TY  - GEN
A1  - Fraschetti, Federico
A1  - Pohl, Martin
T1  - Two-zone model for the broadband crab nebula spectrum
BT  - microscopic interpretation
T2  - The European physical journal : Web of Conferences : proceedings
N2  - We develop a simple two-zone interpretation of the broadband baseline Crab nebula spectrum between 10(-5) eV and similar to 100 TeV by using two distinct log-parabola energetic electrons distributions. We determine analytically the very-high energy photon spectrum as originated by inverse-Compton scattering of the far-infrared soft ambient photons within the nebula off a first population of electrons energized at the nebula termination shock. The broad and flat 200 GeV peak jointly observed by Fermi/LAT and MAGIC is naturally reproduced. The synchrotron radiation from a second energetic electron population explains the spectrum from the radio range up to similar to 10 keV. We infer from observations the energy dependence of the microscopic probability of remaining in proximity of the shock of the accelerating electrons.
Y1  - 2017
U6  - https://doi.org/10.1051/epjconf/201713602009
SN  - 2100-014X
VL  - 136
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Alvarado-Gómez, Julián D.
A1  - Cohen, Ofer
A1  - Drake, Jeremy J.
A1  - Fraschetti, Federico
A1  - Poppenhäger, Katja
A1  - Garraffo, Cecilia
A1  - Chebly, Judy
A1  - Ilin, Ekaterina
A1  - Harbach, Laura
A1  - Kochukhov, Oleg
T1  - Simulating the space weather in the AU Mic system: stellar winds and extreme coronal mass ejections
JF  - Astrophysical journal
N2  - Two close-in planets have been recently found around the M-dwarf flare star AU Microscopii (AU Mic). These Neptune-sized planets (AU Mic b and c) seem to be located very close to the so-called "evaporation valley" in the exoplanet population, making this system an important target for studying atmospheric loss on exoplanets. This process, while mainly driven by high-energy stellar radiation, will be strongly mediated by the space environment surrounding the planets. Here we present an investigation of this last area, performing 3D numerical modeling of the quiescent stellar wind from AU Mic, as well as time-dependent simulations describing the evolution of a highly energetic coronal mass ejection (CME) event in this system. Observational constraints on the stellar magnetic field and properties of the eruption are incorporated in our models. We carry out qualitative and quantitative characterizations of the stellar wind, the emerging CMEs, as well as the expected steady and transient conditions along the orbit of both exoplanets. Our results predict extreme space weather for AU Mic and its planets. This includes sub-Alfvenic regions for the large majority of the exoplanet orbits, very high dynamic and magnetic pressure values in quiescence (varying within 10(2)-10(5) times the dynamic pressure experienced by Earth), and an even harsher environment during the passage of any escaping CME associated with the frequent flaring observed in AU Mic. These space weather conditions alone pose an immense challenge for the survival of exoplanetary atmospheres (if any) in this system.
Y1  - 2022
U6  - https://doi.org/10.3847/1538-4357/ac54b8
SN  - 0004-637X
SN  - 1538-4357
VL  - 928
IS  - 2
PB  - IOP Publishing
CY  - Bristol
ER  -