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Comets as a possible source of nanodust in the Solar System cloud and in planetary debris discs
Mann, Ingrid
Comets, comet-like objects and their fragments are the most plausible source for the dust in both the inner heliosphere and planetary debris discs around other stars. The smallest size of dust particles in debris discs is not known and recent observational results suggest that the size distribution of the dust extends down to sizes of a few nanome…
Impact of Radiogenic Heating on the Formation Conditions of Comet 67P/Churyumov-Gerasimenko
Wurz, P.; Altwegg, K.; Balsiger, H. +19 more
Because of the high fraction of refractory material present in comets, the heat produced by the radiogenic decay of elements such as aluminum and iron can be high enough to induce the loss of ultravolatile species such as nitrogen, argon, or carbon monoxide during their accretion phase in the protosolar nebula (PSN). Here, we investigate how heat …
Multifrequency polarimetry of a complete sample of PACO radio sources
Ricci, R.; Bonaldi, A.; Bonavera, L. +16 more
We present high-sensitivity polarimetric observations (σP ≃0.6 mJy) in six bands covering the 5.5-38 GHz range of a complete sample of 53 compact extragalactic radio sources brighter than 200 mJy at 20 GHz. The observations, carried out with the Australia Telescope Compact Array, achieved a 91 per cent detection rate (at 5σ). Within thi…
Spatial distribution of far-infrared rotationally excited CH+ and OH emission lines in the Orion Bar photodissociation region
Abergel, A.; Godard, B.; Gerin, M. +7 more
Context. The methylidyne cation (CH+) and hydroxyl (OH) are key molecules in the warm interstellar chemistry, but their formation and excitation mechanisms are not well understood. Their abundance and excitation are predicted to be enhanced by the presence of vibrationally excited H2 or hot gas ( 500-1000 K) in photodissociat…
Solar Hα features with hot onsets. II. A contrail fibril
Rouppe van der Voort, L. H. M.; Rutten, R. J.
The solar chromosphere observed in Hα consists mostly of narrow fibrils. The longest typically originate in network or plage and arch far over adjacent internetwork. We use data from multiple telescopes to analyze one well-observed example in a quiet area. It resulted from the earlier passage of an accelerating disturbance in which the gas was hea…
Extreme relativistic electron fluxes in the Earth's outer radiation belt: Analysis of INTEGRAL IREM data
Meredith, Nigel P.; Horne, Richard B.; Sandberg, Ingmar +2 more
Relativistic electrons (E > 500 keV) cause internal charging and are an important space weather hazard. To assess the vulnerability of the satellite fleet to these so-called "killer" electrons, it is essential to estimate reasonable worst cases, and, in particular, to estimate the flux levels that may be reached once in 10 and once in 100 years…
NuSTAR and XMM-Newton observations of the Arches cluster in 2015: fading hard X-ray emission from the molecular cloud
Mori, Kaya; Tomsick, John; Poutanen, Juri +6 more
We present results of long Nuclear Spectroscopic Telescope Array (NuSTAR; 200 ks) and XMM-Newton (100 ks) observations of the Arches stellar cluster, a source of bright thermal (kT ∼ 2 keV) X-rays with prominent Fe xxv Kα 6.7 keV line emission and a nearby molecular cloud, characterized by an extended non-thermal hard X-ray continuum and fluoresce…
Planetary Nebulae and H II Regions in the Starburst Irregular Galaxy NGC 4449 from LBT MODS Data
Tosi, M.; Cusano, F.; Mignoli, M. +7 more
We present deep 3500-10000 Å spectra of H II regions and planetary nebulae (PNe) in the starburst irregular galaxy NGC 4449, acquired with the Multi Object Double Spectrograph at the Large Binocular Telescope. Using the “direct” method, we derived the abundance of He, N, O, Ne, Ar, and S in six H II regions and in four PNe in NGC 4449. This is the…
Evolution of Alfvénic Fluctuations inside an Interplanetary Coronal Mass Ejection and Their Contribution to Local Plasma Heating: Joint Observations from 1.0 to 5.4 au
Li, Hui; Wang, Chi; Richardson, John D. +1 more
Tracking an interplanetary coronal mass ejection (ICME) by widely separated spacecraft could provide us with a good opportunity to study the evolution of embedded Alfvénic fluctuations (AFs) and their possible contribution to local plasma heating directly. In this study, an ICME observed by Wind at 1.0 au on 1998 March 4-6 is tracked to the locati…
The Shock Dynamics of Heterogeneous YSO Jets: 3D Simulations Meet Multi-epoch Observations
Hansen, E. C.; Hartigan, P.; Frank, A. +1 more
High-resolution observations of young stellar object (YSO) jets show them to be composed of many small-scale knots or clumps. In this paper, we report results of 3D numerical simulations designed to study how such clumps interact and create morphologies and kinematic patterns seen in emission line observations. Our simulations focus on clump scale…