Search Publications
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…
Infrared, submillimeter, and millimeter observations of the soft gamma-ray repeaters
Waters, L. B. F. M.; Hurley, K.; Kouveliotou, C. +9 more
The Soft Gamma-Ray Repeaters appear to be a completely new manifestation of neutron stars. SGR 1806-20 and SGR 1900+14 may have highly unusual stellar counterparts, whose spectra peak in the far infrared. They have not been detected at submillimeter or millimeter wavelengths. Their infrared spectra appear to contain several components: the photosp…
Simulation and methods for the data analysis of the hydrogen-deuterium-absorption-cell-experiment on Cassini
Reulke, R.; Warlich, K.; Jahn, H.
The Hydrogen-Deuterium-Absorption-Cell (HDAC) will be flown as part of the UltraViolet Imaging Spectrograph on the Cassini mission with the objective to determine the deuterium-to-hydrogen (D/H) ratio in the exosphere of Titan. The HDAC is a photometer designed to measure separately the H and D resonant scattered solar Lyman alpha radiation. A non…
Verifying the accuracy of the third interplanetary network: localization of the bursting pulsar GRO J1744-28 by triangulation
Cline, T.; Hurley, K.; Kouveliotou, C. +8 more
The bursting pulsar GRO J1744-28 is the first repeating source of intense bursts whose position is accurately known, which has become active since the establishment of the third interplanetary network. We show how observations of this object with Ulysses and BATSE can be used to verify many aspects of the triangulation method. Analysis of the prel…
Acceleration in energetics ions (~1MeV) in corotating interaction regions
Balogh, A.; Forsyth, R. J.; Goldstein, B. E. +4 more
We have correlated the ~1 MeV proton intensity (J) measured at corotating reverse shocks detected by Ulysses near the ecliptic plane and in the southern hemisphere with the shock strength and shock normal angle. We find that J is essentially independent of the shock strength below 29 degS, whereas between 29 deg and 41 degS J showed a good correla…
Rapid continuum variability in NGC 4151
Crenshaw, D. M.; Malkan, M.; Warwick, R. +4 more
Intensive monitoring of NGC 4151 showed strong, correlated variability at X-ray, ultraviolet, and optical wavelengths. The strongest variations were seen in ~1.5 keV X-rays, with weaker variations at ~100 keV and no significant variability in the 0.1-1 keV bands. In the ultraviolet/optical regime, the fractional variability amplitude decreased fro…
The shape of a sublimating ice surface at the bottom of a non-volatile cylinder: Monte Carlo simulations and 2-D analysis
Keller, H. U.; Markiewicz, W. J.; Skorov, Yu. V.
Gas flow rate at a cometary surface depends on the microscopic structure of the porous dust-ice material that makes up the nucleus. The standard model for the structure of such material is a bundle of cylindrical, non-crossing tubes. Even within this idealized model the emergent flux depends on the shape of the sublimating ice surface at the botto…