Abstract
We report the discovery of rising X-ray emission from the binary neutron star merger event GW170817. This is the first detection of X-ray emission from a gravitational-wave (GW) source. Observations acquired with the Chandra X-ray Observatory (CXO) at t≈ 2.3 days post-merger reveal no significant emission, with {L}x≲ 3.2× {10}38 {erg} {{{s}}}-1 (isotropic-equivalent). Continued monitoring revealed the presence of an X-ray source that brightened with time, reaching {L}x≈ 9× {10}38 {erg} {{{s}}}-1 at ≈ 15.1 days post-merger. We interpret these findings in the context of isotropic and collimated relativistic outflows (both on- and off-axis). We find that the broadband X-ray to radio observations are consistent with emission from a relativistic jet with kinetic energy {E}k̃ {10}49-50 {erg}, viewed off-axis with {θ }{obs}̃ 20^\circ {--}40^\circ . Our models favor a circumbinary density ñ {10}-4{--}{10}-2 {{cm}}-3, depending on the value of the microphysical parameter {∊ }B={10}-4{--}{10}-2. A central-engine origin of the X-ray emission is unlikely. Future X-ray observations at t≳ 100 days, when the target will be observable again with the CXO, will provide additional constraints to solve the model degeneracies and test our predictions. Our inferences on {θ }{obs} are testable with GW information on GW170817 from advanced LIGO/Virgo on the binary inclination....
Original language | English |
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Article number | L20 |
Journal | Astrophysical Journal Letters |
Volume | 848 |
Issue number | 2 |
DOIs | |
Publication status | Published - 16 Oct 2017 |
Keywords
- stars: neutron
- gravitational waves
- relativistic processes