Search Publications
Missions
Journals
Publication Years
Redshift distribution of Lyα lines and metal systems
Demiański, M.; Doroshkevich, A. G.; Turchaninov, V.
The observed redshift distribution of Lyα lines and metal systems is examined in order to discriminate and to trace the evolution of structure elements observed in the galaxy distribution, at small redshifts, and to test the theoretical description of structure evolution. We show that the expected evolution of a filamentary component of structure …
Sumer Observations of the Quiet Sun: Transition Region and Low Corona
Wilhelm, Klaus
SUMER - the Solar Ultraviolet Measurements of Emitted Radiation instrument on the Solar and Helio-spheric Observatory (SOHO) of ESA and NASA - observed its first light on January 24, 1996 and covered the minimum of the sunspot activty between the solar cycles 22 and 23 with nearly continuous observations. Consequently, in many studies particular e…
Solar Analogs: Spectral Energy Distributions and Physical Parameters of Their Atmospheres
Shenavrin, V. I.; Glushneva, I. N.; Roshchina, I. A.
The angular diameters, radii, and effective temperatures of 16 G0-G5 main-sequence stars with color excesses 0.60≤ B-V≤0.68 and parallaxes derived from Hipparcos data have been determined using their infrared fluxes, obtained from JHKLM photometric observations. For all the stars except BS 483, these effective temperatures differ from the spectros…
Periodicities in the Ultraviolet Flux of α Orionis
Houck, J. R.; Hajian, Arsen R.; Terzian, Yervant +1 more
We have used low-resolution spectra from the International Ultraviolet Explorer (IUE) to look for periodicities in the ultraviolet flux from α Orionis. The total continuum flux for each observation was integrated, producing longwave (1900-3200 Å) and shortwave (1250-1750 Å) light curves. The periodograms resulting from the shortwave data are noise…
The Orbit of the Nearby Low-Mass Binary Gliese 600
Weigelt, G.; Hofmann, K. -H.; Tokovinin, A. A. +1 more
We have computed a combined spectroscopic-interferometric orbit for the nearby binary Gliese 600 discovered by us. The orbital period is 2.78 years, and the semimajor axis is 100 mas (0.1"). Its M0V components are almost identical and have a mass of 0.5 M_solar. The mass ratio is uncertain because of the low radial-velocity semiamplitude (7 km/s) …
Limits on the Spatial Extent of Active Galactic Nuclei Measured with the Fine Guidance Sensors of the Hubble Space Telescope
Hook, Richard N.; Miley, George; Schreier, Ethan J.
The optical structures of several active galactic nuclei (AGNs) have been studied using the fine guidance sensors (FGSs) on the Hubble Space Telescope (HST). The FGSs are interferometric devices that can resolve structure on scales of 20 mas or less and hence have the potential to improve on the resolution attainable by HST's cameras. The FGSs pro…
Faint field galaxies: an explanation of the faint blue excess using number evolution models
Zhang, Yuan-Zhong; He, Ping; Zou, Zhen-Long
Pure luminosity evolution models for galaxies provide an unacceptable fit to the redshifts and colors of faint galaxies. In this paper we demonstrate, using HST morphological number counts derived both from the I814-band of WFPC2 in the Medium Deep Survey (MDS) and the Hubble Deep Field (HDF) and from the H1.6-band of NICMOS,…
The central star of the Planetary Nebula NGC 6537
Pottasch, S. R.
The fact that Space Telescope WFPC2 images of the planetary nebula NGC 6537 fail to show the central star is used to derive a limit to its magnitude: it is fainter than a magnitude of 22.4 in the visible. This is used to derive a lower limit to the temperature of the star. The Zanstra temperature is at least 500 000 K. The Energy Balance temperatu…
Status of the SOLAR2000 Solar Irradiance Model
Tobiska, W. K.
Extreme-Ultraviolet Flare Loop Emissions in an Eruptive Event
Qiu, Jiong; Wang, Haimin; Chae, Jongchul +1 more
The TRACE/BBSO joint campaign on 27 September 1998 observed an eruptive flare event which lasted for half an hour. The observation covered several ultraviolet (UV) and extreme-ultraviolet (EUV) lines and Hα center and off-band emissions with very high spatial resolution. We find the EUV emissions in different stages of the flare display different …