Search Publications
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 …
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…
Production of Sulfur Allotropes in Electron Irradiated Jupiter Trojans Ice Analogs
Ehlmann, Bethany L.; Brown, Michael E.; Choukroun, Mathieu +7 more
In this paper, we investigate sulfur chemistry in laboratory analogs of Jupiter Trojans and Kuiper Belt Objects (KBOs). Electron irradiation experiments of CH3OH-NH3-H2O and H2S-CH3OH-NH3-H2O ices were conducted to better understand the chemical differences between primor…
A New Approach to Convective Core Overshooting: Probabilistic Constraints from Color-Magnitude Diagrams of LMC Clusters
Williams, Benjamin F.; Johnson, L. Clifton; Dolphin, Andrew +7 more
We present a framework to simultaneously constrain the values and uncertainties of the strength of convective core overshooting, metallicity, extinction, distance, and age in stellar populations. We then apply the framework to archival Hubble Space Telescope observations of six stellar clusters in the Large Magellanic Cloud that have reported ages…
A Ulysses Detection of Secondary Helium Neutrals
Wood, Brian E.; Müller, Hans-Reinhard; Witte, Manfred
The Interstellar Boundary EXplorer (IBEX) mission has recently studied the flow of interstellar neutral He atoms through the solar system and discovered the existence of a secondary He flow that likely originates in the outer heliosheath. We find evidence for this secondary component in Ulysses data. By coadding hundreds of Ulysses He beam maps to…
Masses of the Planetary Nebula Central Stars in the Galactic Globular Cluster System from HST Imaging and Spectroscopy
Bond, Howard E.; De Marco, Orsola; Lanz, Thierry +4 more
The globular cluster (GC) system of our Galaxy contains four planetary nebulae (PNe): K 648 (or Ps 1) in M15, IRAS 18333-2357 in M22, JaFu 1 in Pal 6, and JaFu 2 in NGC 6441. Because single-star evolution at the low stellar mass of present-epoch GCs was considered incapable of producing visible PNe, their origin presented a puzzle. We imaged the P…
The Solar Flare Complex Network
Safari, Hossein; Gheibi, Akbar; Javaherian, Mohsen
We investigate the characteristics of the solar flare complex network. The limited predictability, nonlinearity, and self-organized criticality of the flares allow us to study systems of flares in the field of the complex systems. Both the occurrence time and the location of flares detected from 2006 January 1 to 2016 July 21 are used to design th…
Evidence for Reduced Specific Star Formation Rates in the Centers of Massive Galaxies at z = 4
Papovich, Casey; Finkelstein, Steven L.; Dickinson, Mark +11 more
We perform the first spatially resolved stellar population study of galaxies in the early universe (z = 3.5-6.5), utilizing the Hubble Space Telescope Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey imaging data set over the GOODS-S field. We select a sample of 418 bright and extended galaxies at z = 3.5-6.5 from a parent sample of …