Search Publications
Astro-1 and Ground-based Observations of Markarian 335: Evidence for an Accretion Disk
Malkan, M. A.; Zheng, W.; Kriss, G. A. +8 more
Simultaneous UV and optical observations of the Seyfert galaxy Markarian 335 (z = 0.026) during the Astro-1 mission yield a spectrum spanning the wavelength range of 912-8410 A. In the sub-Lyα region a prominent blended emission feature of O VI λλ1032, 1038, and Lyβ is nearly as strong as C IV λ1549. The continuum flux extends beyond the redshifte…
Fine-Scale Filamentary Structure in Coronal Streamers
Bird, Michael K.; Woo, Richard; Armstrong, John W. +1 more
Doppler scintillation measurements of a coronal streamer lasting several solar rotations have been conducted by Ulysses in 1991 over a heliocentric distance range of 14--77 R0. By showing that the solar corona is filamentary, and that Doppler frequency is the radio counterpart of white-light eclipse pictures processed to enhance spatial gradients,…
Flow downstream of the heliospheric terminal shock: Magnetic field line topology and solar cycle imprint
Suess, S. T.; Nerney, Steven; Schmahl, E. J.
The topology of the magnetic field in the heliosheath is illustrated using plots of the field lines. It is shown that the Archimedean spiral inside the terminal shock is rotated back in the heliosheath into nested spirals that are advected in the direction of the interstellar wind. The 22-year solar magnetic cycle is imprinted onto these field lin…
Eclipse observations of an accretion disc wind
Knigge, C.; Horne, Keith; Mason, K. O. +5 more
The Goddard High Resolution Spectrometer on the Hubble Space Telescope has been used to monitor, through eclipse, the C iv 1550-A and He ii 1640-A lines in the spectrum of the nova-like cataclysmic variable UX UMa. Previous work has suggested that the Civ line arises in an accretion disc wind. The HST data confirm this, in that the line shows a br…
High-resolution IUE spectroscopy of fast winds from cataclysmic variables
Prinja, Raman K.; Rosen, R.
The winds from six dwarf novae and four nova-like cataclysmic variables are studied using 31 high-resolution IUE spectra. The data provide details on athe time- and phase-averaged nature of disc-driven outflows, which are diagnosed via the presence of P Cygni-like and extended absorption profiles due to the C IV, N V and Si IV resonance line doubl…
Co-rotating Particle Enhancements Out of the Ecliptic Plane
Simnett, G. M.; Tappin, S. J.; Roelof, E. C. +1 more
The characteristics of the recurrent electron (38 53 keV) and ion (>∼0.5 MeV) enhancements observed by Ulysses from mid-1992 to April 1994 are presented. The magnitude of the ion flux increases reached a maximum at a latitude of ∼20°S and decreased afterwards by ∼23%/degree until early 1994. The magnitude of the electron increases showed a simi…
Emission Spectrum Integrated over an Accretion Disk: Comparison with Observations of Active Galactic Nuclei
Shimura, Toshiya; Takahara, Fumio
Emission spectrum from an accretion disk for active galactic nuclei is obtained by solving the vertical structure and radiative transfer self-consistently and by integrating the local spectrum over radii. We found that even for moderate accretion rates, disks emit a significant portion of the total luminosity in UV through soft X-ray range; for th…
The EXOSAT GSPC iron line catalog.
Parmar, A. N.; White, N. E.; Taylor, B. G. +3 more
We report on the global properties of the Fe feature seen in the 6-7keV spectra of X-ray sources observed with the EXOSAT Gas Scintillation Proportional Counter (GSPC). Of a total of 431 spectra extracted from the EXOSAT archive, 205 required the addition of a Gaussian emission line to the continuum spectrum in order to obtain satisfactory fits. T…
Gas Phase Abundances and Conditions along the Sight Line to the Low-Halo, Inner Galaxy Star HD 167756
Sembach, Kenneth R.; Savage, Blair D.; Cardelli, Jason A.
We present high-resolution (3.5 km/s) Goddard High Resolution Spectrograph (GHRS) measurements of the Mg II, Si II, Cr II, Fe II, and Zn II lines toward HD 167756, a low-latitude halo star at a distance of 4 kpc in the direction l = 351.5 deg, b = -12.3 and at a Galactic altitude of z = -0.85 kpc. Supplemental Na I, Ca II, and H I data are also pr…
High-resolution radio images of the symbiotic star R Aquarii
Davis, R. J.; Bode, M. F.; Dougherty, S. M. +2 more
We present MERLIN radio observations of the nearby symbiotic star R Aquarii at 5 and 1.7 GHz with respective nominal resolutions of ~0.04 and 0.13 arcsec, comparable to the resolution of the optical and ultraviolet images obtained with the HST. Comparison with the HST images shows that the radio emission is associated with features observed at opt…