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We present near- and mid-infrared observations of the pulsar-wind nebula (PWN) SNR B0540-69.3 and its associated supernova remnant made with the Spitzer Space Telescope. We report detections of the PWN with all four IRAC bands, the 24 mm band of MIPS, and the Infrared Spectrograph (IRS). We find no evidence of IR emission from the X-ray/radio shell surrounding the PWN resulting from the forward shock of the supernova blast wave. The flux of the PWN itself is dominated by synchrotron emission at shorter (IRAC) wavelengths, with a warm dust component longward of 20 mm. We show that this dust continuum can be explained by a small amount [~ (1-3) x 10[?]3 M] of dust at a temperature of ~50-65 K, heated by the shock wave generated by the PWN being driven into the inner edge of the ejecta. This is evidently dust synthesized in the supernova. We also report the detection of several lines in the spectrum of the PWN and present kinematic information about the PWN as determined from these lines. Kinematics are consistent with previous optical studies of this object. Line strengths are also broadly consistent with what one expects from optical line strengths. We find that lines arise from slow (~20 km s[?]1) shocks driven into oxygen-rich clumps in the shell swept up by an iron-nickel bubble, which have a density contrast of ~100-200 relative to the bulk of the ejecta, and that faster shocks (~250 km s[?]1) in the hydrogen envelope are required to heat dust grains to observed temperatures. We infer from estimates of heavy-element ejecta abundances that the progenitor star was likely in the range of 20-25 M.

Recent high spatial and spectral resolution investigations of the diffuse interstellar medium (ISM) have found significant evidence for small-scale variations in the interstellar gas on scales [?]1 pc. To better understand the nature of small-scale variations in the ISM, we have used the Kitt Peak National Observatory (KPNO) WIYN Hydra multiobject spectrograph, which has a mapping advantage over the single-axis, single-scale limitations of studies using high proper motion stars and binary stars, to obtain moderate-resolution ([?]12 km s-1) interstellar Na i D absorption spectra of 172 stars toward the double open cluster h and kh Persei. All of the sight lines toward the 150 stars with spectra that reveal absorption from the Perseus spiral arm show different interstellar Na i D absorption profiles in the Perseus arm gas. Additionally, we have utilized the KPNO coude feed spectrograph to obtain high-resolution ([?]3 km s-1) interstellar Na i D absorption spectra of 24 of the brighter stars toward h and kh Per. These spectra reveal an even greater complexity in the interstellar Na i D absorption in the Perseus arm gas and show individual components changing in number, velocity, and strength from sight line to sight line. If each of these individual velocity components represents an isolated cloud, then it would appear that the ISM of the Perseus arm gas consists of many small clouds. Although the absorption profiles vary even on the smallest scales probed by these high-resolution data ([?]30'', [?]0.35 pc), our analysis reveals that some interstellar Na i D absorption components from sight line to sight line are related, implying that the ISM toward h and kh Per is probably composed of sheets of gas in which we detect variations due to differences in the local physical conditions of the gas.

Recent high spatial and spectral resolution investigations of the diffuse interstellar medium (ISM) have found significant evidence for small-scale variations in the interstellar gas on scales ?1 pc. To better understand the nature of small-scale variations in the ISM, we have used the Kitt Peak National Observatory (KPNO) WIYN Hydra multiobject spectrograph, which has a mapping advantage over the single-axis, single-scale limitations of studies using high proper motion stars and binary stars, to obtain moderate-resolution (?12 km s?1) interstellar Na iD absorption spectra of 172 stars toward the double open cluster h and ? Persei. All of the sight lines toward the 150 stars with spectra that reveal absorption from the Perseus spiral arm show different interstellar Na iD absorption profiles in the Perseus arm gas. Additionally, we have utilized the KPNO coudé feed spectrograph to obtain high-resolution (?3 km s?1) interstellar Na iD absorption spectra of 24 of the brighter stars toward h and ? Per. These spectra reveal an even greater complexity in the interstellar Na iD absorption in the Perseus arm gas and show individual components changing in number, velocity, and strength from sight line to sight line. If each of these individual velocity components represents an isolated cloud, then it would appear that the ISM of the Perseus arm gas consists of many small clouds. Although the absorption profiles vary even on the smallest scales probed by these high-resolution data (?30?, ?0.35 pc), our analysis reveals that some interstellar Na iD absorption components from sight line to sight line are related, implying that the ISM toward h and ? Per is probably composed of sheets of gas in which we detect variations due to differences in the local physical conditions of the gas.

The giant H IIcomplex N11 in the Large Magellanic Cloud contains OB associations at several different stages in their life histories. We have obtained ROSATPSPC and HRI X-ray observations, Curtis Schmidt CCD images, echelle spectra in H? and [N II] lines, and IUEinterstellar absorption line observations of this region. The central bubble of N11 has an X-ray luminosity a factor of only 3-7 brighter than that predicted for an energy-conserving superbubble, making this the first detection of X-ray emission from a superbubble without a strong X-ray excess. The region N11B contains an extremely young OB association analogous to the central association of the Carina Nebula, apparently still embedded in its natal molecular cloud. We find that N11B emits diffuse X-ray emission, probably powered by stellar winds. Finally, we compare the tight cluster HD 32228 in N11 to R136 in 30 Dor. The latter is a strong X-ray source, while the former is not detected, showing that strong X-ray emission from compact objects is not a universal property of such tight clusters.

We present results from mid-IR spectroscopic observations of two young supernova remnants (SNRs) in the Large Magellanic Cloud made with the Spitzer Space Telescope. We imaged SNRs B0509-67.5 and B0519-69.0 with Spitzer in 2005, and follow-up spectroscopy presented here confirms the presence of warm, shock-heated dust, with no lines present in the spectrum. We use model fits to Spitzer Infrared Spectrograph (IRS) data to estimate the density of the post-shock gas. Both remnants show asymmetries in the infrared images, and we interpret bright spots as places where the forward shock is running into material that is several times denser than elsewhere. The densities we infer for these objects depend on the grain composition assumed, and we explore the effects of differing grain porosity on the model fits. We also analyze archival XMM-Newton RGS spectroscopic data, where both SNRs show strong lines of both Fe and Si, coming from ejecta, as well as strong O lines, which may come from ejecta or shocked ambient medium. We use model fits to IRS spectra to predict X-ray O line strengths for various grain models and values of the shock compression ratio. For 0509-67.5, we find that compact (solid) grain models require nearly all O lines in X-ray spectra to originate in reverse-shocked ejecta. Porous dust grains would lower the strength of ejecta lines relative to those arising in the shocked ambient medium. In 0519-69.0, we find significant evidence for a higher than standard compression ratio of 12, implying efficient cosmic-ray acceleration by the blast wave. A compact grain model is favored over porous grain models. We find that the dust-to-gas mass ratio of the ambient medium is significantly lower than what is expected in the interstellar medium.