The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. V. Rising X-Ray Emission from an Off-axis Jet
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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DOI：
10.3847/2041-8213/aa9057
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发表时间：
2017-10
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通讯作者：
R. Margutti;E. Berger;W. Fong;C. Guidorzi;K. Alexander;B. Metzger;P. Blanchard;P. Cowperthwaite;R. Chornock;T. Efterkari;M. Nicholl;V. Villar;P. G. Williams;J. Annis;D. Brown;H. Chen;Zoheyr Doctor;J. Frieman;D. Holz;M. Sako;M. Soares-Santos
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作者：
R. Margutti;E. Berger;W. Fong;C. Guidorzi;K. Alexander;B. Metzger;P. Blanchard;P. Cowperthwaite;R. Chornock;T. Efterkari;M. Nicholl;V. Villar;P. G. Williams;J. Annis;D. Brown;H. Chen;Zoheyr Doctor;J. Frieman;D. Holz;M. Sako;M. Soares-Santos
本文报道了中子星星合并事件GW 170817中X射线辐射的发现。这是第一次探测到来自引力波（GW）源的X射线发射。钱德拉X射线天文台（CXO）在合并后2.3天的观测结果显示没有显著的辐射，其辐射强度为Lx = 3.2 × 10 38 erg s − 1（各向同性当量）。持续的监测显示X射线源的存在，随着时间的推移而变亮，在合并后的15.1天达到L x 109 × 10 38 erg s − 1。我们解释这些研究结果的上下文中的各向同性和准直相对论流出（轴上和轴外）。我们发现，从射电观测到的宽带X射线与动能为Ek = 10 49 − 50 erg的相对论喷流的发射是一致的，离轴观察θ obs = 20 ° - 40 °。我们的模型倾向于环双星的密度n = 10 − 4 - 10 − 2 cm − 3，这取决于微物理参数B = 10 − 4 - 10 − 2的值。X射线发射的中央引擎起源是不可能的。未来的X射线观测在t = 100天，当目标将再次观察到CXO，将提供额外的约束，以解决模型退化和测试我们的预测。我们对θ obs的推断是可以用来自先进LIGO/Virgo的GW 170817上的GW信息进行检验的。
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 k ∼ 10 49 − 50 erg , 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 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.