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The distribution of radioactive ^(44)Ti in Cassiopeia A

Grefenstette, Brian W. and Fryer, Chris L. and Harrison, Fiona A. and Boggs, Steven E. and Delaney, Tracey and Laming, J. Martin and Reynolds, Stephen P. and Alexander, David M. and Barret, Didier and Christensen, Finn E. and Craig, William W. and Forster, Karl and Giommi, Paolo and Hailey, Charles J. and Hornstrup, Alan and Kitaguchi, Takao and Koglin, J. E. and Lopez, Laura and Mao, Peter H. and Madsen, Kristin K. and Miyasaka, Hiromasa and Mori, Kaya and Perri, Matteo and Pivovaroff, Michael J. and Puccetti, Simonetta and Rana, Vikram and Stern, Daniel and Westergaard, Niels J. and Wik, Daniel R. and Zhang, William W. and Zoglauer, Andreas (2017) The distribution of radioactive ^(44)Ti in Cassiopeia A. Astrophysical Journal, 834 (1). Art. No. 19. ISSN 0004-637X. doi:10.3847/1538-4357/834/1/19.

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The distribution of elements produced in the innermost layers of a supernova explosion is a key diagnostic for studying the collapse of massive stars. Here we present the results of a 2.4 Ms NuSTAR observing campaign aimed at studying the supernova remnant Cassiopeia A (Cas A). We perform spatially resolved spectroscopic analyses of the ^(44)Ti ejecta, which we use to determine the Doppler shift and thus the three-dimensional (3D) velocities of the ^(44)Ti ejecta. We find an initial ^(44)Ti mass of (1.54 ± 0.21) × 10^(−4) M_⊙, which has a present-day average momentum direction of 340° ± 15° projected onto the plane of the sky (measured clockwise from celestial north) and is tilted by 58° ± 20° into the plane of the sky away from the observer, roughly opposite to the inferred direction of motion of the central compact object. We find some ^(44)Ti ejecta that are clearly interior to the reverse shock and some that are clearly exterior to it. Where we observe ^(44)Ti ejecta exterior to the reverse shock we also see shock-heated iron; however, there are regions where we see iron but do not observe ^(44)Ti. This suggests that the local conditions of the supernova shock during explosive nucleosynthesis varied enough to suppress the production of ^(44)Ti by at least a factor of two in some regions, even in regions that are assumed to be the result of processes like α-rich freezeout that should produce both iron and titanium.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Grefenstette, Brian W.0000-0002-1984-2932
Fryer, Chris L.0000-0003-2624-0056
Harrison, Fiona A.0000-0003-2992-8024
Boggs, Steven E.0000-0001-9567-4224
Laming, J. Martin0000-0002-3362-7040
Alexander, David M.0000-0002-5896-6313
Barret, Didier0000-0002-0393-9190
Christensen, Finn E.0000-0001-5679-1946
Forster, Karl0000-0001-5800-5531
Lopez, Laura0000-0002-1790-3148
Madsen, Kristin K.0000-0003-1252-4891
Miyasaka, Hiromasa0000-0002-8074-4186
Mori, Kaya0000-0002-9709-5389
Puccetti, Simonetta0000-0002-2734-7835
Rana, Vikram0000-0003-1703-8796
Stern, Daniel0000-0003-2686-9241
Wik, Daniel R.0000-0001-8952-676X
Zhang, William W.0000-0002-1426-9698
Alternate Title:The distribution of radioactive 44Ti in Cassiopeia A
Additional Information:© 2016. The American Astronomical Society. Received 2016 August 30; revised 2016 October 17; accepted 2016 October 29; published 2016 December 27. We would like thank Dan Milisavljevic for providing the [S iii] data files, as well as Thomas Janka, Raph Hix, and Adam Burrows for their helpful comments. This 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. J.M.L. was supported by the NASA ADAP grant NNH16AC24I. 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). This research also made extensive use of the IDL Astronomy Library ( Additional figures were produced using the Veusz plotting package (© 2003–2016 Jeremy Sanders). 3D figures and movies were produced via the Anaconda Software Distribution ( of python and mayavi2 (Ramachandran & Varoquaux 2011). Facilities: NuSTAR, Chandra, Spitzer.
Group:NuSTAR, Space Radiation Laboratory, Infrared Processing and Analysis Center (IPAC), Astronomy Department
Funding AgencyGrant Number
Subject Keywords:gamma rays: general; ISM: supernova remnants; nuclear reactions, nucleosynthesis, abundances; X-rays: individual (Cassiopeia A)
Issue or Number:1
Record Number:CaltechAUTHORS:20170104-115334892
Persistent URL:
Official Citation:Brian W. Grefenstette et al 2017 ApJ 834 19
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:73210
Deposited By: George Porter
Deposited On:04 Jan 2017 21:03
Last Modified:11 Nov 2021 05:13

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