Search Publications
An Investigation of Gravitational Lensing in the Southern BL Lac PKS 0537-441
Lewis, Geraint F.; Ibata, Rodrigo A.
The BL Lac family of active galaxies possess almost featureless spectra and exhibit rapid variability over their entire spectral range. A number of models have been developed to explain these extreme properties, several of which have invoked the action of microlensing by substellar mass objects in a foreground galaxy; this not only introduces vari…
Observed Associations between the Solar Interior, Corona, and Solar Wind
Habbal, Shadia Rifai; Woo, Richard; Armstrong, J. W.
Using polarized brightness (pB) measurements made by the High Altitude Observatory (HAO) Mauna Loa Mk III K-coronameter, we investigate the daily changes of path-integrated density at 1.15 Rsolar. During 1996, when simultaneous pB and helioseismology data were available, we find that the correlation of pB (at zero time lag and 20° latit…
Interstellar Gas in the NGC 4410 Galaxy Group
Smith, Beverly J.
We present new radio continuum, 21 cm H I, and 2.6 mm CO data for the peculiar radio galaxy NGC 4410A and its companion NGC 4410B and compare with available optical and X-ray maps. Our radio continuum maps show an asymmetric double-lobed structure, with a high surface brightness lobe extending 3.6‧ (~100 kpc) to the southeast and a 6.2‧ (~180 kpc)…
A Synoptic View of the Subphotospheric Horizontal Velocity Flows in the Sun
Hill, F.; González Hernández, I.; Bogart, R. S. +3 more
Ring diagram analysis, a technique of local helioseismology, has been applied to 120 regions of 15deg×15deg over the solar surface in order to study the mass motions in the upper layers of the convection zone. The horizontal flows from ~0.95 Rsolar up to the surface have been investigated in a region spanning 360
Simultaneous SOHO andYohkoh Observations of a Small Solar Active Region
Siegmund, O. H. W.; Fisher, G. H.; Acton, L. W. +2 more
We present new results from observations of a small active region taken with the SUMER spectrograph and Extreme Ultraviolet Imaging Telescope (EIT) on SOHO and with the Soft X-Ray Telescope (SXT) on Yohkoh. The SUMER study features line and continuum emission covering a wide range of temperatures and includes the density-sensitive O IV] λ1400 mult…
X-Ray and Ultraviolet Spectral Properties of the X-Ray Transient Quasar PG 0844+349
Matsuoka, M.; Brinkmann, W.; Wang, J. X. +2 more
Despite the fact that quasars are generally strong X-ray emitters, ROSAT discovered several objects with only very weak X-ray emission. In this paper, the X-ray data from ASCA and ROSAT and the UV spectra from Hubble Space Telescope (HST) and IUE of one of these quasars, PG 0844+349, are analyzed. The ROSAT spectrum can be well fitted by a single …
SOHO/Energetic and Relativistic Nucleon and Electron Experiment Measurements of Energetic H, He, O, and Fe Fluxes during the 1997 November 6 Solar Event
Teittinen, M.; Torsti, J.; Mäkelä, P. +1 more
A brilliant solar X-ray and Hα flare and a coronal mass ejection (CME) on 1997 November 6 were associated with high particle fluxes in interplanetary space at energies above MeV. The CME had an exceptionally high leading edge velocity (1560 km s-1) as observed by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar a…
Far-Infrared ISO Maps of Active Galaxies
Pérez García, A. M.; Rodríguez Espinosa, J. M.; Fuensalida, J. J.
Far-IR Infrared Space Observatory (ISO) maps of four Seyfert galaxies are presented and compared with their optical counterpart images. The far-IR maps resemble the optical images of these galaxies when degraded to the ISO resolution. The spatial extension of the far-IR maps is also comparable to the optical extension of these objects, an indicati…
A Possible Evolutionary Connection between Active Galactic Nuclei and Starbursts in LINERS
Zheng, W.; Lei, S. J.; Huang, J. H. +2 more
Our analysis of the two magnitude-limited samples of LINERs suggests a correlation between LFIR/LB, or f(25 µm)/f(60 µm), and Hubble-type index at greater than 99.99% significance level. As LFIR/LB and f(25 µm)/f(60 µm) are considered to be indicators of star formation activity an…
Ultraviolet Spectral Variability and the Lyα Forest in the Lensed Quasar Q0957+561
Michalitsianos, A. G.; Dolan, J. F.; Hill, R. J. +1 more
Far-ultraviolet spectra of the gravitational lens components Q0957+561A, B were obtained with the Hubble Space Telescope Faint Object Spectrograph (FOS) at five equally spaced epochs, one every 2 weeks. We confirm the flux variability of the quasar's Lyα and O VI λ1037 emission lines in IUE spectra reported in earlier work of Dolan et al. The flux…