Search Publications
XMM-Newton EPIC Background Modeling for Extended Sources
Markevitch, M.; Lumb, D.; Nevalainen, J.
We use XMM-Newton blank-sky and closed-cover background data to explore background subtraction methods for large extended sources filling the EPIC field of view, such as nearby galaxy clusters, for which local background estimation is difficult. In particular, we investigate the uncertainties of the background modeling in the 0.8-7.0 keV band that…
Stars in the Hubble Ultra Deep Field
Panagia, N.; Walsh, J. R.; Koekemoer, A. M. +11 more
We identified 46 unresolved source candidates in the Hubble Ultra Deep Field (HUDF) down to i775=29.5. Unresolved objects were identified using a parameter S, which measures the deviation from the curve of growth of a point source. Extensive testing of this parameter was carried out, including the effects of decreasing signal-to-noise r…
Resolving the Inner Cavity of the HD 100546 Disk: A Candidate Young Planetary System?
Heap, S. R.; Grady, C. A.; Woodgate, B. +4 more
The inner 100 AU of HD 100546 is studied via far-ultraviolet long-slit spectroscopy with the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS). The star is surrounded by reflection nebulosity, which can be traced 100 AU in the continuum, and by emission from H I Lyα, N I, Si II, and fluorescent H2 transitions. The Lyα e…
Measurement of the Energy Release Rate and the Reconnection Rate in Solar Flares
Shibata, Kazunari; Isobe, Hiroaki; Takasaki, Hiroyuki
By using the method presented by Isobe et al., the nondimensional reconnection rate vin/vA has been determined for the impulsive phase of three two-ribbon flares, where vin is the velocity of the reconnection inflow and vA is the Alfvén velocity. The nondimensional reconnection rate is important to make …
The Link between Star Formation and Accretion in LINERs: A Comparison with Other Active Galactic Nucleus Subclasses
O'Halloran, B.; Dudik, R. P.; Satyapal, S. +1 more
We present archival high-resolution X-ray imaging observations of 25 nearby LINERs observed by ACIS on board Chandra. This sample builds on our previously published proprietary and archival X-ray observations and includes the complete set of LINERs with published black hole masses and FIR luminosities that have been observed by Chandra. Of the 82 …
Halos of Spiral Galaxies. I. The Tip of the Red Giant Branch as a Distance Indicator
Ferguson, H. C.; Rich, R. M.; Mouhcine, M. +2 more
We have imaged the halo populations of a sample of nearby spiral galaxies using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope with the aim of studying the stellar population properties and relating them to those of the host galaxies. In four galaxies, the red giant branch is sufficiently well populated to measure the magnit…
A Coherent Timing Solution for the Nearby Isolated Neutron Star RX J0720.4-3125
van Kerkwijk, M. H.; Kaplan, D. L.
We present the results of a dedicated effort to measure the spin-down rate of the nearby isolated neutron star RX J0720.4-3125. Comparing arrival times of the 8.39 s pulsations for data from Chandra, we derive an unambiguous timing solution for RX J0720.4-3125 that is accurate to <0.1 cycles over >5 years. Adding data from XMM and ROSAT, the…
Moving Magnetic Features as Prolongation of Penumbral Filaments
Martínez Pillet, V.; Sainz Dalda, A.
A sequence of 633 high spatial resolution magnetograms and continuum images from SOHO MDI of NOAA AR 0330 is used to study moving magnetic feature (MMF) activity in the moat surrounding a mature leader sunspot. The time-averaged frame shows that the moat region is covered by a magnetic field that exhibits the same polarity distribution as that obs…
Variations of the Mid-Infrared Emission Spectrum in Reflection Nebulae
Temi, Pasquale; Bregman, Jesse
Using spatial-spectral data cubes of reflection nebulae obtained by ISOCAM, we have observed a shift in the central wavelength of the 7.7 µm band within several reflection nebulae. This band, composed of components at 7.85 and 7.65 µm, shows a centroid shift from 7.75 µm near the edge of the nebulae to 7.65 µm toward the ce…
Detection of Water in the Shocked Gas Associated with IC 443: Constraints on Shock Models
Wang, Z.; Bergin, E. A.; Melnick, G. J. +5 more
We have used the Submillimeter Wave Astronomy Satellite (SWAS) to observe the ground-state 110-->101 transition of ortho-H2O at 557 GHz in three of the shocked molecular clumps associated with the supernova remnant IC 443. We also observed simultaneously the 487 GHz line (3,1-->3,2) of O2, the 492 …