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arXiv 2104.04540astro-ph.HE
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用LOFAR观测天鹅座X-3的强低频射电耀斑

Strong low-frequency radio flaring from Cygnus X-3 observed with LOFAR

J. W. Broderick, T. D. Russell, R. P. Fender, S. A. Trushkin, D. A. Green, J. Chauhan, N. A. Nizhelskij, P. G. Tsybulev, N. N. Bursov, A. V. Shevchenko, G. G. P… 展开作者

J. W. Broderick, T. D. Russell, R. P. Fender, S. A. Trushkin, D. A. Green, J. Chauhan, N. A. Nizhelskij, P. G. Tsybulev, N. N. Bursov, A. V. Shevchenko, G. G. Pooley, D. R. A. Williams, J. S. Bright, A. Rowlinson, S. Corbel

摘要:

我们介绍了2019年5月期间X射线双星天鹅座X-3的低频阵列(LOFAR)143.5 MHz射电观测。与天鹅座X-3之前爆发的无线电观测类似,我们发现该源在低频时变化显着,最大通量密度约为5.8 Jy。我们比较我们的LOFAR光变曲线与同期的观测在1.25和2.3 GHz的RATAN-600望远镜,并在15 GHz的弧分钟Microkelvin成像仪(AMI)大阵列。最初的143.5兆赫的通量密度水平,$\sim$ 2 Jy,被认为是延迟和可能的混合发射,至少有一些耀斑活动,已被发现在较高的频率之前,我们的LOFAR观测已经开始。也有证据表明,在5月6日的2.3和15 GHz的明亮耀斑与143.5 MHz的相应峰值($\gtrsim$ 5.8 Jy)之间有超过4天的延迟。根据多频光变曲线,我们估计产生这种耀斑所需的最小能量和磁场分别约为10 $^{44}$ erg和40 mG,对应于$\sim$ 10 $^{38}$ erg s $^{-1}$的最小平均功率。此外,我们表明,宽带无线电频谱演变的过程中,我们的观测活动,特别是143.5 MHz和1.25 GHz之间的两点光谱指数从光学厚过渡到光学薄的耀斑同时在143.5 MHz和衰落GHz的频率。

英文摘要:

We present Low-Frequency Array (LOFAR) 143.5-MHz radio observations of flaring activity during 2019 May from the X-ray binary Cygnus X-3. Similar to radio observations of previous outbursts from Cygnus X-3, we find that this source was significantly variable at low frequencies, reaching a maximum flux density of about 5.8 Jy. We compare our LOFAR light curve with contemporaneous observations taken at 1.25 and 2.3 GHz with the RATAN-600 telescope, and at 15 GHz with the Arcminute Microkelvin Imager (AMI) Large Array. The initial 143.5-MHz flux density level, $\sim$2 Jy, is suggested to be the delayed and possibly blended emission from at least some of the flaring activity that had been detected at higher frequencies before our LOFAR observations had begun. There is also evidence of a delay of more than four days between a bright flare that initially peaked on May 6 at 2.3 and 15 GHz, and the corresponding peak ($\gtrsim$ 5.8 Jy) at 143.5 MHz. From the multi-frequency light curves, we estimate the minimum energy and magnetic field required to produce this flare to be roughly 10$^{44}$ erg and 40 mG, respectively, corresponding to a minimum mean power of $\sim$10$^{38}$ erg s$^{-1}$. Additionally, we show that the broadband radio spectrum evolved over the course of our observing campaign; in particular, the two-point spectral index between 143.5 MHz and 1.25 GHz transitioned from being optically thick to optically thin as the flare simultaneously brightened at 143.5 MHz and faded at GHz frequencies.

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