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Spectral analysis of ultra-cool white dwarfs polluted by planetary debris
Gänsicke, Boris T.; Gentile Fusillo, Nicola Pietro; Koester, Detlev +5 more
We identify two ultra-cool (${T_\mathrm{eff}}\lt 4000$ K) metal-polluted (DZ) white dwarfs WD J2147-4035 and WD J1922+0233 as the coolest and second coolest DZ stars known to date with ${T_\mathrm{eff}}\approx 3050$ K and ${T_\mathrm{eff}}\approx 3340$ K, respectively. Strong atmospheric collision-induced absorption (CIA) causes the suppression of…
Forbidden hugs in pandemic times. III. Observations of the luminous red nova AT 2021biy in the nearby galaxy NGC 4631
Lundqvist, P.; Zheng, W.; Galbany, L. +73 more
We present an observational study of the luminous red nova (LRN) AT 2021biy in the nearby galaxy NGC 4631. The field of the object was routinely imaged during the pre-eruptive stage by synoptic surveys, but the transient was detected only at a few epochs from ∼231 days before maximum brightness. The LRN outburst was monitored with unprecedented ca…
Stellar graveyards: clustering of compact objects in globular clusters NGC 3201 and NGC 6397
Bellini, Andrea; Libralato, Mattia; Mamon, Gary A. +2 more
We analyse Gaia EDR3 and re-calibrated HST proper motion data from the core-collapsed and non-core-collapsed globular clusters NGC 6397 and NGC 3201, respectively, with the Bayesian mass-orbit modelling code MAMPOSST-PM. We use Bayesian evidence and realistic mock data sets constructed with AGAMA to select between different mass models. In both cl…
Identification and characterization of a new ensemble of cometary organic molecules
Altwegg, K.; Fuselier, S. A.; Rubin, M. +4 more
In-situ study of comet 1P/Halley during its 1986 apparition revealed a surprising abundance of organic coma species. It remained unclear, whether or not these species originated from polymeric matter. Now, high-resolution mass-spectrometric data collected at comet 67P/Churyumov-Gerasimenko by ESA's Rosetta mission unveil the chemical structure of …
A New Magnetic Parameter of Active Regions Distinguishing Large Eruptive and Confined Solar Flares
Hou, Yijun; Li, Ting; Yang, Shuhong +3 more
With the aim of investigating how the magnetic field in solar active regions (ARs) controls flare activity, i.e., whether a confined or eruptive flare occurs, we analyze 106 flares of Geostationary Operational Environmental Satellite class ≥M1.0 during 2010-2019. We calculate mean characteristic twist parameters α FPIL within the "flari…
New Insights into the Structure of Open Clusters in the Gaia Era
Chen, Li; Zhong, Jing; Hou, Jinliang +2 more
With the help of Gaia data, it is noted that in addition to the core components, there are low-density outer halo components in the extended region of open clusters. In order to study the extended structure beyond the core radius of the cluster (~10 pc), based on Gaia Early Data Release 3, taking up to 50 pc as the searching radius, we use the pyU…
Galaxy cluster strong lensing cosmography. Cosmological constraints from a sample of regular galaxy clusters
Grillo, C.; Rosati, P.; Caminha, G. B. +1 more
Cluster strong lensing cosmography is a promising probe of the background geometry of the Universe and several studies have emerged thanks to the increased quality of observations using space- and ground-based telescopes. For the first time, we used a sample of five cluster strong lenses to measure the values of cosmological parameters and combine…
Asteroseismology of the multiple stellar populations in the globular cluster M4
Milone, A. P.; Tailo, M.; Bragaglia, A. +6 more
We present a new asteroseismic analysis of the stars in the globular cluster (GC) M4 based on the data collected by the K2 mission. We report the detection of solar-like oscillation in 37 stars, 32 red giant branch (RGB) and six red horizontal branch (rHB) stars, which is the largest sample for this kind of study in GCs up to date. Combining infor…
The Sun and Space Weather
Gopalswamy, Nat
The explosion of space weather research since the early 1990s has been partly fueled by the unprecedented, uniform, and extended observations of solar disturbances from space- and ground-based instruments. Coronal mass ejections (CMEs) from closed magnetic field regions and high-speed streams (HSS) from open-field regions on the Sun account for mo…
Integrated mass-loss of evolved stars in M4 using asteroseismology
Stello, Dennis; De Silva, Gayandhi M.; Howell, Madeline +1 more
Mass-loss remains a major uncertainty in stellar modelling. In low-mass stars, mass-loss is most significant on the red giant branch (RGB), and will impact the star's evolutionary path and final stellar remnant. Directly measuring the mass difference of stars in various phases of evolution represents one of the best ways to quantify integrated mas…