Search Publications
Time-distance helioseismology
Kosovichev, A. G.; Scherrer, P. H.; Duvall, T. L.
The time-distance helioseismology (or helioseismic tomography) is a new promising method for probing 3-D structures and flows beneath the solar surface, which is potentially important for studying the birth of active regions in the sun's interior and for understanding the relation between the internal dynamics of active regions and chromospheric a…
Solar irradiances of UV and EUV lines during the minimum of the sunspot activity in 1996
Wilhelm, K.; Curdt, W.; Schühle, U. +6 more
Full Sun observations in UV and EUV emission lines were performed by SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on SOHO (Solar and Heliospheric Observatory) in 1996. The radiometric preflight calibration of SUMER is traceable to a primary radiometric source standard - the electron storage ring BESSY. Based on this calibration and …
Results from the GOLF instrument on SOHO
Baudin, F.; García, R. A.; Pallé, P. L. +9 more
An 800 day series of GOLF velocity data, with uniquely high continuity and stability, offers the best ever signal to noise ratio obtained in global Sun observations. Following meticulous efforts to provide reliable calibration, these data have been used for measurements of frequencies, line-widths and power in the p-modes, which are used for inver…
Ground-based and HST optical-infrared studies of quasar host galaxies at low redshift
McLure, R. J.; Dunlop, J. S.; Hughes, D. H. +3 more
We describe the results from a series of ground-based and HST programs aimed at investigating the host galaxies of both radio-loud and radio-quiet quasars (RLQs & RQQs) and FRII radio galaxies (RGs) at low redshifts (0.1 < z < 0.3). Our results are in good agreement with those of other recent studies of host galaxies. In general the host…
Studies of the cosmic ray radial and latitudinal intensity gradients over the cycle 22 solar minimum period
Kunow, H.; Wibberenz, G.; Heber, B. +7 more
The spatial intensity gradients of galactic and anomalous cosmic ray helium are studied over the 1993.0-1998.0 time period using data from cosmic ray experiments on IMP 8, Ulysses, Voyagers 1 and 2 and Pioneer 10. When combined with the results of previous studies, a remarkable ordering of the radial gradients for the galactic component is found o…
Massive accretion disks in galactic nuclei
Scoville, N. Z.
In the luminous infrared galaxies, very large masses of interstellar matter have been concentrated in the galactic nuclei at radii less than 300 pc as a result of galactic merging, while in lower luminosity systems, this material is probably concentrated by stellar bars and viscous accretion. In both cases, the nuclear region will be highly obscur…
Disks in the Arp220 nuclei: modeling high resolution line and continuum observations
Genzel, R.; Tacconi, L. J.; Yun, M. S. +4 more
We model molecular and near-infrared emission from the central region of the ultra-luminous infrared galaxy Arp220. We use high angular resolution CO data taken with the Owens Valley millimeter array and NIR images from HST/NICMOS to compare with Monte Carlo line radiative transfer and scattering models. The models suggest that each one of the two…
Multiwavelength properties of blazars
Urry, C. Megan
The multiwavelength spectra of blazars appear to be dominated by nonthermal emission from a relativistic jet oriented close to the line of sight. The recent detection of many blazars at gamma-ray energies strongly supports this scenario. High quality multiwavelength monitoring data for the brightest one or two blazars suggest the optical through X…
HST observations of middle aged isolated neutron stars
Caraveo, P. A.; Bignami, G. F.; Mignani, R.
We report the results of recent HST observations of three Middle Aged Isolated Neutron Stars i.e. PSR1055-52, Geminga and PSR0656+14. For PSR1055-52, a probable optical counterpart has been identified with the FOC. For PSR0656+14, WFPC2 imaging provided a clear detection of the proposed optical counterpart and was used to obtain a tentative measur…
AGN watch continuum monitoring of radio-quiet and radio-loud AGN
O'Brien, Paul T.; Leighly, Karen M.
The International AGN Watch has monitored a number of radio-quiet and radio-loud Active Galactic Nuclei - the most luminous objects in the universe. We present a review of the main observational results from the continuum monitoring campaigns, concentrating on those which aim to quantify the simultaneous ultraviolet to X-ray variability characteri…