Search Publications
Modeling Solar Oscillation Power Spectra. I. Adaptive Response Function for Doppler Velocity Measurements
Jefferies, Stuart M.; Vorontsov, Sergei V.
Improving the accuracy and resolution of helioseismic inversions calls for more accurate modeling of the observational p-mode power spectra from which the solar oscillation frequencies are traditionally measured. We present a new technique of calculating the response function (leakage matrix) for Doppler velocity measurements that is based largely…
Diffuse Component Spectra of Solar Active Regions at Submillimeter Wavelengths
Silva, Adriana V. R.; Kaufmann, Pierre; Levato, Hugo +4 more
Solar maps at 212 and 405 GHz obtained by the Solar Submillimetric Telescope (SST) show regions of enhanced brightness temperature, which coincide with the location of active regions. A statistical study of the radio emission from these active regions was performed for the first time at such high frequencies during 23 days on June and July 2002, w…
Host Galaxies of High-Redshift Active Galactic Nuclei in the Great Observatories Origins Deep Surveys Fields
Akiyama, Masayuki
The star formation rates and the stellar masses of the host galaxies of active galactic nuclei (AGNs) at high redshifts are key to understanding the evolution of the relation between the mass of the spheroidal component of a galaxy and the mass of its central black hole (Mbulge-M• relation). We investigate the host galaxies o…
OH Rotational Lines as a Diagnostic of the Warm Neutral Gas in Galaxies
Cernicharo, José; Goicoechea, Javier R.; Martín-Pintado, Jesus
We present Infrared Space Observatory (ISO) observations of several OH, CH, and H2O rotational lines toward the bright infrared galaxies NGC 253 and NGC 1068. As found in the Galactic clouds in Sgr B2 and Orion, the extragalactic far-IR OH lines change from absorption to emission depending on the physical conditions and distribution of …
Detection of Absorption Features in the X-Ray Spectrum of the Narrow-Line Quasar PG 1404+226: Possible Evidence of Accretion Disk Winds
Rao, A. R.; Dewangan, G. C.; Dasgupta, Surajit +1 more
We present the results of an analysis of data from XMM-Newton and Chandra observations of the high-luminosity narrow-line quasar PG 1404+226. We confirm a strong soft X-ray excess in the X-ray spectrum, and we find rapid variability (a factor of 2 in about 5000 s). When the X-ray spectrum is fitted with a two-component model that includes a power-…
Optical Sources near the Bright X-Ray Source in NGC 1073
Kaaret, Philip
New HST observations show that the bright X-ray source in the face-on spiral galaxy NGC 1073 is located near a ring of recent star formation with an age of 8-16 Myr. This strengthens the association of X-ray sources in spiral galaxies emitting near or above the Eddington limit for a 20 Msolar black hole with recent star formation events…
X-ray spectral and timing characteristics of the stars in the young open cluster IC 2391
Micela, G.; Peres, G.; Sciortino, S. +2 more
We present X-ray spectral and timing analysis of members of the young open cluster IC 2391 observed with the XMM-Newton observatory. We detected 99 X-ray sources by analysing the summed data obtained from MOS1, MOS2 and pn detectors of the EPIC camera; 24 of them are members, or probable members, of the cluster. Stars of all spectral types have be…
Direct Evidence for a Polar Spot on SV Camelopardalis
Jeffers, S. V.; Collier Cameron, A.; Barnes, J. R. +2 more
We have used spectrophotometric data from the Hubble Space Telescope (HST) to eclipse-map the primary component of the RS CVn binary SV Cam over nine HST orbits. We find from these observations and the Hipparcos parallax that the surface flux in the eclipsed low-latitude region of the primary is about 30% lower than that computed from a PHOENIX mo…
Forward modeling of coronal funnels
Peter, H.; Aiouaz, T.; Keppens, R.
We propose a forward modeling approach of coronal funnels to investigate the outer layers of the solar atmosphere with respect to their thermodynamical properties and resulting emission line spectra. We investigate the plasma flow out of funnels with a new 2D MHD time dependent model including the solar atmosphere all the way from the chromosphere…
A universal characteristic of type II radio bursts
Kaiser, M. L.; Gopalswamy, N.; Aguilar-Rodriguez, E. +2 more
We present a study on the spectral properties of interplanetary type II radio bursts observed by the Radio and Plasma Wave (WAVES) experiment on board the Wind spacecraft. We investigated the relative bandwidth of the type II radio bursts observed by WAVES from 1997 up to 2003. We obtained three sets of events, based on the frequency domain of occ…