Pulsating Pulsars: Adventures Outside the Gridding Iron

1. Sagitta Altair Team Hulse J1853-0649 Ophiuchus Scutum J1744-1134 J1643-1224 Serpens Cauda 350 MHz Viewing Area Viewable area approaches 100% with gridding 820 MHz Viewing Area Pulsating Pulsars: Adventures Outside the Gridding Iron Susan Booth (VAST), Nick Borowicz (Argo Community HS, Summit, IL), Rob Culbertson (Langley HS, McLean, VA), Dottie Edwards (Strasburg HS, Strasburg, VA), Russ Kohrs (Broadway HS, Broadway, VA), Duncan Lorimer (WVU), Steve Rapp (Linwood Holton Governor’s School, Abingdon, VA) Abstract Fifteen pointings, each containing plots of data were analyzed. The purpose of this analysis was to examine data collected during several Green Bank Telescope (GBT) 350MHz drift scan surveys. Three prepfold plots indicated the presence of two known pulsars (J1643-1224 and J1744-1134) and one potential candidate pulsar. It was later determined that this candidate pulsar was recently validated and is now known as J1853-0649. The data from this 820MHz survey confirmed the presence of J1643-1224. The observation of J1744-1134 suggested (based on period and DM) that the follow up observation actually detected a possible separate radio source. For J1853-0649, the data collected displayed a large amount of RFI with a very faint pulsar signature which when refolded confirmed the presence of the pulsar at that location. Thus, gridding at that location may have provided more data from that pointing and reduced the need to refold the data. Conclusion Pulsar astronomy is often a tedious and frustrating activity. Of the fifteen pointings: 1.6% of the survey data contained known or candidate pulsars, 36.2% of the plots contained RFI, 63.8% contained unintelligible noise. Gridding of pulsars J1853-0649 and J1744-1134 at 820MHz may lead to a better understanding of these regions. Astronomical Setting The narrower beam width of the 820MHz receiver requires ‘gridding” in order to cover the same beam area as the 350MHz receiver. Above: The locations in the night sky of the 3 pulsars that were observed using the Green Bank Telescope on July 21, 2011 Below: The locations of the same 3 pulsars in Milky Way Galaxy. Team Hulse hard at work slewing the telescope and collecting data. Method A random assortment of fifteen pointings, twelve previously viewed and three unanalyzed, were examined by a team of six Pulsar Search Collaboratory (PSC) members. Plots within these pointings containing RFI or noise were eliminated and plots indicating the potential presence of a pulsar were selected for follow up observations. Follow up observations of two known pulsars and one candidate pulsar at 820MHz were conducted using the Green Bank Telescope. Results and Discussion The data collected on J1643-1224 revalidated the presence of that pulsar. Given a negligible Pdot in the survey plot and the knowledge that this pulsar is part of a binary system, the observed “spin down rate” of 1.1x10-16 can be attributed to Doppler variations in straight line velocity (Lorimer, personal communication). The follow up observation of J1744-1134 appears to be of a different radio source. Period and DM differences between the survey and follow up observations were each on the scale of 2 orders of magnitude. There was also an observed difference in the period. After refolding the data collected on J1853-0649 the presence of this pulsar was revalidated. The source of the RFI in the original observation is still unexplained. • Extensions/Further Research • Validation of the presence of two pulsars in the vicinity of J1744-1134 • Gridding of J1854-0649 in order to investigate the possible presence of one or more pulsars in that location • More detailed observations of J1643-1224 in order to better characterize this binary pulsar system The plot below shows the same data, folded differently, using a different period. Acknowledgements Special thanks to the National Radio Astronomy Observatory in Green Bank, WV. Data on pulsar J1843-0649 indicating the presence of large amounts of RFI. The pulsar signal can be seen faintly in the Time/Phase plot as a diagonal signal.