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Register a new userXMM-Newton Observations of Two Candidate Supernova Remnants
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Candidate supernova remnants G23.5+0.1 and G25.5+0.0 were observed by XMM-Newton in the course of a snap-shot survey of plerionic and composite SNRs in the Galactic plane. In the field of G23.5+0.1, we detected an extended source, ~3 in diameter, which we tentatively interpret as a pulsar-wind nebula (PWN) of the middle-aged radio pulsar B1830-08. Our analysis suggests an association between PSR B1830-08 and the surrounding diffuse radio emission. If the radio emission is due to the SNR, then the pulsar must be significantly younger than its characteristic age. Alternatively, the radio emission may come from a relic PWN. In the field of G25.5+0.0, which contains the extended TeV source HESS J1837-069, we detected the recently discovered young high-energy pulsar J1838-0655 embedded in a PWN with extent of 1.3. We also detected another PWN candidate (AX J1837.3-0652) with an extent of 2 and unabsorbed luminosity L_(2-10 keV) ~ 4 x 10^33 erg/s at d=7 kpc. The third X-ray source, located within the extent of the HESS J1837-069, has a peculiar extended radio counterpart, possibly a radio galaxy with a double nucleus or a microquasar. We did not find any evidence of the SNR emission in the G25.5+0.0 field. We provide detailed multiwavelength analysis and identifications of other field sources and discuss robustness of the G25.5+0.0 and G23.5+0.1 classifications as SNRs. (abstract abridged)
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We present the analysis of supernova remnants (SNRs) and candidates in M31 identified in the XMM-Newton large programme survey of M31. SNRs are among the bright X-ray sources in a galaxy. They are good indicators of recent star formation activities of a galaxy and of the interstellar environment in which they evolve. By combining the X-ray data of sources in M31 with optical data as well as with optical and radio catalogues, we aim to compile a complete, revised list of SNRs emitting X-rays in M31 detected with XMM-Newton, study their luminosity and spatial distribution, and understand the X-ray spectrum of the brightest SNRs. We analysed the X-ray spectra of the twelve brightest SNRs and candidates using XMM-Newton data. The four brightest sources allowed us to perform a more detailed spectral analysis and the comparison of different models to describe their spectrum. For all M31 large programme sources we searched for optical counterparts on the Ha, [Sii], and [Oiii] images of the Local Group Galaxy Survey. We confirm 21 X-ray sources as counterparts of known SNRs. In addition, we identify five new X-ray sources as X-ray and optically emitting SNRs. Seventeen sources are no longer considered as SNR candidates. We have thus created a list of 26 X-ray SNRs and 20 candidates in M31 based on their X-ray, optical, and radio emission, which is the most recent complete list of X-ray SNRs in M31. The brightest SNRs have X-ray luminosities of up to 8 x 10^36 erg/s in the 0.35 - 2.0 keV band.
We have carried out a study of the X-ray properties of the supernova remnant (SNR) population in M33 with XMM-Newton, comprising deep observations of 8 fields in M33 covering all of the area within the D$_{25}$ contours, and with a typical luminosity of 7.1$times$10$^{34}$ erg s$^{-1}$ (0.2-2.0 keV) . Here we report our work to characterize the X-ray properties of the previously identified SNRs in M33, as well as our search for new X-ray detected SNRs. With our deep observations and large field of view we have detected 105 SNRs at the 3$sigma$ level, of which 54 SNRs are newly detected in X-rays, and three are newly discovered SNRs. Combining XMM-Newton data with deep Chandra survey data allows detailed spectral fitting of 15 SNRs, for which we have measured temperatures, ionization timescales, and individual abundances. This large sample of SNRs allows us to construct an X-ray luminosity function, and compare its shape to luminosity functions from host galaxies of differing metallicities and star formation rates to look for environmental effects on SNR properties. We conclude that while metallicity may play a role in SNR population characteristics, differing star formation histories on short timescales, and small-scale environmental effects appear to cause more significant differences between X-ray luminosity distributions. In addition, we analyze the X-ray detectability of SNRs, and find that in M33 SNRs with higher [SII]/H$alpha$ ratios, as well as those with smaller galactocentric distances, are more detectable in X-rays.
During a search for X-ray transients in the XMM-Newton archive within the EXTraS project, we discovered a new X-ray source that is detected only during a ~5 min interval of a ~21 h-long observation performed on 2011 June 21 (EXMM 023135.0-603743, probability of a random Poissonian fluctuation: ~$1.4times10^{-27}$). With dedicated follow-up observations, we found that its position is consistent with a star-forming galaxy (SFR = 1-2 $M_odot$ yr$^{-1}$) at redshift $z=0.092pm0.003$ ($d=435pm15$ Mpc). At this redshift, the energy released during the transient event was $2.8times10^{46}$ erg in the 0.3-10 keV energy band (in the source rest frame). The luminosity of the transient, together with its spectral and timing properties, make EXMM 023135.0-603743 a gripping analog to the X-ray transient associated to SN 2008D, which was discovered during a Swift/XRT observation of the nearby ($d=27$ Mpc) supernova-rich galaxy NGC 2770. We interpret the XMM-Newton event as a supernova shock break-out or an early cocoon, and show that our serendipitous discovery is compatible with the rate of core-collapse supernovae derived from optical observations and much higher than that of tidal disruption events.
W49B is a supernova remnant (SNR) discovered over 60 years ago in early radio surveys. It has since been observed over the entire wavelength range, with the X-ray morphology resembling a centrally-filled SNR. The nature of its progenitor star is still debated. Applying Smoothed Particle Inference techniques to analyze the X-Ray emission from W49B, we characterize the morphology and abundance distribution over the entire remnant. We also infer the density structure and derive the mass of individual elements present in the plasma. The morphology is consistent with an interaction between the remnant and a dense medium along the eastern edge, and some obstruction towards the west. We find a total mass of 130 $(pm 16)$ M$_{odot}$ and an estimated ejecta mass of 1.2 $(pm 0.2)$ M$_{odot}$. Comparison of the inferred abundance values and individual element masses with a wide selection of SN models suggests that deflagration-to-detonation (DDT) Type Ia models are the most compatible, with Fe abundance being the major discriminating factor. The general agreement between our abundance measurements and those from previous studies suggests that disagreement between various authors is more likely due to the choice of models used for comparison, rather than the abundance values themselves. While our abundance results lean toward a Type Ia origin, ambiguities in the interpretation of various morphological and spectral characteristics of W49B do not allow us to provide a definitive classification.
Supernova remnants (SNRs) are widely considered the most likely source of cosmic rays below the knee ($10^{15}$ eV). Studies of GeV and TeV gamma-ray emission in the vicinity of SNRs, in combination with multi-wavelength observations, can trace and constrain the nature of the charged particle population believed to be accelerated within SNR shocks. They may also speak to the diffusion and propagation of these energetic particles and to the nature of the acceleration mechanisms involved. We report here on recent observations of SNRs with VERITAS, including the discoveries of VHE gamma-ray emission from from G120.1+1.4 (Tychos SNR) and from the northwest shell of G78.2+2.1 (gamma-ray source VER J2019+407, which was discovered as a consequence of the VERITAS Cygnus region survey).
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