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A hot subdwarf-white dwarf super-Chandrasekhar candidate supernova Ia progenitor
Geier, S.; Heber, U.; Irrgang, A. +8 more
Supernovae Ia are bright explosive events that can be used to estimate cosmological distances, allowing us to study the expansion of the Universe. They are understood to result from a thermonuclear detonation in a white dwarf that formed from the exhausted core of a star more massive than the Sun. However, the possible progenitor channels leading …
Most lithium-rich low-mass evolved stars revealed as red clump stars by asteroseismology and spectroscopy
Zhao, Gang; Zhao, Jing-Kun; Li, Yaguang +19 more
Lithium has confused scientists for decades at almost every scale of the universe. Lithium-rich giants are peculiar stars with lithium abundances greater than model prediction. A large fraction of lithium-rich low-mass evolved stars are traditionally supposed to be red giant branch (RGB) stars. Recent studies, however, report that red clump (RC) s…
Fast magnetic field amplification in distant galaxy clusters
Gastaldello, Fabio; Simionescu, Aurora; Brunetti, Gianfranco +16 more
In the present-day Universe, magnetic fields pervade galaxy clusters1 and have strengths of a few microgauss, as measured from Faraday rotation2. Evidence for cluster magnetic fields is also provided by the observation of megaparsec-scale radio emission, namely radio halos and relics3. These are commonly found in m…
Chemical evidence for planetary ingestion in a quarter of Sun-like stars
Bedell, Megan; Casey, Andrew R.; Carlos, Marília +5 more
Stellar members of binary systems are formed from the same material, and therefore they should be chemically identical. However, recent studies have unveiled chemical differences between the two members of binary pairs composed of Sun-like stars. These chemically inhomogeneous binaries represent one of the most contradictory examples in stellar as…
Ultra-low-frequency gravitational waves from cosmological and astrophysical processes
Moore, Christopher J.; Vecchio, Alberto
Gravitational waves at ultra-low frequencies (≲100 nHz) are key to understanding the assembly and evolution of astrophysical black hole binaries with masses ~106-109 M⊙ at low redshifts1-3. These gravitational waves also offer a unique window into a wide variety of cosmological processes4-11. …
A new class of fossil fragments from the hierarchical assembly of the Galactic bulge
Dalessandro, E.; Saracino, S.; Valenti, E. +12 more
The formation and evolutionary processes of galaxy bulges are still unclear, and the presence of young stars in the bulge of the Milky Way is largely debated. We recently demonstrated that Terzan 5, in the Galactic bulge, is a complex stellar system hosting stars with very different ages and a striking chemical similarity to the field population. …
Evidence for a compact object in the aftermath of the extragalactic transient AT2018cow
Steiner, James F.; Homan, Jeroen; Chakrabarty, Deepto +16 more
The brightest fast blue optical transients (FBOTs) are mysterious extragalactic explosions that may represent a new astrophysical phenomenon1. Their fast time to maximum brightness of less than a week, decline over several months, and atypical optical spectra and evolution are difficult to explain within the context of the core collapse…
Haze evolution in temperate exoplanet atmospheres through surface energy measurements
Fortney, Jonathan J.; Moran, Sarah E.; Valenti, Jeff A. +13 more
Photochemical hazes are important opacity sources in temperate exoplanet atmospheres, hindering current observations from characterizing exoplanet atmospheric compositions. The haziness of an atmosphere is determined by the balance between haze production and removal. However, the material-dependent removal physics of the haze particles are curren…
Strong toroidal magnetic fields required by quiescent X-ray emission of magnetars
Igoshev, Andrei P.; Hollerbach, Rainer; Wood, Toby +1 more
Magnetars are neutron stars (NSs) with extreme magnetic fields1 of strength 5 × 1013-1015 G. These fields are generated by dynamo action during the proto-NS phase, and are expected to have both poloidal and toroidal components2-6, although the energy of the toroidal component could be ten times larger
A sublimated water atmosphere on Ganymede detected from Hubble Space Telescope observations
Saur, Joachim; Roth, Lorenz; Grodent, Denis +5 more
Ganymede's atmosphere is produced by charged particle sputtering and sublimation of its icy surface. Previous far-ultraviolet observations of the O I 1,356 å and O I 1,304 å oxygen emissions were used to infer sputtered molecular oxygen (O2) as an atmospheric constituent, but an expected sublimated water (H2O) component remai…