H. Fehrmann

Fast Radio Burst Discovered in the Arecibo Pulsar ALFA Survey

Recent work has exploited pulsar survey data to identify temporally isolated, millisecond-duration radio bursts with large dispersion measures (DMs). These bursts have been interpreted as arising from a population of extragalactic sources, in which case they would provide unprecedented opportunities for probing the intergalactic medium; they may also be linked to new source classes. Until now, however, all so-called fast radio bursts (FRBs) have been detected with the Parkes radio telescope and its 13-beam receiver, casting some concern about the astrophysical nature of these signals. Here we present FRB 121102, the first FRB discovery from a geographic location other than Parkes. FRB 121102 was found in the Galactic anti-center region in the 1.4?GHz Pulsar Arecibo L-band Feed Array (ALFA) survey with the Arecibo Observatory with a DM = 557.4 ? 2.0 pc cm?3, pulse width of 3.0 ? 0.5 ms, and no evidence of interstellar scattering. The observed delay of the signal arrival time with frequency agrees precisely with the expectation of dispersion through an ionized medium. Despite its low Galactic latitude (b = ?0.?2), the burst has three times the maximum Galactic DM expected along this particular line of sight, suggesting an extragalactic origin. A peculiar aspect of the signal is an inverted spectrum; we interpret this as a consequence of being detected in a sidelobe of the ALFA receiver. FRB 121102s brightness, duration, and the inferred event rate are all consistent with the properties of the previously detected Parkes bursts.

DISCOVERY OF NINE GAMMA-RAY PULSARS IN FERMI LARGE AREA TELESCOPE DATA USING A NEW BLIND SEARCH METHOD

We report the discovery of nine previously unknown gamma-ray pulsars in a blind search of data from the Fermi Large Area Telescope (LAT). The pulsars were found with a novel hierarchical search method originally developed for detecting continuous gravitational waves from rapidly rotating neutron stars. Designed to find isolated pulsars spinning at up to kHz frequencies, the new method is computationally efficient and incorporates several advances, including a metric-based gridding of the search parameter space (frequency, frequency derivative, and sky location) and the use of photon probability weights. The nine pulsars have spin frequencies between 3 and 12 Hz, and characteristic ages ranging from 17 kyr to 3 Myr. Two of them, PSRs J1803-2149 and J2111+ 4606, are young and energetic Galactic-plane pulsars (spin-down power above 6 Multiplication-Sign 10{sup 35} erg s{sup -1} and ages below 100 kyr). The seven remaining pulsars, PSRs J0106+4855, J0622+3749, J1620-4927, J1746-3239, J2028+3332, J2030+4415, and J2139+4716, are older and less energetic; two of them are located at higher Galactic latitudes (|b| > 10 Degree-Sign ). PSR J0106+4855 has the largest characteristic age (3 Myr) and the smallest surface magnetic field (2 Multiplication-Sign 10{sup 11} G) of all LAT blind-search pulsars. PSR J2139+4716 has the lowestmorexa0» spin-down power (3 Multiplication-Sign 10{sup 33} erg s{sup -1}) among all non-recycled gamma-ray pulsars ever found. Despite extensive multi-frequency observations, only PSR J0106+4855 has detectable pulsations in the radio band. The other eight pulsars belong to the increasing population of radio-quiet gamma-ray pulsars.«xa0less

Discovery of Nine Gamma-Ray Pulsars in Fermi-LAT Data Using a New Blind Search Method

We report the discovery of nine previously unknown gamma-ray pulsars in a blind search of data from the Fermi Large Area Telescope (LAT). The pulsars were found with a novel hierarchical search method originally developed for detecting continuous gravitational waves from rapidly rotating neutron stars. Designed to find isolated pulsars spinning at up to kHz frequencies, the new method is computationally efficient and incorporates several advances, including a metric-based gridding of the search parameter space (frequency, frequency derivative, and sky location) and the use of photon probability weights. The nine pulsars have spin frequencies between 3 and 12 Hz, and characteristic ages ranging from 17 kyr to 3 Myr. Two of them, PSRs J1803-2149 and J2111+ 4606, are young and energetic Galactic-plane pulsars (spin-down power above 6 Multiplication-Sign 10{sup 35} erg s{sup -1} and ages below 100 kyr). The seven remaining pulsars, PSRs J0106+4855, J0622+3749, J1620-4927, J1746-3239, J2028+3332, J2030+4415, and J2139+4716, are older and less energetic; two of them are located at higher Galactic latitudes (|b| > 10 Degree-Sign ). PSR J0106+4855 has the largest characteristic age (3 Myr) and the smallest surface magnetic field (2 Multiplication-Sign 10{sup 11} G) of all LAT blind-search pulsars. PSR J2139+4716 has the lowestmorexa0» spin-down power (3 Multiplication-Sign 10{sup 33} erg s{sup -1}) among all non-recycled gamma-ray pulsars ever found. Despite extensive multi-frequency observations, only PSR J0106+4855 has detectable pulsations in the radio band. The other eight pulsars belong to the increasing population of radio-quiet gamma-ray pulsars.«xa0less

Pulsar discovery by global volunteer computing

Einstein@Home, a distributed computing project, discovered a rare, isolated pulsar with a low magnetic field. Einstein@Home aggregates the computer power of hundreds of thousands of volunteers from 192 countries to mine large data sets. It has now found a 40.8-hertz isolated pulsar in radio survey data from the Arecibo Observatory taken in February 2007. Additional timing observations indicate that this pulsar is likely a disrupted recycled pulsar. PSR J2007+2722’s pulse profile is remarkably wide with emission over almost the entire spin period; the pulsar likely has closely aligned magnetic and spin axes. The massive computing power provided by volunteers should enable many more such discoveries.

THE EINSTEIN@HOME SEARCH FOR RADIO PULSARS AND PSR J2007+2722 DISCOVERY

Einstein@Home aggregates the computer power of hundreds of thousands of volunteers from 193 countries, to search for new neutron stars using data from electromagnetic and gravitational-wave detectors. This paper presents a detailed description of the search for new radio pulsars using Pulsar ALFA survey data from the Arecibo Observatory. The enormous computing power allows this search to cover a new region of parameter space; it can detect pulsars in binary systems with orbital periods as short as 11xa0minutes. We also describe the first Einstein@Home discovery, the 40.8xa0Hz isolated pulsar PSR J2007+2722, and provide a full timing model. PSR J2007+2722s pulse profile is remarkably wide with emission over almost the entire spin period. This neutron star is most likely a disrupted recycled pulsar, about as old as its characteristic spin-down age of 404xa0Myr. However, there is a small chance that it was born recently, with a low magnetic field. If so, upper limits on the X-ray flux suggest but cannot prove that PSR J2007+2722 is at least ~100 kyr old. In the future, we expect that the massive computing power provided by volunteers should enable many additional radio pulsar discoveries.

PSR J1838-0537: Discovery of a young, energetic gamma-ray pulsar

We report the discovery of PSR J1838−0537, a gamma-ray pulsar found through a blind search of data from the Fermi Large Area Telescope (LAT). The pulsar has a spin frequency of 6.9 Hz and a frequency derivative of −2.2 × 10 −11 Hz s −1 , implying a young characteristic age of 4970 yr and a large spin-down power of 5.9 × 10 36 erg s −1 . Follow-up observations with radio telescopes detected no pulsations; thus PSR J1838−0537 appears radio-quiet as viewed from Earth. In 2009 September the pulsar suffered the largest glitch so far seen in any gamma-ray-only pulsar, causing a relative increase in spin frequency of about 5.5 × 10 −6 . After the glitch, during a putative recovery period, the timing analysis is complicated by the sparsity of the LAT photon data, the weakness of the pulsations, and the reduction in average exposure from a coincidental, contemporaneous change in LAT’s sky-survey observing pattern. The pulsar’s sky position is coincident with the spatially extended TeV source HESS J1841−055 detected by the High Energy Stereoscopic System (H.E.S.S.). The inferred energetics suggest that HESS J1841−055 contains a pulsar wind nebula powered by the pulsar.

Einstein@Home Discovery of 24 Pulsars in the Parkes Multi-beam Pulsar Survey

We have conducted a new search for radio pulsars in compact binary systems in the Parkes multi-beam pulsar survey (PMPS) data, employing novel methods to remove the Doppler modulation from binary motion. This has yielded unparalleled sensitivity to pulsars in compact binaries. The required computation time of 17, 000xa0CPU core years was provided by the distributed volunteer computing project Einstein@Home, which has a sustained computing power of about 1 PFlopxa0s–1. We discovered 24 new pulsars in our search, 18 of which were isolated pulsars, and 6 were members of binary systems. Despite the wide filterbank channels and relatively slow sampling time of the PMPS data, we found pulsars with very large ratios of dispersion measure (DM) to spin period. Among those is PSR J1748–3009, the millisecond pulsar with the highest known DM (420xa0pcxa0cm–3). We also discovered PSR J1840–0643, which is in a binary system with an orbital period of 937xa0days, the fourth largest known. The new pulsar J1750–2536 likely belongs to the rare class of intermediate-mass binary pulsars. Three of the isolated pulsars show long-term nulling or intermittency in their emission, further increasing this growing family. Our discoveries demonstrate the value of distributed volunteer computing for data-driven astronomy and the importance of applying new analysis methods to extensively searched data.

Arecibo PALFA survey and Einstein@Home: Binary pulsar discovery by volunteer computing

We report the discovery of the 20.7 ms binary pulsar J1952+2630, made using the distributed computing project Einstein@Home in Pulsar ALFA survey observations with the Arecibo telescope. Follow-up observations with the Arecibo telescope confirm the binary nature of the system. We obtain a circular orbital solution with an orbital

Einstein@Home Discovery of Four Young Gamma-Ray Pulsars in Fermi LAT Data

We report the discovery of four gamma-ray pulsars, detected in computing-intensive blind searches of data from the Fermi Large Area Telescope (LAT). The pulsars were found using a novel search approach, combining volunteer distributed computing via Einstein@Home and methods originally developed in gravitational-wave astronomy. The pulsars PSRs J0554+3107, J1422–6138, J1522–5735, and J1932+1916 are young and energetic, with characteristic ages between 35 and 56 kyr and spin-down powers in the range 6 × 1034—1036 erg s–1. They are located in the Galactic plane and have rotation rates of less than 10 Hz, among which the 2.1 Hz spin frequency of PSR J0554+3107 is the slowest of any known gamma-ray pulsar. For two of the new pulsars, we find supernova remnants coincident on the sky and discuss the plausibility of such associations. Deep radio follow-up observations found no pulsations, suggesting that all four pulsars are radio-quiet as viewed from Earth. These discoveries, the first gamma-ray pulsars found by volunteer computing, motivate continued blind pulsar searches of the many other unidentified LAT gamma-ray sources.

Einstein@Home Discovery of a PALFA Millisecond Pulsar in an Eccentric Binary Orbit

We report the discovery of the millisecond pulsar (MSP) PSR J1950+2414 (P = 4.3 ms) in a binary system with an eccentric (e = 0.08) 22 day orbit in Pulsar Arecibo L-band Feed Array survey observations with the Arecibo telescope. Its companion star has a median mass of 0.3 M⊙ and is most likely a white dwarf (WD). Fully recycled MSPs like this one are thought to be old neutron stars spun-up by mass transfer from a companion star. This process should circularize the orbit, as is observed for the vast majority of binary MSPs, which predominantly have orbital eccentricities e < 0.001. However, four recently discovered binary MSPs have orbits with 0. 027 < e < 0.44; PSR J1950+2414 is the fifth such system to be discovered. The upper limits for its intrinsic spin period derivative and inferred surface magnetic field strength are comparable to those of the general MSP population. The large eccentricities are incompatible with the predictions of the standard recycling scenario: something unusual happened during their evolution. Proposed scenarios are (a) initial evolution of the pulsar in a triple system which became dynamically unstable, (b) origin in an exchange encounter in an environment with high stellar density, (c) rotationally delayed accretion-induced collapse of a super-Chandrasekhar WD, and (d) dynamical interaction of the binary with a circumbinary disk. We compare the properties of all five known eccentric MSPs with the predictions of these formation channels. Future measurements of the masses and proper motion might allow us to firmly exclude some of the proposed formation scenarios.