University of Massachusetts Amherst ScholarWorks@UMass Amherst Doctoral Dissertations 1896 - February 2014 1-1-1983 A search for radio pulsars in the northern sky : discovery of a pulsar in a unique binary system. Marc, Damashek University of Massachusetts Amherst Follow this and additional works at: https://scholarworks.umass.edu/dissertations_1 Recommended Citation Damashek, Marc,, "A search for radio pulsars in the northern sky : discovery of a pulsar in a unique binary system." (1983). Doctoral Dissertations 1896 - February 2014. 1869. https://scholarworks.umass.edu/dissertations_1/1869 This Open Access Dissertation is brought to you for free and open access by ScholarWorks@UMass Amherst. It has been accepted for inclusion in Doctoral Dissertations 1896 - February 2014 by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. A SEARCH FOR RADIO PULSARS IN THE NORTHERN SKY: DISCOVERY OF A PULSAR IN A UNIQUE BINARY SYSTEM A Dissertation Presented By MARC DAMASHEK Submitted to the Graduate School of the University of Massachusetts in partial fulfillment of the requirements for the degree of FIVE-COLLEGE DOCTOR OF PHILOSOPHY February 1983 Astronomy A SEARCH FOR RADIO PULSARS IN THE NORTHERN SKY: DISCOVERY OF A PULSAR IN A UNIQUE BINARY SYSTEM A Dissertation Presented By MARC DAMASHEK Approved as to style and content by: Joseph ^H. TaylcEl/'' Chairperson of Committ ee Thomas T. Arny, Member George S. Greenstein, Member Robert Krotkov, Member Leroy F. Cook, Department Head Physics and Astronomy Dedicated to Laurel Jane that she may some day experience the love of Nature iii S ACKNOWLEDGMENT I owe a great deal to people who have helped along the way. The list is long, and would be longer but for my imperfect memory. Joe Taylor has been an encouraging and inspiring adviser from the beginning, and a warm personal friend. It is difficult to imagine ever being able to repay the debt I owe him. Bob Brown and Bob Vance were responsible for bringing me to NRAO, and I owe them more than they realize as well. The Green Bank staff have always been ready to help— special thanks go to Bill Brundage, Ron Weimer, and Jim Coe for consistent support. Pete Backus created and shared in much of the excitement described here, and patiently put up with endless telephone calls asking if he had a position for 0655 yet. Midnight pizza stuck to the pan at the 140-foot will never be the same. He's been a joy to work with. Jeff Pier has always been an enthusiastic and able collaborator. He made a very significant contribution to this work, and I appreciate it. Jerry Kristian and Don Schneider have also provided important results. Dave Helfand has been generous in supplying X-ray vision as needed; I'd like to be able to return the favor. George Greenstein and Tom Arny were instrumental in bringing me beck into astronomy after a hiatus of several years. Discussions with George have always been productive, and have certainly sharpened IV my calculating ability. I've known Tom for 17 years now, and I'm delighted to have him as a member of my committee, since I remember him as a brand new Ph.D. Richard Huguenin first took me in as an auditor, and made me feel welcome at U. Mass. He, Read Predmore, and Antal Hartai made it a rewarding place to study and work. Martha Haynes, Rick Fisher, and Bob Brown have all been generous in granting telescope time, and in providing a relaxed work environment. Dan Stinebring, Joel Weisberg, and Juan Uson have partaken of much stimulating and useful discussion, and I'm grateful for their friendship and advice. I thank my parents for their early support of my strange tendency to love school and my bizarre childhood desire to become an astronomer. I would simply not have been able to do this work without the love and support of my wife Nina. I owe her all the pulsars in the Galaxy, and more. V ABSTRACT A SEARCH FOR RADIO PULSARS IN THE NORTHERN SKY: DISCOVERY OF A PULSAR IN A UNIQUE BINARY SYSTEM (February 1983) Marc Damashek, B.A., Amherst College M.S., Stanford University Ph.D., University of Massachusetts Directed by: Professor Joseph H. Taylor A sensitive search for pulsars has been conducted using the 92-meter transit telescope of the National Radio Astronomy Observatory. Nearly 50% of the sky north of +20° declination was searched, using an on-line computer to process all search data in real time. The search program was sensitive to pulsars in the period range 0.0333 to 3.9 seconds, with dispersion measures between and cm" 0 130 pc. The limiting flux density reached was approximately 10 mJy at 390 MHz. Twenty-three previously unknown pulsars were discovered in the course of the search, and three of these are noteworthy. PSR 0320+39, 28with a pulse period of 3.0321 seconds, has recently been found to exhibit subpulses which drift exclusively from the leading to the trailing edge of the pulse profile. The position and dispersion measure of PSR 0458+46 are consistent with a physical association between that pulsar and the supernova remnant HB 9. PSR 0655+64 has vi been found to be a member of a binary system. The pulsar parameters and orbital elements of the PSR 0655^4 system were determined througb an extensive series of pulse timing Observations at the NRAO 43-meter telescope. The orbital eccentricity is unmeasurablvxy small,small wi't-v, ,. -c; with an upper limit of 4x10^, and the pulsar's period derivativeve isIS smallersmall at- ^v,. than any previously known. Evolutionary considerations have suggested that the pulsar's companion might be a visible star, and an extremely faint star has been identified optically at the pulsar position. Observations With the Einstein X-ray satellite have detected no X-rays from the system. The available evidence indicates that the pulsar's companion may be an unusually faint dwarf star. vii ^ TABLE OF CONTENTS ACKNOWLEDGMENTS ABSTRACT iv vi Chapter I. INTRODUCTION AND OUTLINE ^ Pulsars as Objects of Study Pulsar Searches ] Early efforts * * Large-scale surveys .... ^ The third binary ........ ^ Outline of the Text ^ II. DESCRIPTION OF THE SEARCH ^ Scanning Technique and Receiver ''7 Scanning the sky [ ^ Receiver Data Analysis Sampling ]^ Analysis for periodicities ........ Confirmation of suspects •*•••••... _L9 III. RESULTS OF THE SEARCH 2i Sensitivity and Sky Coverage 21 Sensitivity calibration 21 Sky coverage Pulsars Detected ...... 2Q Known pulsars 29 ' ' Newly '. discovered pulsars '. 33 IV. PSR 0655+64: THE THIRD RADIO PULSAR IN A BINARY SYSTEM Early Observations ^9 Recognition as a binary 39 Early radio observations 40 Subsequent Measurements: Radio, Optical, and X-^ay 44 Improved radio measurements 44 Optical observations 47 X-ray observations 49 Implications of the Observations 50 Pulsar and orbital parameters 50 X-ray measurements 53 Optical measurements 54 viii V. SUMMARY 55 Pulsar Searches: Past and Future The UMass-NRAO Search, 1977-1979 The Princeton-NRAO Search, 1982-1983 PSR 0655+64 \ 56 Identification ' 58 58 Evolution . 58 BIBLIOGRAPHY . 60 APPENDIX . 63 ix LIST OF ILLUSTRATIONS 5. Sky Coverage Plotted in Polar Coordinates . 11 '"''""^ 7' ^"'"^^^^ Search ' * ' Earlv r ! 1 ! ] 37 vs. ^ Orbit Phase . Arrival " 8. Time Residuals * ' * vs.' Caie;d;r 'tL; (PSR* 0655+64) for Measurements Made between November 1980 and August 1982 46 X LIST OF TABLES 2* ^^^^^ U^^d in RightiTl^T^""' Y"""-^^ Wobbling n 2. Ascension and ' * * Declination Limits of Sky CovSa.; 3. Previously 2^ Known Pulsars Detected ' ' ' * While Searchinr on 4. Previously Known Pulsars Detected While Testing 5. Newly Discovered Pulsars 32 6. Pulsar and * Orbital Parameters of PSR 0655+64 Derived from Timing Measurements . 7. Parameters of Five Additional Pulsars Discovered during Preparations for the Princeton-NRAO Search 57 xl ; : CHAPTER I INTRODUCTION AND OUTLINE 1. Pulsars as Objects of Study The fascination of pulsars has not been diminished by fifteen years' familiarity. There are many reasons why they continue to hold their place of astronomical and astrophyslcal distinction (recent reviews of these and other aspects of pulsars are contained in Sieber and Wielebinski 1981) a) since pulsars are believed to be neutron stars, they afford us our sole opportunity to observe the behavior of matter in this extraordinary state; b) as an astronomical population, they provide insight into stellar evolutionary processes; c) they serve as unique probes (through dispersion and polarization effects) of the interstellar medium in our Galaxy d) they provide a possible source for the high-energy particles, X-rays, and gamma rays observed from space; e) interesting individual cases, illuminating one or more of the aspects above, are discovered from time to time. 1 2 since any one of these facets of pulsar lore would provide a.ple Justification for their continued study, it Is no wonder that they continue to excite a high level of interest. Clearly, the .ore pulsars we know about, the more likely we are to solve the problems they address. 2. Pulsar Searches Early_efforts. To date, approximately 335 radio pulsars^ have been discovered by searching, and one by accident. The one accidental' pulsar, PSR 1919+21, is arguably the most important one of all, having initiated the entire field of study; however, further discoveries could hardly be left to chance. Systematic searches for pulsars were immediately fruitful. Early searches showed pulsars to be concentrated toward the galactic plane (Large 1971), and attention was directed primarily toward those regions of the sky. These efforts typically relied upon detection of single pulses on chart records (Large et al . 1968), and were responsible for the discovery of some of the ^Unless otherwise noted, "pulsar" refers to a radio pulsar (either the observed radio phenomenon or the neutron star) as opposed to an X-ray pulsar.