THE RISE AND FALL OF TYPE Ia SUPERNOVA LIGHT CURVES IN THE SDSS-II SUPERNOVA SURVEY
THE RISE AND FALL OF TYPE Ia SUPERNOVA LIGHT CURVES IN THE SDSS-II SUPERNOVA SURVEY
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DOI：
10.1088/0004-637x/712/1/350
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发表时间：
2010-01
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通讯作者：
B. Hayden;P. Garnavich;R. Kessler;J. Frieman;S. Jha;B. Bassett;D. Cinabro;B. Dilday;D. Kasen;J. Marriner;R. Nichol;A. Riess;M. Sako;D. Schneider;Mathew Smith;J. Sollerman
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作者：
B. Hayden;P. Garnavich;R. Kessler;J. Frieman;S. Jha;B. Bassett;D. Cinabro;B. Dilday;D. Kasen;J. Marriner;R. Nichol;A. Riess;M. Sako;D. Schneider;Mathew Smith;J. Sollerman
我们分析了斯隆数字巡天- ii （SDSS-II）超新星巡天发现的Ia型超新星（SN Ia）光曲线的上升和下降时间。从一组391条经过k校正的光曲线到休息帧B和V波段，我们发现光曲线上升部分的色散比下降部分小。这在定性上与计算机模型一致，该模型预测放射性镍产率的变化对上升的影响小于对下降率的影响。我们发现的上升和下降性质的差异表明，对光曲线相位的单一“拉伸”修正并不能正确地模拟SN Ia光曲线形状的范围。我们选择了105条光曲线的子集，在光曲线的上升和下降部分都很好地观察到，并开发了一个“2-stretch”拟合算法，该算法独立估计上升和下降时间。我们发现从爆炸到b波段峰值亮度的平均时间为17.38±0.17天，但上升时间从13天到23天不等。我们的平均上升时间比之前研究发现的19.5天短；这既反映了所使用的不同光曲线模板，也反映了2-stretch算法的应用。SDSS-II超新星群和具有良好早期光曲线的局部超新星Ia在平均上升时间特性上没有显著差异。我们发现缓慢下降的事件往往有快速的上升时间，但上升时间减去下降时间的分布是广泛的和单峰的。这种分布与Strovink首先通过对一小组局部Ia型SNe的分析提出的该参数的双峰分布相反。我们根据上升-下降值tr−tf≥2天和tr−tf≥2天将SDSS-II样本分成两半，以寻找它们的宿主星系特性和哈勃残差的差异；在我们的样本中，我们没有发现宿主星系属性或哈勃残差的差异。
We analyze the rise and fall times of Type Ia supernova (SN Ia) light curves discovered by the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. From a set of 391 light curves k-corrected to the rest-frame B and V bands, we find a smaller dispersion in the rising portion of the light curve compared to the decline. This is in qualitative agreement with computer models which predict that variations in radioactive nickel yield have less impact on the rise than on the spread of the decline rates. The differences we find in the rise and fall properties suggest that a single “stretch” correction to the light curve phase does not properly model the range of SN Ia light curve shapes. We select a subset of 105 light curves well observed in both rise and fall portions of the light curves and develop a “2-stretch” fit algorithm which estimates the rise and fall times independently. We find the average time from explosion to B-band peak brightness is 17.38 ± 0.17 days, but with a spread of rise times which range from 13 days to 23 days. Our average rise time is shorter than the 19.5 days found in previous studies; this reflects both the different light curve template used and the application of the 2-stretch algorithm. The SDSS-II supernova set and the local SNe Ia with well-observed early light curves show no significant differences in their average rise-time properties. We find that slow-declining events tend to have fast rise times, but that the distribution of rise minus fall time is broad and single peaked. This distribution is in contrast to the bimodality in this parameter that was first suggested by Strovink from an analysis of a small set of local SNe Ia. We divide the SDSS-II sample in half based on the rise minus fall value, tr − tf ⩽ 2 days and tr − tf > 2 days, to search for differences in their host galaxy properties and Hubble residuals; we find no difference in host galaxy properties or Hubble residuals in our sample.