Search Publications
XMM-Newton View of PKS 2155-304: Hardness Ratio and Cross-Correlation Analysis of EPIC pn Observations
Maraschi, L.; Treves, A.; Zhang, Y. H. +2 more
With currently available XMM-Newton EPIC pn observations spanned over about 3 yr, we present a detailed spectral and temporal variability of the 0.2-10 keV X-ray emission from the X-ray-bright BL Lac object PKS 2155-304. The spectral variability is examined with a model-independent hardness ratio method. We find that the spectral evolution of the …
Direct Measurement of the Size of 2003 UB313 from the Hubble Space Telescope
Brown, M. E.; Schaller, E. L.; Roe, H. G. +2 more
We have used the Hubble Space Telescope to directly measure the angular size of the large Kuiper Belt object 2003 UB313. By carefully calibrating the point-spread function of a nearby field star, we measure the size of 2003 UB313 to be 34.3+/-1.4 mas, corresponding to a diameter of 2400+/-100 km or a size ~5% larger than Pluto. The V-band geometri…
GALEX Observations of ``Passive Spirals'' in the Cluster Cl 0024+17: Clues to the Formation of S0 Galaxies
Smith, Graham P.; Treu, Tommaso; Ellis, Richard S. +4 more
We present new results from deep GALEX UV imaging of the cluster Cl 0024+17 at z~0.4. Rest-frame far-UV emission is detected from a large fraction of so-called passive spiral galaxies-a significant population that exhibits spiral morphology with little or no spectroscopic evidence of ongoing star formation. This population is thought to represent …
Quasi-periodic Oscillations and Strongly Comptonized X-Ray Emission from Holmberg IX X-1
Rao, A. R.; Dewangan, G. C.; Griffiths, R. E.
We report the discovery of a 200 mHz quasi-periodic oscillation (QPO) in the X-ray emission from a bright ultraluminous X-ray source (ULX), Holmberg IX X-1, using a long XMM-Newton observation. The QPO has a centroid at νQPO=202.5+4.9-3.8 mHz, a coherence Q≡νQPO/ΔνFWHM~9.3, and an amplitude (r…
An Ultraviolet to Mid-Infrared Study of the Physical and Wind Properties of HD 164270 (WC9) and Comparison to BD +30 3639 ([WC9])
Smith, J. D.; Morris, P. W.; Crowther, Paul A.
We present new Spitzer IRS observations of HD 164270 (WC9, WR103). A quantitative analysis of the UV, optical, near-, and mid-IR spectra of HD 164270 is presented, allowing for line blanketing and wind clumping, revealing T*~48 kK, logL/Lsolar~4.9, and M˙~10-5 Msolar yr-1 for a volume filling …
Far-Ultraviolet and X-Ray Observations of VV 114: Feedback in a Local Analog to Lyman Break Galaxies
Ptak, A.; Meurer, G.; Aloisi, A. +4 more
We have analyzed Far Ultraviolet Spectroscopic Explorer (FUSE), XMM-Newton, and Chandra observations of VV 114, a local galaxy merger with strong similarities to typical high-redshift Lyman break galaxies (LBGs). Diffuse thermal X-ray emission encompassing VV 114 has been observed by Chandra and XMM-Newton. This region of hot (kT~0.59 keV) gas has…
Tracking Large-Scale Propagating Coronal Wave Fronts (EIT Waves) using Automated Methods
Wills-Davey, M. J.
Recently developed mapping algorithms allow automated tracking of a propagating coronal wave, enabling the finding of reproducible fronts and propagation trajectories. Coronal observations taken by the Transition Region and Coronal Explorer (TRACE) on 1998 June 13 show a large-scale bright wave front, comparable to ``EIT waves'' seen with the Extr…
A Spitzer Study of Comets 2P/Encke, 67P/Churyumov-Gerasimenko, and C/2001 HT50 (LINEAR-NEAT)
Gehrz, Robert D.; Woodward, Charles E.; Pittichová, Jana +8 more
We present infrared images and spectra of comets 2P/Encke, 67P/Churyumov-Gerasimenko, and C/2001 HT50 (LINEAR-NEAT) as part of a larger program to observe comets inside of 5 AU from the Sun with the Spitzer Space Telescope. The nucleus of comet 2P/Encke was observed at two vastly different phase angles (20° and 63°). Model fits to the spectral ene…
MAGIC Observations of Very High Energy γ-Rays from HESS J1813-178
Bastieri, D.; Ciprini, S.; Longo, F. +130 more
Recently, the HESS collaboration has reported the detection of γ-ray emission above a few hundred GeV from eight new sources located close to the Galactic plane. The source HESS J1813-178 has sparked particular interest, as subsequent radio observations imply an association with supernova remnant G12.82-0.02. Triggered by the detection in very hig…
White Dwarf-Red Dwarf Systems Resolved with the Hubble Space Telescope. I. First Results
Hoard, D. W.; Farihi, J.; Wachter, S.
First results are presented for a Hubble Space Telescope (HST) Advanced Camera for Surveys snapshot study of white dwarfs with likely red dwarf companions. Of 48 targets observed and analyzed so far, 27 are totally or partially resolved into two or more components, while an additional 15 systems are almost certainly unresolved binaries. These resu…