2000ApJ...545..385L

We have extensively searched for periodic signals from the soft gamma repeater SGR 1900+14 at 430 and 1410 MHz with the Arecibo Telescope. Our observations did not reveal the 5.16 s periodicity discovered at X-ray wavelengths by Hurley and coworkers. We place pulsed flux-density upper limits of 150 and 30 µJy at 430 and 1410 MHz, respectively. In the course of the 1410 MHz search we discovered a 226 ms radio pulsar, PSR J1907+0918. Its period derivative implies that the age of J1907+0918 is only 38 kyr, making it one of the youngest members of the known pulsar population. Independent lines of evidence in support of this apparent youth are the unusually high degree of circular polarization and a relatively flat radio spectrum. The close proximity of this young radio pulsar to the supernova remnant G42.8+0.6 poses a problem for the proposed association between the G42.8+0.6 and SGR 1900+14.