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A single galaxy population? Statistical evidence that the star-forming main sequence might be the tip of the iceberg
Ascasibar, Y.; López-Sánchez, Á. R.; Corcho-Caballero, P.
According to their specific star formation rate (sSFR), galaxies are often divided into 'star-forming' and 'passive' populations. It is argued that the former define a narrow 'main sequence of star-forming galaxies' (MSSF) of the form sSFR(M*), whereas 'passive' galaxies feature negligible levels of star formation activity. Here we use …
The stringent upper limit on jet power in the persistent soft-state source 4U 1957+11
Maccarone, Thomas J.; McHardy, Ian M.; Miller-Jones, James C. A. +5 more
We present extremely deep upper limits on the radio emission from 4U 1957+11, an X-ray binary that is generally believed to be a persistently accreting black hole that is almost always in the soft state. We discuss a more comprehensive search for Type I bursts than in past work, revealing a stringent upper limit on the burst rate, bolstering the c…
K2 observations of the pulsating subdwarf B stars UY Sex and V1405 Ori
Reed, M. D.; Jeffery, C. S.; Baran, A. S. +5 more
We processed and analysed K2 observations of the pulsating subdwarf-B (sdBV) stars UY Sex and V1405 Ori. We detect 97 p-mode pulsations in UY Sex while we discover V1405 Ori to be a rare rich hybrid pulsator with over 100 p-mode pulsations and 19 g-mode pulsations. We detect frequency multiplets, which we use to identify pulsation modes as well as…
High-amplitude γ Doradus variables
Paunzen, Ernst; Hambsch, Franz-Josef; Hümmerich, Stefan +3 more
According to most literature sources, the amplitude of the pulsational variability observed in γ Doradus stars does not exceed 0.1 mag in Johnson V. We have analysed fifteen high-amplitude γ Doradus stars with photometric peak-to-peak amplitudes well beyond this limit, with the aim of unraveling the mechanisms behind the observed high amplitudes a…
Spectral library of age-benchmark low-mass stars and brown dwmarfs
Béjar, V. J. S.; Boudreault, S.; Bonnefoy, M. +3 more
In recent years, some extremely red brown dwarfs have been discovered. They were believed to have a low surface gravity, but many of their spectral characteristics are similar to those of high-surface-gravity brown dwarfs, showing that the spectral characteristics of young brown dwarfs are poorly understood. We aim to test surface-gravity indicato…
Seeds of Life in Space (SOLIS). VIII. SiO isotopic fractionation, and a new insight into the shocks of L1157-B1
Podio, L.; Codella, C.; Ceccarelli, C. +4 more
Context. Contrary to what is expected from models of Galactic chemical evolution, the isotopic fractionation of silicon (Si) in the Galaxy has recently been found to be constant. This finding calls for new observations, also at core scales, to re-evaluate the fractionation of Si.
Aims: L1157-B1 is one of the outflow-shocked regions along the …
Detection of pristine circumstellar material from the Cassiopeia A supernova progenitor
Koo, Bon-Chul; Raymond, John C.; Jaffe, Daniel T. +4 more
Cassiopeia A is a nearby young supernova remnant that provides a unique laboratory for the study of core-collapse supernova explosions1. Cassiopeia A is known to be a type IIb supernova from the optical spectrum of its light echo2, but the immediate progenitor of the supernova remains uncertain3. Here, we report re…
A new trigger mechanism for coronal mass ejections. The role of confined flares and photospheric motions in the formation of hot flux ropes
van Driel-Gesztelyi, L.; Green, L. M.; Valori, G. +1 more
Context. Many previous studies have shown that the magnetic precursor of a coronal mass ejection (CME) takes the form of a magnetic flux rope, and a subset of them have become known as "hot flux ropes" due to their emission signatures in ∼10 MK plasma.
Aims: We seek to identify the processes by which these hot flux ropes form, with a view of …
Power-law energy distributions of small-scale impulsive events on the active Sun: results from IRIS
Ramsay, Gavin; Mathioudakis, Mihalis; Doyle, J. Gerry +2 more
Numerous studies have analysed inferred power-law distributions between frequency and energy of impulsive events in the outer solar atmosphere in an attempt to understand the predominant energy supply mechanism in the corona. Here, we apply a burst detection algorithm to high-resolution imaging data obtained by the Interface Region Imaging Spectro…
Intermediate-mass Stars Become Magnetic White Dwarfs
Caiazzo, Ilaria; Heyl, Jeremy; Richer, Harvey +8 more
When a star exhausts its nuclear fuel, it either explodes as a supernova or more quiescently becomes a white dwarf, an object about half the mass of our Sun with a radius of about that of the Earth. About one-fifth of white dwarfs exhibit the presence of magnetic fields, whose origin has long been debated as either the product of previous stages o…