Long-Term Radio Monitoring of SN 1993J
Long-Term Radio Monitoring of SN 1993J
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DOI：
10.1086/523258
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发表时间：
2007-09
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影响因子：
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通讯作者：
K. Weiler;Christopher L. Williams;Christopher L. Williams;N. Panagia;N. Panagia;C. Stockdale;M. Kelley;R. Sramek;S. V. Dyk;J. Marcaide
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作者：
K. Weiler;Christopher L. Williams;Christopher L. Williams;N. Panagia;N. Panagia;C. Stockdale;M. Kelley;R. Sramek;S. V. Dyk;J. Marcaide
我们提出了我们对超新星（SN）1993 J的无线电发射的广泛观测，在M81（NGC 3031），在90，20，6，3.6，2，1.2，和0.7厘米，以及从其他望远镜和其他波长的许多测量。合并后的数据集可能是对本星系群以外任何波长范围内的任何SN所确定的最详细的一套测量数据。无线电发射在时间和频率上都有规律地演变，通常的解释是激波与由前超新星恒星风形成的星周介质（CSM）相互作用，这很好地描述了观测结果。然而，（1）早期（<40天）在85-110 GHz的最高频率测量值不能很好地拟合描述厘米波长测量的参数化。(2)在中厘米波长处，经常会出现与拟合的射电光曲线的偏差。(3)在冲击波爆发后约3100天，射电辐射的衰减率从（t+ β）β <$− 0.7陡升到-2.7，而谱指数（ν+ α; α <$− 0.81）没有变化;然而，这种衰减最好不是用幂律来描述，而是用指数衰减来描述，e折叠时间约为1100天。(4)所有数据的最佳整体拟合是一个模型，包括非热同步加速器自吸收（SSA）和热自由吸收（FFA）组件在早期，发展到一个恒定的光谱指数，光学薄下降率，直到打破。(5)无线电和X射线光变曲线显示出非常相似的行为，都表明超新星前身质量损失率的突然增加发生在冲击爆发前约8000年。
We present our extensive observations of the radio emission from supernova (SN) 1993J, in M81 (NGC 3031), made with the Very Large Array, at 90, 20, 6, 3.6, 2, 1.2, and 0.7 cm, as well as numerous measurements from other telescopes and at other wavelengths. The combined data set constitutes probably the most detailed set of measurements ever established for any SN outside of the Local Group in any wavelength range. The radio emission evolves regularly in both time and frequency, and the usual interpretation in terms of shock interaction with a circumstellar medium (CSM) formed by a pre-supernova stellar wind describes the observations rather well. However, (1) The highest frequency measurements at 85-110 GHz at early times (<40 days) are not well fitted by the parameterization which describes the centimeter wavelength measurements. (2) At midcentimeter wavelengths there is often deviation from the fitted radio light curves. (3) At a time ~3100 days after shock breakout, the decline rate of the radio emission steepens from (t+ β) β ∼ − 0.7 to –2.7 without change in the spectral index (ν+ α; α ∼ − 0.81); however, this decline is best described not as a power-law, but as an exponential decay with an e-folding time of ~1100 days. (4) The best overall fit to all of the data is a model including both nonthermal synchrotron self-absorption (SSA) and thermal free-free absorbing (FFA) components at early times, evolving to a constant spectral index, optically thin decline rate until the break. (5) The radio and X-ray light curves display quite similar behavior and both suggest a sudden increase in the supernova progenitor mass-loss rate occurred at ~8000 yr prior to shock breakout.