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Title: BRIGHT HOT IMPACTS BY ERUPTED FRAGMENTS FALLING BACK ON THE SUN: UV REDSHIFTS IN STELLAR ACCRETION

A solar eruption after a flare on 2011 June 7 produced EUV-bright impacts of fallbacks far from the eruption site, observed with the Solar Dynamics Observatory. These impacts can be taken as a template for the impact of stellar accretion flows. Broad redshifted UV lines have been commonly observed in young accreting stars. Here we study the emission from the impacts in the Atmospheric Imaging Assembly's UV channels and compare the inferred velocity distribution to stellar observations. We model the impacts with two-dimensional hydrodynamic simulations. We find that the localized UV 1600 Å emission and its timing with respect to the EUV emission can be explained by the impact of a cloud of fragments. The first impacts produce strong initial upflows. The following fragments are hit and shocked by these upflows. The UV emission comes mostly from the shocked front shell of the fragments while they are still falling, and is therefore redshifted when observed from above. The EUV emission instead continues from the hot surface layer that is fed by the impacts. Fragmented accretion can therefore explain broad redshifted UV lines (e.g., C IV 1550 Å) to speeds around 400 km s{sup –1} observed in accreting young stellar objects.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Dipartimento di Fisica and Chimica, Università di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy)
  2. INAF-Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy)
  3. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 58, Cambridge, MA 02138 (United States)
  4. Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109 (United States)
  5. Lockheed Martin Advanced Technology Center, Palo Alto, CA 94304 (United States)
Publication Date:
OSTI Identifier:
22364878
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 797; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CARBON IONS; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; ERUPTION; EXTREME ULTRAVIOLET RADIATION; GAMMA RADIATION; HYDRODYNAMICS; LAYERS; RED SHIFT; SOLAR FLARES; STAR ACCRETION; SUN; SURFACES; X RADIATION