High-resolution radio imaging of the two particle-accelerating colliding-wind binaries HD 167971 and HD 168112
High-resolution radio imaging of the two particle-accelerating colliding-wind binaries HD 167971 and HD 168112
复制标题
两个粒子加速碰撞风双星 HD 167971 和 HD 168112 的高分辨率射电成像
DOI：
10.1051/0004-6361/202348622
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发表时间：
2024
影响因子：
6.5
通讯作者：
De Becker M
中科院分区：
文献类型：
--
作者：
De Becker M
上下文。由大质量恒星组成的双星系统中的碰撞风区使我们能够研究激波物理学的各个方面，包括粒子加速。这类粒子加速器主要是由于它们的同步辐射而被识别出来的，并被称为粒子加速对撞风双星。我们的目标是首先验证这样一个概念，即获得大质量双星的快照高分辨率无线电图像构成了明确识别粒子加速器的相关方法。其次，我们打算利用这些图像来表征两个特定目标的同步辐射，HD 167971和HD 168112，这是已知的粒子加速器。我们用欧洲甚长基线干涉测量（VLBI）网络追踪了两个目标在1.6 GHz的无线电发射，角度分辨率为几毫弧秒。我们的测量使我们能够获得两个目标的图像。对于HD 167971，我们的观测发生在接近apastron的轨道阶段，同步辐射最小。对于hd168112，我们首次解析了同步辐射区域。发射区域略显拉长，与预期的碰撞风区域一致。在这两种情况下，测量到的辐射都明显强于预期的恒星风的热发射，这有力地支持了它们的非热性质。我们的研究为碰撞风双星的高角分辨率无线电成像问题提供了重要的贡献。我们表明，快照VLBI测量构成了研究这些物体的有效方法，在识别额外的粒子加速器方面取得了有希望的结果，加上它们在揭示长周期双星方面的适用性。
Context. The colliding-wind region in binary systems made up of massive stars allows us to investigate various aspects of shock physics, including particle acceleration. Particle accelerators of this kind are mainly identified thanks to their synchrotron radio emission and dubbed particle-accelerating colliding-wind binaries.Aims. Our objective is first to validate the notion that obtaining snapshot high-resolution radio images of massive binaries constitutes a relevant approach to unambiguously identifying particle accelerators. Second, we intend to exploit these images to characterise the synchrotron emission of two specific targets, HD 167971 and HD 168112, which are known particle accelerators.Methods. We traced the radio emission from the two targets at 1.6 GHz with the European Very Long Baseline Interferometry (VLBI) Network, with an angular resolution of a few milli-arcseconds.Results. Our measurements allowed us to obtain images for both targets. For HD 167971, our observation occurs close to apastron, at an orbital phase where the synchrotron emission is at minimum. For HD 168112, we resolved for the very first time the synchrotron emission region. The emission region appears slightly elongated, in agreement with the expectations for a colliding-wind region. In both cases, the measured emission is significantly stronger than the expected thermal emission from the stellar winds, lending strong support to their non-thermal nature.Conclusions. Our study offers a significant contribution to the still poorly addressed question of high angular resolution radio imaging of colliding-wind binaries. We show that snapshot VLBI measurements constitute an efficient approach to investigate these objects, with promising results in terms of the identification of additional particle accelerators, coupled with their applicability in revealing long-period binaries.