We present Spitzer Space Telescope spectra of the supernova remnant (SNR) N63A and its native HII region N63 in the Large Magellanic Cloud. We measure nebular fine-structure lines, H-2 lines, and polycyclic aromatic hydrocarbons (PAHs). The lines contribute half of the flux in the Spitzer 24 mu m image of N63A shocked lobes, but only <= 10% elsewhere. The mid-IR flux is largely due to thermal continuum emission from dust in and around N63A plasma. Electron densities are low everywhere; the differences in mid-IR line ratios separate N63A plasma and its high-excitation surroundings from N63A low-excitation optical lobes. We compare the observed line fluxes and ratios within N63A's shocked lobes and plasma with the predictions from models for moderate and fast shocks to constrain pre-shock densities and shock velocities. N63A's photoionized lobe contains a warm photodissociation region in pressure equilibrium with optically ionized gas. We apply a physical dust model to our spectra supplemented by MIPS photometry. We derive the intensity of radiation heating the dust, the mass fraction due to PAHs, and the masses of dust within our sampled regions and of cooler grains in the diffuse interstellar medium. N63A's shocked lobes and plasma contain similar to 0.07 M-circle dot of hot grains, comparable to amounts in other SNRs. Within N63A there is similar to 0.7 M-circle dot of warm grains exposed to >= 100 times the intensity of the local interstellar radiation field. Within the regions, 92% of the total dust mass resides in cool grains emitting <= 27% of their mid-IR luminosity.

A compact complex of line emission filaments in the galactic plane has the appearance of those expected of an evolved supernova remnant though non-thermal radio and X-ray emission have not yet been detected. This optical emission line region has now been observed with deep imagery and both low and high-dispersion spectroscopy. Diagnostic diagrams of the line intensities from the present spectra and the new kinematical observations both point to a supernova origin. However, several features of the nebular complex still require an explanation within this interpretation.

Spitzer MIPS 24 um images were obtained for 36 Galactic planetary nebulae (PNe) whose central stars are hot white dwarfs (WDs) or pre-WDs with effective temperatures of ~100,000 K or higher. Diffuse 24 um emission is detected in 28 of these PNe. The eight non-detections are angularly large PNe with very low H-alpha surface brightnesses. We find three types of correspondence between the 24 um emission and H-alpha line emission of these PNe: six show 24 um emission more extended than H-alpha emission, nine have a similar extent at 24 um and H-alpha, and 13 show diffuse 24 um emission near the center of the H-alpha shell. The sizes and surface brightnesses of these three groups of PNe and the non-detections suggest an evolutionary sequence, with the youngest ones being brightest and the most evolved ones undetected. The 24 um band emission from these PNe is attributed to [O IV] 25.9 um and [Ne V] 24.3 um line emission and dust continuum emission, but the relative contributions of these three components depend on the temperature of the central star and the distribution of gas and dust in the nebula.

We used Spitzer infrared observations to find the young stars of two H II regions in the Large Magellanic Cloud, N63 and N180. The young stellar object (YSO) candidates were identified in each nebula by means of color-color, color-magnitude diagrams, and the shapes of their spectral energy distributions (SEDs). The most luminous YSOs are found near the ionization fronts within strong 8 μm emission clumps. Most YSOs, less luminous, are seen in projection inside the H II regions. HST images show several Class I stars that have emerged along the borders of the H II regions; other YSOs are embedded in cometary clouds. The most luminous YSO of N63 is connected to a string of pointlike sources. Its SED can be modeled by a central source of stellar mass M⋆ between 7 and 11 M☉, with a circumstellar disk of outer radius Rd of ~55 AU, and an envelope of moderate accretion rate, of ~2 × 10−5 M☉ yr−1. N180 is experiencing a phase of star formation more intense than N63, attested by the properties of its most luminous YSO: M⋆ of 25 M☉, Rd of ~200 AU, and of ~1.5 × 10−3 M☉ yr−1. The modes of triggered star formation in N63 and N180 appear similar to those seen in Galactic H II regions.

Four mosaics of deep, continuum-subtracted, CCD images have been obtained over the extensive Galactic radio continuum shell, W50, which surrounds the remarkable stellar system SS 433. Two of these mosaics in the Hα + [N II] and [O III] 5007 A emission lines, respectively, cover a field of ∼2. ◦ 3 × 2. 5 which contains all of W50 but at a low angular resolution of 5 arcsec. The third and fourth mosaics cover the eastern (in [O III] 5007 A) and western (in Hα + [N II] 6548, 6584 A) filamentary nebulosity, respectively, but at an angular resolution of 1 arcsec. These observations are supplemented by new low-dispersion spectra and longslit, spatially resolved echelle spectra. The [O III] 5007 A images show for the first time the distribution of this emission in both the eastern and western filaments while new Hα + [N II] emission features are also found in both of these regions. Approaching flows of faintly emitting material from the bright eastern filaments of up 100 km s −1 in radial velocity are detected. The present observations also suggest that the heliocentric systemic radial velocity of the whole system is 56 ± 2k m s −1 . Furthermore, very deep imagery and high-resolution spectroscopy of a small part of the northern radio ridge of W50 has revealed for the first time the very faint optical nebulosity associated with this edge. It is suggested that patchy foreground dust along the ≈5 kpc sightline is inhibiting the detection of all of the optical nebulosity associated with W50. The interaction of the microquasar jets of SS 433 with the W50 shell is discussed.

We report the discovery of LSR 1826+3014, a very faint (V = 19.36) star with a very large proper motion (mu = 2."38 yr(-1)). A low- resolution red spectrum reveals that LSR 1826+3014 is an ultracool red dwarf with spectral type M8.5 V and with a radial velocity v(rad) = +77 +/- 10 km s(-1). LSR 1826+3014 is thus the faintest red dwarf ever discovered with a proper motion larger than 2" yr(-1). Optical and infrared photometry suggest that the star is at a distance d = 13.9 +/- 3.5 pc from the Sun, which implies that it is moving relative to the local standard of rest with a total velocity of 175 +/- 25 km s(-1). The numerical integration of its orbit suggests that LSR 1826+3014 is on a halo-like Galactic orbit.

We report the discovery of LSR1826+3014, a very faint (V=19.36) star with a very large proper motion (µ = 2.38 ′′ yr −1 ). A low resolution red spectrum reveals that LSR1826+3014 is an ultra-cool red dwarf with spectral type M8.5 V and with a radial velocity vrad = +77 ±10km s −1 . LSR1826+3014 is thus the faintest red dwarf ever discovered with a proper motion larger than 2 ′′ yr −1 . Optical and infrared photometry suggest that the star is at a distance d = 13.9 ± 3.5pc from the Sun, which implies it is moving relative to the local standard of rest with a total velocity of 175 ±25km s −1 . Numerical integration of its orbit suggests that LSR1826+3014 is on a halo-like galactic orbit.

We report the first orbital period determination for a dwarf nova (DN) in a globular cluster: V101 in M5 has a period of 5.796 ± 0.036 hr. We derived this period from I-band photometry acquired with the Calypso Observatory High Resolution Camera operating with tip-tilt adaptive optics correction. Observations from the South African Astronomical Observatory in the V band were also analyzed and exhibit a periodic signal of the same period. This orbital period suggests that V101 has a secondary of mid to late K spectral type with MV = +8.2 ± 0.5. The predicted spectral type is consistent with previous spectral observations in quiescence, which show a fairly red continuum. From the observed minimum brightness of V = 22.5, we derive a distance modulus of (m - M)V = 14.3 ± 0.5 to the DN, which supports V101's membership in the globular cluster M5. Measurement of the ellipsoidality effect indicates that the orbital plane of the V101 system is moderately inclined, but not enough to exhibit eclipses.

We have investigated the stellar content of the blue compact dwarf galaxies (BCDG) Tol 0610-387 by combining near infrared and optical images, complemented by spectroscopic data. The color maps, combined with the H-alpha image allowed us to identify clusters possibly dominated by red supergiant stars (RSG) associated with the current ongoing starburst episode. The analysis shows that the local colors and H-alpha emission, when compared with the predictions from population synthesis models, are consistent with an aging stellar population of around 10-15 Myrs dominated by red supergiant stars. This galaxy could therefore become a preferred target for the spectroscopic confirmation and analysis of its RSG population. Since the presence of such stars in BCDGs is seldom observed, we discuss the implications of RSG detection for the study of the starburst dynamics and evolution.

We present J, H and K surface photometry of 12 Blue Compact Dwarf Galaxies (BCDGs) selected from the southern sample (Doublier et al. 1999). A systematic excess of light in the K band with respect to the other bands in the visible and the near infrared is observed, indicating, since nebular emission is negligible, that a stellar population of red giants dominates the global flux from the galaxy. Moreover, comparisons of the metallicity-color relations of BCDGs and globular clusters show very little differences, indicating that BCDGs are most probably old, in the cosmological sense, systems. Local colors of the star forming regions show that these regions are indeed very young and possibly coeval across the galaxy when several starburst locations exist. At least 4 BCDGs (UM 465A and B, Haro 14 and Tololo 0610-378) show evidence of the presence of young red supergiant stars. The light distributions in the J, H and K bands are generally consistent with those in the optical, the differences are discussed. We confirm that our optical photometric classification remains valid in the near infrared. Thus, the global light distribution in the galaxy is an intrinsic property of the host galaxy independent of the presence of the starburst.

We present a spectrophotometric imaging study of the emission bubble N70 (DEM 301) in the Large Magellanic Cloud. N70 is approximately 100 pc in size with a nearly circular shell-like morphology. The nebular emission is powered by an uncertain combination of EUV photons, intense winds, and supernova shock waves from the central population of high-mass stars (the OB association LH 114). We have obtained narrow-band images (FWHM~6A) of N70 in the light of H-alpha (6563A), [N II] (6584A), [S II] (6717,6731A), and [O III] (5007A) along with the corresponding red and green continua. The resulting line fluxes and flux ratios are used to derive ionization rates, nebular densities, volume filling fractions, and excitation indices. Comparison with similar spectrophotometry of the Orion nebula indicates that the outer shell of N70 is especially enhanced in [SII] emission compared to its H-alpha and [N II] emission. The measured intensity ratios in N70 more closely match the range of excitation spanned by giant and supergiant H II shells and even by some of the supernova remnants observed in the LMC. From these spectral diagnostics, we conclude that EUV photons probably contribute most of the inner nebula's ionization, whereas a combination of photoionization plus collisional ionization and excitation of sulfur atoms by low-velocity shocks is driving the emission-line luminosities and intensity ratios observed in the outer shell. Considerations of the radiative and mechanical energetics that are involved may indicate the need for one or two supernova explosions having occurred during the last ~Myr.

We present the results of surface photometry on a new sample of Blue Compact Dwarf galaxies (BCDGs), in continuation to a previous paper (Doublier et al. 1997, hereafter Paper I). The 22 galaxies (plus two companions) discussed in the present paper have been selected in the Southern Hemisphere, from several lists. An atlas containing isophotal maps, surface brightnesses and B - R color profiles of the sample is given, together with the tables containing the photometric parameters.The results are consistent with those obtained in Paper I fur objects selected from the Byurakan Surveys in the Northern hemisphere. Similarly, we find about one fourth of the BCDGs showing a dominant r(1/4) brightness distribution component, one fourth of the BCDG showing a dominant exponential surface brightness profile, and about half of them show composite brightness distributions. Integrated properties, colors; mean surface brightnesses and luminosity-radius relations are investigated and discussed for the objects presented in this paper and Paper I. We found that r(1/4) BCDGs tend to show a different behaviour compared to the exponential BCDGs, with respect to colors, compactness and luminosity-radius relations. We also include a brief study of the surroundings of the galaxies, where we find several candidate companions.

The interstellar medium of LMC2, a well studied supershell in the Large Magellanic Cloud, has been probed in UV and optical absorption lines. The data allow to derive the kinematics, abundances and depletions of gas clouds in this supershell. The relative gas-phase abundances of observed elements with respect to sulphur are useful to determine the origins of the supershell absorption-line clouds.

The supernova SN 1978K has been noted for its lack of emission lines broader than a few thousand kilometers per second since its discovery in 1990. Modeling of the radio spectrum of the peculiar SN 1978K indicates the existence of H II absorption along the line of sight. To determine the nature of this absorbing region, we have obtained a high-dispersion spectrum of SN 1978K at the wavelength range 6530-6610 Å. The spectrum shows not only the moderately broad Hα emission of the supernova ejecta but also narrow nebular Hα and [N II] emission. The high [N II] λ6583/Hα ratio, 0.8-1.3, suggests that this radio-absorbing region is a stellar ejecta nebula. The expansion velocity and emission measure of the nebula are consistent with those seen in ejecta nebulae of luminous blue variables. Previous low-dispersion spectra have detected a strong [N II] λ5755 line, indicating an electron density of (3–12) × 105 cm-3. We argue that this stellar ejecta nebula is probably part of the preshock dense circumstellar envelope of SN 1978K. We further suggest that SN 1997ab may represent a young version of SN 1978K.

We present a spectrophotometric imaging study of the emission bubble N70 (DEM 301) in the Large Magellanic Cloud: N70 is approximately 100 pc in size with a nearly circular shell-like morphology. The nebular emission is powered by an uncertain combination of EUV photons, intense winds, and supernova shock waves from the central population of high-mass stars (the OB association LH 114). We have obtained narrowband images (FWHM similar to 6 Angstrom) of N70 in the light of H alpha lambda 6563, [N II] lambda 6584, [S II] lambda lambda 6717, 6731, and [O III] lambda 5007, along with the corresponding red and green continua. The resulting line fluxes and flux ratios are used to derive ionization rates, nebular densities, volume filling fractions, and excitation indices. The photoionizing luminosity inferred from the embedded stellar population is more than adequate to account for the observed hydrogen ionization rate.We compare the emission-line photometry with that derived from similar imaging of the Orion Nebula and with data collected from the literature on other emission-line regions in the LMC. Compared with the Orion Nebula, N70 shows much higher [S II]/H alpha intensity ratios that increase smoothly with radius-from less than 0.3 near the center to greater than 1.0 toward the outer filamentary shell. The measured intensity ratios in N70 more closely match the range of excitation spanned by giant and supergiant H II shells and by some of the supernova remnants observed in the LMC. The contending ionization and excitation processes in the interior and outer shell of N70 are evaluated in terms of the available data. EUV photons probably contribute most of the inner nebula's ionization, whereas a combination of photoionization plus collisional ionization and excitation of sulfur atoms by low-velocity shocks seems to best fit the emission-line luminosities and intensity ratios observed in the outer shell. Considerations of the radiative and mechanical energetics that are involved may indicate the need for one or two supernova explosions having occurred during the last similar to Myr.