Engineering topics

Mitchell, Kenneth J.

Publications and source records attributed to Mitchell, Kenneth J..

4 records

NASA NTRS1988

Statistical error analysis in CCD time-resolved photometry with applications to variable stars and quasars

Differential photometric time series obtained from CCD frames are tested for intrinsic variability using a newly developed analysis of variance technique. In general, the objects used for differential photometry will not all be of equal magnitude, so the techniques derived here explicitly correct for differences in the measured variances due to photon statistics. Other random-noise terms are also considered. The technique tests for the presence of intrinsic variability without regard to its random or periodic nature. It is then applied to observations of the variable stars ZZ Ceti and US 943 and the active extragalactic objects OQ 530, US 211, US 844, LB 9743, and OJ 287.

Howell, Steve B.↗

NASA NTRS1988

Faint blue objects at high Galactic latitude. V - Palomar Schmidt field centered on selected area 71

Starlike objects with both blue and ultraviolet excess have been selected from a Palomar 1.2 m Schmidt field centered on Kapteyn selected area 71. The method of selection is that used in the previous papers of this series, but modified to account for the differential reddening that occurs across the field. The color classes, color subclasses, positions, and magnitudes of the selected objects are listed.

Usher, Peter D.↗

NASA NTRS1987

Identification of US 943 as a halo cataclysmic variable

US 943 has been shown to exhibit large (greater than about 5 mag) amplitude variations on time scales of one to two years. New time-resolved CCD photometry presented herein shows it also to be variable on time scales of 20 to 40 minutes with amplitude variation of up to 1 mag. Its membership as a cataclysmic variable is suggested. This assignment would place US 943 at a galactic distance of about 700 pc.

Howell, Steve B.↗

NASA NTRS1987

Reliable samples of quasars and hot stars from a spectrophotometric survey of the U.S. catalogs

The U.S. survey for blue- and ultraviolet-excess starlike objects is reviewed, focusing on the features which have contributed to its accuracy. The spectrophotometric survey is described in terms of the observational setup and procedures. It is suggested that the survey has produced reliably classified samples of quasars and hot evolved stars and that the procedures used in the study provide a means of deriving distance and luminosity information about these objects. Several cumulative number counts and spectra of a DA white dwarf and a quasar with prominent C IV and C III emission are given as examples.

Mitchell, Kenneth J.↗