Shocks and dust formation in nova V809 Cep
Shocks and dust formation in nova V809 Cep
复制标题
nova V809 Cep 中的冲击和灰尘形成
DOI：
10.1093/mnras/stac1366
复制
发表时间：
2022
影响因子：
4.8
通讯作者：
Mukai, Koji
中科院分区：
文献类型：
--
作者：
Babul, Aliya-Nur;Sokoloski, Jennifer L.;Chomiuk, Laura;Linford, Justin D.;Weston, Jennifer H. S.;Aydi, Elias;Sokolovsky, Kirill V.;Kawash, Adam M.;Mukai, Koji
许多经典新星产生可探测的GeV γ射线辐射的发现提出了冲击在新星爆发中的作用的问题。在这里，我们使用Jansky甚大阵列对新星V809 Cep（新星Cep 2013）的射电观测表明，它产生的非热发射表明，从爆发后大约6周开始，在强冲击中粒子加速了一个多月，几乎与尘埃的产生同时发生。一般来说，在火山爆发的后期——大约6个月左右——的无线电发射与自由膨胀的104K喷出物的热辐射是一致的。然而，在4.6 GHz和7.4 GHz处，射电光曲线在发现爆发后的76 d内显示出一个初始的早期峰值。在第76天，4.6 GHz的亮度温度大于105K，比预期的热发射高一个数量级。我们认为，亮度温度是由喷射物内部激波引起的同步辐射的结果。无线电频谱的演变与同步加速器发射在高频之前达到峰值的情况是一致的，这表明来自激波的同步加速器最初受到激波前光学厚电离物质的自由-自由吸收。尘埃形成大约在第37天开始，我们认为喷出物中的内部冲击在尘埃形成之前就已经形成，并导致了尘埃的成核。
The discovery that many classical novae produce detectable GeV γ-ray emission has raised the question of the role of shocks in nova eruptions. Here, we use radio observations of nova V809 Cep (nova Cep 2013) with the Jansky Very Large Array to show that it produced non-thermal emission indicative of particle acceleration in strong shocks for more than a month starting about 6 weeks into the eruption, quasi-simultaneous with the production of dust. Broadly speaking, the radio emission at late times – more than 6 months or so into the eruption – is consistent with thermal emission fromof freely expanding, 104K ejecta. At 4.6 and 7.4 GHz, however, the radio light curves display an initial early-time peak 76 d after the discovery of the eruption in the optical (t0). The brightness temperature at 4.6 GHz on day 76 was greater than 105K, an order of magnitude above what is expected for thermal emission. We argue that the brightness temperature is the result of synchrotron emission due to internal shocks within the ejecta. The evolution of the radio spectrum was consistent with synchrotron emission that peaked at high frequencies before low frequencies, suggesting that the synchrotron from the shock was initially subject to free–free absorption by optically thick ionized material in front of the shock. Dust formation began around day 37, and we suggest that internal shocks in the ejecta were established prior to dust formation and caused the nucleation of dust.