We report on the first proper motion measurement in the supernova remnant RX J1713.7−3946 using the XMM-Newton X-ray telescope on a 13 yr time interval. This expansion measurement is carried out in ...the south-east region of the remnant, where two sharp filament structures are observed. For the outermost filament, the proper motion is 0.75+0.05-0.06 ± 0.069syst arcsec yr-1 which is equivalent to a shock speed of ~3500 km s-1 at a distance of 1 kpc. In contrast with the bright north-west region, where the shock is interacting with the border of the cavity, the shock in the south-east region is probably expanding in the original ambient medium carved by the progenitor and can be used to derive the current density at the shock and the age of the remnant. In the case where the shock is evolving in a wind profile (ρ ∝ r− s, s = 2) or in a uniform medium (s = 0), we estimate an age of ~2300 yr and ~1800 yr respectively for an ejecta power-law index of n = 9. The specific case of an ejecta power-law index of n = 7, and s = 0, yields an age of ~1500 yr, which would reconcile RX J1713.7−3946 with the historical records of SN 393. In all scenarios, we derive similar upstream densities of the order of 0.01 cm-3, compatible with the lack of thermal X-rays from the shocked ambient medium.
ABSTRACT Despite decades of intense efforts, many fundamental aspects of Type Ia supernovae (SNe Ia) remain elusive. One of the major open questions is whether the mass of an exploding white dwarf ...(WD) is close to the Chandrasekhar limit. Here, we report the detection of strong K-shell emission from stable Fe-peak elements in the Suzaku X-ray spectrum of the Type Ia supernova remnant (SNR) 3C 397. The high Ni/Fe and Mn/Fe mass ratios (0.11-0.24 and 0.018-0.033, respectively) in the hot plasma component that dominates the K-shell emission lines indicate a degree of neutronization in the supernova ejecta that can only be achieved by electron capture in the dense cores of exploding WDs with a near-Chandrasekhar mass. This suggests a single-degenerate origin for 3C 397, since Chandrasekhar mass progenitors are expected naturally if the WD accretes mass slowly from a companion. Together with other results supporting the double-degenerate scenario, our work adds to the mounting evidence that both progenitor channels make a significant contribution to the SN Ia rate in star-forming galaxies.
We report new Chandra observations of one of the few Galactic supernova remnants whose X-ray spectrum is dominated by nonthermal synchrotron radiation, G330.2+1.0. We find that between 2006 and 2017, ...some parts of the shell have expanded by about 1%, giving a free-expansion (undecelerated) age of about 1000 yr, and implying shock velocities there of 9000 km s−1 for a distance of 5 kpc. Somewhat slower expansion is seen elsewhere around the remnant periphery, in particular in compact knots. Because some deceleration must have taken place, we infer that G330.2+1.0 is less than about 1000 yr old. Thus, G330.2+1.0 is one of only four Galactic core-collapse remnants of the last millennium. The large size, low brightness, and young age require a very low ambient density, suggesting expansion in a stellar-wind bubble. We suggest that in the east, where some thermal emission is seen and expansion velocities are much slower, the shock has reached the edge of the cavity. The high shock velocities can easily accelerate relativistic electrons to X-ray-emitting energies. A few small regions show highly significant brightness changes by 10%-20%, both brightening and fading, a phenomenon previously observed in only two supernova remnants, indicating strong and/or turbulent magnetic fields.
Using the High Resolution Camera on board the Chandra X-ray Observatory, we have re-examined the proper motion of the central compact object RX J0822-4300 in the supernova remnant Puppis A. New data ...from 2010 August, combined with three archival data sets from as early as 1999 December, provide a baseline of 3886 days (more than 10.5 yr) to perform the measurement. Correlating the four positions of RX J0822-4300 measured in each data set implies a projected proper motion of mu = 71 + or - 12 mas yr super(-1). For a distance of 2 kpc, this proper motion is equivalent to a recoil velocity of 672 + or - 115 km s super(-1). The position angle is found to be 244 + or - 11. Both the magnitude and direction of the proper motion are in agreement with RX J0822-4300 originating near the optical expansion center of the supernova remnant. For a displacement of 371 + or - 31 arcsec between its birthplace and today's position, we deduce an age of (5.2 + or - 1.0) x 10 super(3)yr for RX J0822-4300. The age inferred from the neutron star proper motion and filament motions can be considered as two independent measurements of the same quantity. They average to 4450 + or - 750 yr for the age of the supernova remnant Puppis A.
We present moderately deep (125 ks) XMM-Newton observations of supernova remnant G330.2+1.0. This remnant is one of only a few known that fall into the "synchrotron-dominated" category, with the ...emission almost entirely dominated by a nonthermal continuum. Previous X-ray observations could only characterize the spectra of a few regions. Here, we examine the spectra from 14 regions surrounding the entire rim, finding that the spectral properties of the nonthermal emission do not vary significantly in any systematic way from one part of the forward shock to another, unlike several other remnants of this class. We confirm earlier findings that the power-law index, Γ, ranges from about 2.1-2.5, while the absorbing column density is generally between (2.0-2.6) × 1022 cm−2. Fits with the srcut model find values of the roll-off frequency in the range of 1017.1-1017.5 Hz, implying energies of accelerated electrons of ∼100 TeV. These values imply a high shock velocity of ∼4600 km s−1, favoring a young age of the remnant. Diffuse emission from the interior is nonthermal in origin as well, and fits to these regions yield similar values to those along the rim, also implying a young age. Thermal emission is present in the east, and the spectrum is consistent with a ∼650 km s−1 shock wave encountering interstellar or circumstellar material with a density of ∼1 cm−3.
ABSTRACT X-ray observations of supernova remnants (SNRs) allow us to investigate the chemical inhomogeneity of ejecta, offering unique insight into the nucleosynthesis in supernova explosions. Here ...we present detailed imaging and spectroscopic studies of the "Fe knot" located along the eastern rim of the Type Ia SNR Tycho (SN 1572) using Suzaku and Chandra long-exposure data. Surprisingly, the Suzaku spectrum of this knot shows no emission from Cr, Mn, or Ni, which is unusual for the Fe-rich regions in this SNR. Within the framework of the canonical delayed-detonation models for SN Ia, the observed mass ratios , , and (at 90% confidence) can only be achieved for a peak temperature of (5.3-5.7) K and a neutron excess of . These constraints rule out the deep, dense core of a Chandrasekhar-mass white dwarf as the origin of the Fe knot and favor either incomplete Si burning or an -rich freeze-out regime, probably close to the boundary. An explosive He burning regime is a possible alternative, although this hypothesis is in conflict with the main properties of this SNR.
Abstract
The nature of Type Ia supernovae remains controversial. The youngest remnants of Ia supernovae hold clues to the explosion and to the immediate surroundings. We present a third epoch of ...Chandra observations of the ∼600 yr old Type Ia remnant 0519–69.0 in the Large Magellanic Cloud, extending the time baseline to 21 yr from the initial 2000 observations. We find rapid expansion of X-ray emitting material, with an average velocity of 4760 km s
−1
. At the distance of the LMC, this corresponds to an undecelerated age of 750 yr, with the true age somewhat lower. We also find that the bright ring of emission has expanded by 1.3%, corresponding to a velocity of 1900 km s
−1
and an undecelerated age of 1600 yr. The high velocity of the peripheral X-rays, contrasted with the modest expansion of the main X-ray shell, provides further evidence for a massive shell of circumstellar material.
We present results from XMM-Newton/Reflection Grating Spectrometer (RGS) observations of prominent knots in the southernmost portion of Tycho's supernova remnant, known to be the remnant of a Type Ia ...supernova in 1572 C.E. By dispersing the photons from these knots out of the remnant with very little emission in front of or behind them, we obtained the nearly uncontaminated spectra of the knots. In the southernmost knot, the RGS successfully resolved numerous emission lines from Si, Ne, O He and Ly , and Fe L-shell. This is the first clear detection of O lines in Tycho's supernova remnant. Line broadening was measured to be ∼3 eV for the O He and ∼4.5 eV for the Fe L lines. If we attribute the broadening to pure thermal Doppler effects, then we obtain kTO and kTFe to be ∼400 keV and 1.5 MeV, respectively. These temperatures can be explained by heating in a reverse shock with a shock velocity of ∼3500 km s−1. The abundances obtained from fitting the RGS and MOS data together imply substantially elevated amounts of these materials, confirming previous studies that the knots are heated by a reverse shock, and thus contain ejecta material from the supernova. We are unable to find a Type Ia explosion model that reproduces these abundances, but this is likely the result of this knot being too small to extrapolate to the entire remnant.
Several young supernova remnants, including SN 1006, emit synchrotron X-rays in narrow filaments, hereafter thin rims, along their periphery. The widths of these rims imply 50–100 μG fields in the ...region immediately behind the shock, far larger than expected for the interstellar medium compressed by unmodified shocks, assuming electron radiative losses limit rim widths. However, magnetic field damping could also produce thin rims. Here we review the literature on rim width calculations, summarizing the case for magnetic field amplification. We extend these calculations to include an arbitrary power-law dependence of the diffusion coefficient on energy, D ∝ Eμ. Loss-limited rim widths should shrink with increasing photon energy, while magnetic-damping models predict widths almost independent of photon energy. We use these results to analyze Chandra observations of SN 1006, in particular the southwest limb. We parameterize the FWHM in terms of energy as FWHM ∝ EmE γ. Filament widths in SN 1006 decrease with energy; mE ∼ −0.3 to −0.8, implying magnetic field amplification by factors of 10–50, above the factor of four expected in strong unmodified shocks. For SN 1006, the rapid shrinkage rules out magnetic damping models. It also favors short mean free paths (small diffusion coefficients) and strong dependence of D on energy (μ ≥ 1).
Abstract
The supernova remnant (SNR) 3C 397 is thought to originate from a Type Ia supernova (SN Ia) explosion of a near-Chandrasekhar-mass (
M
Ch
) progenitor, based on the enhanced abundances of Mn ...and Ni revealed by previous X-ray study with Suzaku. Here we report follow-up XMM-Newton observations of this SNR, conducted with the aim of investigating the detailed spatial distribution of the Fe-peak elements. We have discovered an ejecta clump with extremely high abundances of Ti and Cr, in addition to Mn, Fe, and Ni, in the southern part of the SNR. The Fe mass of this ejecta clump is estimated to be ∼0.06
M
⊙
, under the assumption of a typical Fe yield for SNe Ia (i.e., ∼0.8
M
⊙
). The observed mass ratios among the Fe-peak elements and Ti require substantial neutronization that is achieved only in the innermost regions of a near-
M
Ch
SN Ia with a central density of
ρ
c
∼ 5 × 10
9
g cm
−3
, significantly higher than typically assumed for standard near-
M
Ch
SNe Ia (
ρ
c
∼ 2 × 10
9
g cm
−3
). The overproduction of the neutron-rich isotopes (e.g.,
50
Ti and
54
Cr) is significant in such high-
ρ
c
SNe Ia, with respect to the solar composition. Therefore, if 3C 397 is a typical high-
ρ
c
near-
M
Ch
SN Ia remnant, the solar abundances of these isotopes could be reproduced by the mixture of the high- and low-
ρ
c
near-
M
Ch
and sub-
M
Ch
Type Ia events, with ≲20% being high-
ρ
c
near-
M
Ch
.
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