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Electron density along a coronal loop observed with CDS/SOHO
Doyle, J. G.; Madjarska, M. S.; Ugarte-Urra, I. +1 more
The analysis of a coronal loop observed by CDS and EIT on board SOHO is presented. The loop was situated above the North-East limb at a latitude of ~48°, being clearly visible in the hottest lines of the dataset, Fe xvi 360.76 Å, i.e. greater than 2 000 000 K. The cooler lines in the sample (i.e. O v 629.73 Å and He i 584.35 Å) showed only a brigh…
Comparison of Star Clusters With and Without Wolf-Rayet Stars in Wolf-Rayet Galaxies
Kobulnicky, Henry A.; Dufour, Reginald J.; Buckalew, Brent A.
We compare the properties of young star clusters with and without Wolf-Rayet (W-R) stars in W-R galaxies using optical, near-infrared imagery and optical spectroscopy. Our work identifies the clusters with W-R stars in these galaxies for the first time. With this information, comparisons of clusters with and without W-R stars are now possible, ena…
X-ray observations of the old open stellar cluster NGC 188
Gondoin, P.
I present the analysis results from XMM-Newton observations of the old open stellar cluster NGC 188, which has an age of about 7 Gyr and a near solar metallicity. 58 X-ray sources were detected in the field of view of the EPIC MOS and pn cameras, and 46 sources are new X-ray detections. Visible counterparts were found for 20 sources including the …
Heavy element abundances in DAO white dwarfs measured from FUSE data
Barstow, M. A.; Holberg, J. B.; Hubeny, I. +3 more
We present heavy element abundance measurements for 16 DAO white dwarfs, determined from Far-Ultraviolet Spectroscopic Explorer (FUSE) spectra. Evidence of absorption by heavy elements was found in the spectra of all the objects. Measurements were made using models that adopted the temperatures, gravities and helium abundances determined from both…
A Virgo high-resolution Hα kinematical survey. I. NGC 4438
Adami, C.; Chemin, L.; Boselli, A. +8 more
New Hα emission-line observations of the Virgo cluster galaxy NGC 4438 are presented. Fabry-Perot interferometry data at an effective angular resolution of ~2 arcsec are used to map the kinematics of the ionized gas in the galaxy. For the first time we obtain a velocity field covering a large area in NGC 4438, much larger than that deduced from pr…
Spatially Resolved Spectral Analysis of Vela Shrapnel D
Katsuda, Satoru; Tsunemi, Hiroshi
The ROSAT all-sky survey discovered several `shrapnels', showing boomerang structures outside the Vela supernova remnant. We observed shrapnel D with the XMM-Newton satellite. There is an X-ray bright ridge structure in our FOV running from north to south. Applying the VNEI model to X-ray spectra of various regions, we find that the plasma in the …
Spectropolarimetry and Radiative Transfer Modeling of Three Proto-Planetary Nebulae
Gordon, Karl D.; Bieging, John H.; Schmidt, Gary D. +3 more
We measured the spectrum of polarization for three proto-planetary nebulae (PPNs), IRAS 17411-2411, IRAS 08005-2356, and IRAS 04296+3429, and made model calculations with the dust-scattering Monte Carlo code DIRTY and the dust emission code 2Dust. We show that high levels of polarization in these PPNs correlate with extreme asymptotic giant branch…
The Stellar Structure of Irregular Galaxies. Face-on Galaxies
Tikhonov, N. A.
Stellar photometry of nearby irregular galaxies of the Local Group is used to identify and study the young and old stellar populations of these galaxies. An analysis of the spatial distributions of stars of different ages in face-on galaxies shows that the young stellar populations in irregular galaxies are concentrated toward the center, and form…
A 2 Hour Quasi Period in an Ultraluminous X-Ray Source in NGC 628
Bregman, Joel N.; Seitzer, Patrick; Espaillat, Catherine +3 more
Quasi-periodic oscillations and X-ray spectroscopy are powerful probes of black hole masses and accretion disks, and here we apply these diagnostics to an ultraluminous X-ray source (ULX) in the spiral galaxy NGC 628 (M74). This object was observed four times over 2 years with the Chandra X-Ray Observatory and XMM-Newton, with three long observati…
Deep ALTAIR+NIRI Imaging of the Disk and Bulge of M31
Davidge, T. J.; Olsen, K. A. G.; Rigaut, F. +2 more
Deep J, H, and K' images, recorded with the ALTAIR adaptive optics system and NIRI imager on Gemini North, are used to probe the stellar content of the disk and bulge of the Local Group galaxy M31. With an FWHM near 0.08" in K, these are the highest angular resolution near-infrared images yet obtained of this galaxy. One field samples the outer di…