利用MeerKAT与LOFAR对再发新星RS Ophiuchi的低频射电观测
Low-frequency radio observations of recurrent nova RS Ophiuchi with MeerKAT and LOFAR
AI总结：
本研究利用MeerKAT和LOFAR对2021年再发新星RS Ophiuchi爆发开展低频射电观测，通过光变曲线建模验证非热辐射机制，约束红巨星质量损失率，并提出后续观测策略。
摘要：
我们报告了对2021年再发新星RS Ophiuchi爆发事件的低频射电观测结果，这些观测涵盖了该系统迄今为止频率最低的观测数据。我们通过MeerKAT在0.82 GHz与1.28 GHz频段、LOFAR在54 MHz与154 MHz频段获取了详细的光变曲线。这些低频探测结果让我们得以对亮温度施加严格约束，明确支持非热辐射机制的结论。我们将该射电辐射解释并建模为新星抛射物与双星周介质激波相互作用产生的同步辐射。光变曲线在首个峰值后呈现平台化特征，这一现象可由双星周介质密度不均匀或存在第二个辐射分量两种情形解释。在光变曲线建模中引入第二个分量，能够复现晚期的快速衰减过程。此外，将该模型外推至爆发后15年的结果显示，两次爆发之间射电辐射可能不会完全消失。对光变曲线的进一步建模表明，红巨星的质量损失率约为$5 \times 10^{-8}~{\rm M_\bullet~yr^{-1}}$。由于可能存在至少四个辐射分量，目前尚无法对光谱进行详细建模。我们排除了恒星风或同步辐射喷流作为该射电辐射起源的可能性。最后，我们提出了一项未来观测策略，将推动我们对RS Ophiuchi物理性质的理解。
英文摘要：
We report low-frequency radio observations of the 2021 outburst of the recurrent nova RS Ophiuchi. These observations include the lowest frequency observations of this system to date. Detailed light curves are obtained by MeerKAT at 0.82 and 1.28 GHz and LOFAR at 54 and 154 MHz. These low-frequency detections allow us to put stringent constraints on the brightness temperature that clearly favour a non-thermal emission mechanism. The radio emission is interpreted and modelled as synchrotron emission from the shock interaction between the nova ejecta and the circumbinary medium. The light curve shows a plateauing behaviour after the first peak, which can be explained by either a non-uniform density of the circumbinary medium or a second emission component. Allowing for a second component in the light-curve modelling captures the steep decay at late times. Furthermore, extrapolating this model to 15 yr after the outburst shows that the radio emission might not fully disappear between outbursts. Further modelling of the light curves indicates a red giant mass-loss rate of $\sim 5 \cdot 10^{-8}~{\rm M_\odot~yr^{-1}}$. The spectrum cannot be modelled in detail at this stage, as there are likely at least four emission components. Radio emission from stellar wind or synchrotron jets is ruled out as the possible origin of the radio emission. Finally, we suggest a strategy for future observations that would advance our understanding of the physical properties of RS Ophiuchi.
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