The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. V. Rising X-Ray Emission from an Off-axis Jet

R. Margutti; E. Berger; W. Fong; C. Guidorzi; K. D. Alexander; B. D. Metzger; P. K. Blanchard; P. S. Cowperthwaite; R. Chornock; T. Eftekhari; M. Nicholl; V. A. Villar; P. K.G. Williams; J. Annis; D. A. Brown; H. Chen; Z. Doctor; J. A. Frieman; D. E. Holz; M. Sako; M. Soares-Santos

doi:10.3847/2041-8213/aa9057

The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. V. Rising X-Ray Emission from an Off-axis Jet

R. Margutti, E. Berger, W. Fong, C. Guidorzi, K. D. Alexander, B. D. Metzger, P. K. Blanchard, P. S. Cowperthwaite, R. Chornock, T. Eftekhari, M. Nicholl, V. A. Villar, P. K.G. Williams, J. Annis, D. A. Brown, H. Chen, Z. Doctor, J. A. Frieman, D. E. Holz, M. SakoM. Soares-Santos

Department of Physics

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337 Scopus citations

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 ×10³⁸ erg s^-1 (isotropic-equivalent). Continued monitoring revealed the presence of an X-ray source that brightened with time, reaching L_x 9 ×10 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_k ∼ 10 erg^49-50erg, viewed off-axis with θ_obs ∼ 20°-40°. Our models favor a circumbinary density n ∼ 10^-4-10^-2 cm^-3, depending on the value of the microphysical parameter ϵ_B =10^-4-10^-2. A centralengine 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 (US)
Article number	L20
Journal	Astrophysical Journal Letters
Volume	848
Issue number	2
DOIs	https://doi.org/10.3847/2041-8213/aa9057
State	Published - Oct 20 2017

Keywords

gravitational waves
relativistic processes
stars: neutron

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.3847/2041-8213/aa9057

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Margutti, R., Berger, E., Fong, W., Guidorzi, C., 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., Holz, D. E., ... Soares-Santos, M. (2017). The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. V. Rising X-Ray Emission from an Off-axis Jet. Astrophysical Journal Letters, 848(2), Article L20. https://doi.org/10.3847/2041-8213/aa9057

Margutti, R, Berger, E, Fong, W, Guidorzi, C, Alexander, KD, Metzger, BD, Blanchard, PK, Cowperthwaite, PS, Chornock, R, Eftekhari, T, Nicholl, M, Villar, VA, Williams, PKG, Annis, J, Brown, DA, Chen, H, Doctor, Z, Frieman, JA, Holz, DE, Sako, M & Soares-Santos, M 2017, 'The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. V. Rising X-Ray Emission from an Off-axis Jet', Astrophysical Journal Letters, vol. 848, no. 2, L20. https://doi.org/10.3847/2041-8213/aa9057

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title = "The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. V. Rising X-Ray Emission from an Off-axis Jet",

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 Lx 3.2 ×1038 erg s-1 (isotropic-equivalent). Continued monitoring revealed the presence of an X-ray source that brightened with time, reaching Lx 9 ×10 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 Ek ∼ 10 erg49-50erg, viewed off-axis with θobs ∼ 20°-40°. Our models favor a circumbinary density n ∼ 10-4-10-2 cm-3, depending on the value of the microphysical parameter ϵB =10-4-10-2. A centralengine 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 θobs are testable with GW information on GW170817 from advanced LIGO/Virgo on the binary inclination.",

keywords = "gravitational waves, relativistic processes, stars: neutron",

author = "R. Margutti and E. Berger and W. Fong and C. Guidorzi and Alexander, {K. D.} and Metzger, {B. D.} and Blanchard, {P. K.} and Cowperthwaite, {P. S.} and R. Chornock and T. Eftekhari and M. Nicholl and Villar, {V. A.} and Williams, {P. K.G.} and J. Annis and Brown, {D. A.} and H. Chen and Z. Doctor and Frieman, {J. A.} and Holz, {D. E.} and M. Sako and M. Soares-Santos",

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T1 - The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. V. Rising X-Ray Emission from an Off-axis Jet

AU - Margutti, R.

AU - Berger, E.

AU - Fong, W.

AU - Guidorzi, C.

AU - Alexander, K. D.

AU - Metzger, B. D.

AU - Blanchard, P. K.

AU - Cowperthwaite, P. S.

AU - Chornock, R.

AU - Eftekhari, T.

AU - Nicholl, M.

AU - Villar, V. A.

AU - Williams, P. K.G.

AU - Annis, J.

AU - Brown, D. A.

AU - Chen, H.

AU - Doctor, Z.

AU - Frieman, J. A.

AU - Holz, D. E.

AU - Sako, M.

AU - Soares-Santos, M.

PY - 2017/10/20

Y1 - 2017/10/20

N2 - 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 Lx 3.2 ×1038 erg s-1 (isotropic-equivalent). Continued monitoring revealed the presence of an X-ray source that brightened with time, reaching Lx 9 ×10 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 Ek ∼ 10 erg49-50erg, viewed off-axis with θobs ∼ 20°-40°. Our models favor a circumbinary density n ∼ 10-4-10-2 cm-3, depending on the value of the microphysical parameter ϵB =10-4-10-2. A centralengine 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 θobs are testable with GW information on GW170817 from advanced LIGO/Virgo on the binary inclination.

AB - 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 Lx 3.2 ×1038 erg s-1 (isotropic-equivalent). Continued monitoring revealed the presence of an X-ray source that brightened with time, reaching Lx 9 ×10 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 Ek ∼ 10 erg49-50erg, viewed off-axis with θobs ∼ 20°-40°. Our models favor a circumbinary density n ∼ 10-4-10-2 cm-3, depending on the value of the microphysical parameter ϵB =10-4-10-2. A centralengine 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 θobs are testable with GW information on GW170817 from advanced LIGO/Virgo on the binary inclination.

KW - gravitational waves

KW - relativistic processes

KW - stars: neutron

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JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

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The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. V. Rising X-Ray Emission from an Off-axis Jet

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