X-Rays from Superbubbles in the Large Magellanic Cloud. VI. A Sample of Thirteen Superbubbles

The Astrophysical Journal Supplement Series (Impact Factor: 14.14). 04/2001; DOI: 10.1086/321794
Source: arXiv

ABSTRACT We present ROSAT observations and analysis of thirteen superbubbles in the Large Magellanic Cloud. Eleven of these observations have not been previously reported. We have studied the X-ray morphology of the superbubbles, and have extracted and analyzed their X-ray spectra. Diffuse X-ray emission is detected from each of these superbubbles, and X-ray emission is brighter than is theoretically expected for a wind-blown bubble, suggesting that the X-ray emission from the superbubbles has been enhanced by interactions between the superbubble shell and interior SNRs. We have also found significant positive correlations between the X-ray luminosity of a superbubble and its H-alpha luminosity, expansion velocity, and OB star count. Further, we have found that a large fraction of the superbubbles in the sample show evidence of ``breakout'' regions, where hot X-ray emitting gas extends beyond the H-alpha shell. Comment: 25 pages, 8 figures, to be published in Astrophysical Journal Supplement Series


Available from: Sean D. Points, Aug 10, 2013
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Interstellar bubbles appear to be smaller in observations than expected from calculations. Instabilities at the shell boundaries create three-dimensional ef- fects, and are probably responsible for part of this discrepancy. We investigate instabilities and dynamics in superbubbles by 3D hydrodynamics simulations with time-resolved energy input from massive stars, including the supernova explosions. We find that the superbubble shells are accelerated by supernova explosions, coincident with substantial brightening in soft X-ray emission. In between the explosions, the superbubbles lose energy efficiently, approaching the momentum-conserving snowplow limit. This and enhanced radiative losses due to instabilities reduce the expansion compared to the corresponding radiative bubbles in pressure-driven snowplow models with constant energy input. We note generally good agreement with observations of superbubbles and some open issues. In particular, there are hints that the shell velocities in the X-ray-bright phases is underpredicted.
    The Astrophysical Journal Letters 09/2014; 794(2). DOI:10.1088/2041-8205/794/2/L21 · 5.60 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Aims: We present a study of the superbubble (SB) 30 Dor C and the newly identified MCSNR J0536-6913 in the LMC. Methods: All available XMM-Newton data (exposure times of 420 ks EPIC-pn, 556 ks EPIC-MOS1, 614 ks EPIC-MOS2) were used to characterise the thermal X-ray emission in the region. An analysis of the non-thermal X-rays is also presented and discussed in the context of emission mechanisms previously suggested in the literature. These data are supplemented by X-ray data from Chandra, optical data from the MCELS, and radio data from ATCA and MOST. Results: The brightest thermal emission was found to be associated with a new supernova remnant, MCSNR J0536-6913. X-ray spectral analysis of MCSNR J0536-6913 suggested an ejecta-dominated remnant with lines of O, Ne, Mg, and Si, and a total 0.3-10 keV luminosity of ~8E+34 erg/s. Based on derived ejecta abundance ratios, we determined the mass of the stellar progenitor to be either ~18 M_sun or as high as >40 M_sun, though the spectral fits were subject to assumptions (e.g., uniform temperature and well-mixed ejecta). The thermal emission from the SB exhibited enrichment by alpha-process elements, evidence for a recent core-collapse SNR interaction with the SB shell. We detected non-thermal X-ray emission throughout 30 Dor C, with the brightest regions being highly correlated with the H-alpha and radio shells. We created a non-thermal spectral energy distribution for the north-eastern shell of 30 Dor C which was best-fit with an exponentially cut-off synchrotron model. Conclusions: Thermal X-ray emission from 30 Dor C is very complex, consisting of a large scale SB emission at the eastern shell wall with the brightest emission due to MCSNR J0536-6913. The fact that the non-thermal spectral energy distribution of the SB shell was observed to roll-off is further evidence that the non-thermal X-rays from 30 Dor C are synchrotron in origin.
    Astronomy and Astrophysics 09/2014; 573. DOI:10.1051/0004-6361/201424354 · 4.48 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A very sensitive X-ray investigation of the giant HII region N11 in the LMC was performed using the Chandra X-ray Observatory. The 300ks observation reveals X-ray sources with luminosities down to 10^32 erg/s, increasing by more than a factor of 5 the number of known point sources in the field. Amongst these detections are 13 massive stars (3 compact groups of massive stars, 9 O-stars and one early B-star) with log(Lx/Lbol)~-6.5 to -7, which may suggest that they are highly magnetic or colliding wind systems. On the other hand, the stacked signal for regions corresponding to undetected O-stars yields log(Lx/Lbol)~-7.3, i.e., an emission level comparable to similar Galactic stars despite the lower metallicity. Other point sources coincide with 11 foreground stars, 6 late-B/A stars in N11, and many background objects. This observation also uncovers the extent and detailed spatial properties of the soft, diffuse emission regions but the presence of some hotter plasma in their spectra suggests contamination by the unresolved stellar population.
    The Astrophysical Journal Supplement Series 06/2014; 213(2). DOI:10.1088/0067-0049/213/2/23 · 14.14 Impact Factor