The first observational evidence for cosmic acceleration appeared from Type Ia supernovae (SNe Type Ia) Hubble diagram from two different groups. However, the empirical treatment of SNe Type Ia and their ability to show cosmic acceleration have been the subject of some debate in the literature. In this work we probe the assumption of redshift-independent absolute magnitude $(M_{\mathrm{B}})$ of SNe along with its correlation with spatial curvature ($Ω_{k0}$) and cosmic distance duality relation (CDDR) parameter ($η(z)$). This work is divided into two parts. Firstly, we check the validity of CDDR which relates the luminosity distance ($d_L$) and angular diameter distance ($d_A$) via redshift. We use the Pantheon SNe Ia dataset combined with the $H(z)$ measurements derived from the cosmic chronometers. Further, four different redshift-dependent parametrizations of the distance duality parameter $(η(z))$ are used. The CDDR is fairly consistent for almost every parametrization within a $2σ$ confidence level in both flat and a non-flat universe. In the second part, we assume the validity of CDDR and emphasize on the variability of $M_{\mathrm{B}}$ and its correlation with $Ω_{k0}$. We choose four different redshift-dependent parametrizations of $M_{\mathrm{B}}$. The results indicate no evolution of $M_{\mathrm{B}}$ within $2σ$ confidence level. For all parametrizations, the best fit value of $Ω_{k0}$ indicates a flat universe at $2σ$ confidence level. However a mild inclination towards a non flat universe is also observed. We have also examined the dependence of the results on the choice of different priors for $H_0$.
Testing Cosmic Distance Duality Relation and Transparency with DESI DR2
State Key Laboratory of Radio Astronomy and Technology, Xinjiang Astronomical Observatory, Chinese Academy of Sciences（中国科学院新疆天文台射电天文与技术国家重点实验室）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；School of Physics and Electronics, Henan University（河南大学物理与电子学院）；School of Physical Science and Technology, Xinjiang University（新疆大学物理科学与技术学院）；School of Physics and Astronomy, China West Normal University（西华师范大学物理与天文学院）
The reddening law of Type Ia Supernovae: separating intrinsic variability from dust using equivalent widths
我们采用76个Ia型超新星的光学分光光度计在2.5天内的B波段最大光附近的超新星工厂获得的Si和Ca的功能上的超新星的内在光度的影响，并确定一个尘埃红化的法律。我们使用Si II λ4131的等效宽度代替光变曲线的拉伸来解释一阶固有光度变化。由此产生的经验光谱红化定律表现出与Ca II和Si II λ6355相关的强烈特征。在应用基于Ca II H&K等效宽度的校正后，我们发现与Cardelli消光定律一致的红化定律。使用相同的输入数据，我们将此结果与合成静止帧类UBVRI光度学进行比较，以模仿文献观测。在对与Si II λ4131和Ca II H&K等效宽度相关的特征进行校正并引入颜色之间的经验相关性后，我们确定了每个波段中的尘埃成分。我们发现一个值的总选择性消光比，RV = 2.8 \pm 0.3。这与银河系的数值相一致，与大多数以前的分析中发现的低RV值相反。这一结果表明，解释超新星Ia的颜色及其与经典消光定律的兼容性的长期争议，对于它们作为宇宙学探测器的使用至关重要，可以通过处理颜色的分散和超新星Ia光谱中明显特征的可变性来解释。
The colour variability of low-z SNe Ia is entirely explained by dust
SISSA（国际高等研究学院）；INFN – National Institute for Nuclear Physics（意大利国家核物理研究所）；ICSC – Centro Nazionale di Ricerca in High Performance Computing, Big Data e Quantum Computing（高性能计算、大数据与量子计算国家研究中心）；Imperial College London（帝国理工学院）；University of Barcelona（巴塞罗那大学）
Variability in Quasar Light Curves: using quasars as standard candles
测量了58个光谱确认类星体光变曲线的变分斜率$s_F$与平均绝对星等$\langle M \rangle$之间的关系，色散为0.15 dex。假设它适用于一般的类星体，这种关系不仅增加了我们对类星体可变性的工作知识，而且它也显示了以模型独立的方式精确测量类星体的光度距离的巨大希望。一个精确的，独立于模型的光度距离测量将允许类星体被添加到宇宙距离阶梯中，很容易将阶梯延伸到远超过Ia型超新星的红移，在那里宇宙学参数可以更好地受到约束。
A Probabilistic Autoencoder for Type Ia Supernovae Spectral Time Series
University of California, Berkeley（加州大学伯克利分校）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；Sorbonne Université（索邦大学）；Université de Paris（巴黎大学）；University of Washington（华盛顿大学）
A refined method for measuring cosmological distances using variability and proper motions in AGN with VLBI-detected counter-jets
Sejong University（世宗大学）；Korea Astronomy and Space Science Institute（韩国天体宇宙科学研究所）；University of Science and Technology（科学技术联合大学院大学）；York University（约克大学）；Institute of Astrophysics, Foundation for Research and Technology-Hellas（希腊研究与技术基金会天体物理研究所）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）
Little Red Dots as Intermediate Mass, Super-Eddington Engines: Insights from Type IIn Supernovae and The 1837-1856 Great Eruption of $η$ Carinae
MIT Kavli Institute for Astrophysics and Space Research（麻省理工学院卡弗里天体物理与空间研究所）；Institute for Astronomy, University of Hawai‘i（夏威夷大学天文学研究所）；Institute of Science and Technology Austria (ISTA)（奥地利科学技术研究所）；Center for Astrophysics, Harvard & Smithsonian（哈佛-史密森尼天体物理中心）；Max-Planck-Institut für Astronomie（马克斯·普朗克天体物理学研究所）；Department of Astronomy & Astrophysics, University of Chicago（芝加哥大学天文与天体物理系）；Kavli Institute for Cosmological Physics, University of Chicago（芝加哥大学卡弗里宇宙物理学研究所）；Department of Astronomy, The University of Texas at Austin（德克萨斯大学奥斯汀分校天文系）；Cosmic Frontier Center, The University of Texas at Austin（德克萨斯大学奥斯汀分校宇宙前沿中心）
