73 research outputs found
Chandra observation of the Galactic supernova remnant CTB 109 (G109.1-1.0)
Context: We study the X-ray emission of the Galactic supernova remnant (SNR)
CTB 109 (G109.1-1.0), which is well-known for its enigmatic half-shell
morphology both in radio and in X-rays and is associated with the anomalous
X-ray pulsar (AXP) 1E2259+586. Aims: We want to understand the origin of the
X-ray bright feature inside the SNR called the Lobe and the details of the
interaction of the SNR shock wave with the ambient interstellar medium (ISM).
Methods: The Lobe and the northeastern part of the SNR were observed with
Chandra ACIS-I. We analysed the spectrum of the X-ray emission by dividing the
entire observed emission into small regions. The X-ray emission is best
reproduced with one-component or two-component non-equilibrium ionisation
models depending on the position. In the two-component model one emission
component represents the shocked ISM and the other the shocked ejecta. Results:
We detect enhanced element abundances, in particular for Si and Fe, in and
around the Lobe. There is one particular region next to the Lobe with a high Si
abundance of 3.3 (2.6 - 4.0) times the solar value. This is the first,
unequivocal detection of ejecta in CTB 109. Conclusions: The new Chandra data
confirm that the Lobe was created by the interaction of the SNR shock and the
supernova ejecta with dense and inhomogeneous medium in the environment of SNR
CTB 109. The newly calculated age of the SNR is t ~ 1.4 x 10^4 yr.Comment: Accepted for publication in A&A. 9 pages, 10 figure
XMM-Newton Large Program on SN1006 - I: Methods and Initial Results of Spatially-Resolved Spectroscopy
Based on our newly developed methods and the XMM-Newton large program of
SN1006, we extract and analyze the spectra from 3596 tessellated regions of
this SNR each with 0.3-8 keV counts . For the first time, we map out
multiple physical parameters, such as the temperature (), electron density
(), ionization parameter (), ionization age (), metal
abundances, as well as the radio-to-X-ray slope () and cutoff frequency
() of the synchrotron emission. We construct probability
distribution functions of and , and model them with several
Gaussians, in order to characterize the average thermal and ionization states
of such an extended source. We construct equivalent width (EW) maps based on
continuum interpolation with the spectral model of each regions. We then
compare the EW maps of OVII, OVIII, OVII K, Ne, Mg, SiXIII,
SiXIV, and S lines constructed with this method to those constructed with
linear interpolation. We further extract spectra from larger regions to confirm
the features revealed by parameter and EW maps, which are often not directly
detectable on X-ray intensity images. For example, O abundance is consistent
with solar across the SNR, except for a low-abundance hole in the center. This
"O Hole" has enhanced OVII K and Fe emissions, indicating
recently reverse shocked ejecta, but also has the highest , indicating
forward shocked ISM. Therefore, a multi-temperature model is needed to
decompose these components. The asymmetric metal distributions suggest there is
either an asymmetric explosion of the SN or an asymmetric distribution of the
ISM.Comment: 25 pages, 18 figures, 4 tables, MNRAS, in pres
XMM-Newton Large Program on SN1006 - II: Thermal Emission
Based on the XMM-Newton large program on SN1006 and our newly developed
spatially resolved spectroscopy tools (Paper~I), we study the thermal emission
from ISM and ejecta of SN1006 by analyzing the spectra extracted from 583
tessellated regions dominated by thermal emission. With some key improvements
in spectral analysis as compared to Paper~I, we obtain much better spectral
fitting results with less residuals. The spatial distributions of the thermal
and ionization states of the ISM and ejecta show different features, which are
consistent with a scenario that the ISM (ejecta) is heated and ionized by the
forward (reverse) shock propagating outward (inward). Different elements have
different spatial distributions and origins, with Ne mostly from the ISM, Si
and S from the ejecta, and O and Mg from both ISM and ejecta. Fe L-shell lines
are only detected in a small shell-like region SE to the center of SN1006,
indicating that most of the Fe-rich ejecta has not yet or just recently been
reached by the reverse shock. The overall ejecta abundance patterns for most of
the heavy elements, except for Fe and sometimes S, are consistent with typical
Type~Ia SN products. The NW half of the SNR interior probably represents a
region with turbulently mixed ISM and ejecta, so has enhanced emission from O,
Mg, Si, S, lower ejecta temperature, and a large diversity of ionization age.
In addition to the asymmetric ISM distribution, an asymmetric explosion of the
progenitor star is also needed to explain the asymmetric ejecta distribution.Comment: 9 pages, 7 figures, 1 table, MNRAS in pres
On the origin of the jet-like radio/X-ray morphology of G290.1-0.8
The origin and evolution of supernova remnants of the mixed-morphology class
is not well understood. Several remnants present distorted radio or X-ray
shells with jet-like structures. G290.1-0.8 (MSH 11-61A) belongs to this class.
We aim to investigate the nature of this supernova remnant in order to unveil
the origin of its particular morphology. We based our work on the study of the
X-ray emitting plasma properties and the conditions imposed by the cold
interstellar medium where the remnant expanded. We use archival radio, HI line
data and X-ray observations from XMM-Newton and Chandra observatories, to study
G290.1-0.8 and its surrounding medium. Spatially resolved spectral analysis and
mean photon energy maps are used to obtain physical and geometrical parameters
of the source. Radio continuum and HI line maps give crucial information to
understand the radio/X-ray morphology. The X-ray images show that the remnant
presents two opposite symmetric bright spots on a symmetry axis running towards
the NW-SE direction. Spectral analysis and mean photon energy maps confirm that
the physical conditions of the emitting plasma are not homogeneous throughout
the remnant. In fact, both bright spots have higher temperatures than the rest
of the plasma and its constituents have not reached ionization equilibrium yet.
HI line data reveal low density tube-like structures aligned along the same
direction. This evidence supports the idea that the particular X-ray morphology
observed is a direct consequence of the structure of the interstellar medium
where the remnant evolved. However, the possibility that an undetected
point-like object, as a neutron star, exists within the remnant and contributes
to the X-ray emission cannot be discarded. Finally, we suggest that a supernova
explosion due to the collapse of a high-mass star with a strong bipolar wind
can explain the supernova remnant morphology.Comment: 8 pages, 6 figures. Accepted for publication in A&
Discovery of X-ray Emission from the Galactic Supernova Remnant G32.8-0.1 with Suzaku
We present the first dedicated X-ray study of the supernova remnant (SNR)
G32.8-0.1 (Kes 78) with Suzaku. X-ray emission from the whole SNR shell has
been detected for the first time. The X-ray morphology is well correlated with
the emission from the radio shell, while anti-correlated with the molecular
cloud found in the SNR field. The X-ray spectrum shows not only conventional
low-temperature (kT ~ 0.6 keV) thermal emission in a non-equilibrium ionization
state, but also a very high temperature (kT ~ 3.4 keV) component with a very
low ionization timescale (~ 2.7e9 cm^{-3}s), or a hard non-thermal component
with a photon index Gamma~2.3. The average density of the low-temperature
plasma is rather low, of the order of 10^{-3}--10^{-2} cm^{-3}, implying that
this SNR is expanding into a low-density cavity. We discuss the X-ray emission
of the SNR, also detected in TeV with H.E.S.S., together with multi-wavelength
studies of the remnant and other gamma-ray emitting SNRs, such as W28 and RCW
86. Analysis of a time-variable source, 2XMM J185114.3-000004, found in the
northern part of the SNR, is also reported for the first time. Rapid time
variability and a heavily absorbed hard X-ray spectrum suggest that this source
could be a new supergiant fast X-ray transient.Comment: 20 pages, 14 figures, ApJ, in pres
Unraveling the Effects of Dense Medium on a Near to Bohm-Limit Acceleration in Kepler's SNR
The maximum energy of electrons accelerated by supernova remnants (SNR) is
typically limited by radiative losses. In this scenario, the synchrotron
cooling time scale is equal to the acceleration time scale. On the other hand,
the low propagation speed of a shock in a dense medium is expected to result in
an extended acceleration time scale, thus inducing a decrease in the maximum
electron energy for a given SNR age and in the X-ray nonthermal flux. The young
Kepler's SNR shows an enhanced efficiency of the acceleration process, which is
close to the Bohm limit in the north of its shell, where the shock is slowed
down by a dense circumstellar medium. Conversely, in the south, where no
interaction with a dense medium is evident and the shock speed is high, the
acceleration proceeds with a higher Bohm factor. To investigate this scenario,
we studied the temporal evolution of the non-thermal emission, taking advantage
of two Chandra X-ray observations of Kepler's SNR (performed in 2006 and 2014).
We analyzed the spectra of different filaments both in the north and south of
the shell, and measured their proper motion. We found a region with low shock
velocity where we measured a significant decrease in flux from 2006 to 2014.
This could be the first evidence of fading synchrotron emission in Kepler's
SNR. This result suggests that under a certain threshold of shock speed the
acceleration process could exit the loss-limited regime
Suzaku Detection of Diffuse Hard X-Ray Emission outside Vela X
Vela X is a large, 3x2 degrees, radio-emitting pulsar wind nebula (PWN)
powered by the Vela pulsar in the Vela supernova remnant. Using four Suzaku/XIS
observations pointed just outside Vela X, we find hard X-ray emission extending
throughout the fields of view. The hard X-ray spectra are well represented by a
power-law. The photon index is measured to be constant at Gamma~2.4, similar to
that of the southern outer part of Vela X. The power-law flux decreases with
increasing distance from the pulsar. These properties lead us to propose that
the hard X-ray emission is associated with the Vela PWN. The larger X-ray
extension found in this work strongly suggests that distinct populations
relativistic electrons form the X-ray PWN and Vela X, as was recently inferred
from multiwavelength spectral modeling of Vela X.Comment: 18 pages, 7 figures, accepted for publication in PASJ (Suzaku Special
Issue
The origin of the X-ray emitting plasma in the eastern edge of the Cygnus Loop
The Cygnus Loop is interacting with a protrusion of the cavity wall in its
eastern edge (the XA region), where the X-ray emission is very bright. The
complexity of the environment and the non-linear physical processes of the
shock-cloud interaction make the origin of the X-ray emission still not well
understood. Our purpose is to understand the physical origin of the X-ray
emission in the XA region, addressing, in particular, the role of thermal
conduction in the interaction process. We analyzed two XMM-Newton data sets,
performing image analysis and spatially resolved spectral analysis on a set of
homogeneous regions. We applied a recently developed diagnostic tool to compare
spectral analysis results with predictions of theoretical models, and to
estimate the efficiency of thermal conduction on the X-ray emitting shocked
plasma. We found that the inhomogeneous cavity wall contains both large clumps
(the protrusion) and small isolated clumps with different densities. A large
indentation bent over to the south is detected. The abundance of the
surrounding ISM is ~0.2 times solar value. We confirmed the important role of
thermal conduction in the evolution of X-ray emitting plasma during shock-cloud
interaction.Comment: 7 pages, 5 figures, MNRAS in pres
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