pdf/the-qitai-radio-telescope-3sd9no9n.pdf

The Qitai radio telescope


 We report 4 new pulsars discovered in the core-collapsed globular cluster (GC) NGC 6624 by the TRAPUM Large Survey Project with the MeerKAT telescope. All of the new pulsars found are isolated. PSR J1823−3021I and PSR J1823−3021K are millisecond pulsars with period of respectively 4.319 ms and 2.768 ms. PSR J1823−3021J is mildly recycled with a period of 20.899 ms, and PSR J1823−3022 is a long period pulsar with a period of 2.497 s. The pulsars J1823−3021I, J1823−3021J, and J1823−3021K have position and dispersion measure (DM) compatible with being members of the GC and are therefore associated with NGC 6624. Pulsar J1823−3022 is the only pulsar bright enough to be re-detected in archival observations of the cluster. This allowed the determination of a timing solution that spans over two decades. It is not possible at the moment to claim the association of pulsar J1823−3022 with the GC given the long period and large offset in position (∼3 arcminutes) and DM (with a fractional difference of 11 percent compared the average of the pulsars in NGC 6624). The discoveries made use of the beamforming capability of the TRAPUM backend to generate multiple beams in the same field of view which allows sensitive searches to be performed over a few half-light radii from the cluster center and can simultaneously localise the discoveries. The discoveries reflect the properties expected for pulsars in core-collapsed GCs.

/pdf/four-pulsar-discoveries-in-ngc-6624-by-trapum-using-meerkat-24tzoz2y.pdf

Four pulsar discoveries in NGC 6624 by TRAPUM using MeerKAT


               <jats:p>PSR J2150+3427 is a 0.654 s pulsar discovered by the Commensal Radio Astronomy FAST Survey. From the follow-up observations, we find that the pulsar is in a highly eccentric orbit (<jats:italic>e</jats:italic> = 0.601) with an orbital period of 10.592 days and a projected semimajor axis of 25.488 lt-s. Using 2.7 yr of timing data, we also measured the rate of periastron advance <jats:inline-formula>
                     <jats:tex-math>
<?CDATA $\dot{\omega }$?>
</jats:tex-math>
                     <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                        <mml:mover accent="true">
                           <mml:mrow>
                              <mml:mi>ω</mml:mi>
                           </mml:mrow>
                           <mml:mrow>
                              <mml:mo>̇</mml:mo>
                           </mml:mrow>
                        </mml:mover>
                     </mml:math>
                     <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlad0887ieqn1.gif" xlink:type="simple" />
                  </jats:inline-formula> = 0.0115(4) deg yr<jats:sup>−1</jats:sup>. An estimate for the total mass of the system using the <jats:inline-formula>
                     <jats:tex-math>
<?CDATA $\dot{\omega }$?>
</jats:tex-math>
                     <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                        <mml:mover accent="true">
                           <mml:mrow>
                              <mml:mi>ω</mml:mi>
                           </mml:mrow>
                           <mml:mrow>
                              <mml:mo>̇</mml:mo>
                           </mml:mrow>
                        </mml:mover>
                     </mml:math>
                     <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlad0887ieqn2.gif" xlink:type="simple" />
                  </jats:inline-formula> gives <jats:italic>M</jats:italic>
                  <jats:sub>tot</jats:sub> = 2.59(13)<jats:italic>M</jats:italic>
                  <jats:sub>⊙</jats:sub>, which is consistent with most of the known double neutron star (DNS) systems and one neutron star (NS)–white dwarf (WD) system named B2303+46. Combining <jats:inline-formula>
                     <jats:tex-math>
<?CDATA $\dot{\omega }$?>
</jats:tex-math>
                     <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                        <mml:mover accent="true">
                           <mml:mrow>
                              <mml:mi>ω</mml:mi>
                           </mml:mrow>
                           <mml:mrow>
                              <mml:mo>̇</mml:mo>
                           </mml:mrow>
                        </mml:mover>
                     </mml:math>
                     <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlad0887ieqn3.gif" xlink:type="simple" />
                  </jats:inline-formula> with the mass function of the system gives the masses of <jats:italic>M</jats:italic>
                  <jats:sub>
                     <jats:italic>p</jats:italic>
                  </jats:sub> < 1.67 and <jats:italic>M</jats:italic>
                  <jats:sub>
                     <jats:italic>c</jats:italic>
                  </jats:sub> > 0.98 <jats:italic>M</jats:italic>
                  <jats:sub>⊙</jats:sub> for the pulsar and the companion star, respectively. This constraint, along with the spin period and orbital parameters, suggests that it is possibly a DNS system, and we cannot entirely rule out the possibility of an NS–WD system. Future timing observations will vastly improve the uncertainty in <jats:inline-formula>
                     <jats:tex-math>
<?CDATA $\dot{\omega }$?>
</jats:tex-math>
                     <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                        <mml:mover accent="true">
                           <mml:mrow>
                              <mml:mi>ω</mml:mi>
                           </mml:mrow>
                           <mml:mrow>
                              <mml:mo>̇</mml:mo>
                           </mml:mrow>
                        </mml:mover>
                     </mml:math>
                     <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlad0887ieqn4.gif" xlink:type="simple" />
                  </jats:inline-formula>, and are likely to allow the detection of additional relativistic effects, which can be used to modify the values of <jats:italic>M</jats:italic>
                  <jats:sub>
                     <jats:italic>p</jats:italic>
                  </jats:sub> and <jats:italic>M</jats:italic>
                  <jats:sub>
                     <jats:italic>c</jats:italic>
                  </jats:sub>. With a spin-down luminosity of <jats:inline-formula>
                     <jats:tex-math>
<?CDATA $\dot{E}$?>
</jats:tex-math>
                     <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                        <mml:mover accent="true">
                           <mml:mrow>
                              <mml:mi>E</mml:mi>
                           </mml:mrow>
                           <mml:mrow>
                              <mml:mo>̇</mml:mo>
                           </mml:mrow>
                        </mml:mover>
                     </mml:math>
                     <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlad0887ieqn5.gif" xlink:type="simple" />
                  </jats:inline-formula> = 5.07(6) × 10<jats:sup>29</jats:sup> erg s<jats:sup>−1</jats:sup>, PSR J2150+3427 is a very low-luminosity pulsar, with only the binary pulsar J2208+4610 having a smaller <jats:inline-formula>
                     <jats:tex-math>
<?CDATA $\dot{E}$?>
</jats:tex-math>
                     <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                        <mml:mover accent="true">
                           <mml:mrow>
                              <mml:mi>E</mml:mi>
                           </mml:mrow>
                           <mml:mrow>
                              <mml:mo>̇</mml:mo>
                           </mml:mrow>
                        </mml:mover>
                     </mml:math>
                     <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlad0887ieqn6.gif" xlink:type="simple" />
                  </jats:inline-formula>.</jats:p>

PSR J2150+3427: A Possible Double Neutron Star System

We developed a GPU based single-pulse search pipeline (GSP) with candidate-archiving database. Largely based upon the infrastructure of Open source pulsar search and analysis toolkit (PRESTO), GSP implements GPU acceleration of the de-dispersion and integrates a candidate-archiving database. We applied GSP to the data streams from the commensal radio astronomy FAST survey (CRAFTS), which resulted in a quasi-real-time processing. The integrated candidate database facilitates synergistic usage of multiple machine-learning tools and thus improves efficient identification of radio pulsars such as rotating radio transients (RRATs) and Fast Radio Bursts (FRBs). We first tested GSP on pilot CRAFTS observations with the FAST Ultra-Wide Band (UWB) receiver. GSP detected all pulsars known from the the Parkes multibeam pulsar survey in the respective sky area covered by the FAST-UWB. GSP also discovered 13 new pulsars. We measured the computational efficiency of GSP to be ~120 times faster than the original PRESTO and ~60 times faster than a MPI-parallelized version of PRESTO.

A GPU based single-pulse search pipeline (GSP) with database and its application to the commensal radio astronomy FAST survey (CRAFTS).


 The HTRU-S Low Latitude survey data within 1○of the Galactic Centre (GC) were searched for pulsars using the Fast Folding Algorithm (FFA). Unlike traditional Fast Fourier Transform (FFT) pipelines, the FFA optimally folds the data for all possible periods over a given range, which is particularly advantageous for pulsars with low-duty cycle. For the first time, a search over acceleration was included in the FFA to improve its sensitivity to binary pulsars. The steps in dispersion measure (DM) and acceleration were optimised, resulting in a reduction of the number of trials by 86 per cent. This was achieved over a search period range from 0.6-s to 432-s, i.e. 10 per cent of the observation time (4320s), with a maximum DM of 4000 pc cm−3 and an acceleration range of ±128m s−2. The search resulted in the re-detections of four known pulsars, including a pulsar which was missed in previous FFT processing of this survey. This result indicates that the FFA pipeline is more sensitive than the FFT pipeline used in the previous processing of the survey within our parameter range. Additionally, we discovered a 1.89-s pulsar, PSR J1746-2829, with a large DM, located 0.5 from the GC. Follow-up observations revealed that this pulsar has a relatively flat spectrum(α = −0.9 ± 0.1) and has a period derivative of ∼1.3 × 10−12 s s−1, implying a surface magnetic field of ∼5.2 × 1013 G and a characteristic age of ∼23000 yr. While the period, spectral index, and surface magnetic field strength are similar to many radio magnetars, other characteristics such as high linear polarization are absent.

pdf/the-high-time-resolution-universe-pulsar-survey-xviii-the-2hvhqaxpp7.pdf

The High Time Resolution Universe Pulsar Survey – XVIII. The reprocessing of the HTRU-S Low Lat survey around the Galactic centre using a Fast Folding Algorithm pipeline for accelerated pulsars

We report the follow-up of 10 pulsars discovered by the Five-hundred-meter Aperture Spherical radio-Telescope (FAST) during its commissioning. The pulsars were discovered at a frequency of 500-MHz using the ultra-wide-band (UWB) receiver in drift-scan mode, as part of the Commensal Radio Astronomy FAST Survey (CRAFTS). We carried out the timing campaign with the 100-m Effelsberg radio-telescope at L-band around 1.36 GHz. Along with 11 FAST pulsars previously reported, FAST seems to be uncovering a population of older pulsars, bordering and/or even across the pulsar death-lines. We report here two sources with notable characteristics. PSR J1951$+$4724 is a young and energetic pulsar with nearly 100% of linearly polarized flux density and visible up to an observing frequency of 8 GHz. PSR J2338+4818, a mildly recycled pulsar in a 95.2-d orbit with a Carbon-Oxygen white dwarf (WD) companion of $\gtrsim 1\rm{M}_{\odot}$, based on estimates from the mass function. This system is the widest WD binary with the most massive companion known to-date. Conspicuous discrepancy was found between estimations based on NE2001 and YMW16 electron density models, which can be attributed to under-representation of pulsars in the sky region between Galactic longitudes $70^o<l<100^o$. This work represents one of the early CRAFTS results, which start to show potential to substantially enrich the pulsar sample and refine the Galactic electron density model.

/pdf/fast-early-pulsar-discoveries-effelsberg-follow-up-4k84wambcr.pdf

FAST early pulsar discoveries: Effelsberg follow-up

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FAST early pulsar discoveries: Effelsberg follow-up