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First Results from the ISO-IRAS Faint Galaxy Survey
Neugebauer, Gerry; Soifer, B. T.; Elbaz, David +16 more
We present the first results from the ISO-IRAS Faint Galaxy Survey (IIFGS), a program designed to obtain ISO observations of the most distant and luminous galaxies in the IRAS Faint Source Survey by filling short gaps in the ISO observing schedule with pairs of 12 µm ISOCAM and 90 µm ISOPHOT observations. As of 1997 October, over 500 s…
A Recalibration of the Diffraction Efficiency of the Transmission Grating Spectrometers on EXOSAT
Kahn, Steven M.; Paerels, Frits; Wolkovitch, Debra N.
We describe a recalibration of the diffraction efficiency of the transmission gratings on EXOSAT. This recalibration is required in order to quantitatively interpret the soft X-ray spectra obtained with these instruments on Sco X-1. Because this source is extremely bright, the spectra are sensitive enough to reveal residual systematic effects in t…
A Compact Spectral Range and Matching Extreme-Ultraviolet Spectrometer for the Simultaneous Study of 1 × 104-2 × 107 K Solar Plasmas
Doschek, G. A.; Brown, C. M.; Feldman, U. +2 more
An EUV spectral range of less than 100 Å in first order has been found that includes sufficient spectral lines and critical combinations of lines in first and second order to permit dynamic and diagnostic investigations of the solar atmosphere with a relatively simple spectrometer. An optical design of such a spectrometer, based on the performance…
A New Method for Diagnostics of Solar Magnetic Fields and Flows from Time-Distance Analysis
Ryutova, Margarita; Scherrer, Philip
We propose a new method to obtain information on plasma flows and magnetic fields below the visible solar surface using time-distance measurements. The method is based on sine and cosine transforms of propagation times measured as a function of direction. The method allows one to sort out various characteristics of the subsurface medium, the flows…
Diffuse Dark and Bright Objects in the Hubble Deep Field
Park, Changbom; Kim, Juhan
In the Hubble Deep Field (HDF) we have identified candidate regions where primordial galaxies might be forming. These regions are identified from negative or positive peaks in the difference maps obtained from the HDF maps smoothed over 0.8" and 4". They have apparent V magnitudes typically between 29 and 31 (missing flux below the local average l…
Infrared Space Observatory Mapping of 60 Micron Dust Emission around Vega-Type Systems: Erratum
Stencel, R. E.; Backman, D. E.; Fajardo-Acosta, S. B.
In the Letter ``Infrared Space Observatory Mapping of 60 Micron Dust Emission around Vega-type Systems'' by S. B. Fajardo-Acosta, R. E. Stencel, and D. E. Backman (ApJ, 487, L151 [1997]), there is an error in the equatorial coordinates that we assigned to our maps. Using preliminary versions of the PHOT Interactive Analysis (PIA) program, we incor…
Effective Collision Strengths for Fine-Structure Transitions from the 3s23p5 2P Ground State of Chlorine-like Ni XII
Keenan, F. P.; Bell, K. L.; Matthews, A. +1 more
The R-matrix method is used to compute electron impact collision strengths for transitions in Ni XII from its ground-state fine-structure levels. Sophisticated configuration-interaction wave functions are used to represent the 14 lowest LS target states employed in the R-matrix expansion. By transforming the LS-coupled reactance matrices, and by a…
Lyα/Hα Ratio of Singly Ionized Helium in Quasars
Zheng, Wei; Fang, Li-Zhi
He II Lyα λ304/Hα λ1640 emission lines are mainly produced by recombination, and their canonical ratio of ~10 may be a sensitive reddening indicator. We obtain the high signal-to-noise ratio optical spectra of two quasars and combine them with the far-ultraviolet spectra that show the He II λ304 emission. For HS 1700+64, the He II λ1640 emission i…
Kinematic Substructure of Halo Stars from HIPPARCOS Observations
Chen, B.
In the Letter ``Kinematic Substructure of Halo Stars from Hipparcos Observations'' by B. Chen (ApJ, 495, L1 [1998]), the color-magnitude diagram in Figure 6 is plotted upside down. Thus, most stars in the sample are halo main-sequence stars. Other results and the conclusion of the Letter are not affected.
Flows in Sunspot Plumes Detected with SOHO
Fredvik, T.; Kjeldseth-Moe, O.; Haugan, S. V. H. +4 more
In the Letter, ``Flows in Sunspot Plumes Detected with the Solar and Heliospheric Observatory'' by N. Brynildsen, P. Maltby, P. Brekke, T. Fredvik, S. V. H. Haugan, O. Kjeldseth-Moe, and Ø. Wikstøl (ApJ, 502, L85 [1998]), the following correction should be made:
In the last line on page L86, which reads ``peak line intensity I>=5 are locat…