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The Galactic Millisecond Pulsar Population  [PDF]
Duncan R. Lorimer
Physics , 2012, DOI: 10.1017/S1743921312023769
Abstract: Among the current sample of over 2000 radio pulsars known primarily in the disk of our Galaxy, millisecond pulsars now number almost 200. Due to the phenomenal success of blind surveys of the Galactic field, and targeted searches of Fermi gamma-ray sources, for the first time in over a decade, Galactic millisecond pulsars now outnumber their counterparts in globular clusters! In this paper, I briefly review earlier results from studies of the Galactic millisecond pulsar population and present new constraints based on a sample of 60 millisecond pulsars discovered by 20 cm Parkes multibeam surveys. I present a simple model of the population containing $\sim 30,000$ potentially observable millisecond pulsars with a luminosity function, radial distribution and scale height that matches the observed sample of objects. This study represents only a first step towards a more complete understanding of the parent population of millisecond pulsars in the Galaxy and I conclude with some suggestions for further study in this area.
Pulsar Searches of EGRET Sources  [PDF]
Mallory S. E. Roberts
Physics , 2002,
Abstract: The majority of Galactic high-energy gamma-ray sources continue to elude identification. Currently, we have a handful of firm pulsar identifications, one of which is radio quiet, and a few marginal detections, including one millisecond pulsar. Recently, both blind searches of EGRET error boxes and targeted searches of X-ray counterpart candidates have had some success in finding new pulsars. I review these results, and discuss our current program of searching mid-Galactic latitude EGRET error boxes using the Parkes multi-beam system.
Radio Searches of Fermi LAT Sources and Blind Search Pulsars: The Fermi Pulsar Search Consortium  [PDF]
P. S. Ray,A. A. Abdo,D. Parent,D. Bhattacharya,B. Bhattacharyya,F. Camilo,I. Cognard,G. Theureau,E. C. Ferrara,A. K. Harding,D. J. Thompson,P. C. C. Freire,L. Guillemot,Y. Gupta,J. Roy,J. W. T. Hessels,S. Johnston,M. Keith,R. Shannon,M. Kerr,P. F. Michelson,R. W. Romani,M. Kramer,M. A. McLaughlin,S. M. Ransom,M. S. E. Roberts,P. M. Saz Parkinson,M. Ziegler,D. A. Smith,B. W. Stappers,P. Weltevrede,K. S. Wood
Physics , 2012,
Abstract: We present a summary of the Fermi Pulsar Search Consortium (PSC), an international collaboration of radio astronomers and members of the Large Area Telescope (LAT) collaboration, whose goal is to organize radio follow-up observations of Fermi pulsars and pulsar candidates among the LAT gamma-ray source population. The PSC includes pulsar observers with expertise using the world's largest radio telescopes that together cover the full sky. We have performed very deep observations of all 35 pulsars discovered in blind frequency searches of the LAT data, resulting in the discovery of radio pulsations from four of them. We have also searched over 300 LAT gamma-ray sources that do not have strong associations with known gamma-ray emitting source classes and have pulsar-like spectra and variability characteristics. These searches have led to the discovery of a total of 43 new radio millisecond pulsars (MSPs) and four normal pulsars. These discoveries greatly increase the known population of MSPs in the Galactic disk, more than double the known population of so-called `black widow' pulsars, and contain many promising candidates for inclusion in pulsar timing arrays.
Targeted searches for gravitational waves from radio pulsars  [PDF]
Réjean J. Dupuis
Physics , 2005, DOI: 10.1088/1742-6596/32/1/009
Abstract: An overview of the searches for gravitational waves from radio pulsars with LIGO and GEO is given. We give a brief description of the algorithm used in these targeted searches and provide end-to-end validation of the technique through hardware injections. We report on some aspects of the recent S3/S4 LIGO and GEO search for signals from several pulsars. The gaussianity of narrow frequency bands of S3/S4 LIGO data, where pulsar signals are expected, is assessed with Kolmogorov-Smirnov tests. Preliminary results from the S3 run with a network of four detectors are given for pulsar J1939+2134.
Searching for Millisecond Pulsars: Surveys, Techniques and Prospects  [PDF]
K. Stovall,D. R. Lorimer,R. S Lynch
Physics , 2013, DOI: 10.1088/0264-9381/30/22/224003
Abstract: Searches for millisecond pulsars (which we here loosely define as those with periods $<$ 20 ms) in the Galactic field have undergone a renaissance in the past five years. New or recently refurbished radio telescopes utilizing cooled receivers and state-of-the art digital data acquisition systems are carrying out surveys of the entire sky at a variety of radio frequencies. Targeted searches for millisecond pulsars in point sources identified by the {\it Fermi} Gamma-ray Space Telescope have proved phenomenally successful, with over 50 discoveries in the past five years. The current sample of millisecond pulsars now numbers almost 200 and, for the first time in 25 years, now outnumbers their counterparts in Galactic globular clusters. While many of these searches are motivated to find pulsars which form part of pulsar timing arrays, a wide variety of interesting systems are now being found. Following a brief overview of the millisecond pulsar phenomenon, we describe these searches and present some of the highlights of the new discoveries in the past decade. We conclude with predictions and prospects for ongoing and future surveys.
Discovery of millisecond pulsars in radio searches of southern Fermi LAT sources  [PDF]
M. J. Keith,S. Johnston,P. S. Ray,E. C. Ferrara,P. M. Saz Parkinson,O. Celik,A. Belfiore,D. Donato,C. C. Cheung,A. A. Abdo,F. Camilo,P. C. C. Freire,L. Guillemot,A. K. Harding,M. Kramer,P. F. Michelson,S. M. Ransom,R. W. Romani,D. A. Smith,D. J. Thompson,P. Weltevrede,K. S. Wood
Physics , 2011, DOI: 10.1111/j.1365-2966.2011.18464.x
Abstract: Using the Parkes radio telescope we have carried out deep observations of eleven unassociated gamma-ray sources. Periodicity searches of these data have discovered two millisecond pulsars, PSR J1103-5403 (1FGL J1103.9-5355) and PSR J2241-5236 (1FGL J2241.9-5236), and a long period pulsar, PSR J1604-44 (1FGL J1604.7-4443). In addition we searched for but did not detect any radio pulsations from six gammaray pulsars discovered by the Fermi satellite to a level of - 0.04 mJy (for pulsars with a 10% duty cycle). Timing of the millisecond pulsar PSR J1103-5403 has shown that its position is 9' from the centroid of the gamma-ray source. Since these observations were carried out, independent evidence has shown that 1FGL J1103.9-5355 is associated with the flat spectrum radio source PKS 1101-536. It appears certain that the pulsar is not associated with the gamma-ray source, despite the seemingly low probability of a chance detection of a radio millisecond pulsar. We consider that PSR J1604-44 is a chance discovery of a weak, long period pulsar and is unlikely to be associated with 1FGL J1604.7-4443. PSR J2241-5236 has a spin period of 2.2 ms and orbits a very low mass companion with a 3.5 hour orbital period. The relatively high flux density and low dispersion measure of PSR J2241-5236 makes it an excellent candidate for high precision timing experiments. The gamma-rays of 1FGL J2241.9-5236 have a spectrum that is well modelled by a power law with exponential cutoff, and phasebinning with the radio ephemeris results in a multi-peaked gamma-ray pulse profile. Observations with Chandra have identified a coincident X-ray source within 0.1" of the position of the pulsar obtained by radio timing
Three Millisecond Pulsars in FERMI LAT Unassociated Bright Sources  [PDF]
S. M. Ransom,P. S. Ray,F. Camilo,M. S. E. Roberts,O. Celik,M. T. Wolff,C. C. Cheung,M. Kerr,T. Pennucci,M. E. DeCesar,I. Cognard,A. G. Lyne,B. W. Stappers,P. C. C. Freire,J. E. Grove,A. A. Abdo,G. Desvignes,D. Donato,E. C. Ferrara,N. Gehrels,L. Guillemot,C. Gwon,A. K. Harding,S. Johnston,M. Keith,M. Kramer,P. F. Michelson,D. Parent,P. M. Saz Parkinson,R. W. Romani,D. A. Smith,G. Theureau,D. J. Thompson,P. Weltevrede,K. S. Wood,M. Ziegler
Physics , 2010, DOI: 10.1088/2041-8205/727/1/L16
Abstract: We searched for radio pulsars in 25 of the non-variable, unassociated sources in the Fermi LAT Bright Source List with the Green Bank Telescope at 820 MHz. We report the discovery of three radio and gamma-ray millisecond pulsars (MSPs) from a high Galactic latitude subset of these sources. All of the pulsars are in binary systems, which would have made them virtually impossible to detect in blind gamma-ray pulsation searches. They seem to be relatively normal, nearby (<=2 kpc) millisecond pulsars. These observations, in combination with the Fermi detection of gamma-rays from other known radio MSPs, imply that most, if not all, radio MSPs are efficient gamma-ray producers. The gamma-ray spectra of the pulsars are power-law in nature with exponential cutoffs at a few GeV, as has been found with most other pulsars. The MSPs have all been detected as X-ray point sources. Their soft X-ray luminosities of ~10^{30-31} erg/s are typical of the rare radio MSPs seen in X-rays.
X-ray observations and the search for Fermi-LAT gamma-ray pulsars  [PDF]
P. M. Saz Parkinson,A. Belfiore,P. Caraveo,A. De Luca,M. Marelli
Physics , 2013, DOI: 10.1002/asna.201312034
Abstract: The Large Area Telescope (LAT) on Fermi has detected ~150 gamma-ray pulsars, about a third of which were discovered in blind searches of the $\gamma$-ray data. Because the angular resolution of the LAT is relatively poor and blind searches for pulsars (especially millisecond pulsars, MSPs) are very sensitive to an error in the position, one must typically scan large numbers of locations. Identifying plausible X-ray counterparts of a putative pulsar drastically reduces the number of trials, thus improving the sensitivity of pulsar blind searches with the LAT. I discuss our ongoing program of Swift, XMM-Newton, and Chandra observations of LAT unassociated sources in the context of our blind searches for gamma-ray pulsars.
Detection of 16 Gamma-Ray Pulsars Through Blind Frequency Searches Using the Fermi LAT  [PDF]
The Fermi-LAT Collaboration
Physics , 2010, DOI: 10.1126/science.1175558
Abstract: Pulsars are rapidly-rotating, highly-magnetized neutron stars emitting radiation across the electromagnetic spectrum. Although there are more than 1800 known radio pulsars, until recently, only seven were observed to pulse in gamma rays and these were all discovered at other wavelengths. The Fermi Large Area Telescope makes it possible to pinpoint neutron stars through their gamma-ray pulsations. We report the detection of 16 gamma-ray pulsars in blind frequency searches using the LAT. Most of these pulsars are coincident with previously unidentified gamma-ray sources, and many are associated with supernova remnants. Direct detection of gamma-ray pulsars enables studies of emission mechanisms, population statistics and the energetics of pulsar wind nebulae and supernova remnants.
Fermi-LAT searches for gamma-ray pulsars  [PDF]
Pablo M. Saz Parkinson,for the Fermi LAT Collaboration
Physics , 2012, DOI: 10.1017/S174392131202323X
Abstract: The Large Area Telescope (LAT) on the Fermi satellite is the first gamma-ray instrument to discover pulsars directly via their gamma-ray emission. Roughly one third of the 117 gamma-ray pulsars detected by the LAT in its first three years were discovered in blind searches of gamma-ray data and most of these are undetectable with current radio telescopes. I review some of the key LAT results and highlight the specific challenges faced in gamma-ray (compared to radio) searches, most of which stem from the long, sparse data sets and the broad, energy-dependent point-spread function (PSF) of the LAT. I discuss some ongoing LAT searches for gamma-ray millisecond pulsars (MSPs) and gamma-ray pulsars around the Galactic Center. Finally, I outline the prospects for future gamma-ray pulsar discoveries as the LAT enters its extended mission phase, including advantages of a possible modification of the LAT observing profile.
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