PROBING SHOCK BREAKOUT AND PROGENITORS OF STRIPPED-ENVELOPE SUPERNOVAE THROUGH THEIR EARLY RADIO EMISSIONS
PROBING SHOCK BREAKOUT AND PROGENITORS OF STRIPPED-ENVELOPE SUPERNOVAE THROUGH THEIR EARLY RADIO EMISSIONS
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DOI：
10.1088/0004-637x/762/1/14
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发表时间：
2012-09
期刊：
影响因子：
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通讯作者：
K. Maeda
中科院分区：
文献类型：
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作者：
K. Maeda
我们研究了剥离包层超新星（SNe， IIb/Ib/Ic型超新星）早期射电发射的性质。根据它们的射电特性，我们认为存在一个剥离包膜SNe的亚类，包括光学上得到充分研究的Ic型SNe (SNe Ic) 2002ap和2007gr，它们在10天内迅速上升到射电峰值，并达到低亮度（至少比大多数SNe IIb/Ib/Ic暗一个数量级）。它们的峰后衰减幅度比其他带状包络SNe的峰后衰减幅度浅，但它们的光谱指数相似。我们表明，如果星周物质（CSM）密度低，那么所有这些特性都可以自然解释，因此正向激波在没有减速的情况下扩展到CSM。由于在这种情况下，根据射电特性估计的正向激波速度仍然记录了激波爆发后SN喷射的最大速度，因此在射电波长中观察这些SNe提供了对爆发和前身性质的新诊断，否则需要在其他波长中进行相当快速的跟踪。推断出snic 2002ap和2007gr的震后爆发速度是次相对论性的，约0.3c。这些都比SN II 1987A推断的要高，与所建议的致密祖星系一致。然而，这些比沃尔夫-拉叶（W-R）祖先的预期要低。这可能反映了爆炸前祖星尚未确定的性质，我们认为W-R祖星包膜可能已经膨胀，这可能会迅速降低初始激波爆发速度的最大喷射速度。
We study properties of early radio emission from stripped-envelope supernovae (SNe; those of Type IIb/Ib/Ic). We suggest there is a sub-class of stripped-envelope SNe based on their radio properties, including the optically well-studied Type Ic SNe (SNe Ic) 2002ap and 2007gr, showing a rapid rise to a radio peak within ∼10 days and reaching a low luminosity (at least an order of magnitude fainter than a majority of SNe IIb/Ib/Ic). They show a decline after the peak that is shallower than that of other stripped-envelope SNe while their spectral index is similar. We show that all these properties are naturally explained if the circumstellar material (CSM) density is low and therefore the forward shock is expanding into the CSM without deceleration. Since the forward shock velocity in this situation, as estimated from the radio properties, still records the maximum velocity of the SN ejecta following the shock breakout, observing these SNe in radio wavelengths provides new diagnostics on the nature of both the breakout and the progenitor which otherwise require a quite rapid follow-up in other wavelengths. The inferred post-shock breakout velocities of SNe Ic 2002ap and 2007gr are sub-relativistic, ∼0.3c. These are higher than that inferred for SN II 1987A, in line with suggested compact progenitors. However, these are lower than expected for a Wolf–Rayet (W-R) progenitor. It may reflect an as yet unresolved nature of the progenitors just before the explosion, and we suggest that the W-R progenitor envelopes might have been inflated which could quickly reduce the maximum ejecta velocity from the initial shock breakout velocity.