The first MeerKAT S-band globular cluster pulsar survey

Le résumé fourni par la source

Globular clusters are efficient factories of recycled pulsars, but searches towards high dispersion-measure (DM) clusters can be strongly limited around 1,GHz---which is where most pulsar surveys are typically conducted---due to dispersive smearing and interstellar scattering. Observations at higher radio frequencies provide a complementary route to mitigate these effects and improve sensitivity. We present the first results from a MeerKAT S-band (ν pulsar survey of 14 globular clusters. Our aims were to discover new pulsars, re-detect known pulsars with a uniform high-frequency dataset, and assess practical S-band sensitivity and DM-search requirements for future globular cluster pulsar surveys. High time and frequency resolution S-band observations were searched in the Fourier domain using segmented acceleration and jerk techniques to maintain sensitivity to pulsars in compact binaries, followed by candidate identification and folding. For selected detections and non-detections, we additionally folded the S-band data together with archival MeerKAT L-band observations using available timing ephemerides to derive flux-density measurements and spectral-index constraints. We re-detected 39 previously known pulsars across 14 clusters and discovered four new millisecond pulsars in Glimpse-C01 (J1848-0129C, D, E, and F). Multi-epoch follow-up enabled preliminary Keplerian orbital fits for two of the new systems based on their observed barycentric spin-period modulation. J1848-0129C is an eclipsing millisecond pulsar with Pb ∼ 5 d, placing it among the long-period eclipsing systems known as `huntsman' binaries. J1848-0129D is in a Pb ∼ 3.4, ̊m d nearly circular orbit with a ∼ 1, massive white dwarf companion. Two Glimpse-C01 pulsars exhibit substantial DM offsets relative to the average cluster value. Comparison with other Galactic globular clusters showed that large intracluster DM spreads become increasingly common at high foreground DMs, implying that searches confined to narrow DM windows may be sub-optimal for high-DM clusters. From detections and non-detections, we inferred a practical single-epoch S-band tied-array detectability scale of ∼10--20 μJy, which serves as an operational benchmark rather than a strict completeness limit. MeerKAT S-band observations are highly effective for probing globular clusters affected by strong dispersion and scattering, enabling both reliable re-detections and the discovery of new millisecond pulsars in high-DM environments such as Glimpse-C01. The results of our work highlight the importance of high-frequency surveys for expanding the known pulsar population in obscured clusters.

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