ALFA Pulsar Studies


Pulsar surveys
The ALFA Pulsar Consortium


Most of the advances in pulsar astronomy were due to the discovery of new objects. A major increase in search sensitivity has already started a new era of discovery at the Arecibo Observatory.

This increase in search sensitivity is due first and foremost by the ALFA receiver and the pulsar surveys it makes possible, which are now being carried by the Pulsar Consortium. Preliminary estimates (see below) indicate that the Arecibo Galactic plane survey using ALFA could find many hundreds of new pulsars. As of March 1 2018, we have already discovered a total of 181 new pulsars.

From the superior spectral and time resolution of the survey, it was expected at the start that it should be able to find pulsars deep in the Galaxy that were undetectable to previous surveys because of dispersive smearing. This expectation is now being comfirmed, with the discovery of many distant millisecond pulsars (the number of discoveries with spin periods smaller than 20 ms is 25 as of March 2018). A fine example of such systems is PSR J1903+0327, the first eccentric binary millisecond pulsar in the Galactic plane. This system is also unusual for having a main-sequence companion. It is the first of a new class of systems that is thought to have started their evolution as triple systems. Another unusual system is PSR J1950+2414, a MSP-WD system with a low-mass companion, an orbital period of 22 days and orbital eccentricity of 0.08. The origin of this system is still mysterious, but there are a few others that are very similar.

Given the very high sensitivity of the Arecibo telescope, we can combine very high sensitivity with very short (5 minute) pointings. This allows us to retain sensitivity to extremely compact binary systems, which are likely to represent the best laboratories for the study of gravitational physics. Great examples of this are PSR J1946+2052, the most compact pulsar - neutron star system known (the orbital period is only 1h 53m), PSR J1913+1102, discovered in PALFA data by the Einstein@Home pipeline and likely to be asymmetric, and PSR J1906+0746 - which is by far the youngest pulsar known to be in a binary system. The companion to this pulsar is likely to be a recycled pulsar, but it could also be a heavy white dwarf.

Apart from pulsars, one of the types of objects targeted by the PALFA survey is fast radio bursts (FRBs). The first FRB to be discovered with a telescope other than the Parkes radio telescope was found in the PALFA survey. However, the unparallelled sensitivity of the Arecibo telescope has allowed us to see what no other telescope has been able to see before: FRBs repeat!

New pulsar discoveries in Galaxy New pulsar discoveries in DM
Left: Galactic location of the new P-ALFA pulsar survey discoveries. The center of the Galaxy is indicated with a cross, the position of the Solar System is indicated by the black dot at the center of the black circle. Right: Positions of the pulsars as a function of Galactic longitude and DM. The black curve indicates the maximum Galactic column density according to the Cordes and Lazio (2001) model of the electron distribution of the Galaxy. In both plots, red dots indicate positions of known pulsars with Galactic latitude smaller than 5 degrees, blue indicates new discoveries by the Arecibo P-ALFA survey. There seems to be a deficiency in the number of pulsars at Galactic latitudes of 60 degrees.

Pulsar Surveys

Data acquisition

With ALFA, we need about 47 pointings to cover one square degree, compared to about 330 pointings needed to cover one square degree with similar density with a single-pixel feed. Until 2009, we were using the Wideband Arecibo Pulsar Processors (WAPPs) to detect the signal from ALFA's seven beams. These cover 100 MHz of band (with dual polarization capability), initially centered at 1420 MHz and later at 1440 MHz. In 2009, the survey transitioned to new and improved back-ends, the Mock polyphase filterbank spectrometers, which are capable of covering 300 MHz (from 1225 MHz to 1525 MHz, the bandwidth covered by ALFA) for each of the seven beams (see detailed technical specifications here). This will lead to greatly increased search sensitivity, provided we can effectively deal with all the radio frequency interference.
From August 1 to October 8 2004, we conducted a preliminary survey that covered the two regions closest to the Galactic plane (|b| < 1 degrees) visible from Arecibo: the "Inner Galaxy" (40 < l < 75 degrees) and the "Anti-center" (170 < l < 210 degrees). Each pointing was 134 seconds for the Inner Galaxy and 67 seconds for the Anti-center. This was done in sparse mode, where we do only 1/3 of the pointings needed to cover the whole region. This preliminary survey found a total of 11 new pulsars, and detected 30 previously known pulsars. For a detailed description of this survey, and the strategy of the present survey, see Cordes et al. (2006).

The survey will cover the Galactic plane (|b| < 5 degrees) visible with the Arecibo 305-m radio telescope (35 < l < 75 degrees). Each pointing lasts about 268 seconds in the Inner Galaxy and 134 seconds in the Anti-center.

Data processing and storage

It is expected that, over the next several years, this survey will generate over 1000 Terabytes of data. The data is stored at the Cornell University Center for Advanced Computing, the publicly available data can be retrieved here. These are processed by three independent software pipelines: The data processed thus far has revealed that the radio frequency interference (RFI) environment at Arecibo significantly affects the detection threshold of the survey, creating unforseen challenges in identifying the many weak pulsars that are likely lurking in the data. To address this, the PALFA consortium is actively developing novel techniques for identification, mitigation, and excision of RFI. We are also implementing a variety of heuristics as well as machine learning algorithms for identifying real pulsars among the millions of signal candidates, most of which appear to be due to RFI. The inevitable growth in the incidence and variety of man-made RFI suggests that this problem will likely be important for all future radio pulsar surveys.

Outreach Efforts

The Arecibo Remote Command Center (ARCC) at the University of Texas at Brownsville and the University of Wisconsin at Miwaukee is currently engaged in searching for radio pulsars in ALFA data. ARCC is an integrated research/education facility that allows students at the high school and undergraduate level to be directly involved with the research at the Arecibo telescope. Web based tools have been developed so that students could rank the pulsar candidates created by the PRESTO analysis.


* The most compact pulsar - neutron star system ever!!
* A pulsar - neutron star discovered by Einstein@Home!
* A Repeating Fast Radio Burst!
* The disappearance of the cosmic spinning top!
* Arecibo confirms Fast Radio Bursts from outer space!
* First Pulsar Discovery by Global Volunteer Computing!
* ALFA Finds its first MSP! This is the first eccentric binary millisecond pulsar in the galactic plane!
* ALFA Finds the Youngest Binary Pulsar Ever! (see also Jodrell Bank Observatory press release),
* PSR J1928+1746: First pulsar discovered with ALFA!
* ALFA pulsar surveys start!


Refereed (29):

* PALFA Discovery of a Highly Relativistic Double Neutron Star Binary (Stovall et al., 2018, ApJ Lett, 854, 22).
* Timing of 29 Pulsars Discovered in the PALFA survey (Lyne et al., 2017, ApJ, 834, 137).
* Two long-term intermittent pulsars discovered in the PALFA survey (Lyne et al., 2017, ApJ, 834, 72).
* Timing of Five PALFA-Discovered Millisecond Pulsars (Stovall et al. 2016, ApJ, 833, 192).
* The repeating Fast Radio Burst FRB 121102: Multi-wavelength observations and additional bursts (Scholz et al., 2016, ApJ, 833, 177).
* Einstein@Home discovery of a Double-Neutron Star Binary in the PALFA survey (Lazarus et al. 2016, ApJ, 831, 150).
* A repeating fast radio burst (Spitler et al., 2016, Nature, 531, 202).
* Arecibo Pulsar Survey Using ALFA. IV. Mock Spectrometer Data Analysis, Survey Sensitivity, and the Discovery of 40 Pulsars (Lazarus et al., 2015, ApJ, 812, 81).
* Einstein@Home Discovery of a PALFA Millisecond Pulsar in an Eccentric Binary Orbit (Knispel et al. 2015, ApJ, 806, 140).
* Timing of five millisecond pulsars discovered in the PALFA survey (Scholz et al. 2015, ApJ, 800, 123).
* The Binary Companion of Young, Relativistic Pulsar J1906+0746 (van Leeuwen et al. 2015, ApJ, 798, 115).
* Fast Radio Burst Discovered in the Arecibo Pulsar ALFA Survey (Spitler et al. 2014, ApJ, 790, 101).
* Arecibo Pulsar Survey Using ALFA. III. Precursor Survey and Population Synthesis (Swiggum et al. 2014, ApJ, 787, 137).
* Searching for pulsars using image pattern recognition (Zhu et al. 2014, ApJ, 781, 117).
* Timing of a Young Mildly Recycled Pulsar with a Massive White Dwarf Companion (P. Lazarus et al. 2014, MNRAS, 437, 1485).
* The Einstein@home Search for Radio Pulsars and PSR J2007+2022 Discovery (B. Allen et al. 2013, ApJ, 773, 91).
* Properties of Thirty-Five Pulsars Discovered in the PALFA Survey (D. Nice et al. 2013, ApJ, 772, 50).
* PEACE: Pulsar Evaluation Algorithm for Candidate Extraction - A software package for post-analysis processing of pulsar survey candidates (Lee et al. 2013, MNRAS, 433, 688).
* Four Highly Dispersed Millisecond Pulsars Discovered in the Arecibo PALFA Galactic Plane Survey (F. Crawford et al. 2012, ApJ, 757, 90).
* Two Millisecond Pulsars Discovered by the PALFA Survey and a Shapiro Delay Measurement (J. Deneva et al. 2012, ApJ, 757, 89).
* Arecibo PALFA Survey and Einstein@Home: Binary Pulsar Discovery by Volunteer Computing (B. Knispel et al. 2011, ApJ, 732, 1).
* On the Nature and Evolution of the Unique Binary Pulsar J1903+0327 (P. Freire et al. 2011, MNRAS, 412, 2763).
* Pulsar Discovery by Global Volunteer Computing (B. Knispel et al. 2010, Science, 329, 1305).
* Arecibo Pulsar Survey Using ALFA: Probing Radio Pulsar Intermittency And Transients (J. S. Deneva et al., 2009, ApJ, 703, 2259).
* PSR J1856+0245: Arecibo Discovery of a Young, Energetic Pulsar Coincident with the TeV Gamma-ray Source HESS J1857+026 (J. W. T. Hessels et al. 2008, ApJ, 703, 2259).
* An Eccentric Binary Millisecond Pulsar in the Galactic Plane (D. Champion et al. 2008, Science, 320, 1309).
* Arecibo and the ALFA Pulsar Survey (J. van Leeuwen et al., 2006, ChJAS, 6b, 311, see .pdf presentation here).
* Arecibo Pulsar Survey Using ALFA. II. The young, highly relativistic binary pulsar J1906+0746 (Lorimer et al., 2006, ApJ 640, 428),
* Arecibo Pulsar Survey Using ALFA. I. Survey Strategy and First Discoveries (Cordes et al., 2006, ApJ, 637, 446).

In Conference Proceedings:

* The PALFA Survey: Going to great depths to find radio pulsars (P. Lazarus and the ALFA Pulsar Consortium).
* Two Millisecond Pulsars Discovered by the PALFA Survey and a Shapiro Delay Measurement (J. Deneva and the ALFA Pulsar Consortium).
* Two Pulsar Discoveries from the Einstein@Home Distributed Computing Project (J. Deneva and the ALFA Pulsar Consortium).
* An Update on the Status of the Pulsar-ALFA Survey (P. Lazarus).
* Finding Pulsars with Einstein@Home (B. Knispel and the ALFA Pulsar Consortium).
* Arecibo Multibeam Pulsar Surveys: Overview and Discovery of a Young Relativistic Binary (F. Camilo and the ALFA Pulsar Consortium).
* ALFA pulsar surveys: Searching for fundamental laboratories of extreme physics (P. Freire and the ALFA Pulsar Consortium, see powerpoint presentation).
* ALFA Arecibo Pulsar Surveys (P. Freire and the ALFA Pulsar Consortium, see powerpoint presentation).

The ALFA Pulsar Consortium

The ALFA Pulsar Consortium is open to all researchers interested in observations of radio pulsars and related science, regardless of country or origin and level of expertise. The Consortium manages its collaboration on the CyberSKA portal.

* Membership and Affiliations

Bruce Allen Albert Einstein Institute - Hannover / University of Wisconsin - Milwaukee / Einstein@Home
Slavko Bogdanov Columbia University
Adam Brazier Cornell University
Fernando Camilo Columbia University
Fernando Cardoso West Virginia University
Shami Chatterjee Cornell University
Jim Cordes Cornell University
Fronefield Crawford Franklin and Marshall College
Julia Deneva Navy Research Laboratory
Gregory Desvignes Max-Planck-Institut für Radioastronomie
Robert Ferdman University of East Anglia
Paulo Freire Max-Planck-Institut für Radioastronomie
Jason Hessels ASTRON
Frederick Jenet University of Texas at Brownsville and Texas Southmost College
Victoria Kaspi McGill University
Benjamin Knispel Albert Einstein Institute
Joeri van Leeuwen ASTRON
Andrea Lommen Franklin & Marshall College
Maura McLaughlin West Virginia University
Ryan Lynch National Radio Astronomy Observatory
David Nice Lafayette College
Scott Ransom National Radio Astronomy Observatory
Paul Scholz McGill University
Xavier Siemens University of Wisconsin - Milwaukee
Laura Spitler Max-Planck-Institut für Radioastronomie
Ingrid Stairs University of British Columbia
Ben Stappers Jodrell Bank Center for Astrophysics
Kevin Stovall University of New Mexico
Weiwei Zhu Max-Planck-Institut für Radioastronomie



Date Title Author
2006 May 4 Tiling strategy for P-ALFA (being updated) Freire
2005 Apr 25 Specifications of new spectrometer. PALFA Consortium
2004 Jul 5 Cornell Simulation of P-ALFA survey. Vlemmings and Cordes
2004 Jul McGill Simulation of P-ALFA survey. Faucher-Giguère and Kaspi
2003 Jan 14 A Report on the First ALFA Pulsar Consortium Workshop PALFA Consortium


Pulsar Astronomy at the Arecibo Observatory
More information on ALFA and its performance.
Proposal submitted for large-scale P-ALFA survey (Now being scheduled with number P2030)
PALFA public data server
Einstein@Home Pulsar Search
The Arecibo Remote Command Center


At the Arecibo Observatory: Julia Deneva
At Cornell University: Jim Cordes