Search Publications
A Study of the Ultraviolet Absorption Lines through the Complete Galactic Halo by the Analysis of HST Faint Object Spectrograph Spectra of Active Galactic Nuclei. I.
Cohen, Ross D.; Shull, J. Michael; Stocke, John T. +7 more
The ultraviolet (1150-2850 A) spectra of a number of active galactic nuclei (AGNs) observed with the Hubble Space Telescope Faint Object Spectrograph (FOS) have been used to study the properties of the Galactic halo. The objects that served as probes are 3C 273, PKS 0454-220, PG 1211+143, CSO 251, Ton 951, and PG 1351+640. The equivalent widths of…
The rotor: A new method to derive rotation between two reference frames
Vityazev, V. V.
The paper presents a study of two techniques to derive the relative orientation of two reference frames: the Standard Method, based on the least squares procedure, and a new method - the ROTOR, based on the representation of systematic differences in terms of orthogonal functions. It is shown that the ROTOR is preferable over the Standard Method s…
Evolution of Lyman-Alpha Clouds at Low Redshifts
Ikeuchi, Satoru; Murakami, Izumi
We examine the evolution of an intergalactic gas cloud confined by the gravity of cold dark matter in the minihalo model. Assuming that the evolution of the diffuse ultraviolet (UV) flux follows a power law function of the form (1 + Z)alphai^ with a change in exponent at redshift z_c_ and a constant comoving number density of gas clouds…
Evidence Signaling the Start of Enhanced Counterjet Flow in the Symbiotic System R Aquarii
Kafatos, M.; Michalitsianos, A. G.; Perez, M.
The velocity struture of strong far-UV emission lines observed in the symbiotic variable R Aqr suggests the start of new jet activity which will probably culminate in the appearance of a series of intense nebular emission knots within a decade. This is indicated by a systematic redward wavelength drift of emission lines, which we have followed wit…
Analysis of the IUE Satellite and the Ground-based Observations of SW Lacertae
Lee, Woo Baik; Jeong, Jang Hae; Kang, Yong Woon +1 more
We present UBV observations of SW Lacertae obtained in 1988. We classify all previous light curves into three groups according to their maxima. The International Ultraviolet Explorer (IUE) spectra of SW Lacertae are used for ultraviolet photometry and for a variation study of chromspheric activity. Five light curves between the wavelengths of 2600…
Observational constraints on the inter-binary stellar flare hypothesis for the gamma-ray bursts
Rao, A. R.; Vahia, M. N.
The Gamma Ray Observatory/Burst and Transient Source Experiment (GRO/BATSE) results on the Gamma Ray Bursts (GRBs) have given an internally consistent set of observations of about 260 GRBs which have been released for analysis by the BATSE team. Using this database we investigate our earlier suggestion (Vahia and Rao, 1988) that GRBs are inter-bin…
Searching for Hard X-Ray Directivity during the Rise, Peak, and Decay Phases of Solar Flares
Li, Peng
We have identified 72 large solar flares (peak counting rates more than 1000 counts/s) observed by Hard X-ray Burst Spectroscopy (HXRBS) on-board the Solar Maximum Mission (SMM). Using a database of these flares, we have studied hard X-ray (50-850 keV) spectral center-to-limb variation and its evolution with time. The major results are the followi…
Whistler mode waves in the Jovian magnetosheath
Tsurutani, B. T.; Lin, Naiguo; Kellogg, P. J. +3 more
During the Ulysses flyby of Jupiter in February 1992, the spacecraft transversed the Jovian magnetosheath for a few hours during the inbound pass and for a few days during the outbound pass. Burstlike electromagnetic waves at frequencies of ~0.1-0.4 of the local electron cyclotron frequency have been observed by the Unified Radio and Plasma Wave (…
The corona of the G-type giant HR 2554: discovery of co-existing, very different temperature regimes.
Schroeder, K. -P.; Huensch, M.
We present direct observational evidence for two different co-existing coronal temperature regimes in the ζ Aur-type binary HR 2554 (G7II + A1V). ROSAT observations reveal the presence of plasma at temperatures around 10^6.7^K, typical of coronal plasma found in giants, while IUE observations, taken during egress from eclipse, show circumstellar (…
The ultraviolet variations of the δ Scuti stars 44 Tauri and 71 Tauri.
Monier, R.; Kreidl, T. J.
We report on low resolution phase resolved ultraviolet spectrophotometry of the δ Scuti stars, 44 Tau (F2 IV-V) and 71 Tau (F0V) at different phases of their pulsation cycles performed with the International Ultraviolet Explorer. For 44 Tau, the amplitude of the flux variations increases towards shorter wavelengths from about 13% around 3000A, to …