科研之友
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摘要
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 gamma-ray burst GRB 170817A. The event occurred on 2017 August 17 and subsequent observations identified an optical counterpart, SSS17a, coincident with NGC 4993 (similar to 10 '' separation). Early Chandra (Delta t similar to 2 days) and Swift (Delta t similar to 1-3 days) observations yielded nondetections at the optical position, but similar to 9 days post-trigger Chandra monitoring revealed an X-ray point source coincident with SSS17a. We present two deep Chandra observations totaling similar to 95 ks, collected on 2017 September 01-02 (Delta t similar to 15- 16 days). We detect X-ray emission from SSS17a with L0.3-10 (keV) = 2.6 (+0.5)(-0.4) x 10(38) ergs(-1), and a power law spectrum of Gamma= 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 gamma- ray burst, with a jet angled. greater than or similar to 23 degrees 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) similar to 9 x 10(38) 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.
- 出版日期2017-10-20
- 单位McGill; 西北大学
