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EnglishWe report the discovery of rising X-ray emission from the binary neutron star (BNS) merger event GW170817. This is the first detection of X-ray emission from a gravitational-wave source. Observations acquired with the Chandra X-ray Observatory (CXO) at t ~ 2:3 days post merger reveal no significant emission, with Lx . 3:2x10^38 ergs-1 (isotropic-equivalent). Continued monitoring revealed the presence of an X-ray source that brightened with time, reaching Lx ~ 9x10^39 ergs-1 at t 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 broad-band X-ray to radio observations are consistent with emission from a relativistic jet with kinetic energy Ek ~ 10^49-50 erg, viewed off-axis with theta_obs ~ 20-40 degrees. Our models favor a circumbinary density n ~ 10^-4 -10^-2 cm-3, depending on the value of the microphysical parameter epsilon_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 theta_obs are testable with gravitational wave information on GW170817 from Advanced LIGO/Virgo on the binary inclination.
| Data di pubblicazione: | 2017 | |
| Titolo: | The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. V. Rising X-Ray Emission from an Off-axis Jet | |
| Autori: | Margutti, R.; Berger, E.; Fong, W.; Guidorzi, Cristiano; Alexander, K. D.; Metzger, B. D.; Blanchard, P. K.; Cowperthwaite, P. S.; Chornock, R.; Eftekhari, T.; Nicholl, M.; Villar, V. A.; Williams, P. K. G.; Annis, J.; Brown, D. A.; Chen, H.; Doctor, Z.; Frieman, J. A.; D. E., Holz; Sako, M.; Soares Santos, M. | |
| Rivista: | THE ASTROPHYSICAL JOURNAL LETTERS | |
| Keywords: | gravitational waves, stars: neutron, gravitational waves, relativistic processes | |
| Abstract in inglese: | We report the discovery of rising X-ray emission from the binary neutron star (BNS) merger event GW170817. This is the first detection of X-ray emission from a gravitational-wave source. Observations acquired with the Chandra X-ray Observatory (CXO) at t ~ 2:3 days post merger reveal no significant emission, with Lx . 3:2x10^38 ergs-1 (isotropic-equivalent). Continued monitoring revealed the presence of an X-ray source that brightened with time, reaching Lx ~ 9x10^39 ergs-1 at t 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 broad-band X-ray to radio observations are consistent with emission from a relativistic jet with kinetic energy Ek ~ 10^49-50 erg, viewed off-axis with theta_obs ~ 20-40 degrees. Our models favor a circumbinary density n ~ 10^-4 -10^-2 cm-3, depending on the value of the microphysical parameter epsilon_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 theta_obs are testable with gravitational wave information on GW170817 from Advanced LIGO/Virgo on the binary inclination. | |
| Digital Object Identifier (DOI): | 10.3847/2041-8213/aa9057 | |
| Handle: | http://hdl.handle.net/11392/2377418 | |
| Appare nelle tipologie: | 03.1 Articolo su rivista |
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http://hdl.handle.net/11392/2377418
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