Abstract
The results of a Suzaku observation of the supernova remnant (SNR) Kesteven 69 = G21.8−0.6 are presented. To estimate the sky background precisely, we conducted a simultaneous fit of the ...source region spectrum with the background region spectrum and found that the SNR spectrum is well represented by a two-component ionizing plasma model composed of a low-temperature plasma at kTe = 0.80 ± 0.11 keV and a high-temperature plasma at kTe = 1.5 ± 0.4 keV. The existence of a low-ionized Fe K line at 6.49 ± 0.07 keV was confirmed. The center energy of the line is consistent with those of type Ia SNRs.
The physical nature of thermal composite supernova remnants (SNRs) remains controversial. We have revisited the archival XMM-Newton and Chandra data of the thermal composite SNR Kesteven 41 (Kes 41 ...or G337.8-0.1) and performed a millimeter observation toward this source in the super(12)CO, super(13)CO, and C super(18)O lines. The X-ray emission, mainly concentrated toward the southwestern part of the SNR, is characterized by distinct S and Ar He-like lines in the spectra. The X-ray spectra can be fitted with an absorbed nonequilibrium ionization collisional plasma model at a temperature of 1.3-2.6 keV and an ionization timescale of 0.1-1.2 x 10 super(12) cm super(-3) s. The metal species S and Ar are overabundant, with 1.2-2.7 and 1.3-3.8 solar abundances, respectively, which strongly indicate the presence of a substantial ejecta component in the X-ray-emitting plasma of this SNR. Kes 41 is found to be associated with a giant molecular cloud (MC) at a systemic local standard of rest velocity of -50km s super(-1) and confined in a cavity delineated by a northern molecular shell, a western concave MC that features a discernible shell, and an H i cloud seen toward the southeast of the SNR. The birth of the SNR in a preexisting molecular cavity implies a mass of > ~18 M sub(middot in circle) for the progenitor if it was not in a binary system. Thermal conduction and cloudlet evaporation seem to be feasible mechanisms to interpret the X-ray thermal composite morphology, and the scenario of gas reheating by the shock reflected from the cavity wall is quantitatively consistent with the observations. An updated list of thermal composite SNRs is also presented in this paper.
ABSTRACT
We present a new optical sample of three Supernova Remnants (SNRs) and 16 Supernova Remnant (SNR) candidates in the Large Magellanic Cloud (LMC). These objects were originally selected using ...deep H α, S ii, and O iii narrow-band imaging. Most of the newly found objects are located in less dense regions, near or around the edges of the LMC’s main body. Together with previously suggested MCSNR J0541–6659, we confirm the SNR nature for two additional new objects: MCSNR J0522–6740 and MCSNR J0542–7104. Spectroscopic follow-up observations for 12 of the LMC objects confirm high S ii/H α emission-line ratios ranging from 0.5 to 1.1. We consider the candidate J0509–6402 to be a special example of the remnant of a possible type Ia Supernova (SN) which is situated some 2° (∼1.75 kpc) north from the main body of the LMC. We also find that the SNR candidates in our sample are significantly larger in size than the currently known LMC SNRs by a factor of ∼2. This could potentially imply that we are discovering a previously unknown but predicted, older class of large LMC SNRs that are only visible optically. Finally, we suggest that most of these LMC SNRs are residing in a very rarefied environment towards the end of their evolutionary span where they become less visible to radio and X-ray telescopes.
Abstract
We present the results of an X-ray spectral analysis of the northeast region of the candidate supernova remnant G189.6+3.3 with Suzaku. K-shell lines from highly ionized Ne, Mg, Si, and S ...were detected in the spectrum for the first time. In addition, a radiative recombining continuum (RRC) from He-like Si was clearly seen near 2.5 keV. This detection of an RRC reveals for the first time that G189.6+3.3 possesses an X-ray-emitting recombining plasma (RP). The extracted X-ray spectrum in the 0.6–10.0 keV energy band is well fitted with a model consisting of a collisional ionization equilibrium plasma component (associated with the interstellar medium) and an RP component (associated with the ejecta). The spectral feature shows that G189.6+3.3 is most likely to be a middle-aged SNR with an RP.
Abstract
We observed the nearby irregular galaxy IC 1613 with the Chandra X-ray Observatory, for 49.9 ks using the ACIS S3 chip, and with the VLA at 6 cm for 0.7 hr. The Chandra observation targeted ...the extensive bubble region in the northeast quadrant. We detect 31 sources within the
D
25
diameter above a significance of 3
σ
corresponding to a point-source luminosity limit
L
X
of ≈2 × 10
35
erg s
−1
(0.3–8 keV band). The VLA observation covered the entire galaxy with an angular resolution of 5″. We detect 11 sources: five do not fall on the ACIS chips, four fall on the S3 CCD, and two sit on the edge of the S2 CCD. We also describe corresponding Spitzer IRAC and MIPS images. Our detected source list matches the lists of two previous global point-source analyses except at the faint end. With the exception of one bright supernova remnant, the sources appear to be low-luminosity stellar sources (e.g., RS CVn stars) or X-ray binaries, or background objects. We identify one candidate supersoft source. All but one of the sources have at least one optical or infrared counterpart; three sources have radio counterparts. We describe our search for diffuse emission from the bubble region. We assign an upper limit of ≈5 × 10
35
erg s
−1
on the integrated flux and ≈1.4 × 10
30
erg s
−1
pc
−2
on the surface brightness emission in the 0.5–2 keV band from that region.
Abstract
We present the results of a spectral analysis of the central region of the mixed-morphology supernova remnant HB 9. A prior Ginga observation of this source detected a hard X-ray component ...above 4 keV, and the origin of this particular X-ray component is still unknown. Our results demonstrate that the extracted X-ray spectra are best represented by a model consisting of a collisional ionization equilibrium plasma with a temperature of ∼0.1–0.2 keV (interstellar matter component) and an ionizing plasma with a temperature of ∼0.6–0.7 keV and an ionization timescale of >1 × 1011 cm−3 s (ejecta component). No significant X-ray emission was found in the central region above 4 keV. The recombining plasma model reported by a previous work does not explain our spectra.
We present a joint analysis of optical emission-line and X-ray observations of the archetypical Galactic mixed-morphology supernova remnant (MMSNR) W28 (G6.4-0.1). MMSNRs comprise a class of sources ...whose shell-like radio morphology contrasts with a filled center in X-rays; the origin of these contrasting morphologies remains uncertain. Our CTIO images reveal enhanced S ii emission relative to H along the northern and eastern rims of W28. Hydroxyl (OH) masers are detected along these same rims, supporting prior studies suggesting that W28 is interacting with molecular clouds at these locations, as observed for several other MMSNRs. Our ROSAT HRI mosaic of W28 provides almost complete coverage of the supernova remnant (SNR). The X-ray and radio emission is generally anti-correlated, except for the luminous northeastern rim, which is prominent in both bands. Our Chandra observation sampled the X-ray-luminous central diffuse emission. Spectra extracted from the bright central peak and from nearby annular regions are best fit with two overionized recombining plasma models. We also find that while the X-ray emission from the central peak is dominated by swept-up material, that from the surrounding regions shows evidence for oxygen-rich ejecta, suggesting that W28 was produced by a massive progenitor. We also analyze the X-ray properties of two X-ray sources (CXOU J175857.55−233400.3 and 3XMM J180058.5-232735) projected into the interior of W28 and conclude that neither is a neutron star associated with the SNR. The former is likely to be a foreground cataclysmic variable or a quiescent low-mass X-ray-binary, while the latter is likely to be a coronally active main-sequence star.
We conducted an observation of the nearby irregular galaxy IC 1613 with the Chandra X-ray Observatory using the S3 chip of the Advanced CCD Imaging Spectrometer (ACIS) with an effective exposure time ...of 49.9 ks. The observation primarily targeted the extensive bubble and star formation region in the northeast quadrant of the galaxy. The only known supernova remnant (SNR) in IC 1613, S8, is also the galaxy's most luminous X-ray source (LX(0.3-8 keV) ∼5-6 × 1036 erg s−1). We resolve the SNR with Chandra and compare its nearly circular X-ray morphology with H and radio images. We assign an upper limit on the luminosity of any possible associated compact central object of 4 × 1035 erg s−1 (0.3-8 keV band) and conclude that we would detect a Crab-like pulsar but not a Cas A-like object. We infer an age for S8 of ∼3400-5600 yr and compare it to other SNRs in the Local Group. We suggest that S8 is a young composite SNR.
We present a multiwavelength examination of the supernova remnant (SNR) S26 in the nearby galaxy NGC 300 using data from Chandra X-ray Observatory, XMM-Newton X-ray Observatory, Hubble Space ...Telescope (HST), the Very Large Array, and the Australia Telescope Compact Array. We simultaneously fit all of the available X-ray data with a thermal plasma model and find a temperature of 0.77 0.13 keV with a hydrogen column density of ( ) × 1020 cm−2. HST imaging allows us to measure a semimajor axis of 0.78 0.10 arcsec ( ) and a semiminor axis of arcsec ( ). This precise size helps to constrain the age and velocity of the shock to be ( ) × 103 yr and km s−1. We also fit photometry of the surrounding stars to infer the age and mass of the progenitor star to be 8 1 Myr and M . Based on measured radio properties of the source and assuming equipartition, the estimated radio luminosity of ∼1.7 × 1034 erg s−1 over the 108-1011 Hz frequency range results in a minimum magnetic field associated with this SNR of 0.067 mG and the minimum energy needed to power the observed synchrotron emission of 1.5 × 1049 erg. The size and temperature of N300-S26 appear to be similar to the Galactic SNR G311.5-0.3 except that G311.5-0.3 has a significantly lower X-ray luminosity, is older, and has a slower shock velocity.
We present a study of the X-ray properties of five Galactic supernova remnants (SNRs)-Kes 17 (G304.6 + 0.1), G311.5-0.3, G346.6-0.2, CTB 37A (G348.5 + 0.1), and G348.5-0.0-that were detected in the ...infrared by Reach et al. in an analysis of data from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) that was conducted by the Spitzer Space Telescope. We present and analyze archival ASCA observations of Kes 17, G311.5-0.3, and G346.6-0.2, archival XMM-Newton observations of Kes 17, CTB 37A, and G348.5-0.0, and an archival Chandra observation of CTB 37A. Our study reveals that the four detected SNRs all feature center-filled X-ray morphologies and that the observed emission from these sources is thermal in all cases.
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