A mildly relativistic wide-angle outflow in the neutron-star merger event GW170817
A mildly relativistic wide-angle outflow in the neutron-star merger event GW170817
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DOI：
10.1038/nature25452
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发表时间：
2017-11
期刊：
影响因子：
64.8
通讯作者：
K. Mooley;E. Nakar;K. Hotokezaka;G. Hallinan;A. Corsi;D. Frail;A. Horesh;T. Murphy;E. Lenc;D. Kaplan;K. De;D. Dobie;P. Chandra;A. Deller;O. Gottlieb;M. Kasliwal;S. Kulkarni;S. Myers;S. Nissanke;T. Piran;C. Lynch;V. Bhalerao;S. Bourke;K. Bannister;L. Oxford;Nrao;Caltech;T. University;P. University;Texas Tech University;The Hebrew University of Jerusalem;U. Sydney;Caastro;U. O. W. Milwaukee;Atnf;Csiro;Ncra;S. University;S. U. Technology;R. University;Iit Bombay;C. Technology;Nasa Gsfc;Jansky Fellow;NRAOCaltech
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作者：
K. Mooley;E. Nakar;K. Hotokezaka;G. Hallinan;A. Corsi;D. Frail;A. Horesh;T. Murphy;E. Lenc;D. Kaplan;K. De;D. Dobie;P. Chandra;A. Deller;O. Gottlieb;M. Kasliwal;S. Kulkarni;S. Myers;S. Nissanke;T. Piran;C. Lynch;V. Bhalerao;S. Bourke;K. Bannister;L. Oxford;Nrao;Caltech;T. University;P. University;Texas Tech University;The Hebrew University of Jerusalem;U. Sydney;Caastro;U. O. W. Milwaukee;Atnf;Csiro;Ncra;S. University;S. U. Technology;R. University;Iit Bombay;C. Technology;Nasa Gsfc;Jansky Fellow;NRAOCaltech
GW170817是第一次利用引力波探测到中子星合并的双星。它伴随着电磁波谱的辐射，并定位于距离40兆秒差距的星系NGC 4993。有人提出，观测到的γ射线、X射线和射电辐射是由于在合并过程中发射的超相对论喷流（并成功地从周围的物质中爆发出来），偏离了我们的视线（离轴）。这种喷流的存在是从模型中预测的，该模型将中子星合并作为短硬γ射线爆发的驱动因素。在这里，我们报告说，无线电光变曲线的GW 170817没有直接的签名的余辉离轴喷流。虽然我们不能完全排除喷流的存在，但观测到的γ射线发射不可能来自这样的喷流。相反，无线电数据需要存在一个温和的相对论性广角外流向我们移动。这种外流可能是在合并过程中动态喷出的富含中子的物质的高速尾部，或者是在合并过程中发射的射流将其能量转移到动态喷出物时破裂的物质茧。由于茧模型解释了GW 170817的射电光变曲线，以及γ射线和X射线发射（也可能是紫外线和光学发射），它是与观测数据最一致的模型。茧可能是中子星合并中产生的普遍现象，在局部宇宙中产生了迄今尚未确定的射电、紫外线、X射线和γ射线瞬变。
GW170817 was the first gravitational-wave detection of a binary neutron-star merger. It was accompanied by radiation across the electromagnetic spectrum and localized to the galaxy NGC 4993 at a distance of 40 megaparsecs. It has been proposed that the observed γ-ray, X-ray and radio emission is due to an ultra-relativistic jet being launched during the merger (and successfully breaking out of the surrounding material), directed away from our line of sight (off-axis),,,. The presence of such a jet is predicted from models that posit neutron-star mergers as the drivers of short hard-γ-ray bursts,. Here we report that the radio light curve of GW170817 has no direct signature of the afterglow of an off-axis jet. Although we cannot completely rule out the existence of a jet directed away from the line of sight, the observed γ-ray emission could not have originated from such a jet. Instead, the radio data require the existence of a mildly relativistic wide-angle outflow moving towards us. This outflow could be the high-velocity tail of the neutron-rich material that was ejected dynamically during the merger, or a cocoon of material that breaks out when a jet launched during the merger transfers its energy to the dynamical ejecta. Because the cocoon model explains the radio light curve of GW170817, as well as the γ-ray and X-ray emission (and possibly also the ultraviolet and optical emission),,,,,,, it is the model that is most consistent with the observational data. Cocoons may be a ubiquitous phenomenon produced in neutron-star mergers, giving rise to a hitherto unidentified population of radio, ultraviolet, X-ray and γ-ray transients in the local Universe.