Search Publications
An Analytic Description of Coronal Proton Trapping
Kocharov, Leon; Torsti, Jarmo; Kovaltsov, Gennadi A.
Analytic steady state solutions of the focused diffusion equation are used to deduce proton trapping time, τtrap, an average residence time for all particles injected into the magnetic loop. We take into account the effect of magnetohydrodynamic (MHD) turbulence and the divergence of magnetic field lines in both the corona and chromosph…
Compact Nuclei in Galaxies at Moderate Redshift. II. Their Nature and Implications for the Active Galactic Nucleus Luminosity Function
Green, Richard F.; Griffiths, Richard E.; Ratnatunga, Kavan +1 more
This study explores the space density and properties of active galaxies to z~=0.8. We have investigated the frequency and nature of unresolved nuclei in galaxies at moderate redshift as indicators of nuclear activity such as active galactic nuclei (AGNs) or starbursts. Candidates are selected by fitting imaged galaxies with multicomponent models u…
The IUE Spectra of the O VI Sequence Planetary Nebulae NGC 2452, NGC 7026, M3-30, and Lo 4
Feibelman, Walter A.
We present emission-line fluxes for NGC 2452, NGC 7026, M3-30, and Lo 4 from IUE low-dispersion spectra that have been processed by the New Spectral Image Processing System (NEWSIPS). For NGC 2452, a terminal wind velocity of -4200+/-300 km s-1 was determined from the C IV λ1549 P Cygni profile, while that of NGC 7026 is -4600+/-300 km …
An INFRARED SPACE OBSERVATORY Upper Limit to the Low-Mass Star Halo in the Edge-on Galaxy NGC 4565
Helou, George; Beichman, Charles; Desert, F. X. +2 more
We present deep ISOCAM observations taken at 4.5 µm (LW1) in search of a faint halo surrounding the edge-on spiral galaxy NGC 4565. Such a halo might exist if the massive halo that is needed to explain the flat rotation curve of this galaxy were attributable to a population of faint, red objects. The upper limit, 5.4 kJy sr-1 (3 σ…
Spectroscopic Monitoring of the BE/X-Ray Pulsar X Persei-4U 0352+309 with the Orbiting and Retrievable Far and Extreme Ultraviolet Spectrometer SPAS II and the IUE
Smith, Myron A.; Roche, Paul
We present phase-resolved spectra of the Be/X-ray pulsar system X Persei/4U 0352+309 obtained with the Tübingen far-UV echelle spectrometer of the Orbiting and Retrievable Far and Extreme Ultraviolet Spectrometer SPAS II (ORFEUS-SPAS II). Data were obtained in 1996 November and folded on the ~837.5 s pulsar period derived from contemporaneous X-ra…
Hubble Space Telescope Observations of the Serendipitous X-Ray Companion to Markarian 273: Cluster at z=0.46?
Lucas, Ray A.; Colina, Luis; Bushouse, Howard +1 more
We have used Hubble Space Telescope (HST) I-band images to identify Mrk 273X, the very unusual high-redshift X-ray-luminous Seyfert 2 galaxy found by ROSAT in the same field of view as Mrk 273. We have measured the photometric properties of Mrk 273X and have also analyzed the luminosity distribution of the faint galaxy population seen in the HST i…
Changes and Absorption Features in the Ultraviolet Spectrum of the PG 1159-Type Central Star RX J2117+3412
Feibelman, Walter A.
Comparison of IUE high- and low-dispersion spectra for the PG 1159-type central star of RX J2117+3412 indicates that the stellar continuum level and some absorption features decreased between 1993 and 1995. These observed changes may represent a new phenomenon not previously known to occur in PG 1159-type DO degenerates. The definite detection of …
Testing a Coupling Relation between Visible and Dark Matter in the MS 2137-2353 Cluster Core
Giraud, Edmond
The empirical coupling relation in Md=γM1/2r between the halo dark mass distribution Md and the visible mass M at radius r, previously demonstrated for spiral galaxies, is extrapolated to the case of a simple cluster core with mass distribution constrained by a lens mass model. In the at present unique case of MS 2…
New Measurements of the Solar Limb Emission in the O I 777.4 and 844.6 Nanometer Lines
Penn, M. J.
Slit spectra of the solar limb emission in the 777.4 and 844.6 nm O I lines are calibrated against the solar disk center brightness. Data from CCD spectrograph instruments at two different observatories show limb emission with identical line intensities and measure a value of R4≡ΣI(844.6 nm)/ΣI(777.4 nm)=0.20+/-0.02, very different from…
Evidence for Advective Flow from Multiwavelength Observations of Nova MUSCAE
Misra, Ranjeev
We model the UV/optical spectrum of the black hole binary Nova Muscae as a sum of blackbody emissions from the outer region of an accretion disk. We show for self-consistency that scattering effects in this region are not important. The black hole mass (M~6 Msolar), the inclination angle (µ~0.5), and the distance to the source (D~…