The ultraviolet spectrum of HH 24A and its relation to optical spectra

The spectrum of the brightest part (HH 24A) of the complex Herbig-Haro object HH 24 in the short wavelength UV range was studied. The object is of special interest since it is known that in the optical range the continuum is due to dust scattered light originating in a young stellar object while the shock excited emission lines are formed in HH 24A itself. The spectrum shows only a continuum or a quasi-continuum and is not comparable to that of the typical high excitation object like HH1 or HH2 nor to that of a low excitation object like HH3 or HH47

Structural origin of gap states in semicrystalline polymers and the implications for charge transport

We quantify the degree of disorder in the {\pi}-{\pi} stacking direction of crystallites of a high performing semicrystalline semiconducting polymer with advanced X-ray lineshape analysis. Using first principles calculations, we obtain the density of states of a system of {\pi}-{\pi} stacked polymer chains with increasing amounts of paracrystalline disorder. We find that for an aligned film of PBTTT the paracrystalline disorder is 7.3%. This type of disorder induces a tail of trap states with a breadth of ~100 meV as determined through calculation. This finding agrees with previous device modeling and provides physical justification for the mobility edge model.Comment: Text and figures are unchanged in the new version of the file. The only modification is the addition of a funding source to the acknowledgment

The Spitzer Archival Far-InfraRed Extragalactic Survey

We present the Spitzer Archival Far-InfraRed Extragalactic Survey (SAFIRES). This program produces refined mosaics and source lists for all far-infrared extragalactic data taken during the more than six years of the cryogenic operation of the Spitzer Space Telescope. The SAFIRES products consist of far-infrared data in two wavelength bands (70 um and 160 um) across approximately 180 square degrees of sky, with source lists containing far-infrared fluxes for almost 40,000 extragalactic point sources. Thus, SAFIRES provides a large, robust archival far-infrared data set suitable for many scientific goals.Comment: 7 pages, 6 figures, published in ApJ

HST NICMOS Images of the HH 7/11 Outflow in NGC1333

We present near infrared images in H2 at 2.12um of the HH 7/11 outflow and its driving source SVS 13 taken with HST NICMOS 2 camera, as well as archival Ha and [SII] optical images obtained with the WFPC2 camera. The NICMOS high angular resolution observations confirm the nature of a small scale jet arising from SVS 13, and resolve a structure in the HH 7 working surface that could correspond to Mach disk H2 emission. The H2 jet has a length of 430 AU (at a distance of 350 pc), an aspect ratio of 2.2 and morphologically resembles the well known DG Tau optical micro-jet. The kinematical age of the jet (approx. 10 yr) coincides with the time since the last outburst from SVS 13. If we interpret the observed H2 flux density with molecular shock models of 20-30 km/s, then the jet has a density as high as 1.e+5 cc. The presence of this small jet warns that contamination by H2 emission from an outflow in studies searching for H2 in circumstellar disks is possible. At the working surface, the smooth H2 morphology of the HH 7 bowshock indicates that the magnetic field is strong, playing a major role in stabilizing this structure. The H2 flux density of the Mach disk, when compared with that of the bowshock, suggests that its emission is produced by molecular shocks of less than 20 km/s. The WFPC2 optical images display several of the global features already inferred from groundbased observations, like the filamentary structure in HH 8 and HH 10, which suggests a strong interaction of the outflow with its cavity. The H2 jet is not detected in {SII] or Ha, however, there is a small clump at approx. 5'' NE of SVS 13 that could be depicting the presence either of a different outburst event or the north edge of the outflow cavity.Comment: 13 pages, 5 figures (JPEGs

Mid-infrared Photometric Analysis of Main Belt Asteroids: A Technique for Color-Color Differentiation from Background Astrophysical Sources

The Spitzer Space Telescope routinely detects asteroids in astrophysical observations near the ecliptic plane. For the galactic or extragalactic astronomer, these solar system bodies can introduce appreciable uncertainty into the source identification process. We discuss an infrared color discrimination tool that may be used to distinguish between solar system objects and extrasolar sources. We employ four Spitzer Legacy data sets, the First Look Survey-Ecliptic Plane Component (FLS-EPC), SCOSMOS, SWIRE, and GOODS. We use the Standard Thermal Model to derive FLS-EPC main belt asteroid (MBA) diameters of 1-4 km for the numbered asteroids in our sample and note that several of our solar system sources may have fainter absolute magnitude values than previously thought. A number of the MBAs are detected at flux densities as low as a few tens of μJy at 3.6 μm. As the FLS-EPC provides the only 3.6-24.0 μm observations of individual asteroids to date, we are able to use this data set to carry out a detailed study of asteroid color in comparison to astrophysical sources observed by SCOSMOS, SWIRE, and GOODS. Both SCOSMOS and SWIRE have identified a significant number of asteroids in their data, and we investigate the effectiveness of using relative color to distinguish between asteroids and background objects. We find a notable difference in color in the IRAC 3.6-8.0 mm and MIPS 24 μm bands between the majority of MBAs, stars, galaxies, and active galactic nuclei, though this variation is less significant when comparing fluxes in individual bands. We find median colors for the FLS-EPC asteroids to be [F(5.8/3.6), F(8.0/4.5), F(24/8)] = (4.9 ± 1.8, 8.9 ± 7.4, 6.4 ± 2.3). Finally, we consider the utility of this technique for other mid-infrared observations that are sensitive to near-Earth objects, MBAs, and trans-Neptunian objects. We consider the potential of using color to differentiate between solar system and background sources for several space-based observatories, including Warm Spitzer, Herschel, and WISE

XTE J0111.2-7317 : a nebula-embedded X-ray binary in the SMC

The observed characteristics of the nebulosity surrounding the SMC High Mass X-ray Binary XTE J0111.2-7317 are examined in the context of three possible nebular types: SNR, bowshock and HII region. Observational evidence is presented which appears to support the interpretation that the nebulosity surrounding XTE J0111.2-7317 is an HII region. The source therefore appears to be a normal SMC Be X-ray binary (BeXRB) embedded in a locally enhanced ISM which it has photoionised to create an HII region. This is supported by observations of the X-ray outburst seen with BATSE and RXTE in 1998-1999. It exhibited characteristics typical of a giant or type II outburst in a BeXRB including large spin-up rates, Lx~10E38 erg/sq.cm-s, and a correlation between spin-up rate and pulsed flux. However, the temporal profile of the outburst was unusual, consisting of two similar intensity peaks, with the first peak of shorter duration than the second.Comment: Accepted for publication by MNRA

Confirmation of SBS 1150+599A As An Extremely Metal-Poor Planetary Nebula

SBS 1150+599A is a blue stellar object at high galactic latitude discovered in the Second Byurakan Survey. New high-resolution images of SBS 1150+599A are presented, demonstrating that it is very likely to be an old planetary nebula in the galactic halo, as suggested by Tovmassian et al (2001). An H-alpha image taken with the WIYN 3.5-m telescope and its "tip/tilt" module reveals the diameter of the nebula to be 9.2", comparable to that estimated from spectra by Tovmassian et al. Lower limits to the central star temperature were derived using the Zanstra hydrogen and helium methods to determine that the star's effective temperature must be > 68,000K and that the nebula is optically thin. New spectra from the MMT and FLWO telescopes are presented, revealing the presence of strong [Ne V] lambda 3425, indicating that the central star temperature must be > 100,000K. With the revised diameter, new central star temperature, and an improved central star luminosity, we can constrain photoionization models for the nebula significantly better than before. Because the emission-line data set is sparse, the models are still not conclusive. Nevertheless, we confirm that this nebula is an extremely metal-poor planetary nebula, having a value for O/H that is less than 1/100 solar, and possibly as low as 1/500 solar.Comment: 19 pages, 6 figures. Accepted for publication in the Astronomical Journa

Green's functions for parabolic systems of second order in time-varying domains

We construct Green's functions for divergence form, second order parabolic systems in non-smooth time-varying domains whose boundaries are locally represented as graph of functions that are Lipschitz continuous in the spatial variables and 1/2-H\"older continuous in the time variable, under the assumption that weak solutions of the system satisfy an interior H\"older continuity estimate. We also derive global pointwise estimates for Green's function in such time-varying domains under the assumption that weak solutions of the system vanishing on a portion of the boundary satisfy a certain local boundedness estimate and a local H\"older continuity estimate. In particular, our results apply to complex perturbations of a single real equation.Comment: 25 pages, 0 figur

The Spitzer c2d Survey of Nearby Dense Cores: VI. The Protostars of Lynds Dark Nebula 1221

Observations of Lynds Dark Nebula 1221 from the Spitzer Space Telescope are presented. These data show three candidate protostars towards L1221, only two of which were previously known. The infrared observations also show signatures of outflowing material, an interpretation which is also supported by radio observations with the Very Large Array. In addition, molecular line maps from the Five College Radio Astronomy Observatory are shown. One-dimensional dust continuum modelling of two of these protostars, IRS1 and IRS3, is described. These models show two distinctly different protostars forming in very similar environments. IRS1 shows a higher luminosity and larger inner radius of the envelope than IRS3. The disparity could be caused by a difference in age or mass, orientation of outflow cavities, or the impact of a binary in the IRS1 core.Comment: accepted for publication in Ap