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arXiv 1502.00645astro-ph.HE
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GRB 101219 B黑洞附近喷流发射的证据--热发射主导的费米GRB

Evidence for jet launching close to the black hole in GRB 101219B - a Fermi GRB dominated by thermal emission

J. Larsson, J. L. Racusin, J. M. Burgess

摘要:

本文介绍费米伽玛射线空间望远镜伽马射线暴监测器(GBM)对附近(z=0.55)GRB 101219 B的观测。这次爆发是一个长的伽玛暴,伴随着一颗超新星和一个黑体成分,在雨燕X射线望远镜(XRT)观测到的早期余辉中被探测到。在这里,我们表明,即时伽马射线发射有一个黑体光谱,使这第二个这样的爆发观察费米GBM。黑体的性质,加上红移和我们对辐射效率的估计,使得有可能计算出流出物性质的绝对值。我们得到了初始洛伦兹因子γ =138 \pm 8,光球半径r_phot=4.4 \pm 1.9 \times 10^{11} cm,发射半径r_0 =2.7 \pm 1.6 \times 10^{7} cm。后一个值接近黑洞,表明喷流在恒星中有一条相对畅通的路径。GBM和XRT观测到的黑体分量之间没有平滑的联系,排除了后期发射是由于高纬度效应的可能性。在解释XRT黑体是由于后期中央发动机活动引起的即时发射时,射流必须非常宽或具有团簇结构,其中发射来自小块。对这一成分的其他解释,例如从围绕射流的茧中发射,也是可能的。

英文摘要:

We present observations by the Fermi Gamma-Ray Space Telescope Gamma-Ray Burst Monitor (GBM) of the nearby (z=0.55) GRB 101219B. This burst is a long GRB, with an associated supernova and with a blackbody component detected in the early afterglow observed by the Swift X-ray Telescope (XRT). Here we show that the prompt gamma-ray emission has a blackbody spectrum, making this the second such burst observed by Fermi GBM. The properties of the blackbody, together with the redshift and our estimate of the radiative efficiency, makes it possible to calculate the absolute values of the properties of the outflow. We obtain an initial Lorentz factor Gamma=138\pm 8, a photospheric radius r_phot=4.4\pm 1.9 \times 10^{11} cm and a launch radius r_0=2.7\pm 1.6 \times 10^{7} cm. The latter value is close to the black hole and suggests that the jet has a relatively unobstructed path through the star. There is no smooth connection between the blackbody components seen by GBM and XRT, ruling out the scenario that the late emission is due to high-latitude effects. In the interpretation that the XRT blackbody is prompt emission due to late central engine activity, the jet either has to be very wide or have a clumpy structure where the emission originates from a small patch. Other explanations for this component, such as emission from a cocoon surrounding the jet, are also possible.

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