Einstein@Home Gamma-ray Pulsar Discoveries in Fermi-LAT Data

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Einstein@Home searches data from NASA's Fermi Gamma-ray Space Telescope for signals from gamma-ray pulsars. Pulsars are very compact stars with extreme physical properties compared to normal matter. They are rapidly spinning neutron stars that emit pulses, observable from radio to gamma-ray wavelengths.

Searching for new pulsars is an enormous computational challenge, because their spin frequencies, sky position and other parameters are unknown in advance. Hence this is called a "blind" search, where one explicitly searches over a dense grid in parameter space. However, the number of discrete grid points to cover such multi-dimensional parameter spaces is tremendous and renders "brute forces approaches" computationally unfeasible.

We have developed novel and much more efficient data-analysis methods for the volunteer supercomputer Einstein@Home, which ranks among the fastest 25 computer systems worldwide. Einstein@Home has enabled the discoveries of new gamma-ray pulsars that were previously inaccessible on computational grounds.

These gamma-ray pulsar discoveries provide important contributions to advance our (yet very poor) understanding these stellar objects, their population, and their role in our Universe.

The Einstein@Home searches for new gamma-ray pulsars

In 2014, we began the 4^th Einstein@Home survey for gamma-ray pulsars, or "FGRP4". This survey incorporated many new advances that we learned during our previous searches and investigation of blind search methods. In addition, we were able to utilised the superior "Pass 8" data from the Fermi-LAT team, and search in longer data sets than ever before. In combination, these improvements led to FGRP4 being our most sensitive survey to date.

With the publication in Science Advances of the discoveries of two millisecond pulsars (J1035-6720 and J1744-7619), we have now published all pulsar discoveries made during FGRP4. These amount to 23 new pulsars, almost a third of all gamma-ray pulsars to be discovered in blind searches.

Of course, this does not mean that our gamma-ray pulsation searches on Einstein@Home are coming to an end! The Fermi mission continues to find new gamma-ray sources for us to target, so we are very optimistic that we will be able to build upon the success of FGRP4 in the near future. Currently FGRP5 is searching for pulsars in gamma-ray sources detected near the Galactic Centre, while FGRPB1 is searching for pulsations from binary millisecond pulsar candidates.

As always, we are extremely grateful to all of our volunteers, especially those whose computers contributed to these new discoveries. To say "we couldn't have done it without you!" would be a terrible understatement!

The above plot illustrates the number of gamma-ray pulsars discovered in blind searches using NASA's Fermi Gamma-ray Space Telescope as a function of time (when the discoveries were published). Since the Fermi satellite was launched in 2008, it has been continuously scanning the entire sky and thus is providing an ever increasing data set. In principle, having more data available allows us to do more sensitive pulsar searches. However, at the same time, the computational cost also increases rapidly with the longer data time spans. Thus, as the graphic shows, over the last few years the only new such discoveries were made with Einstein@Home, thanks to the massive collective computing power provided by the Einstein@Home volunteers.

The discoveries made by Einstein@Home volunteers in detail

Below we list for each pulsar the volunteers whose computers discovered the pulsar, and the date at which the pulsar was found.

We also provide a list of selected characteristics for each of the pulsars. Right ascension is one of the two celestial coordinates that specify the sky position of the pulsar. Declination is the second of these. The spin frequency describes how many time per second the pulsar is rotating. The first frequency derivative describes how much the pulsar is slowing down over time. The energy required to emit electromagnetic radiation is drawn from the pulsar rotation. The characteristic age is a rough estimate of the pulsar's age, computed from the spin frequency and its derivative. Finally, the spin-down power is a measure of the total energy emitted by the pulsar. For comparison, our Sun outputs roughly 4 x 10³³ erg per second. All pulsars below have a much higher spin-down power.

The graphics on the right show the pulse profile of each pulsar in green, and the phase-folded arrival times of all the gamma-ray photons on the far right. These plots require precise knowledge of the pulsar sky position, its spin frequency, and spin frequency derivative. Using these, each photon can be assigned a rotational phase, i.e., in which direction the pulsar was pointing when the gamma-ray photon was emitted. Thus, we can reconstruct the gamma-ray emission as a function of pulsar rotation phase and resolve the pulse profile.

Discoveries to be Announced Soon Pulsar Jxxxx+xxxx Volunteers (Country): Hapsburg (Taiwan) and TGWakko (USA) Survey: FGRPB1 Pulsar Jxxxx+xxxx Volunteers (Country): jbencin (USA) and Peter Survey: FGRPB1 Discoveries Pulsar J0002+6216 Volunteers (Country): UW-Madison CAE (USA) and RUElwell (USA) Date: 31 Dec 2014 Survey: FGRP4 Selected pulsar parameters: Right ascension: 00:02 Declination: +62:16 Spin frequency: 8.67 Hz First frequency derivate: -4.48 x 10-13 Hz/s Characteristic age: 306.3 kyrs Spin-down power: 1.5 x 1035 erg/s Pulsar J0359+5414 Volunteers (Country): Whelton Miller (USA), ATLAS AEI Hannover (Germany) and Delty (USA) Date: 15 Dec 2014 Survey: FGRP4 Selected pulsar parameters: Right ascension: 03:59 Declination: +54:14 Spin frequency: 12.59 Hz First frequency derivate: -2.65 x 10-12 Hz/s Characteristic age: 75.2 kyrs Spin-down power: 1.3 x 1036 erg/s Pulsar J0554+3107 Volunteers (Country): David Z (Canada) and Test (France) Date: 06 Jan 2012 Survey: FGRP1 Selected pulsar parameters: Right ascension: 05:54:05.01(3) Declination: +31:07:41(4) Spin frequency: 2.15 Hz First frequency derivate: -0.66 x 10-12 Hz/s Characteristic age: 51.7 kyrs Spin-down power: 5.6 x 1034 erg/s Pulsar J0631+0646 Volunteers (Country): KataJun (Japan) and huwar Date: 20 Jan 2015 Survey: FGRP4 Selected pulsar parameters: Right ascension: 06:31 Declination: +06:46 Spin frequency: 9.01 Hz First frequency derivate: -2.94 x 10-13 Hz/s Characteristic age: 486.1 kyrs Spin-down power: 1.0 x 1035 erg/s Pulsar J1035-6720 Volunteers (Country): ATLAS AEI Hannover (Germany), Magpoo (USA), WSyS Date: 09 Dec 2014 Survey: FGRP4 Selected pulsar parameters: Right ascension: 10:35 Declination: -67:20 Spin frequency: 348.19 Hz First frequency derivate: -5.63 x 10-15 Hz/s Characteristic age: 1.0 Gyrs Spin-down power: 7.5 x 1034 erg/s Pulsar J1057-5851 Volunteers (Country): Syracuse University (USA) and LLO_LDAS (USA) Date: 28 Oct 2014 Survey: FGRP4 Selected pulsar parameters: Right ascension: 10:57 Declination: -58:51 Spin frequency: 1.61 Hz First frequency derivate: -2.61 x 10-13 Hz/s Characteristic age: 97.7 kyrs Spin-down power: 1.7 x 1034 erg/s Pulsar J1105-6037 Volunteers (Country): ATLAS AEI Hannover (Germany) and Syracuse University (USA) Date: 03 Oct 2014 Survey: FGRP4 Selected pulsar parameters: Right ascension: 11:05 Declination: -60:37 Spin frequency: 5.13 Hz First frequency derivate: -5.75 x 10-13 Hz/s Characteristic age: 141.4 kyrs Spin-down power: 1.2 x 1035 erg/s Pulsar J1208-6238 Volunteers (Country): UW-Madison CAE (USA) and UH RCC - Maxwell (USA) Date: 03 Oct 2014 Survey: FGRP4 Selected pulsar parameters: Right ascension: 12:08:13.96(6) Declination: -62:38:02.3(4) Spin frequency: 2.27 Hz First frequency derivate: -1.68 x 10-11 Hz/s Characteristic age: 2,700 yrs Spin-down power: 1.5 x 1036 erg/s Pulsar J1350-6225 Volunteers (Country): PeRu (Czech Republic) and Bryden Kanngiesser (Canada) Date: 19 Jun 2015 Survey: FGRP4 Selected pulsar parameters: Right ascension: 13:50 Declination: -62:25 Spin frequency: 7.24 Hz First frequency derivate: -4.65 x 10-13 Hz/s Characteristic age: 246.4 kyrs Spin-down power: 1.3 x 1035 erg/s Pulsar J1422-6138 Volunteers (Country): Mak-ino (Japan) and Thomas M. Jackson (USA) Date: 14 Dec 2011 Survey: FGRP1 Selected pulsar parameters: Right ascension: 14:22:27.07(1) Declination: -61:38:28(1) Spin frequency: 2.93 Hz First frequency derivate: -0.83 x 10-12 Hz/s Characteristic age: 55.8 kyrs Spin-down power: 9.6 x 1034 erg/s Pulsar J1522-5735 Volunteers (Country): The NEMO computing cluster (USA) and Chen (USA) Date: 30 Sep 2011 Survey: FGRP1 Selected pulsar parameters: Right ascension: 15:22:05.3(1) Declination: -57:35:00(1) Spin frequency: 9.79 Hz First frequency derivate: -2.99 x 10-12 Hz/s Characteristic age: 51.8 kyrs Spin-down power: 115.7 x 1034 erg/s Pulsar J1528-5838 Volunteers (Country): fred c (USA) and Gabriel Vasquez Date: 25 Mar 2015 Survey: FGRP4 Selected pulsar parameters: Right ascension: 15:28 Declination: -58:38 Spin frequency: 2.81 Hz First frequency derivate: -1.96 x 10-13 Hz/s Characteristic age: 227.6 kyrs Spin-down power: 2.2 x 1034 erg/s Pulsar J1623-5005 Volunteers (Country): r4p and Greg Dorais (USA) Date: 04 Oct 2014 Survey: FGRP4 Selected pulsar parameters: Right ascension: 16:23 Declination: -50:05 Spin frequency: 11.75 Hz First frequency derivate: -5.75 x 10-13 Hz/s Characteristic age: 323.9 kyrs Spin-down power: 2.7 x 1035 erg/s Pulsar J1624-4041 Volunteers (Country): xio.nyc (Antarctica) and Hung Tran (USA) Date: 20 Dec 2014 Survey: FGRP4 Selected pulsar parameters: Right ascension: 16:24 Declination: -40:41 Spin frequency: 5.96 Hz First frequency derivate: -1.68 x 10-13 Hz/s Characteristic age: 562.9 kyrs Spin-down power: 3.9 x 1034 erg/s Pulsar J1641-5317 Volunteers (Country): UW-Madison CAE (USA) and ATLAS AEI Hannover (Germany) Date: 30 Dec 2015 Survey: FGRP4 Selected pulsar parameters: Right ascension: 16:41 Declination: -53:17 Spin frequency: 5.71 Hz First frequency derivate: -1.21 x 10-13 Hz/s Characteristic age: 750 kyrs Spin-down power: 2.7 x 1034 erg/s Pulsar J1650-4601 Volunteers (Country): Syracuse University (USA) and Eric Schwartz (USA) Date: 17 Oct 2014 Survey: FGRP4 Selected pulsar parameters: Right ascension: 16:50 Declination: -46:01 Spin frequency: 7.87 Hz First frequency derivate: -9.37 x 10-13 Hz/s Characteristic age: 133.0 kyrs Spin-down power: 2.9 x 1035 erg/s Pulsar J1744-7619 Volunteers (Country): DarrellH (USA), ATLAS AEI Hannover (Germany), LLO_LDAS (USA), and harvy (UK) Date: 07 Dec 2014 Survey: FGRP4 Selected pulsar parameters: Right ascension: 17:44 Declination: -76:19 Spin frequency: 213.33 Hz First frequency derivate: -4.41 x 10-16 Hz/s Characteristic age: 7.7 Gyrs Spin-down power: 3.7 x 1033 erg/s Pulsar J1817-1742 Volunteers (Country): dbillenness (Canada) and Jon Kerfoot (USA) Date: 24 Dec 2015 Survey: FGRP4 Selected pulsar parameters: Right ascension: 18:17 Declination: -17:42 Spin frequency: 6.68 Hz First frequency derivate: -9.18 x 10-13 Hz/s Characteristic age: 115 kyrs Spin-down power: 2.42 x 1035 erg/s Pulsar J1827-1446 Volunteers (Country): ATLAS AEI Hannover (Germany) and LLO_LDAS (USA) Date: 19 Dec 2014 Survey: FGRP4 Selected pulsar parameters: Right ascension: 18:27 Declination: -14:46 Spin frequency: 2.00 Hz First frequency derivate: -1.82 x 10-13 Hz/s Characteristic age: 174.5 kyrs Spin-down power: 1.4 x 1034 erg/s Pulsar J1844-0346 Volunteers (Country): Aurelien FAUCHEUX (France) and Roger (USA) Date: 18 Nov 2014 Survey: FGRP4 Selected pulsar parameters: Right ascension: 18:44 Declination: -03:46 Spin frequency: 8.86 Hz First frequency derivate: -1.21 x 10-11 Hz/s Characteristic age: 11.6 kyrs Spin-down power: 4.2 x 1036 erg/s Pulsar J1906+0722 Volunteers (Country): Connor Barry (USA) and Richard Johnson (USA) Date: 11 Sep 2014 Survey: FGRP4 Selected pulsar parameters: Right ascension: 19:06:31.20(1) Declination: +07:22:55.8(4) Spin frequency: 8.97 Hz First frequency derivate: -2.88 x 10-12 Hz/s Characteristic age: 49.2 kyrs Spin-down power: 1.02 x 1036 erg/s Pulsar J1932+1916 Volunteers (Country): Doug Lean (Australia) and Hans-Peter Tobler (Germany) Date: 19 Sep 2011 Survey: FGRP1 Selected pulsar parameters: Right ascension: 19:32:19.70(4) Declination: +19:16:39(1) Spin frequency: 4.80 Hz First frequency derivate: -2.15 x 10-12 Hz/s Characteristic age: 35.4 kyrs Spin-down power: 40.7 x 1034 erg/s Pulsar J2017+3625 Volunteers (Country): gramoll (USA) and Rogir (Germany) Date: 09 Sep 2014 Survey: FGRP4 Selected pulsar parameters: Right ascension: 20:17 Declination: +36:25 Spin frequency: 6.00 Hz First frequency derivate: -4.89 x 10-14 Hz/s Characteristic age: 1942.8 kyrs Spin-down power: 1.2 x 1034 erg/s Einstein@Home Lars Nieder (Last Update: Feb 03, 2020)