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, Duncan Brown, H. Chen, Z. Doctor, J. A. Frieman, D. E. Holz, M. Sako & 1 others M. Soares-Santos

Research output: Contribution to journalArticle

135 Citations (Scopus)

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.

Original languageEnglish (US)
Article numberL20
JournalAstrophysical Journal Letters
Volume848
Issue number2
DOIs
StatePublished - Oct 20 2017

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LIGO (observatory)
binary stars
merger
neutron stars
electromagnetism
x rays
erg
gravitational waves
observatories
observatory
radio observation
inference
kinetic energy
inclination
outflow
radio
broadband
monitoring
prediction
predictions

Keywords

  • gravitational waves
  • relativistic processes
  • stars: neutron

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. V. Rising X-Ray Emission from an Off-axis Jet. / 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, Duncan; Chen, H.; Doctor, Z.; Frieman, J. A.; Holz, D. E.; Sako, M.; Soares-Santos, M.

In: Astrophysical Journal Letters, Vol. 848, No. 2, L20, 20.10.2017.

Research output: Contribution to journalArticle

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, D, 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
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, Duncan ; Chen, H. ; Doctor, Z. ; Frieman, J. A. ; Holz, D. E. ; Sako, M. ; Soares-Santos, M. / The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. V. Rising X-Ray Emission from an Off-axis Jet. In: Astrophysical Journal Letters. 2017 ; Vol. 848, No. 2.
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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.",
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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, Duncan

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

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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.

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