Search Publications
Comparison of source detection procedures for XMM-Newton images
Valtchanov, I.; Pierre, M.; Gastaud, R.
Procedures based on current methods to detect sources in X-ray images are applied to simulated XMM-Newton images. All significant instrumental effects are taken into account, and two kinds of sources are considered - unresolved sources represented by the telescope PSF and extended ones represented by a beta -profile model. Different sets of test c…
The MACHO Project Hubble Space Telescope Follow-Up: Preliminary Results on the Location of the Large Magellanic Cloud Microlensing Source Stars
Alcock, C.; Allsman, R. A.; Alves, D. R. +21 more
We attempt to determine whether the MACHO microlensing source stars are drawn from the average population of the LMC or from a population behind the LMC by examining the Hubble Space Telescope (HST) color-magnitude diagram (CMD) of microlensing source stars. We present WFPC2 HST photometry of eight MACHO microlensing source stars and the surroundi…
1997 December 12 Helical Coronal Mass Ejection. II. Density, Energy Estimates, and Hydrodynamics
Raymond, J. C.; Ciaravella, A.; Peres, G. +2 more
We use Ultraviolet Coronagraph and Spectrometer (UVCS) spectra to investigate the density range of the plasma ejected during the coronal mass ejection (CME) on 1997 December 12. Time-dependent ionization states for several phenomenological models, with the boundary conditions derived from the EUV Imaging Telescope (EIT) and UVCS observations, were…
Validating the solar EUV proxy, E10.7
Tobiska, W. Kent
A demonstration of the improvement in thermospheric densities using the daily E10.7 proxy compared to F10.7 is shown. The daily altitude decay for the Solar Mesosphere Explorer (SME) satellite from April 1, 1982 through August 9, 1983, using both proxies and the actual altitude data, are compared. The F10.7 case fi…
Seeing Galaxies through Thick and Thin. IV. The Superposed Spiral Galaxies of NGC 3314
White, Raymond E., III; Keel, William C.
The superposed pair of spiral galaxies making up NGC 3314 offers a unique opportunity to trace the dust properties in a spiral galaxy. We analyze multicolor Hubble Space Telescope imaging, supported by ground-based near-IR imaging and fiber-array spectroscopy, to measure dust extinction in the foreground Sc galaxy NGC 3314A, which is backlit by th…
Low-frequency limit of Jovian radio emissions and implications on source locations and Io plasma wake
Zarka, Philippe; Crary, Frank J.; Queinnec, Julien
After deriving from Ulysses-URAP measurements the low-frequency limit of the Jovian hectometer emission spectrum ( 250±50 kHz at the -20 dB level below the emission peak), and confirming the absence of Io's control on Jovian radio emission below ∼1 MHz, we propose a single common explanation for these low-frequency limits: both are well explained …
Episodic dust formation by HD 192641 (WR 137) - II
Caldwell, J. J.; Morris, P. W.; van der Hucht, K. A. +9 more
We present new infrared photometry of the WC7-type Wolf-Rayet star HD 192641 (WR137) from 1985 to 1999. These data track the cooling of the dust cloud formed in the 1982-84 dust-formation episode from 1985 to 1991, the increase of the infrared flux from 1994.5 to a new dust-formation maximum in 1997 and its subsequent fading. From these and earlie…
The early-type galaxy population in Abell 2218
Smail, Ian; Davies, Roger L.; Bower, Richard G. +2 more
We present high signal-to-noise, moderate-resolution spectroscopy of 48 early-type members of the rich cluster Abell 2218 at z=0.18, taken with the LDSS2 spectrograph on the 4.2-m William Herschel Telescope. This sample both is larger and spans a wider galaxy luminosity range, down to MB*+1, than previous studies. In addition to the relatively lar…
Internal kinematics of the TW Hya association of young stars
Makarov, V. V.; Fabricius, C.
Thirty one probable kinematic members of the nearby TW Hya association of young stars are selected from the RASSBSC/Tycho-2 sample of stars luminous in X-rays, detected by ROSAT. Eight of them have been listed already as members of the association, and 23 are new candidates. The association occupies a volume of some 106 pc3, …
The nature of network oscillations
Doyle, J. G.; Banerjee, D.; O'Shea, E. +1 more
We examine time-series of spectral data obtained from the Coronal Diagnostic Spectrometer (CDS) and the Solar Ultraviolet Measurements of Emitted Radiation instrument (SUMER) onboard the Solar Heliospheric Observatory (SOHO) spacecraft, in the period 30-31 July 1996. The observations were obtained in lines, ranging in temperature from 12 000 K to …