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Title: A spatially resolved study of the synchrotron emission and titanium in Tycho's supernova remnant using NuSTAR

Here, we report results from deep observations (~750 ks) of Tycho's supernova remnant (SNR) with NuSTAR. Using these data, we produce narrow-band images over several energy bands to identify the regions producing the hardest X-rays and to search for radioactive decay line emission from 44Ti. We find that the hardest (>10 keV) X-rays are concentrated in the southwest of Tycho, where recent Chandra observations have revealed high emissivity "stripes" associated with particles accelerated to the knee of the cosmic-ray spectrum. We do not find evidence of 44Ti, and we set limits on its presence and distribution within the SNR. Furthermore, these limits correspond to an upper-limit 44Ti mass of M44 < 2.4 × 10-4 M⊙ for a distance of 2.3 kpc. We perform a spatially resolved spectroscopic analysis of 66 regions across Tycho. We map the best-fit rolloff frequency of the hard X-ray spectra, and we compare these results to measurements of the shock expansion and ambient density. We also find that the highest energy electrons are accelerated at the lowest densities and in the fastest shocks, with a steep dependence of the rolloff frequency with shock velocity. Such a dependence is predicted by models where the maximum energy ofmore » accelerated electrons is limited by the age of the SNR rather than by synchrotron losses, but this scenario requires far lower magnetic field strengths than those derived from observations in Tycho. One way to reconcile these discrepant findings is through shock obliquity effects, and future observational work is necessary to explore the role of obliquity in the particle acceleration process.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [5] ;  [7] ;  [7] ;  [8] ;  [2] ;  [2] ;  [9] ;  [10] ;  [5]
  1. The Ohio State Univ., Columbus, OH (United States). Dept. of Astronomy and Center for Cosmology and Astro-Particle Physics
  2. California Inst. of Technology (CalTech), Pasadena, CA (United States). Cahill Center for Astrophysics
  3. North Carolina State Univ., Raleigh, NC (United States). Physics Dept.
  4. McGill Univ., Montreal, QC (Canada). Dept. of Physics
  5. Univ. of California, Berkeley, CA (United States). Space Sciences Lab.
  6. Technical Univ. of Denmark, Lyngby (Denmark). National Space Inst.
  7. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). CCS-2
  8. Columbia Univ., New York, NY (United States). Columbia Astrophysics Lab.
  9. California Inst. of Technology (CalTech), Pasadena, CA (United States). Jet Propulsion Lab.
  10. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
Publication Date:
OSTI Identifier:
1329582
Report Number(s):
LA-UR--15-21498
Journal ID: ISSN 1538-4357
Grant/Contract Number:
AC52-06NA25396; HST-HF2-51342.001; NNG08FD60C; NAS5-26555
Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 814; Journal Issue: 2; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS ISM: individual objects: (Tycho's SNR); ISM: supernova remnants; X-rays: ISM