeh0https://orcid.org/0009-0003-0141-6171Eli Waxman1https://orcid.org/0000-0002-9038-5877Dept. of Particle Phys. & Astrophys., Weizmann Institute of Science , Rehovot 76100, IsraelDept. of Particle Phys. & Astrophys., Weizmann Institute of Science , Rehovot 76100, IsraelWe show that the nonthermal radio to X-ray emission following the neutron star merger GW170817 is consistent with synchrotron emission from a collisionless shock driven into the interstellar medium (ISM) by a conical radially stratified outflow observed ≈0.25 rad off-axis, with a power-law mass dependence on momentum, M (> γβ ) ∝ ( γβ ) ^−4 , maximum Lorenz factor γ = 10, opening (half-)angle ≈0.15 rad, and total energy of ≈5 × 10 ^50 erg. The temporal dependence of the flux during its rising phase is determined by the radial stratification structure, which determines the rate at which outflow energy is deposited in the ISM. This is in contrast with highly relativistic, γ ≈ 100, structured jet models, where the angular jet structure determines the time dependence through the gradual “unveiling” by deceleration of larger angular sections of the jet (which are initially “hidden” by relativistic beaming), typically leading to a predicted flux decline after the peak that is faster than observed. Our model predicts a dependence on the observing angle, which is different than that predicted by highly relativistic jet models. Particularly, similar merger events observed closer to the symmetry axis are predicted to show a similarly extended duration of flux increase with time. Our analysis demonstrates that the data do not require a highly relativistic γ ≈ 100 component, but the presence of such a component with opening angle ≪0.15 rad and energy ≪5 × 10 ^50 erg cannot be excluded.https://doi.org/10.3847/1538-4357/ade150Neutron starsGravitational wave sourcesRelativistic jetsNon-thermal radiation sourcesRadio transient sourcesX-ray transient sources |
| spellingShingle | Gilad Sadeh Eli Waxman The Nonthermal Emission Following GW170817 is Consistent with a Conical Radially Stratified Outflow with Initial Lorentz Factor ≲10 The Astrophysical Journal Neutron stars Gravitational wave sources Relativistic jets Non-thermal radiation sources Radio transient sources X-ray transient sources |
| title | The Nonthermal Emission Following GW170817 is Consistent with a Conical Radially Stratified Outflow with Initial Lorentz Factor ≲10 |
| title_full | The Nonthermal Emission Following GW170817 is Consistent with a Conical Radially Stratified Outflow with Initial Lorentz Factor ≲10 |
| title_fullStr | The Nonthermal Emission Following GW170817 is Consistent with a Conical Radially Stratified Outflow with Initial Lorentz Factor ≲10 |
| title_full_unstemmed | The Nonthermal Emission Following GW170817 is Consistent with a Conical Radially Stratified Outflow with Initial Lorentz Factor ≲10 |
| title_short | The Nonthermal Emission Following GW170817 is Consistent with a Conical Radially Stratified Outflow with Initial Lorentz Factor ≲10 |
| title_sort | nonthermal emission following gw170817 is consistent with a conical radially stratified outflow with initial lorentz factor ≲10 |
| topic | Neutron stars Gravitational wave sources Relativistic jets Non-thermal radiation sources Radio transient sources X-ray transient sources |
| url | https://doi.org/10.3847/1538-4357/ade150 |
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