Photoelectric and Spectroscopic Observations Related to a Possible Optical Counterpart for Pulsar CP 1919+21.

Spectroscopic observations of the two stars near the pulsar CP 1919+21 are not sufficiently conclusive to permit an identification of either object with the source of the radio pulses. However, our most extensive series of photometric observations of a region of sky near the radio source position, which region includes the brighter of the two stars, suggests an approximately sinusoidal variation. It is significant that the period of the variation is double the period of the radio pulsations.