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The Warped Circumstellar Disk of HD 100546
Quillen, Alice C.
We propose that the two-armed spiral features seen in visible Hubble Space Telescope images of scattered light in HD 100546's circumstellar disk are caused by the illumination of a warped outer disk. A tilt of 6°-15° from the symmetry plane can cause the observed surface brightness variations, providing the disk is very twisted (highly warped) at …
XMM-Newton View of the z > 0 Warm-Hot Intergalactic Medium toward Markarian 421
Elvis, Martin; Williams, Rik J.; Nicastro, Fabrizio +1 more
The recent detection with Chandra of two warm-hot intergalactic medium (WHIM) filaments toward Mrk 421 by Nicastro et al. provides a measurement of the bulk of the ``missing baryons'' in the nearby universe. Since Mrk 421 is a bright X-ray source, it is also frequently observed by the XMM-Newton Reflection Grating Spectrometer (RGS) for calibratio…
Direct Measurements of Energetic Neutral Hydrogen in the Interplanetary Medium
Fedorov, A.; Barabash, S.; Lundin, R. +16 more
We present an analysis of hydrogen energetic neutral atoms (ENAs) measured by the ASPERA-3 instrument on board Mars Express. We focus on ENAs that have no Martian origin. The energy spectra of these ENAs are all very similar and can be fitted well by a two-component power law. The fluxes, integrated from 0.2 to 10 keV, vary between 5×103
Deep HST Photometry of NGC 6388: Age and Horizontal-Branch Luminosity
Kinemuchi, Karen; Rich, R. M.; Catelan, M. +5 more
Using the Hubble Space Telescope, we have obtained the first color-magnitude diagram (CMD) to reach the main-sequence turnoff of the Galactic globular cluster NGC 6388. From a comparison between the cluster CMD and that of 47 Tucanae, we find that the bulk of the stars in these two clusters have nearly the same age and chemical composition. On the…
Simple Magnetic Flux Balance as an Indicator of Ne VIII Doppler Velocity Partitioning in an Equatorial Coronal Hole
McIntosh, Scott W.; Davey, Alisdair R.; Hassler, Donald M.
We present a novel investigation into the relationship between simple estimates of magnetic flux balance and the Ne VIII Doppler velocity partitioning of a large equatorial coronal hole observed by the Solar Ultraviolet Measurements of Emitted Radiation spectrometer (SUMER) on the Solar and Heliospheric Observatory in 1999 November. We demonstrate…
Testing Rotational Mixing Predictions with New Boron Abundances in Main-Sequence B-Type Stars
Lambert, D. L.; Mendel, J. T.; Venn, K. A. +2 more
New boron abundances for seven main-sequence B-type stars are determined from HST STIS spectroscopy around the B III 2066 Å line. Boron abundances provide a unique and critical test of stellar evolution models that include rotational mixing, since boron is destroyed in the surface layers of stars through shallow mixing long before other elements a…
The Water Vapor Abundance in Orion KL Outflows
Cernicharo, José; Viti, Serena; Barlow, Michael J. +7 more
We present the detection and modeling of more than 70 far-IR pure rotational lines of water vapor, including the 18O and 17O isotopologues, toward Orion KL. Observations were performed with the Long Wavelength Spectrometer in Fabry-Pérot mode (λ/Δλ~6800-9700) on board the Infrared Space Observatory between ~43 and 197 µ…
Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. III. Optical Variability and X-Ray/UV/Optical Correlations
O'Neill, Paul M.; Kaspi, Shai; Laor, Ari +11 more
We present optical observations of the low-luminosity Seyfert 1 nucleus of NGC 4395, as part of a multiwavelength reverberation-mapping program. Observations were carried out over two nights in 2004 April at Lick, Wise, and Kitt Peak Observatories. We obtained V- and B-band photometry, and spectra over the range 3500-6800 Å. Simultaneous Hubble Sp…
Spatially Resolved X-Ray Spectroscopy of Vela Shrapnel A
Katsuda, S.; Tsunemi, H.
We present detailed X-ray spectroscopy of Vela shrapnel A with the XMM-Newton satellite. Vela shrapnel A is one of several protrusions identified as bullets from the Vela supernova explosion. The XMM-Newton image shows that shrapnel A consists of a bright knot and a faint trailing wake. We extracted spectra from various regions, finding a prominen…
Disk-Jet Coupling in the Low-Mass X-Ray Binary 4U 1636-53 from INTEGRAL Observations
Ubertini, Pietro; Bazzano, Angela; Fiocchi, Mariateresa +1 more
We report on the spectral analysis of the neutron star (atoll-type) low-mass X-ray binary 4U 1636-53 as observed by the INTEGRAL and BeppoSAX satellites. The spectral behavior in three different epochs, corresponding to three different spectral states, has been investigated in depth. Spectra from two data sets show a continuum that is well describ…