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Register a new userThe Northern High Time Resolution Universe Pulsar Survey I: Setup and initial discoveries
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We report on the setup and initial discoveries of the Northern High Time Resolution Universe survey for pulsars and fast transients, the first major pulsar survey conducted with the 100-m Effelsberg radio telescope and the first in 20 years to observe the whole northern sky at high radio frequencies. Using a newly developed 7-beam receiver system combined with a state-of-the-art polyphase filterbank, we record an effective bandwidth of 240 MHz in 410 channels centred on 1.36 GHz with a time resolution of 54 $mu$s. Such fine time and frequency resolution increases our sensitivity to millisecond pulsars and fast transients, especially deep inside the Galaxy, where previous surveys have been limited due to intra-channel dispersive smearing. To optimise observing time, the survey is split into three integration regimes dependent on Galactic latitude, with 1500-s, 180-s and 90-s integrations for latitude ranges $|b|<3.5^{circ}$, $|b|<15^{circ}$ and $|b|>15^{circ}$, respectively. The survey has so far resulted in the discovery of 15 radio pulsars, including a pulsar with a characteristic age of $sim18$ kyr, {PSR J2004+3429}, and a highly eccentric, binary millisecond pulsar, {PSR J1946+3417}. All newly discovered pulsars are timed using the 76-m Lovell radio telescope at the Jodrell Bank Observatory and the Effelsberg radio telescope. We present timing solutions for all newly discovered pulsars and discuss potential supernova remnant associations for {PSR J2004+3429}.
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We have embarked on a survey for pulsars and fast transients using the 13-beam Multibeam receiver on the Parkes radio telescope. Installation of a digital backend allows us to record 400 MHz of bandwidth for each beam, split into 1024 channels and sampled every 64 us. Limits of the receiver package restrict us to a 340 MHz observing band centred at 1352 MHz. The factor of eight improvement in frequency resolution over previous multibeam surveys allows us to probe deeper into the Galactic plane for short duration signals such as the pulses from millisecond pulsars. We plan to survey the entire southern sky in 42641 pointings, split into low, mid and high Galactic latitude regions, with integration times of 4200, 540 and 270 s respectively. Simulations suggest that we will discover 400 pulsars, of which 75 will be millisecond pulsars. With ~30% of the mid-latitude survey complete, we have re-detected 223 previously known pulsars and discovered 27 pulsars, 5 of which are millisecond pulsars. The newly discovered millisecond pulsars tend to have larger dispersion measures than those discovered in previous surveys, as expected from the improved time and frequency resolution of our instrument.
We report the discovery and the results of follow-up timing observations of PSR J2045+3633 and PSR J2053+4650, two binary pulsars found in the Northern High Time Resolution Universe pulsar survey being carried out with the Effelsberg radio telescope. Having spin periods of 31.7 ms and 12.6 ms respectively, and both with massive white dwarf companions, $M_{c}, > , 0.8, M_{odot}$, the pulsars can be classified as mildly recycled. PSR J2045+3633 is remarkable due to its orbital period (32.3 days) and eccentricity $e, = , 0.01721244(5)$ which is among the largest ever measured for this class. After almost two years of timing the large eccentricity has allowed the measurement of the rate of advance of periastron at the 5-$sigma$ level, 0.0010(2)$^circ~rm yr^{-1}$. Combining this with a detection of the orthometric amplitude of the Shapiro delay, we obtained the following constraints on the component masses (within general relativity): $M_{p}, = , 1.33^{+0.30}_{-0.28}, M_{odot}$, and $M_{c}, = , 0.94^{+0.14}_{-0.13}, M_{odot}$. PSR J2053+4650 has a 2.45-day circular orbit inclined to the plane of the sky at an angle $i, = , 85.0^{+0.8}_{-0.9},{^circ}$. In this nearly edge-on case the masses can be obtained from the Shapiro delay alone. Our timing observations resulted in a significant detection of this effect giving: $M_{p}, = , 1.40^{+0.21}_{-0.18}, M_{odot}$, and $M_{c}, = , 0.86^{+0.07}_{-0.06}, M_{odot}$.
We are conducting a survey for pulsars and transients using the Giant Metrewave Radio Telescope (GMRT). The GMRT High Resolution Southern Sky (GHRSS) survey is an off-Galactic-plane (|b|>5) survey in the declination range -40 deg to -54 deg at 322 MHz. With the high time (up to 30.72 micro-sec) and frequency (up to 0.016275 MHz) resolution observing modes, the 5-sigma detection limit is 0.5 mJy for a 2 ms pulsar with 10% duty cycle at 322 MHz. Total GHRSS sky coverage of 2866 square-deg, will result from 1953 pointing, each covering 1.8 square-deg. The 10-sigma detection limit for a 5 milli-sec transient burst is 1.6 Jy for the GHRSS survey. In addition, the GHRSS survey can reveal transient events like rotating radio transients or fast radio bursts. With 35% of the survey completed (i.e. 1000 square-deg), we report the discovery of 10 pulsars, one of which is a millisecond pulsar (MSP), one of the highest pulsar per square degree discovery rates for any off-Galactic plane survey. We re-detected 23 known in-beam pulsars. Utilising the imaging capability of the GMRT we also localised 4 of the GHRSS pulsars (including the MSP) in the gated image plane within +/- 10 arc-second. We demonstrated rapid convergence in pulsar timing with a more precise position than is possible with single dish discoveries. We also exhibited that we can localise the brightest transient sources with simultaneously obtained lower time resolution imaging data, demonstrating a technique that may have application in the SKA.
We describe an ongoing search for pulsars and dispersed pulses of radio emission, such as those from rotating radio transients (RRATs) and fast radio bursts (FRBs), at 350 MHz using the Green Bank Telescope. With the Green Bank Ultimate Pulsar Processing Instrument, we record 100 MHz of bandwidth divided into 4,096 channels every 81.92 $mu s$. This survey will cover the entire sky visible to the Green Bank Telescope ($delta > -40^circ$, or 82% of the sky) and outside of the Galactic Plane will be sensitive enough to detect slow pulsars and low dispersion measure ($<$30 $mathrm{pc,cm^{-3}}$) millisecond pulsars (MSPs) with a 0.08 duty cycle down to 1.1 mJy. For pulsars with a spectral index of $-$1.6, we will be 2.5 times more sensitive than previous and ongoing surveys over much of our survey region. Here we describe the survey, the data analysis pipeline, initial discovery parameters for 62 pulsars, and timing solutions for 5 new pulsars. PSR J0214$+$5222 is an MSP in a long-period (512 days) orbit and has an optical counterpart identified in archival data. PSR J0636$+$5129 is an MSP in a very short-period (96 minutes) orbit with a very low mass companion (8 $M_mathrm{J}$). PSR J0645$+$5158 is an isolated MSP with a timing residual RMS of 500 ns and has been added to pulsar timing array experiments. PSR J1434$+$7257 is an isolated, intermediate-period pulsar that has been partially recycled. PSR J1816$+$4510 is an eclipsing MSP in a short-period orbit (8.7 hours) and may have recently completed its spin-up phase.
We report the discovery of PSR J1757$-$1854, a 21.5-ms pulsar in a highly-eccentric, 4.4-h orbit around a neutron star (NS) companion. PSR J1757$-$1854 exhibits some of the most extreme relativistic parameters of any known pulsar, including the strongest relativistic effects due to gravitational-wave (GW) damping, with a merger time of 76 Myr. Following a 1.6-yr timing campaign, we have measured five post-Keplerian (PK) parameters, yielding the two component masses ($m_text{p}=1.3384(9),text{M}_odot$ and $m_text{c}=1.3946(9),text{M}_odot$) plus three tests of general relativity (GR), which the theory passes. The larger mass of the NS companion provides important clues regarding the binary formation of PSR J1757$-$1854. With simulations suggesting 3-$sigma$ measurements of both the contribution of Lense-Thirring precession to the rate of change of the semi-major axis and the relativistic deformation of the orbit within $sim7-9$ years, PSR J1757$-$1854 stands out as a unique laboratory for new tests of gravitational theories.
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