Abstract
About two years ago the writer reported the results of an objective-prism search for possible white-dwarf members of the Ursa Major galactic cluster.1 The low-dispersion ultraviolettransparent objective prism enabled us to recognize the spectra of white dwarfs having strong hydrogen lines, and three new white dwarfs in the Ursa Major region were found. The proper motions available for two of the stars1 showed that they were not members of the cluster. Subsequently, Luyten determined a substantial proper motion2 for the third star, LB 253, which unambiguously indicates that this star too is not a cluster member. Even if rather less than half of all white dwarfs brighter than magnitude 14 have been discovered specifically, if we take the undiscovered number as 100 the probability of finding at random as many as three in the Ursa Major area searched is only about 0 . 01 .1 Hence, when the proper motion of LB 253 became known, it seemed worth while to undertake an extensive survey for new white dwarfs in an attempt to determine whether the Ursa Major results were typical. Eight hundred square degrees of sky about three times as large an area as the one searched in Ursa Major have now been surveyed with the same equipment, and two new probable white dwarfs have been found.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
