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Uncertainty Quantification in Sunspot Counts
Mathieu, Sophie; von Sachs, Rainer; Ritter, Christian +2 more
Observing and counting sunspots constitutes one of the longest-running scientific experiments, with first observations dating back to Galileo (around 1610). Today the sunspot number (SN) time series acts as a benchmark of solar activity in a large range of physical models. An appropriate statistical modeling, adapted to the time series’ complex na…
Nitrogen-containing Anions and Tholin Growth in Titan’s Ionosphere: Implications for Cassini CAPS-ELS Observations
Coates, Andrew J.; Carrasco, Nathalie; Desai, Ravindra T. +4 more
The Cassini Plasma Spectrometer (CAPS) Electron Spectrometer (ELS) instrument on board Cassini revealed an unexpected abundance of negative ions above 950 km in Titan’s ionosphere. In situ measurements indicated the presence of negatively charged particles with mass-over-charge ratios up to 13,800 u/q. At present, only a handful of anions have bee…
Is Supernova Remnant Cassiopeia A a PeVatron?
Zhang, Xiao; Liu, Siming
Cassiopeia A, a well-observed young core-collapse supernova remnant (SNR), is considered to be one of the best candidates for studying very high-energy particle acceleration up to PeV via the diffusive shock mechanism. Recently, MAGIC observations revealed a γ-ray spectral cutoff at ∼ 3.5 {TeV}, suggesting that if the TeV γ-rays have a hadronic or…
Chandra-HETGS Characterization of an Outflowing Wind in the Accreting Millisecond Pulsar IGR J17591-2342
Wilms, Jörn; Chenevez, Jérôme; Rodriguez, Jérôme +5 more
An accreting millisecond X-ray pulsar, IGR J17591-2342 was discovered in 2018 August in scans of the Galactic bulge and center by the International Gamma-Ray Astrophysics Laboratory X-ray and gamma-ray observatory. It exhibited an unusual outburst profile with multiple peaks in the X-ray, as observed by several X-ray satellites over 3 months. Here…
The Influence of Polar Coronal Holes on the Polar ENA Flux Observed by IBEX
Reisenfeld, D. B.; McComas, D. J.; Schwadron, N. A. +6 more
Polar coronal holes (PCHs) fill the high-latitude heliosphere with fast solar wind during the minimum phase of the solar cycle. This leads to a hardening of the energy spectrum of the proton plasma in the inner heliosheath (IHS), observed as energetic neutral atoms (ENAs) by the Interstellar Boundary Explorer (IBEX). In particular, the highest-ene…
Simulating Solar Coronal Mass Ejections Constrained by Observations of Their Speed and Poloidal Flux
Singh, T.; Yalim, M. S.; Pogorelov, N. V. +1 more
We demonstrate how the parameters of a Gibson-Low flux-rope-based coronal mass ejection (CME) can be constrained using remote observations. Our Multi-Scale Fluid-Kinetic Simulation Suite has been used to simulate the propagation of a CME in a data-driven solar corona background computed using the photospheric magnetogram data. We constrain the CME…
X-Ray and Gamma-Ray Emission from Core-collapse Supernovae: Comparison of Three-dimensional Neutrino-driven Explosions with SN 1987A
Fransson, Claes; Janka, Hans-Thomas; Alp, Dennis +7 more
During the first few hundred days after the explosion, core-collapse supernovae (SNe) emit down-scattered X-rays and gamma-rays originating from radioactive line emissions, primarily from the 56Ni → 56Co → 56Fe chain. We use supernova (SN) models based on three-dimensional neutrino-driven explosion simulations of s…
Physical Properties of Galactic RV Tauri Stars from Gaia DR2 Data
Kiss, L. L.; Bódi, A.
We present the first period-luminosity and period-radius relation of Galactic RV Tauri variable stars. We have surveyed the literature for all variable stars belonging to this class and compiled the full set of their photometric and spectroscopic measurements. We crossmatched the final list of stars with the Gaia Data Release 2 database and took t…
The MOSDEF Survey: No Significant Enhancement in Star Formation or Deficit in Metallicity in Merging Galaxy Pairs at 1.5 ≲ z ≲ 3.5
Barro, Guillermo; Siana, Brian; Shapley, Alice E. +15 more
We study the properties of 30 spectroscopically identified pairs of galaxies observed during the peak epoch of star formation in the universe. These systems are drawn from the MOSFIRE Deep Evolution Field (MOSDEF) Survey at 1.4 ≤ z ≤ 3.8, and are interpreted as early-stage galaxy mergers. Galaxy pairs in our sample are identified as two objects wh…
Observations of Solar Wind from Earth-directed Coronal Pseudostreamers
Panasenco, O.; Wang, Y. -M.
Low-speed (≲450 km s-1) solar wind is widely considered to originate from streamer loops that intermittently release their contents into the heliosphere, in contrast to high-speed wind, which has its source in large coronal holes. To account for the presence of slow wind far from the heliospheric current sheet (HCS), it has been suggest…