Nebular-Phase Spectra of Type Ia Supernovae from the Las Cumbres Observatory Global Supernova Project
M. L. Graham, T. D. Kennedy, S. Kumar, R. C. Amaro, D. J. Sand, S. W. Jha, L. Galbany, J. Vinko, J. C. Wheeler, E. Y. Hsiao, K. A. Bostroem, J. Burke, D. Hirama… 展开作者
M. L. Graham, T. D. Kennedy, S. Kumar, R. C. Amaro, D. J. Sand, S. W. Jha, L. Galbany, J. Vinko, J. C. Wheeler, E. Y. Hsiao, K. A. Bostroem, J. Burke, D. Hiramatsu, G. Hosseinzadeh, C. McCully, D. A. Howell, T. Diamond, P. Hoeflich, X. Wang, W. Li
The observed diversity in Type Ia supernovae (SNe Ia) -- the thermonuclear explosions of carbon-oxygen white dwarf stars used as cosmological standard candles -- is currently met with a variety of explosion models and progenitor scenarios. To help improve our understanding of whether and how often different models contribute to the occurrence of SNe Ia and their assorted properties, we present a comprehensive analysis of seven nearby SNe Ia. We obtained one to two epochs of optical spectra with Gemini Observatory during the nebular phase ($>$200 days past peak) for each of these events, all of which had time-series of photometry and spectroscopy at early times (the first $\sim$8 weeks after explosion). We use the combination of early- and late-time observations to assess the predictions of various models for the explosion (e.g., double-detonation, off-center detonation, stellar collisions), progenitor star (e.g., ejecta mass, metallicity), and binary companion (e.g., another white dwarf or a non-degenerate star). Overall, we find general consistency in our observations with spherically-symmetric models for SN Ia explosions, and with scenarios in which the binary companion is another degenerate star. We also present an in-depth analysis of SN 2017fzw, a member of the sub-group of SNe Ia which appear to be transitional between the subluminous "91bg-like" events and normal SNe Ia, and for which nebular-phase spectra are rare.
Las Cumbres Observatory Gravitational-Wave Follow-up in the Third and Fourth Observing Runs: Strengths and Weaknesses of a Rapid Response Galaxy Targeted Strategy
Tel Aviv University（特拉维夫大学）；Las Cumbres Observatory（拉斯坎伯斯天文台）；University of California, Santa Barbara（加州大学圣塔芭芭拉分校）；Goddard Space Flight Center（戈达德太空飞行中心）；Weizmann Institute of Science（魏茨曼科学研究所）；Shady Side Academy（阴影边学院）；University of Florida（佛罗里达大学）；Center for Astrophysics — Harvard & Smithsonian（天体物理中心——哈佛大学与史密森尼学会）
The unusually red delay spectrum of the low-mass black hole AGN NGC\,4051 as revealed by intensive continuum reverberation mapping with the Las Cumbres Observatory
Wayne State University（韦恩州立大学）；University of St Andrews（圣安德鲁斯大学）；Durham University（杜伦大学）；Spectral Sciences Inc.（光谱科学公司）；University of Johannesburg（约翰内斯堡大学）；University of California, Irvine（加州大学尔湾分校）；University of Leicester（莱斯特大学）
NGC 4051低质量黑洞的异常红色延迟光谱通过密集连续反照率测绘揭示，其i和z_s波段延迟显著超出预期，可能由尘埃reddening或连续贡献解释。
Constraints on the Progenitor of SN 2016gkg From Its Shock-Cooling Light Curve
SN 2016 gkg是一颗在超新星爆发后不久被发现的IIb型超新星。与其他几个有早期数据的IIb型事件一样，SN 2016 gkg显示出双峰的光变曲线，第一个峰值与低质量扩展祖包层的冷却有关。我们提出了前所未有的intrinight-cadence多波段测光覆盖SN 2016 gkg的第一个光变曲线峰值从拉斯坎布雷斯天文台全球望远镜网络，小行星地球撞击最后警报系统，斯威夫特卫星和各种业余操作的望远镜。将这些数据与激波冷却模型进行拟合，可以得到原始星系半径约为25-140个太阳半径，扩展包层中的物质质量约为2-30 x 10^-2（取决于模型和假设的主星系灭绝）。我们的半径估计是大致一致的价值观独立得出（在其他作品）从HST成像的祖星。然而，冲击冷却模型半径是在爆炸前成像所指示的值的下端。流体动力学模拟可以精确的祖参数推导出的冲击冷却发射和测试的分析模型。
The Berkeley Sample of Stripped-Envelope Supernovae
我们提出了完整的样本的剥离信封超新星（SN）光谱观测的利克天文台超新星搜索（LOSS）合作在过去的三十年中：888光谱的302 SNe，652在这里首次公布，与384光谱（92 SNe）具有光度测定的阶段。在校正红移和银河系尘埃红化和重新评估每个SN的光谱分类后，我们构建了三个主要光谱亚型（IIb型，Ib型和Ic型）的平均光谱。我们比较了这个样本的谱线强度和宽度的测量结果与以前的结果，证实了在峰值亮度后的前30天内，Ic型SNe中O I λ7774的吸收比Ib或IIb型SNe更强，并且速度更快，尽管星云发射谱线的宽度在亚型之间是一致的。我们还强调了一些罕见的感兴趣的亚群的新观察。
