The light curve of the explosion of a star with a radius 10-100 R ☉ is powered mostly by radioactive decay. Observationally, such events are dominated by hydrogen-deficient progenitors and classified as Type I supernovae (SNe I), i.e., white dwarf thermonuclear explosions (Type Ia), and core collapses of hydrogen-stripped massive stars (Type Ib/c). Current transient surveys are finding SNe I in increasing numbers and at earlier times, allowing their early emission to be studied in unprecedented detail. Motivated by these developments, we summarize the physics that produces their rising light curves and discuss ways in which observations can be utilized to study these exploding stars. The early radioactive-powered light curves probe the shallowest deposits of 56Ni. If the amount of 56Ni mixing in the outermost layers of the star can be deduced, then it places important constraints on the progenitor and properties of the explosive burning. In practice, we find that it is difficult to determine the level of mixing because it is hard to disentangle whether the explosion occurred recently and one is seeing radioactive heating near the surface or whether the explosion began in the past and the radioactive heating is deeper in the ejecta. In the latter case, there is a "dark phase" between the moment of explosion and the first observed light emitted once the shallowest layers of 56Ni are exposed. Because of this, simply extrapolating a light curve from radioactive heating back in time is not a reliable method for estimating the explosion time. The best solution is to directly identify the moment of explosion, either through observing shock breakout (in X-ray/UV) or the cooling of the shock-heated surface (in UV/optical), so that the depth being probed by the rising light curve is known. However, since this is typically not available, we identify and discuss a number of other diagnostics that are helpful for deciphering how recently an explosion occurred. As an example, we apply these arguments to the recent SN Ic PTF 10vgv. We demonstrate that just a single measurement of the photospheric velocity and temperature during the rise places interesting constraints on its explosion time, radius, and level of 56Ni mixing.
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机译：半径为10-100 R radius的恒星爆炸的光曲线主要由放射性衰变提供动力。观察到，此类事件主要由缺氢的祖先控制，被分类为I型超新星（SNe I），即白矮星热核爆炸（Ia型）和氢剥落的大质量恒星的核心坍塌（Ib / c型）。当前的瞬态调查发现SNe I的数量越来越多，而且出现的时间更早，因此可以对它们的早期排放进行前所未有的详细研究。受这些发展的推动，我们总结了产生其上升光曲线的物理学，并讨论了利用观测方法研究这些爆炸恒星的方法。早期的放射性光曲线探测了56Ni最浅的沉积物。如果可以推断出恒星最外层中56Ni的混合量，那么它将对爆炸物的祖先和性质产生重要的限制。在实践中，我们发现很难确定混合水平，因为很难弄清爆炸是否是最近发生的，人们是否在地表附近看到放射性加热或过去是否发生爆炸以及放射性加热是否更深。弹出。在后一种情况下，一旦暴露出最浅的56Ni层，则在爆炸时刻与首次观察到的光之间存在“暗相”。因此，简单地从放射性加热中及时推断出光曲线并不是估算爆炸时间的可靠方法。最好的解决方案是直接观察爆炸时刻，方法是观察震动的爆发（在X射线/紫外线下）或冷却被加热的表面（在紫外线/光学下），以便通过上升来探测深度光曲线是已知的。但是，由于通常不可用，因此我们确定并讨论了许多其他诊断方法，这些方法有助于破译爆炸的发生时间。例如，我们将这些参数应用于最近的SN Ic PTF 10vgv。我们证明，仅对上升过程中光球速度和温度的单个测量就对其爆炸时间，半径和56Ni混合水平产生了有趣的约束。
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