FAST Globular Cluster Pulsar Survey: Twenty-Four Pulsars Discovered in Fifteen Globular Clusters

Pan, Zhichen; Qian, Lei; Ma, Xiaoyun; Liu, Kuo; Wang, Lin; Luo, Jintao; Yan, Zhen; Ransom, Scott; Lorimer, Duncan; Li, Di; Jiang, Peng

doi:10.48550/arxiv.2106.08559

Cited by 3 publications

(3 citation statements)

References 17 publications

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“…The inauguration of a new generation of extremely sensitive radio telescopes such as FAST (Nan & Li 2013) and MeerKAT (Booth & Jonas 2012;Jonas & MeerKAT Team 2016;Camilo et al 2018) and major upgrades to existing facilities, such as the installation of technologically advanced digital back-ends and new broad-As of 2022 April 6, see https://www3.mpifr-bonn.mpg.de/ staff/pfreire/GCpsr.html band receivers with lower system temperatures, is now resulting in another wave of discoveries, with close to 100 new pulsars found as of April 2022 (e.g. Ridolfi et al 2021;Pan et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Upgraded GMRT survey for pulsars in globular clusters

Gautam

Ridolfi

Freire

et al. 2022

A&A

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Context. Globular clusters (GCs) contain a unique pulsar population, with many exotic systems that can form only in their dense stellar environments. Such systems are potentially very interesting for new tests of gravity theories and neutron-star mass measurements. Aims. The leap in sensitivity of the upgraded Giant Metrewave Radio Telescope (uGMRT) in India, especially at low radio frequencies (< 1 GHz), motivated a new search for radio pulsars in a group of eight southern GCs. We aim to image these clusters in order to have independent measurements of the radio fluxes of known pulsars and the identification of bright radio sources that could be pulsars missed by pulsation search pipelines due to their inherent limitations. Methods. The observations were conducted at 650 MHz (Band 4 receivers) on Terzan 5, NGC 6441, NGC 6440, and NGC 6544, and at 400 MHz (Band 3 receivers) on NGC 6652, NGC 6539, NGC 1851, and M 30. Segmented acceleration and jerk searches were performed on the data. Simultaneously, we obtained interferometric data on these clusters, which were later converted into radio images.Results. We discovered PSR J1835−3259B, a 1.83-ms pulsar in NGC 6652; this is in a near-circular wide orbit of 28.7-hr with an unidentified low-mass (∼ 0.2) companion, likely a helium white dwarf. We derived a ten-year timing solution for this system. We also present measurements of scattering, flux densities, and spectral indices for some of the previously known pulsars in these GCs. Conclusions. A significant fraction of the pulsars in these clusters have steep spectral indices. Additionally, we detected eight radio point sources not associated with any known pulsar positions in the radio images. There are four newly identified sources, three in NGC 6652 and one in NGC 6539, as well as one previously identified source in NGC 1851, NGC 6440, NGC 6544, and Terzan 5. Surprisingly, our images show that our newly discovered pulsar, PSR J1835−3259B, is the brightest pulsar in all GCs we have imaged; like other pulsars with broad profiles (Terzan 5 C and O), its flux density in the radio images is much larger than in its pulsations. This indicates that their pulsed emission is only a fraction of their total emission. The detection of radio sources outside the core radii but well within the tidal radii of these clusters show that future GC surveys should complement the search analysis by using the imaging capability of interferometers, and preferentially synthesise large number of search beams in order to obtain a larger field of view.

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Section: Introductionmentioning

confidence: 99%

Upgraded GMRT survey for pulsars in globular clusters

Gautam

Ridolfi

Freire

et al. 2022

A&A

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“…discovered with FAST 2 (e.g. Pan et al 2020;Wang et al 2020;Pan et al 2021). Both FAST and MeerKAT, one in the northern hemisphere and the other in the southern hemisphere, respectively, have higher sensitivity than other telescopes that have recently been used for pulsars searches in GCs.…”

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confidence: 99%

Discoveries and Timing of Pulsars in NGC 6440

Vleeschower,

Stappers,

Bailes

et al. 2022

Preprint

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Using the MeerKAT radio telescope, a series of observations have been conducted to time the known pulsars and search for new pulsars in the globular cluster NGC 6440. As a result, two pulsars have been discovered, NGC 6440G and NGC 6440H, one of which is isolated and the other a non-eclipsing (at frequencies above 962 MHz) "Black Widow", with a very low mass companion (M c > 0.006 M ). It joins the other binary pulsars discovered so far in this cluster which all have low companion masses (M c < 0.30 M ). We present the results of long-term timing solutions obtained using data from both Green Bank and MeerKAT telescopes for these two new pulsars and an analysis of the pulsars NGC 6440C and NGC 6440D. For the isolated pulsar NGC 6440C, we searched for planets using a Markov Chain Monte Carlo technique. We find evidence for significant unmodelled variations but they cannot be well modelled as planets nor as part of a power-law red-noise process. Studies of the eclipses of the "Redback" pulsar NGC 6440D at two different frequency bands reveal a frequency dependence with longer and asymmetric eclipses at lower frequencies (962-1283 MHz).

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“…Pan et al 2021) and MeerKAT (see e.g. Ridolfi et al 2021) are currently leading a surge in discoveries of MSPs in globular clusters 4 .…”

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confidence: 99%

Timing observations of three Galactic millisecond pulsars

Lorimer,

Kawash,

Freire

et al. 2021

Preprint

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We report observed and derived timing parameters for three millisecond pulsars (MSPs) from observations collected with the Parkes 64-m telescope, Murriyang. The pulsars were found during re-processing of archival survey data by Mickaliger et al. One of the new pulsars (PSR J1546-5925) has a spin period 𝑃 = 7.8 ms and is isolated. The other two (PSR J0921-5202 with 𝑃 = 9.7 ms and PSR J1146-6610 with 𝑃 = 3.7 ms) are in binary systems around low-mass (> 0.2𝑀 ) companions. Their respective orbital periods are 38.2 d and 62.8 d. While PSR J0921-5202 has a low orbital eccentricity 𝑒 = 1.3 × 10 −5 , in keeping with many other Galactic MSPs, PSR J1146-6610 has a significantly larger eccentricity, 𝑒 = 7.4 × 10 −3 . This makes it a likely member of a group of eccentric MSP-He white dwarf binary systems in the Galactic disk whose formation is poorly understood. Two of the pulsars are co-located with previously unidentified point sources discovered with the Fermi satellite's Large Area Telescope, but no 𝛾-ray pulsations have been detected, likely due to their low spin-down powers. We also show that, particularly in terms of orbital diversity, the current sample of MSPs is far from complete and is subject to a number of selection biases.

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FAST Globular Cluster Pulsar Survey: Twenty-Four Pulsars Discovered in Fifteen Globular Clusters

Cited by 3 publications

References 17 publications

Upgraded GMRT survey for pulsars in globular clusters

Upgraded GMRT survey for pulsars in globular clusters

Discoveries and Timing of Pulsars in NGC 6440

Timing observations of three Galactic millisecond pulsars

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