标题： 使用Swift对M51中的IIP型超新星2005cs的早期紫外、光学和X射线观测 显示英文标题

标题： Early Ultraviolet, Optical and X-Ray Observations of the Type IIP SN 2005cs in M51 with Swift

摘要： 我们报告了由Swift的紫外-光学和X射线望远镜获得的IIP型超新星(SN) 2005cs的早期光球相观测。观测在发现后两天内开始，并持续了三周。在此期间，V波段的亮度基本保持不变，而紫外光最初明亮但逐渐变暗，直到低于一个潜在的明亮HII区域的紫外亮度。这种紫外衰减类似于通过国际紫外探测器观测到的II型超新星。紫外光栅光谱显示了MgII 2798Å的P-Cygni吸收，表明紫外通量具有光球起源。基于使用CMFGEN代码的非局部热平衡模型大气计算，我们将紫外通量的快速演化与喷发物质的冷却联系起来，光谱能量分布（SED）的峰值从6月30日的~700Å移动到7月5日的~1200Å。此外，喷发物质相应的再结合，例如从FeIII到FeII的转变，在光球及其上方诱导了金属线屏蔽的显著增强，更有效地阻挡了这种衰减的紫外通量。SN2005cs在X射线中未被探测到，X射线亮度的上限给出了前身星质量损失率的大致限制，约为每年10^-5太阳质量。总体而言，Swift提供了捕捉II型超新星早期和快速演化的独特机会，为红化、短于4000Å的SED、以及光解耦区域的电离状态和温度提供了额外的约束。 显示英文摘要

摘要： We report early photospheric-phase observations of the Type IIP Supernova (SN) 2005cs obtained by Swift's Ultraviolet-Optical and X-Ray Telescopes. Observations started within two days of discovery and continued regularly for three weeks. During this time the V-band magnitude remained essentially constant, while the UV was initially bright but steadily faded until below the brightness of an underlying UV-bright HII region. This UV decay is similar to SNe II observed by the International Ultraviolet Explorer. UV grism spectra show the P-Cygni absorption of MgII 2798A, indicating a photospheric origin of the UV flux. Based on non-LTE model atmosphere calculations with the CMFGEN code, we associate the rapid evolution of the UV flux with the cooling of the ejecta, the peak of the spectral energy distribution (SED) shifting from ~700A on June 30th to ~1200A on July 5th. Furthermore, the corresponding recombination of the ejecta, e.g., the transition from FeIII to FeII, induces considerable strengthening of metal line-blanketing at and above the photosphere, blocking more effectively this fading UV flux. SN2005cs was not detected in X-rays, and the upper limit to the X-ray luminosity yields a limit to the mass loss rate of the progenitor of about 10^-5 solar masses per year. Overall, Swift presents a unique opportunity to capture the early and fast evolution of Type II SNe in the UV, providing additional constraints on the reddening, the SED shortward of 4000A, and the ionization state and temperature of the photon-decoupling regions.