Search Publications

Evidence for sub-Chandrasekhar Type Ia supernovae from the last major merger

Belokurov, Vasily; Sanders, Jason L.; Man, Kai T. F.

We investigate the contribution of sub-Chandrasekhar mass Type Ia supernovae to the chemical enrichment of the Gaia Sausage galaxy, the progenitor of a significant merger event in the early life of the Milky Way. Using a combination of data from Nissen & Schuster, the GALactic Archaeology with HERMES (GALAH) Data Release 3 [with 1D non-local t…

Planets Across Space and Time (PAST). I. Characterizing the Memberships of Galactic Components and Stellar Ages: Revisiting the Kinematic Methods and Applying to Planet Host Stars

Huang, Yang; Dong, Subo; Liu, Chao +7 more

Over 4000 exoplanets have been identified and thousands of candidates are to be confirmed. The relations between the characteristics of these planetary systems and the kinematics, Galactic components, and ages of their host stars have yet to be well explored. To address these questions, we conduct a research project, dubbed Planets Across Space an…

Most "Young" α-rich Stars Have High Masses but are Actually Old

Xiang, Maosheng; Huang, Yang; Ting, Yuan-Sen +8 more

Recent observations have revealed a population of α-element abundances, enhanced giant stars with unexpected high masses (≳1 M _⊙) from asteroseismic analysis and spectroscopy. Assuming single-star evolution, their masses imply young ages (τ < 6 Gyr) incompatible with the canonical Galactic chemical evolution scenario. Here we study t…

VVV CL001: Likely the Most Metal-poor Surviving Globular Cluster in the Inner Galaxy

Majewski, Steven R.; Beers, Timothy C.; Minniti, Dante +11 more

We present the first high-resolution abundance analysis of the globular cluster VVV CL001, which resides in a region dominated by high interstellar reddening toward the Galactic bulge. Using H-band spectra acquired by the Apache Point Observatory Galactic Evolution Experiment, we identified two potential members of the cluster, and estimated from …

ALMA Observations of the Asymmetric Dust Disk around DM Tau

Dong, Ruobing; Liu, Hauyu Baobab; Tsukagoshi, Takashi +5 more

We report an analysis of the dust disk around DM Tau, newly observed with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3 mm. The ALMA observations with high sensitivity (8.4 µJy beam^-1) and high angular resolution (35 mas, 5.1 au) detect two asymmetries on the ring at r ∼ 20 au. They could be two vortices in early …

Constraining the AGN duty cycle in the cool-core cluster MS 0735.6+7421 with LOFAR data

Edge, Alastair C.; Bonafede, Annalisa; Brienza, Marisa +6 more

Context. MS 0735.6+7421 is a galaxy cluster that hosts a central radio galaxy with a very steep spectrum. The spectrum is produced by one of the most powerful known jetted active galactic nuclei (AGN). The radio plasma, ejected at nearly light speed from the central AGN, has displaced the intra-cluster medium, leaving two pairs of cavities observa…

Likelihood-free Cosmological Constraints with Artificial Neural Networks: An Application on Hubble Parameters and SNe Ia

Zhang, Tong-Jie; Wang, Yu-Chen; Xie, Yuan-Bo +3 more

The errors of cosmological data generated from complex processes, such as the observational Hubble parameter data (OHD) and the Type Ia supernova (SN Ia) data, cannot be accurately modeled by simple analytical probability distributions, e.g., a Gaussian distribution. To constrain cosmological parameters from these data, likelihood-free inference i…

Wave-Particle Interactions in the Earths Magnetosphere

Ma, Qianli; Thorne, Richard M.; Li, Wen +1 more

Bayesian analysis of Enceladus's plume data to assess methanogenesis

Affholder, Antonin; Guyot, François; Sauterey, Boris +2 more

Observations from NASA's Cassini spacecraft established that Saturn's moon Enceladus has an internal liquid ocean. Analysis of a plume of ocean material ejected into space suggests that alkaline hydrothermal vents are present on Enceladus's seafloor. On Earth, such deep-sea vents harbour microbial ecosystems rich in methanogenic archaea. Here we u…

A calibration of the Rossby number from asteroseismology

García, R. A.; Mathur, S.; Khalatyan, A. +4 more

Stellar activity and rotation are tightly related in a dynamo process. Our understanding of this mechanism is mainly limited by our capability of inferring the properties of stellar turbulent convection. In particular, the convective turnover time is a key ingredient through the estimation of the stellar Rossby number, which is the ratio of the ro…