THE VERY YOUNG TYPE Ia SUPERNOVA 2012cg: DISCOVERY AND EARLY-TIME FOLLOW-UP OBSERVATIONS
THE VERY YOUNG TYPE Ia SUPERNOVA 2012cg: DISCOVERY AND EARLY-TIME FOLLOW-UP OBSERVATIONS
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DOI：
10.1088/2041-8205/756/1/l7
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发表时间：
2012-06
期刊：
影响因子：
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通讯作者：
J. Silverman;M. Ganeshalingam;S. Cenko;A. Filippenko;Weidong Li;A. Barth;Daniel J. Carson;M. Chil
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文献类型：
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作者：
J. Silverman;M. Ganeshalingam;S. Cenko;A. Filippenko;Weidong Li;A. Barth;Daniel J. Carson;M. Chil
2012年5月17.2UT，在超新星爆发后1.5 ± 0.2天，我们在NGC 4424（d = 15Mpc）中发现了一颗Ia型超新星SN 2012cg。由于利克天文台超新星搜索采用了新修改的策略，在发现后161秒开始获得了一系列过滤图像。利用最近的模型描述的超新星（SN）喷出物与伴星星星的相互作用，我们排除了一个101 M的所有视角的一半和红巨星伴星几乎所有的方向。SN 2012 cg在2012年6月2.0日达到B波段最大值12.09 ± 0.02等，从爆炸到达到这一点花了大约17.3天，这是超新星Ia的典型情况。我们的预最大亮度测光显示SN 2012cg的B波段光变曲线比平均值窄，尽管在最大亮度时稍微过亮，颜色演变正常（包括一些最早的SN Ia过滤测光）。SN 2012 cg的光谱拟合揭示了在超新星Ia早期发现的典型离子，在爆炸后2.5天的膨胀速度为14，000 km s−1。早期检测到来自C ii的吸收，以及Si ii λ6355和Ca ii的高速分量。我们最后的光谱（爆炸后13.5天）类似于有点特殊的SN Ia 1999aa。这表明SN 2012 cg的光变曲线下降速度慢于平均值，考虑到光变曲线上升速度快于平均值，这可能令人惊讶。
On 2012 May 17.2 UT, only 1.5 ± 0.2 days after explosion, we discovered SN 2012cg, a Type Ia supernova (SN Ia) in NGC 4424 (d ≈ 15 Mpc). As a result of the newly modified strategy employed by the Lick Observatory Supernova Search, a sequence of filtered images was obtained starting 161 s after discovery. Utilizing recent models describing the interaction of supernova (SN) ejecta with a companion star, we rule out a ∼1 M☉ companion for half of all viewing angles and a red-giant companion for nearly all orientations. SN 2012cg reached a B-band maximum of 12.09 ± 0.02 mag on 2012 June 2.0 and took ∼17.3 days from explosion to reach this, typical for SNe Ia. Our pre-maximum-brightness photometry shows a narrower-than-average B-band light curve for SN 2012cg, though slightly overluminous at maximum brightness and with normal color evolution (including some of the earliest SN Ia filtered photometry ever obtained). Spectral fits to SN 2012cg reveal ions typically found in SNe Ia at early times, with expansion velocities ≳14,000 km s−1 at 2.5 days past explosion. Absorption from C ii is detected early, as well as high-velocity components of both Si ii λ6355 and Ca ii. Our last spectrum (13.5 days past explosion) resembles that of the somewhat peculiar SN Ia 1999aa. This suggests that SN 2012cg will have a slower-than-average declining light curve, which may be surprising given the faster-than-average rising light curve.