The Distribution of Radioactive 44Ti in Cassiopeia A
Journal
Date Issued
2017
Author(s)
Grefenstette, Brian W.
•
Fryer, Chris L.
•
Harrison, Fiona A.
•
Boggs, Steven E.
•
DeLaney, Tracey
•
Laming, J. Martin
•
Reynolds, Stephen P.
•
Alexander, David M.
•
Barret, Didier
•
Christensen, Finn E.
•
Craig, William W.
•
Forster, Karl
•
Giommi, Paolo
•
Hailey, Charles J.
•
Hornstrup, Alan
•
Kitaguchi, Takao
•
Koglin, J. E.
•
Lopez, Laura
•
Mao, Peter H.
•
Madsen, Kristin K.
•
Miyasaka, Hiromasa
•
Mori, Kaya
•
•
Pivovaroff, Michael J.
•
Puccetti, Simonetta
•
Rana, Vikram
•
Stern, Daniel
•
Westergaard, Niels J.
•
Wik, Daniel R.
•
Zhang, William W.
•
Zoglauer, Andreas
Abstract
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 Ti-44 ejecta, which we use to determine the Doppler shift and thus the three-dimensional (3D) velocities of the Ti-44 ejecta. We find an initial Ti-44 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 Ti-44 ejecta that are clearly interior to the reverse shock and some that are clearly exterior to it. Where we observe Ti-44 ejecta exterior to the reverse shock we also see shock-heated iron; however, there are regions where we see iron but do not observe Ti-44. This suggests that the local conditions of the supernova shock during explosive nucleosynthesis varied enough to suppress the production of Ti-44 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.
Volume
834
Issue
1
Start page
19
Issn Identifier
0004-637X
Ads BibCode
2017ApJ...834...19G
Rights
open.access
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