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XRISM Observation of the Supernova Remnant N103B: Velocity Structure and Thermal Properties

Tyler Holland-Ashford, Brian J. Williams

Abstract

We present the first analysis of the X-ray Imaging and Spectroscopy Mission (XRISM) observation of the supernova remnant (SNR) N103B. We fit the X-ray spectrum taken with the Resolve microcalorimeter, which captured emission lines from the predominantly ejecta elements Si, S, Ar, Ca, Cr, Mn, and Fe. Notably, our fits require a previously unidentified high-temperature, highly-ionized, Fe-dominated plasma component with particularly high Cr and Mn abundances, matching a feature also present in the recent XRISM analysis of the SNR N132D. We find that all ejecta in N103B exhibits significant line broadening arising mostly from thermal Doppler broadening: increasing from $σ_{\rm th}\sim1700$ km s$^{-1}$ for intermediate-mass element (IME: Si, S, Ar, and Ca) ejecta to $\sim$2800 km s$^{-1}$ for Fe-rich ejecta. These velocities correspond to reverse shock velocities of $\sim$3500 and $\sim$5900 km s$^{-1}$, respectively, in the ejecta frame of rest. Finally, we find that the IMEs are redshifted with a bulk velocity of $\sim$360 km s$^{-1}$ while the Fe-dominated components are split: one redshifted at $\sim$1560 km s$^{-1}$ and the other blueshifted at $\sim$1020 km s$^{-1}$. Our results provide further support for the double-ring structure of N103B as it expands into the bipolar winds of a non-degenerate companion and highlight the strength of high-resolution spectroscopic observations of SNRs.

XRISM Observation of the Supernova Remnant N103B: Velocity Structure and Thermal Properties

Abstract

We present the first analysis of the X-ray Imaging and Spectroscopy Mission (XRISM) observation of the supernova remnant (SNR) N103B. We fit the X-ray spectrum taken with the Resolve microcalorimeter, which captured emission lines from the predominantly ejecta elements Si, S, Ar, Ca, Cr, Mn, and Fe. Notably, our fits require a previously unidentified high-temperature, highly-ionized, Fe-dominated plasma component with particularly high Cr and Mn abundances, matching a feature also present in the recent XRISM analysis of the SNR N132D. We find that all ejecta in N103B exhibits significant line broadening arising mostly from thermal Doppler broadening: increasing from km s for intermediate-mass element (IME: Si, S, Ar, and Ca) ejecta to 2800 km s for Fe-rich ejecta. These velocities correspond to reverse shock velocities of 3500 and 5900 km s, respectively, in the ejecta frame of rest. Finally, we find that the IMEs are redshifted with a bulk velocity of 360 km s while the Fe-dominated components are split: one redshifted at 1560 km s and the other blueshifted at 1020 km s. Our results provide further support for the double-ring structure of N103B as it expands into the bipolar winds of a non-degenerate companion and highlight the strength of high-resolution spectroscopic observations of SNRs.
Paper Structure (13 sections, 7 equations, 5 figures)

This paper contains 13 sections, 7 equations, 5 figures.

Table of Contents

  1. Introduction
  2. Observations and Data Reduction
  3. Data Analysis
  4. IME Ejecta
  5. IGE NEI Fitting
  6. Discussion
  7. Ejecta Kinematics
  8. Spatially-Resolved Spectral Analysis
  9. Ion Temperatures & Shock Kinematics
  10. Conclusion
  11. Best-fit NEI Parameters
  12. Gaussian Fitting
  13. Caveats of Gaussian Fitting

Figures (5)

  • Figure 1: The 1.75--8.0 keV spectrum and best fit model of the SNR N103B, showing (Top): Resolve data to which the model is fit, (Middle): the same Resolve data, but without the dedicated 10 keV component to capture the Fe Ly$\alpha$ emission at 6.95 keV (the grey highlighted region), and (Bottom): Suzaku data overlaid with a model fit to Resolve data and including an added systematic uncertainty of 0.1 to reflect effective area uncertainties. In addition to the optimal binning of kaastra16 used during fitting, the data is binned by an additional factor of 4 for plotting purposes only.
  • Figure 2: The 1.7--4.0 keV Resolve spectra of N103B, fit with non-equilibrium ionization models including variable components for line width, Doppler shift, ionization timescale, electron temperature, and ejecta abundances. The blue dashed line captures emission from shocked ejecta elements: mainly Si, S, Ar, and Ca. The cyan dash-dotted line captures the swept-up CSM/ISM emission found by fitting Suzaku data, and the black lines are the contributions from the non X-ray background. In addition to the optimal binning of kaastra16 used for fitting, the data is binned by an additional factor of 4 for plotting purposes only.
  • Figure 3: Top: The 1.7--2.33 keV (Si emission lines), Middle: The 2.39--3.0 keV (S emission lines), and Bottom: 2.93--4.7 keV (Ar & Ca emission lines) Resolve spectra of N103B, fit with non-equilibrium ionization models. The blue line captures emission from shocked ejecta emission, the cyan dash-dotted line captures the swept-up CSM/ISM emission, and the black dotted lines are the contributions from the non X-ray background. In addition to the optimal binning of kaastra16 used for fitting, the data is binned by an additional factor of 4 for plotting purposes only.
  • Figure 4: The 5.4--7.1 keV Resolve spectra of N103B fit with non-equilibrium ionization models to the 3.5--7.38 keV bandpass. The blue dashed line captures emission from the colder IME-dominated plasma component. The magenta dashed line captures emission from the lowly-ionized IGE-dominated component. The orange dash-dotted line captures emission from the high temperature, highly-ionized IGE-only component. The black dotted lines are the contributions from the non X-ray background. In addition to the optimal binning of kaastra16 used for fitting, the data is binned by an additional factor of 4 for plotting purposes only.
  • Figure 5: Top: The 1.75--3.0 keV Resolve spectrum of N103B, fit with Gaussians to capture emission lines from silicon (magenta dotted) and sulfur (blue dashed). Middle: The 3.0--4.65 keV Resolve spectrum of N103B, fit with Gaussian lines to capture emission from sulfur (blue dashed), argon (green doted-dashed), and calcium (magenta dotted). Bottom: The 5.1--7.38 keV Resolve spectrum of N103B, fit with Gaussians to capture emission lines from chromium (blue dashed), manganese (green dash-dotted), and iron (magenta dotted). The cyan dashed line is a bremsstrahlung model fit to the continuum, and the black dotted lines are the contributions from the non X-ray background. The Cr and Mn lines have normalizations set to match the emissivity ratios at 6.845 keV. In addition to the optimal binning of kaastra16 used for fitting, the data is binned by an additional factor of 4 for plotting purposes only.