Early-time observations of the Type II supernovae (SNe) 2013cu and 2013fs have revealed an interaction of ejecta with material near the star surface. Unlike the Type IIn SN2010jl, which interacts with a dense wind for ~1yr, the interaction ebbs after 2-3d, suggesting a dense and compact circumstellar envelope. Here, we use multi-group radiation-hydrodynamics and non-local-thermodynamic-equilibrium radiative transfer to explore the properties of red supergiant (RSG) star explosions embedded in a variety of dense envelopes. We consider the cases of an extended static atmosphere or a steady-state wind, adopting a range of mass loss rates. The shock-breakout signal, the SN radiation up to 10d, and the ejecta dynamics are strongly influenced by the properties of this nearby environment. This compromises the use of early-time observations to constrain Rstar. The presence of narrow lines for 2-3d in 2013fs and 2013cu require a cocoon of material of ~0.01Msun out to 5-10Rstar. Spectral lines evolve from electron-scattering to Doppler broadened, with a growing blueshift of their emission peaks. Recent studies propose a super-wind phase with a mass loss rate from 0.001 up to 1Msun/yr in the last months/years of the RSG life, although there is no observational constraint that this external material is a steady-state outflow. Alternatively, observations may be explained by the explosion of a RSG star inside its complex atmosphere. Indeed, spatially resolved observations reveal that RSG stars have extended atmospheres, with the presence of downflows and upflows out to several Rstar, even in a standard RSG like Betelgeuse. Mass loading in the region intermediate between star and wind can accommodate the 0.01Msun needed to explain the observations of 2013fs. A puzzling super-wind phase prior to core-collapse may be therefore superfluous [Abridged].
Using Athena++, we perform 3D Radiation-Hydrodynamic calculations of the radiative breakout of the shock wave in the outer envelope of a red supergiant (RSG) which has suffered core collapse and will become a Type IIP supernova. The intrinsically 3D structure of the fully convective RSG envelope yields key differences in the brightness and duration of the shock breakout (SBO) from that predicted in a 1D stellar model. First, the lower-density `halo' of material outside of the traditional photosphere in 3D models leads to a shock breakout at lower densities than 1D models. This would prolong th…
Multi-wavelength Signatures of Supernova Shock Breakout from Red Supergiants in Two Dimensions
National Taiwan University（台湾大学）；Academia Sinica, Institute of Astronomy and Astrophysics（中央研究院天文及天文物理研究所）；Heidelberger Institut für Theoretische Studien（海德堡理论研究所）；RIKEN Pioneering Research Institute (PRI)（理化学研究所前沿研究 institutes）；Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechenzentrum（海德堡大学天文学中心天文计算中心）
A modeling perspective on the diversity of red-supergiant stars exploding within circumstellar material
Institut d’Astrophysique de Paris, CNRS-Sorbonne Université（巴黎天体物理研究所，CNRS-索邦大学）；Cahill Center for Astrophysics, California Institute of Technology（加州理工学院卡希尔天体物理学中心）
High cadence ultraviolet, optical and near-infrared photometric and low-resolution spectroscopic observations of the peculiar Type II supernova (SN) 2018hna are presented. The early phase multiband light curves exhibit the adiabatic cooling envelope emission following the shock breakout up to ~14 days from the explosion. SN~2018hna has a rise time of $\sim$\,88 days in the V-band, similar to SN 1987A. A $\rm^{56}Ni$ mass of ~0.087$\pm$0.004 $\rm M_{\odot}$ is inferred for SN 2018hna from its bolometric light curve. Hydrodynamical modelling of the cooling phase suggests a progenitor with a radi…
Multicolor light curves simulations of Population III core-collapse supernovae: from shock breakout to $^{56}$Co decay
由于缺乏实际观测，第一代恒星及其超新星（SN）爆炸的性质仍然未知。最近进行了许多瞬态调查和探测超新星（SNe）的Pop III星的可行性正在增长。本文研究了一些无金属核坍缩超新星模型（25-100 M $_{\odot}$）的光变曲线，为寻找和鉴别第一代超新星提供了指示。我们使用混合回落超新星爆炸模型，解释所观察到的丰富的贫金属恒星的模式。用多群辐射流体动力学程序STELLA对双光子光变曲线进行了数值计算。计算的光变曲线的非零金属丰度模型和几个观察到的SNe进行了比较。我们发现，冲击波爆发特征、光球速度演化、亮度、坪期和坪色演化等SN相都有助于估算SN祖星的质量、半径、爆炸能量和金属丰度等参数。我们的结论是，在当前（斯巴鲁/HSC）和未来的瞬态调查（LSST，JWST）的第一代SNe的潜在的光曲线可以被用来识别。它们也适用于识别附近宇宙中的低金属丰度SNe（PTF，Pan-STARRS，Gaia）。
From the early radiation of type II-P supernovae (SNe), it has been claimed that the majority of their red supergiant (RSG) progenitors are enshrouded by large amounts of circumstellar material (CSM) at the point of explosion. The inferred density of this CSM is orders of magnitude above that seen around RSGs in the field, and is therefore indicative of a short phase of elevated mass-loss prior to explosion. It is not known over what timescale this material gets there: is it formed over several decades by a `superwind' with mass-loss rate $\dot{M} \sim10^{-3}\,{\rm M_\odot\,yr^{-1}}$; or is it…
We present extensive optical/ultraviolet observations and modelling analysis for the nearby SN 1987A-like peculiar Type II supernova (SN) 2018hna. Both photometry and spectroscopy covered phases extending to $>$500 days after the explosion, making it one of the best-observed SN II of this subtype. SN 2018hna is obviously bluer than SN 1987A during the photospheric phase, suggesting higher photospheric temperature, which may account for weaker BaII $\mathrmλ$6142 lines in its spectra. Analysis of early-time temperature evolution suggests a radius of $\sim$45 $\mathrm{R_{\odot}}$ for the progeni…
There are currently many large-field surveys operational and planned including the powerful Vera C. Rubin Observatory Legacy Survey of Space and Time. These surveys will increase the number and diversity of transients dramatically. However, for some transients, like supernovae (SNe), we can gain more understanding by directed observations (e.g. shock breakout, $γ$-ray detections) than by simply increasing the sample size. For example, the initial emission from these transients can be a powerful probe of these explosions. Upcoming ground-based detectors are not ideally suited to observe the ini…
The lowest metallicity type II supernova from the highest mass red-supergiant progenitor
红超巨星已经被证实是大多数富氢II型超新星的祖先。然而，虽然这些恒星的质量大于25 M $_\odot$，但探测到大于18 M $_\odot$的祖先仍然难以捉摸。红超巨星也有望在所有金属丰度下形成，但从低金属丰度祖先爆发的发现很少。在这里，我们报告的II型超新星，SN 2015 bs的观测，我们推断的祖先金属丰度$\leq$ 0.1 Z $_\odot$通过比较光球相光谱模型，和零年龄主序列质量17- 25 M $_\odot$通过比较星云相光谱模型。SN 2015 bs显示出正常的“平台”光变曲线形态和典型的光谱特性，暗示着它是一颗红超巨星的前身。这是第一个这样的高质量祖先的“正常”II型超新星的例子，表明高质量红超巨星爆炸和低金属量祖先之间的联系。
Recent studies on direct imaging of Type II core-collapse supernova progenitors indicate a possible threshold around $M_{\rm ZAMS}\sim 16-20$ M$_\odot$, where red supergiants with larger birth masses do not appear to result in supernova explosions and instead implode directly into a black hole. In this study we argue that it is not a coincidence that this threshold closely matches the critical transition of central Carbon burning in massive stars from the convective to radiative regime. In lighter stars, Carbon burns convectively in the center and result in compact final presupernova cores tha…
Massive stars undergo fundamental-mode and first-overtone radial pulsations with periods of 100-1000 days as Red Supergiants (RSGs). At large amplitudes, these pulsations substantially modify the outer envelope's density structure encountered by the outgoing shock wave from the eventual core collapse of these $M>9M_\odot$ stars. Using Modules for Experiments in Stellar Astrophysics (MESA), we model the effects of fundamental-mode and first-overtone pulsations in the RSG envelopes, and the resulting Type IIP supernovae (SNe) using MESA+STELLA. We find that, in the case of fundamental mode pulsa…
Shock breakout (SBO), the first expected electromagnetic signature of a supernova (SN), can be an important probe of the progenitors of these explosions. Unfortunately, SBO is difficult to capture with current surveys due to its brief timescale ($\lesssim 1\,$hr). However, SBO may be lengthened when dense circumstellar material (CSM) is present. Indeed, recent photometric modeling studies of SNe, as well as early spectroscopy, suggest that such dense CSM may be present more often than previously expected. If true, this should also affect the features of SBO. We present an exploration of the im…
We perform three-dimensional hydrodynamic simulations of aspherical core-collapse supernovae focusing on the matter mixing in SN 1987A. The impacts of four progenitor (pre-supernova) models and parameterized aspherical explosions are investigated. The four pre-supernova models include a blue supergiant (BSG) model based on a slow merger scenario developed recently for the progenitor of SN 1987A (Urushibata et al. 2018). The others are a BSG model based on a single star evolution and two red supergiant (RSG) models. Among the investigated explosion (simulation) models, a model with the binary m…
During the core collapse of massive stars that do not undergo a canonical energetic explosion, some of the hydrogen envelope of a red supergiant (RSG) progenitor may infall onto the newborn black hole (BH). Within the Athena++ framework, we perform three-dimensional, hydrodynamical simulations of idealized models of supergiant convection and collapse in order to assess whether the infall of the convective envelope can give rise to rotationally-supported material, even if the star has zero angular momentum overall. Our dimensionless, polytropic models are applicable to the optically-thick hydro…
The relativistic hydrodynamics equations are adapted for the spherically symmetric case and the Lagrangian form. They are used to model the explosive disruption of a minimum-mass neutron star: a key ingredient of the stripping model for short gamma-ray bursts. The shock breakout from the neutron star surface accompanied by the acceleration of matter to ultrarelativistic velocities is studied. A comparison with the results of previously published nonrelativistic calculations is made.
Active galactic nuclei (AGN) are prominent environments for stellar capture, growth and formation. These environments may catalyze stellar mergers and explosive transients, such as thermonuclear and core-collapse supernovae (SNe). SN explosions in AGN discs generate strong shocks, leading to unique observable signatures. We develop an analytical model which follows the evolution of the shock propagating in the disc until it eventually breaks out. We derive the peak luminosity, bolometric lightcurve, and breakout time. The peak luminosities may exceed $10^{45}$ erg s$^{-1}$ and last from hours …
SN 2010jl is a Type IIn core collapse supernova whose radiative output is powered by the interaction of the SN shock wave with its surrounding dense circumstellar medium (CSM). After day ~60, its light curve developed a NIR excess emission from dust. This excess could be a thermal IR echo from pre-existing CSM dust, or emission from newly-formed dust either in the cooling postshock region of the CSM, or in the cooling SN ejecta. Recent analysis has shown that dust formation in the CSM can commence only after day ~380, and has also ruled out newly-formed ejecta dust as the source of the NIR emi…
The Initial Masses of the Red Supergiant Progenitors to Type-II Supernovae
有越来越多的附近SNe的祖先恒星被发现在档案爆炸前成像。从这些图像中可以测量爆炸前几年的祖星亮度，并最终估计其初始质量。先前的研究表明，II-P和II-L超新星（SNe）有红超巨星（RSG）的祖先，这些祖先的初始质量范围似乎仅限于$<$ 17 M $_\odot$。这与演化模型预测的25- 30 M $_\odot$的截止值形成对比，这一结果被称为“红超巨星问题”。在这里，我们调查一个特定的来源，系统误差目前在转换爆炸前测光到一个初始质量，即用于转换成一个单波段通量的热辐射光度的热辐射校正（BC）。我们表明，使用星团，RSG演变到后来的光谱类型，因为它们接近SN，这反过来又导致BC变得更大。不考虑这一点会导致系统性地低估恒星的光度，从而低估其初始质量。使用我们的经验动机的BC，我们重新评估的II-P和II-L SNe，其祖细胞在爆炸前成像检测。将初始质量函数拟合到这些更新的质量导致$M_{\rm hi}$的质量上限截断值增加= $19.0^{+2.5}_{-1.3}$ M $_\odot$，95%置信上限为$<$ 27 M $_\odot$。考虑到有限的样本量效应和质量-光度关系中的系统不确定性，将截止值提高到$M_{\rm hi}$ = 25 M $_\odot$（$<$ 33 M $_\odot$，95%置信度）。因此，我们的结论是，目前没有强有力的证据“失踪”的高质量祖核心崩…
