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A Spatially Resolved Study of the Synchrotron Emission and Titanium in Tycho's Supernova Remnant with NuSTAR

Lopez, Laura A. and Grefenstette, Brian W. and Reynolds, Stephen P. and An, Hongjun and Boggs, Steven E. and Christensen, Finn E. and Craig, William W. and Eriksen, Kristoffer A. and Fryer, Chris L. and Hailey, Charles J. and Harrison, Fiona A. and Madsen, Kristin K. and Stern, Daniel K. and Zhang, William W. and Zoglauer, Andreas (2015) A Spatially Resolved Study of the Synchrotron Emission and Titanium in Tycho's Supernova Remnant with NuSTAR. Astrophysical Journal, 814 (2). Art. No. 132. ISSN 0004-637X. doi:10.1088/0004-637X/814/2/132.

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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 ^(44)Ti. 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 ^(44)Ti, and we set limits on its presence and distribution within the SNR. These limits correspond to a upper-limit 44Ti mass of M44 < 2.4x10^(-4) M_sun for a distance of 2.3 kpc. We perform spatially resolved spectroscopic analysis of sixty-six 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 find that the highest energy electrons are accelerated at the lowest densities and in the fastest shocks, with a steep dependence of the roll-off frequency with shock velocity. Such a dependence is predicted by models where the maximum energy of 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.

Item Type:Article
Related URLs:
URLURL TypeDescription
Lopez, Laura A.0000-0002-1790-3148
Grefenstette, Brian W.0000-0002-1984-2932
Boggs, Steven E.0000-0001-9567-4224
Christensen, Finn E.0000-0001-5679-1946
Fryer, Chris L.0000-0003-2624-0056
Harrison, Fiona A.0000-0003-2992-8024
Madsen, Kristin K.0000-0003-1252-4891
Stern, Daniel K.0000-0003-2686-9241
Zhang, William W.0000-0002-1426-9698
Additional Information:© 2015 American Astronomical Society. Received 2015 April 26; accepted 2015 October 11; published 2015 November 30. We acknowledge helpful discussions with Drs. Marco Miceli, Lorenzo Sironi, and Patrick Slane. L.A.L. received support for this work from NASA through Hubble Fellowship grant number HST-HF2-51342.001 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. Additionally, the work was supported under NASA contract NNG08FD60C and made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by NASA. We thank the NuSTAR Operations, Software, and Calibration teams for support with the execution and analysis of these observations. This research made use of the NuSTAR Data Analysis Software (NuSTARDAS), jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). Facilities: NuSTAR, CXO, VLA.
Group:NuSTAR, Space Radiation Laboratory
Funding AgencyGrant Number
NASA Hubble FellowshipHST-HF2-51342.001
NASANAS 5-26555
Subject Keywords:ISM: individual objects:Tycho's SNR; ISM: supernova remnants; X-rays: ISM
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2015-20
Issue or Number:2
Record Number:CaltechAUTHORS:20160203-095010885
Persistent URL:
Official Citation:Laura A. Lopez et al 2015 ApJ 814 132
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64192
Deposited By: Joy Painter
Deposited On:03 Feb 2016 18:18
Last Modified:10 Nov 2021 23:27

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