A Deep Chandra X-Ray Study of Neutron Star Coalescence GW170817

Daryl Haggard; Melania Nynka; John J. Ruan; Vicky Kalogera; S. Bradley Cenko; Phil Evans; Jamie A. Kennea

doi:10.3847/2041-8213/aa8ede

A Deep Chandra X-Ray Study of Neutron Star Coalescence GW170817

Daryl Haggard, Melania Nynka, John J. Ruan, Vicky Kalogera, S. Bradley Cenko, Phil Evans, Jamie A. Kennea

Physics and Astronomy

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194 Scopus citations

Abstract

We report Chandra observations of GW170817, the first neutron star-neutron star merger discovered by the joint LIGO-Virgo Collaboration, and the first direct detection of gravitational radiation associated with an electromagnetic counterpart, Fermi short γ-ray burst GRB 170817A. The event occurred on 2017 August 17 and subsequent observations identified an optical counterpart, SSS17a, coincident with NGC 4993 (∼10″ separation). Early Chandra (Δt ∼ 2 days) and Swift (Δt ∼ 1-3 days) observations yielded non-detections at the optical position, but ∼9 days post-trigger Chandra monitoring revealed an X-ray point source coincident with SSS17a. We present two deep Chandra observations totaling ∼95 ks, collected on 2017 September 01-02 (Δt ∼ 15-16 days). We detect X-ray emission from SSS17a with L_{0.3-10 keV} = 2.6^+0.5_-0.4 × 10³⁸erg s^-1, and a power law spectrum of Γ = 2.4 ± 0.8. We find that the X-ray light curve from a binary NS coalescence associated with this source is consistent with the afterglow from an off-axis short γ-ray burst, with a jet angled ≳23° from the line of sight. This event marks both the first electromagnetic counterpart to a LIGO-Virgo gravitational-wave source and the first identification of an off-axis short GRB. We also confirm extended X-ray emission from NGC 4993 (L_{0.3-10 keV} ∼9 ×10³⁸ erg s^-1) consistent with its E/S0 galaxy classification, and report two new Chandra point sources in this field, CXOU J130948 and CXOU J130946.

Original language	English (US)
Article number	L25
Journal	Astrophysical Journal Letters
Volume	848
Issue number	2
DOIs	https://doi.org/10.3847/2041-8213/aa8ede
State	Published - Oct 20 2017

Keywords

X-rays: binaries
galaxies: individual (NGC 4993)
gamma-ray burst: individual (GRB 170817A)
gravitational waves
stars: neutron

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.3847/2041-8213/aa8ede

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@article{e07820b627ea4971af857ce6b7e17748,

title = "A Deep Chandra X-Ray Study of Neutron Star Coalescence GW170817",

abstract = "We report Chandra observations of GW170817, the first neutron star-neutron star merger discovered by the joint LIGO-Virgo Collaboration, and the first direct detection of gravitational radiation associated with an electromagnetic counterpart, Fermi short γ-ray burst GRB 170817A. The event occurred on 2017 August 17 and subsequent observations identified an optical counterpart, SSS17a, coincident with NGC 4993 (∼10″ separation). Early Chandra (Δt ∼ 2 days) and Swift (Δt ∼ 1-3 days) observations yielded non-detections at the optical position, but ∼9 days post-trigger Chandra monitoring revealed an X-ray point source coincident with SSS17a. We present two deep Chandra observations totaling ∼95 ks, collected on 2017 September 01-02 (Δt ∼ 15-16 days). We detect X-ray emission from SSS17a with L0.3-10 keV = 2.6+0.5-0.4 × 1038erg s-1, and a power law spectrum of Γ = 2.4 ± 0.8. We find that the X-ray light curve from a binary NS coalescence associated with this source is consistent with the afterglow from an off-axis short γ-ray burst, with a jet angled ≳23° from the line of sight. This event marks both the first electromagnetic counterpart to a LIGO-Virgo gravitational-wave source and the first identification of an off-axis short GRB. We also confirm extended X-ray emission from NGC 4993 (L0.3-10 keV ∼9 ×1038 erg s-1) consistent with its E/S0 galaxy classification, and report two new Chandra point sources in this field, CXOU J130948 and CXOU J130946.",

keywords = "X-rays: binaries, galaxies: individual (NGC 4993), gamma-ray burst: individual (GRB 170817A), gravitational waves, stars: neutron",

author = "Daryl Haggard and Melania Nynka and Ruan, {John J.} and Vicky Kalogera and Cenko, {S. Bradley} and Phil Evans and Kennea, {Jamie A.}",

note = "Funding Information: We dedicate this work to the memory of Neil Gehrels, one of the original PIs for our Chandra proposal and an active participant in the early months of the program. Neil{\textquoteright}s stewardship of Swift has influenced our entire community—this short γ-ray burst and its coincidence with a LIGO-Virgo GW source would have thrilled him. The authors also owe a debt of gratitude to Belinda Wilkes and the Chandra scheduling, data processing, and archive teams. Their incredibly fast work was essential to making these time-sensitive observations possible. We also thank our anonymous referee for their timely review and useful comments. We thank Sean McWilliams for his useful input. This work was supported by Chandra Award Number GO7-18033X, issued by the Chandra X-Ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration (NASA) under contract NAS8-03060. D.H. acknowledges support from the Canadian Institute for Advanced Research (CIFAR). D.H., M.N., and J.J.R. also acknowledge support from a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant and a Fonds de recherche du Qu{\'e}bec-Nature et Technologies (FRQNT) Nouveaux Chercheurs Grant. P.A.E. acknowledges UKSA support. J.A.K. acknowledges the support of NASA grant NAS5-00136. Publisher Copyright: {\textcopyright} 2017. The American Astronomical Society. All rights reserved.",

year = "2017",

month = oct,

day = "20",

doi = "10.3847/2041-8213/aa8ede",

language = "English (US)",

volume = "848",

journal = "Astrophysical Journal Letters",

issn = "2041-8205",

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TY - JOUR

T1 - A Deep Chandra X-Ray Study of Neutron Star Coalescence GW170817

AU - Haggard, Daryl

AU - Nynka, Melania

AU - Ruan, John J.

AU - Kalogera, Vicky

AU - Cenko, S. Bradley

AU - Evans, Phil

AU - Kennea, Jamie A.

N1 - Funding Information: We dedicate this work to the memory of Neil Gehrels, one of the original PIs for our Chandra proposal and an active participant in the early months of the program. Neil’s stewardship of Swift has influenced our entire community—this short γ-ray burst and its coincidence with a LIGO-Virgo GW source would have thrilled him. The authors also owe a debt of gratitude to Belinda Wilkes and the Chandra scheduling, data processing, and archive teams. Their incredibly fast work was essential to making these time-sensitive observations possible. We also thank our anonymous referee for their timely review and useful comments. We thank Sean McWilliams for his useful input. This work was supported by Chandra Award Number GO7-18033X, issued by the Chandra X-Ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration (NASA) under contract NAS8-03060. D.H. acknowledges support from the Canadian Institute for Advanced Research (CIFAR). D.H., M.N., and J.J.R. also acknowledge support from a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant and a Fonds de recherche du Québec-Nature et Technologies (FRQNT) Nouveaux Chercheurs Grant. P.A.E. acknowledges UKSA support. J.A.K. acknowledges the support of NASA grant NAS5-00136. Publisher Copyright: © 2017. The American Astronomical Society. All rights reserved.

PY - 2017/10/20

Y1 - 2017/10/20

N2 - We report Chandra observations of GW170817, the first neutron star-neutron star merger discovered by the joint LIGO-Virgo Collaboration, and the first direct detection of gravitational radiation associated with an electromagnetic counterpart, Fermi short γ-ray burst GRB 170817A. The event occurred on 2017 August 17 and subsequent observations identified an optical counterpart, SSS17a, coincident with NGC 4993 (∼10″ separation). Early Chandra (Δt ∼ 2 days) and Swift (Δt ∼ 1-3 days) observations yielded non-detections at the optical position, but ∼9 days post-trigger Chandra monitoring revealed an X-ray point source coincident with SSS17a. We present two deep Chandra observations totaling ∼95 ks, collected on 2017 September 01-02 (Δt ∼ 15-16 days). We detect X-ray emission from SSS17a with L0.3-10 keV = 2.6+0.5-0.4 × 1038erg s-1, and a power law spectrum of Γ = 2.4 ± 0.8. We find that the X-ray light curve from a binary NS coalescence associated with this source is consistent with the afterglow from an off-axis short γ-ray burst, with a jet angled ≳23° from the line of sight. This event marks both the first electromagnetic counterpart to a LIGO-Virgo gravitational-wave source and the first identification of an off-axis short GRB. We also confirm extended X-ray emission from NGC 4993 (L0.3-10 keV ∼9 ×1038 erg s-1) consistent with its E/S0 galaxy classification, and report two new Chandra point sources in this field, CXOU J130948 and CXOU J130946.

AB - We report Chandra observations of GW170817, the first neutron star-neutron star merger discovered by the joint LIGO-Virgo Collaboration, and the first direct detection of gravitational radiation associated with an electromagnetic counterpart, Fermi short γ-ray burst GRB 170817A. The event occurred on 2017 August 17 and subsequent observations identified an optical counterpart, SSS17a, coincident with NGC 4993 (∼10″ separation). Early Chandra (Δt ∼ 2 days) and Swift (Δt ∼ 1-3 days) observations yielded non-detections at the optical position, but ∼9 days post-trigger Chandra monitoring revealed an X-ray point source coincident with SSS17a. We present two deep Chandra observations totaling ∼95 ks, collected on 2017 September 01-02 (Δt ∼ 15-16 days). We detect X-ray emission from SSS17a with L0.3-10 keV = 2.6+0.5-0.4 × 1038erg s-1, and a power law spectrum of Γ = 2.4 ± 0.8. We find that the X-ray light curve from a binary NS coalescence associated with this source is consistent with the afterglow from an off-axis short γ-ray burst, with a jet angled ≳23° from the line of sight. This event marks both the first electromagnetic counterpart to a LIGO-Virgo gravitational-wave source and the first identification of an off-axis short GRB. We also confirm extended X-ray emission from NGC 4993 (L0.3-10 keV ∼9 ×1038 erg s-1) consistent with its E/S0 galaxy classification, and report two new Chandra point sources in this field, CXOU J130948 and CXOU J130946.

KW - X-rays: binaries

KW - galaxies: individual (NGC 4993)

KW - gamma-ray burst: individual (GRB 170817A)

KW - gravitational waves

KW - stars: neutron

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U2 - 10.3847/2041-8213/aa8ede

DO - 10.3847/2041-8213/aa8ede

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SN - 2041-8205

VL - 848

JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

IS - 2

M1 - L25

ER -

A Deep Chandra X-Ray Study of Neutron Star Coalescence GW170817

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Keywords

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