PSR J0311+1402: Slow-Spinning, Intermittent Pulsar

• The pulsar J0311+1402 is a slow-spinning (≈41 s) radio source bridging normal pulsars and RRATs, initially discovered with ASKAP and later reanalyzed at 111 MHz.
• Detailed observations revised its dispersion measure to ~1 pc cm⁻³, placing it at a close distance (~94 pc) with minimal pseudo-luminosity.
• Extensive timing and single-pulse analyses reveal extreme nulling (up to 99.5%) and complex pulse morphology, reshaping our understanding of low-frequency pulsar emission.

Searching arXiv for the specified pulsar and closely related papers. Pulsar J0311+1402, also designated PSR J0311+1402, is an unusually slow-spinning radio pulsar with a period of about $41$ s that was discovered with the Australian Square Kilometre Array Pathfinder and subsequently re-analysed in Pushchino Large Phased Array observations at $111$ MHz (Wang et al., 11 Mar 2025, Tyul'bashev et al., 9 Aug 2025). The source occupies an intermediate regime between normal pulsars and long-period radio transients, while its low-frequency phenomenology is strongly intermittent: at $111$ MHz, the Pushchino study reports that pulsar pulses arrive sporadically and that the source is similar in its properties to a rotating radio transient (RRAT) (Tyul'bashev et al., 9 Aug 2025). The same study also revises the dispersion measure to $\mathrm{DM} = 1 \pm 0.5\ \mathrm{pc\,cm^{-3}}$, implying a distance of about $94$ pc and making J0311+1402 the pulsar with the minimal dispersion measure, the minimal distance from the Sun, and the minimal pseudo-luminosity of all known pulsars in the authors’ comparison set (Tyul'bashev et al., 9 Aug 2025).

1. Discovery and observational identification

PSR J0311+1402 was discovered serendipitously in a 2-minute ASKAP observation on 2024 January 14 during commissioning of the CRACO backend at a central frequency of $887.5$ MHz (Wang et al., 11 Mar 2025). In that short test pointing, CRACO detected three consecutive dispersed pulses with widths $\sim 0.5$ s, spaced by $\sim 40.9$ s, and the brightest pulse had $\mathrm{S/N}\sim 10$ (Wang et al., 11 Mar 2025). A dispersion-measure fit yielded $\mathrm{DM} = 21\pm 3\ \mathrm{pc\,cm^{-3}}$, and the period was measured as $111$0 s from the three pulses (Wang et al., 11 Mar 2025).

The discovery was followed by ASKAP, Parkes, MeerKAT, and Green Bank Telescope observations (Wang et al., 11 Mar 2025). MeerKAT imaging provided a refined position of RA $111$1, Dec $111$2 (J2000) (Wang et al., 11 Mar 2025). In the discovery paper, the source is presented as an object bridging the gap between normal pulsars and the emerging population of long-period radio transients, with observed radio properties that remain compatible with a rotation-powered neutron star interpretation (Wang et al., 11 Mar 2025).

The Pushchino re-analysis at $111$3 MHz shifts the observational emphasis from discovery to intermittency and proximity (Tyul'bashev et al., 9 Aug 2025). In 3321 observation sessions lasting 5 minutes, periodic pulsar radiation at $111$4 MHz was not detected with the fast folding algorithm, but 35 strong pulses with $111$5 were found (Tyul'bashev et al., 9 Aug 2025). This combination of discovery at decimeter wavelengths and highly sporadic meter-wavelength behavior defines the current empirical picture of the source.

2. Rotational and propagation parameters

The discovery timing solution reported a spin period of

$111$6

and a $111$7 upper limit on the period derivative,

$111$8

with a dispersion measure

$111$9

(Wang et al., 11 Mar 2025). On that basis, the source was placed at $111$0 pc in NE2001 and $111$1 pc in YMW16 (Wang et al., 11 Mar 2025).

The Pushchino timing analysis, based on 10.5 years of data at $111$2 MHz, refines the rotational ephemeris at reference epoch MJD 51544 to

$111$3

$111$4

(Tyul'bashev et al., 9 Aug 2025). In frequency notation, the corresponding values are

$111$5

$111$6

(Tyul'bashev et al., 9 Aug 2025). Relative to the discovery paper, this changes the status of $111$7 from an upper limit to a measured quantity.

The most consequential revision concerns the dispersion measure. The Pushchino study reports

$111$8

arguing that this value is supported both by DM-profile optimisation of 35 strong pulses and by narrow features in dynamic spectra whose drift across the full $111$9 MHz band corresponds to approximately $\mathrm{DM} = 1 \pm 0.5\ \mathrm{pc\,cm^{-3}}$0 ms, consistent with $\mathrm{DM} = 1 \pm 0.5\ \mathrm{pc\,cm^{-3}}$1 (Tyul'bashev et al., 9 Aug 2025). Using that DM, the inferred distance is $\mathrm{DM} = 1 \pm 0.5\ \mathrm{pc\,cm^{-3}}$2 pc in YMW16 and $\mathrm{DM} = 1 \pm 0.5\ \mathrm{pc\,cm^{-3}}$3 pc in NE2001, with an adopted average distance $\mathrm{DM} = 1 \pm 0.5\ \mathrm{pc\,cm^{-3}}$4 pc (Tyul'bashev et al., 9 Aug 2025).

This revision suggests that J0311+1402 is not merely an extreme long-period pulsar, but also an exceptionally local one. A plausible implication is that some of the earlier interpretation based on $\mathrm{DM} = 1 \pm 0.5\ \mathrm{pc\,cm^{-3}}$5 requires recontextualization in light of the much smaller line-of-sight electron column inferred from the Pushchino data.

3. Meter-wavelength observations with the LPA LPI

The Pushchino observations were conducted with the Large Phased Array of the P.N. Lebedev Physical Institute in LPA3 stationary multibeam mode (Tyul'bashev et al., 9 Aug 2025). The relevant instrumental parameters are a central observing frequency of about $\mathrm{DM} = 1 \pm 0.5\ \mathrm{pc\,cm^{-3}}$6 MHz, a total bandwidth of $\mathrm{DM} = 1 \pm 0.5\ \mathrm{pc\,cm^{-3}}$7 MHz, 128 beams in meridian scan mode, a beam size of approximately $\mathrm{DM} = 1 \pm 0.5\ \mathrm{pc\,cm^{-3}}$8 in right ascension and declination, and an effective area $\mathrm{DM} = 1 \pm 0.5\ \mathrm{pc\,cm^{-3}}$9 (Tyul'bashev et al., 9 Aug 2025). Two data streams were used: a high-time-resolution stream with $94$0 ms sampling, $94$1 kHz channels, and 32 channels across $94$2 MHz, and a low-time-resolution stream with $94$3 ms sampling, $94$4 kHz channels, and 6 channels (Tyul'bashev et al., 9 Aug 2025).

The data span for the re-analysis extends from 2015-01-01 to 2025-04-28, comprising $94$5 to $94$6 sessions depending on the subsample, with each session contributing about $94$7–$94$8 s for this source (Tyul'bashev et al., 9 Aug 2025). Within the broader Pushchino Multibeam Pulsar Search, the survey processed a ten-year data set for long periods $94$9 using a fast folding algorithm over declinations $887.5$0 (Tyul'bashev et al., 9 Aug 2025).

For J0311+1402, periodic emission was expected to be detectable if the source behaved as a continuously emitting slow pulsar. Scaling from $887.5$1 MHz using $887.5$2, the expected peak flux at $887.5$3 MHz was estimated as

$887.5$4

and for an approximate triangular pulse of width $887.5$5 ms,

$887.5$6

(Tyul'bashev et al., 9 Aug 2025). Since the FFA survey sensitivity after summation is approximately $887.5$7–$887.5$8 mJy for long periods outside the Galactic plane, the absence of an FFA detection indicates that periodic emission is not continuously present at detectable levels (Tyul'bashev et al., 9 Aug 2025).

The single-pulse search therefore became central. Visual inspection of 0.1 s sampled data in 4-minute segments yielded 145 sessions with 2–5 pulses separated by multiples of the known period, and six sessions showed 5 pulses in 200–240 s, corresponding to nearly every rotation being present during those short intervals (Tyul'bashev et al., 9 Aug 2025). Of about 300 low-resolution pulses, 62 could be confidently identified in the high-resolution data, and after timing-guided searches within $887.5$9 s windows around predicted phases, the analysis found 35 strong pulses directly visible in high-resolution data and 180 additional weaker pulses in averaged data that passed timing and RFI checks (Tyul'bashev et al., 9 Aug 2025).

4. Pulse morphology, flux density, and intermittency

At $\sim 0.5$0 MHz, individual pulses show heterogeneous morphology (Tyul'bashev et al., 9 Aug 2025). Some are simple single-component pulses, while some bright pulses exhibit complex multi-peak structure with several narrow sub-pulses, each one sample wide, or $\sim 0.5$1 ms in the high-resolution data (Tyul'bashev et al., 9 Aug 2025). Asymmetric leading and trailing edges are also reported in some pulses (Tyul'bashev et al., 9 Aug 2025).

The peak flux densities of the narrow details of the strong pulses range from $\sim 0.5$2 to $\sim 0.5$3 Jy (Tyul'bashev et al., 9 Aug 2025). The brightest detected sub-feature has

$\sim 0.5$4

while the weakest among the strong-pulse sample has

$\sim 0.5$5

(Tyul'bashev et al., 9 Aug 2025). Using the average profile constructed from strong pulses, the Pushchino study obtains

$\sim 0.5$6

(Tyul'bashev et al., 9 Aug 2025). The authors explicitly note that these are not canonical average fluxes, because they are derived from summing only the 35 strongest pulses (Tyul'bashev et al., 9 Aug 2025).

A separate fold over all 3201 sessions, including non-detections, is treated as an upper limit and yields

$\sim 0.5$7

with $\sim 0.5$8 ms (Tyul'bashev et al., 9 Aug 2025). For the strongest-pulse average profile, the reported width is

$\sim 0.5$9

corresponding to a duty cycle of about $\sim 40.9$0 to $\sim 40.9$1 of the $\sim 40.9$2 s rotation period (Tyul'bashev et al., 9 Aug 2025). The average profile from all sessions is broader, with

$\sim 40.9$3

(Tyul'bashev et al., 9 Aug 2025). For the 180 weaker pulses found with averaging, the FWHM range is $\sim 40.9$4–$\sim 40.9$5 ms, with median $\sim 40.9$6 ms and mean $\sim 40.9$7 ms (Tyul'bashev et al., 9 Aug 2025).

The intermittency is extreme. Over $\sim 40.9$8 years, the total observation time per beam is approximately $\sim 40.9$9 h, yet only 35 strong pulses and 180 weaker pulses are found in at least 3200 sessions (Tyul'bashev et al., 9 Aug 2025). Using only the central 2-minute interval of each transit, the estimated nulling fraction is

$\mathrm{S/N}\sim 10$0

under strict selection, and

$\mathrm{S/N}\sim 10$1

under relaxed selection (Tyul'bashev et al., 9 Aug 2025). The authors therefore conclude that at $\mathrm{S/N}\sim 10$2 MHz the source behaves like a RRAT: pulses are sporadic, the folded periodic signal is weak even after decade-long accumulation, and the vast majority of rotations produce no detectable meter-wavelength emission (Tyul'bashev et al., 9 Aug 2025).

5. Timing behavior and long-term residual structure

The discovery paper reports a several-month timing baseline based on MeerKAT, GBT, and one Parkes detection, analyzed with TEMPO2 and temponest while fitting the spin frequency, its derivative, and two noise parameters $\mathrm{S/N}\sim 10$3 and $\mathrm{S/N}\sim 10$4 in the effective TOA uncertainty model

$\mathrm{S/N}\sim 10$5

(Wang et al., 11 Mar 2025). No glitches, obvious timing noise, or evidence of binarity were reported within MJD 60323.6–60496.2 (Wang et al., 11 Mar 2025).

The Pushchino timing analysis uses a distinct methodology necessitated by the LPA3 timing system (Tyul'bashev et al., 9 Aug 2025). Because the instrument uses quartz oscillators rather than a high-precision observatory time standard, the analysis proceeds in two stages: intra-session timing, with $\mathrm{S/N}\sim 10$6 s accuracy over a single 5-minute session, followed by a “pulsar time scale” constructed from bright, well-timed pulsars to calibrate long-term drift and offsets (Tyul'bashev et al., 9 Aug 2025). Initial timing used 62 strong pulses found visually in high-resolution data, starting from the Wang et al. parameters; after deriving a preliminary solution, additional pulses were located, and the final fit used 97 pulses, comprising the 62 initial pulses and 35 additional strong pulses (Tyul'bashev et al., 9 Aug 2025).

The timing solution spans 10.5 years and shows that the different pulse subsets are consistent with the same rotational ephemeris (Tyul'bashev et al., 9 Aug 2025). A distinctive feature is the presence of long gaps in detections: intervals of 100 to several hundred days with no detected pulses at all (Tyul'bashev et al., 9 Aug 2025). These are described as discontinuities in the dependence of timing residuals on pulse arrival times, but the phase-connected timing solution bridges the gaps smoothly, without requiring phase jumps or changes in $\mathrm{S/N}\sim 10$7 or $\mathrm{S/N}\sim 10$8 (Tyul'bashev et al., 9 Aug 2025).

This distinction is important. The discontinuities are not presented as classical glitches or as rotational irregularities; rather, they are long intervals of radio non-detection (Tyul'bashev et al., 9 Aug 2025). The authors interpret them as prolonged nulling or strong intermittency of the emission at $\mathrm{S/N}\sim 10$9 MHz rather than changes in the star’s spin evolution (Tyul'bashev et al., 9 Aug 2025).

6. Physical interpretation and placement among neutron-star radio populations

Using standard dipole spin-down formulae, the discovery paper inferred $\mathrm{DM} = 21\pm 3\ \mathrm{pc\,cm^{-3}}$0 Myr, $\mathrm{DM} = 21\pm 3\ \mathrm{pc\,cm^{-3}}$1 G, and $\mathrm{DM} = 21\pm 3\ \mathrm{pc\,cm^{-3}}$2 from the upper limit on $\mathrm{DM} = 21\pm 3\ \mathrm{pc\,cm^{-3}}$3 (Wang et al., 11 Mar 2025). With the measured $\mathrm{DM} = 21\pm 3\ \mathrm{pc\,cm^{-3}}$4 from Pushchino, the corresponding derived parameters become

$\mathrm{DM} = 21\pm 3\ \mathrm{pc\,cm^{-3}}$5

$\mathrm{DM} = 21\pm 3\ \mathrm{pc\,cm^{-3}}$6

and a quoted light-cylinder magnetic field of approximately

$\mathrm{DM} = 21\pm 3\ \mathrm{pc\,cm^{-3}}$7

(Tyul'bashev et al., 9 Aug 2025). The Pushchino interpretation is that these values are typical for slow pulsars in the magneto-dipole framework, even though the source has an unusually long period (Tyul'bashev et al., 9 Aug 2025).

In the discovery paper, PSR J0311+1402 is emphasized as a bridge between normal pulsars and long-period radio transients (Wang et al., 11 Mar 2025). Its steep median spectral index,

$\mathrm{DM} = 21\pm 3\ \mathrm{pc\,cm^{-3}}$8

low linear polarization of $\mathrm{DM} = 21\pm 3\ \mathrm{pc\,cm^{-3}}$9–$111$00, low circular polarization of $111$01–$111$02, and duty cycle of $111$03 at MeerKAT frequencies are all described as consistent with normal pulsar phenomenology rather than the more extreme properties of many long-period radio transients (Wang et al., 11 Mar 2025). The paper further argues that its radio luminosity can plausibly be powered by rotation, unlike isolated long-period radio transients whose radio luminosities can greatly exceed $111$04 (Wang et al., 11 Mar 2025).

The death-line discussion is central to the discovery paper. With $111$05 s and $111$06, the source lies below the death lines for pure and twisted dipole fields and near the most permissive twisted-multipole death line in the formulations discussed there (Wang et al., 11 Mar 2025). The Pushchino paper, using the measured $111$07, states that the source lies near or beyond theoretical death lines where pair production and coherent radio emission are usually thought to cease, and suggests that its long period and proximity to the death line likely contribute to its unusual emission behavior, including sporadic bursts and extreme nulling at $111$08 MHz (Tyul'bashev et al., 9 Aug 2025).

Taken together, the two studies suggest a frequency-dependent classification. At decimeter wavelengths the source can sometimes appear as a normal slow pulsar with nearly every rotation visible in some MeerKAT sessions, whereas at meter wavelengths its behavior is dominated by extreme nulling and RRAT-like bursts (Wang et al., 11 Mar 2025, Tyul'bashev et al., 9 Aug 2025). A plausible implication is that J0311+1402 occupies an intermediate physical as well as phenomenological regime, with a magnetosphere capable of sustained radio emission under some conditions but manifesting highly intermittent low-frequency visibility.

7. Distance, luminosity, and population significance

The Pushchino revision of the dispersion measure to $111$09 leads to a distance estimate of approximately $111$10 pc and drastically lowers the inferred pseudo-luminosity (Tyul'bashev et al., 9 Aug 2025). Using the standard definition $111$11 and the upper limit $111$12 mJy from all sessions, the paper gives

$111$13

(Tyul'bashev et al., 9 Aug 2025). Scaling to $111$14 MHz with $111$15 yields

$111$16

which the authors state is about an order of magnitude below the smallest pseudo-luminosity listed in the ATNF pulsar catalogue at the time of writing (Tyul'bashev et al., 9 Aug 2025).

These values underpin the claim that J0311+1402 has the minimal pseudo-luminosity, minimal dispersion measure, and minimal distance from the Sun among known pulsars in the cited comparison (Tyul'bashev et al., 9 Aug 2025). The source thereby becomes a concrete example of strong selection effects in pulsar surveys. Both papers emphasize observational bias, though in different ways: the discovery paper argues that traditional searches are insensitive to the $111$17–$111$18 s regime because of high-pass filtering, red noise, RFI, and the customary upper period limit of about $111$19 s, while imaging surveys smear out sub-second pulses (Wang et al., 11 Mar 2025). The Pushchino study adds that even if such a source is extremely nearby, extreme nulling and very low average luminosity can keep it below the threshold of periodic searches at meter wavelengths (Tyul'bashev et al., 9 Aug 2025).

This suggests a broader population implication. If an object at only $111$20 pc can remain difficult to identify because its detectable emission occupies only a very small fraction of rotations, then the local neutron-star census may be incomplete in a direction not captured by standard luminosity functions alone. A plausible implication is that a substantial population of similarly faint, long-period, and highly intermittent pulsars could remain undetected in the solar neighborhood, with consequences for estimates of survey completeness, the RRAT fraction, and the extent of the long-period tail of the radio pulsar population (Wang et al., 11 Mar 2025, Tyul'bashev et al., 9 Aug 2025).