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标题：Magnetic field estimates from the X-ray synchrotron emitting rims of the 30 Dor C superbubble and the implications for the nature of 30 Dor C’s TeV emission
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作者：Patrick J. Kavanagh ; Jacco Vink ; Manami Sasaki 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2019
卷号：621
DOI：10.1051/0004-6361/201833659
语种：English
出版社：EDP Sciences
摘要：Context.The 30 Dor C superbubble is unique for its synchrotron X-ray shell, as well as being the first superbubble to be detected in TeVγ-rays, though which is the dominant TeV emission mechanism, leptonic or hadronic, is still unclear.Aims.We aim to use newChandraobservations of 30 Dor C to resolve the synchrotron shell in unprecedented detail and to estimate the magnetic (B) field in the postshock region, a key discriminator between TeVγ-ray emission mechanisms.Methods.We extracted radial profiles in the 1.5–8 keV range from various sectors around the synchrotron shell and fitted these with a projected and point spread function convolved postshock volumetric emissivity model to determine the filament widths. We then calculated the postshock magnetic field strength from these widths.Results.We find that most of the sectors were well fitted with our postshock model and the determinedB-field values were low, all with best fits ≲20 μG. Upper limits on the confidence intervals of three sectors reached ≳30 μG though these were poorly constrained. The generally lowB-field values suggests a leptonic-dominated origin for the TeVγ-rays. Our postshock model did not provide adequate fits to two sectors. We find that one sector simply did not provide a clean enough radial profile, while the other could be fitted with a modified postshock model where the projected profile falls off abruptly below ~0.8 times the shell radius, yielding a postshockB-field of 4.8 (3.7–11.8)μG which is again consistent with the leptonic TeVγ-ray mechanism. Alternatively, the observed profiles in these sectors could result from synchrotron enhancements around a shock–cloud interaction as suggested in previous works.Conclusions.The average postshockB-field determined around the X-ray synchrotron shell of 30 Dor C suggests the leptonic scenario as the dominant emission mechanism for the TeVγ-rays.
关键词：Key wordsenISM: supernova remnantsISM: bubblesMagellanic CloudsX-rays: ISMISM: magnetic fields