PSR J2021 Research Articles

Analysis of the Emission and Morphology of the Pulsar Wind Nebula Candidate HAWC J2031+415

The first TeV γ-ray source with no lower energy counterparts, TeV J2032+4130, was discovered by HEGRA. It appears in the third HAWC catalog as 3HWC J2031+415 and it is a bright TeV γ-ray source whose emission has previously been resolved as two sources: HAWC J2031+415 and HAWC J2030+409. While HAWC J2030+409 has since been associated with the Fermi Large Area Telescope Cygnus Cocoon, no such association for HAWC J2031+415 has yet been found. In this work, we investigate the spectrum and energy-dependent morphology of HAWC J2031+415. We associate HAWC J2031+415 with a γ-ray binary system containing the pulsar PSR J2032+4127 and its companion MT91 213. We study HAWC data to observe their periastron in 2017. Additionally, we perform a combined multiwavelength analysis using radio, X-ray, and γ-ray emission. We conclude that HAWC J2031+415 and, by extension, TeV J2032+4130 are most probably a pulsar wind nebula powered by PSR J2032+4127.

Spatio-spectral-temporal modelling of two young pulsar wind nebulae

Abstract Recent observations of a few young pulsar wind nebulae (PWNe) have revealed their morphologies in some detail. Given the availability of spatio-spectral-temporal data, we use our multi-zone (1D) leptonic emission code to model the PWNe associated with G29.7−0.3 (Kes 75) and G21.5−0.9 (G21.5) and obtain (by-eye) constraints on additional model parameters compared to spectral-only modelling. Kes 75 is a Galactic composite supernova remnant (SNR) with an embedded pulsar, PSR J1846−0258. X-ray studies reveal rapid expansion of Kes 75 over the past two decades. PWN G21.5 is also a composite SNR, powered by PSR J1833−1034. For Kes 75, we study a sudden plasma bulk speed increase that may be due to the magnetar-like outbursts of the central pulsar. An increase of a few percent in this speed does not result in any significant change in the model outputs. For G21.5, we investigate different diffusion coefficients and pulsar spin-down braking indices. We can reproduce the broadband spectra and X-ray surface brightness profiles for both PWNe, and the expansion rate, flux over different epochs, and X-ray photon index vs epoch and central radius for Kes 75 quite well. The latter three features are also investigated for G21.5. Despite obtaining reasonable fits overall, some discrepancies remain, pointing to further model revision. We find similar values to overlapping parameters between our 1D code and those of an independent 0D dynamical code (tide). Future work will incorporate spatial data from various energy wavebands to improve model constraints.

Multiwavelength Investigation of γ-Ray Source MGRO J1908+06 Emission Using Fermi-LAT, VERITAS and HAWC

This paper investigates the origin of the γ-ray emission from MGRO J1908+06 in the GeV–TeV energy band. By analyzing the data collected by the Fermi Large Area Telescope, the Very Energetic Radiation Imaging Telescope Array System, and High Altitude Water Cherenkov, with the addition of spectral data previously reported by LHAASO, a multiwavelength study of the morphological and spectral features of MGRO J1908+06 provides insight into the origin of the γ-ray emission. The mechanism behind the bright TeV emission is studied by constraining the magnetic field strength, the source age, and the distance through detailed broadband modeling. Both spectral shape and energy-dependent morphology support the scenario that inverse Compton emission of an evolved pulsar wind nebula associated with PSR J1907+0602 is responsible for the MGRO J1908+06 γ-ray emission with a best-fit true age of T = 22 ± 9 kyr and a magnetic field of B = 5.4 ± 0.8 μG, assuming the distance to the pulsar d PSR = 3.2 kpc.

Study of X-ray emission from the S147 nebula by SRG/eROSITA: Supernova-in-the-cavity scenario

The Simeis 147 nebula (S147) is particularly well known for a spectacular net of Hα-emitting filaments. It is often considered one of the largest and oldest (∼105 yr) cataloged supernova remnants in the Milky Way, although the kinematics of the pulsar PSR J0538+2817 suggests that this supernova remnant might be a factor of three younger. The former case is considered in a companion paper, while here we pursue the latter. Both studies are based on the data of SRG/eROSITA All-Sky Survey observations. Here, we confront the inferred properties of the X-ray emitting gas data with the scenario of a supernova explosion in a low-density cavity, such as a wind-blown-bubble. This scenario assumes that a ∼20 M⊙ progenitor star has had a low velocity with respect to the ambient interstellar medium, and so stayed close to the center of a dense shell created during its main-sequence evolution till the moment of the core-collapse explosion. The ejecta first propagate through the low-density cavity until they collide with the dense shell, and only then does the reverse shock go deeper into the ejecta and power the observed X-ray emission of the nebula. The part of the remnant inside the dense shell remains non-radiative till this point, plausibly in a state with Te < Ti and nonequilibrium ionization. On the contrary, the forward shock becomes radiative immediately after entering the dense shell, and, being subject to instabilities, gives the nebula its characteristic “foamy” appearance in Hα and radio emission.

Timing irregularities and glitches from the pulsar monitoring campaign at IAR

Pulsars have a very stable rotation overall. However, sudden increases in their rotation frequency, known as glitches, perturb their evolution. While many observatories commonly detect large glitches, small glitches are harder to detect because of the lack of daily cadence observations over long periods of time (years). We aim to explore and characterise the timing behaviour of young pulsars on daily timescales, looking for small glitches and other irregularities, in order to further our comprehension of the real distribution of glitch sizes. Our findings have consequences for the theoretical modelling of the glitch mechanism. We observed six pulsars with up to daily cadence between December 2019 and January 2024 with the two antennas of the Argentine Institute of Radio Astronomy (IAR). We used standard pulsar timing tools to obtain the times of arrival of the pulses and to characterise the pulsar's rotation. We developed an algorithm to look for small timing events in the data and calculate the changes in the frequency (nu ) and its derivative ($ at those epochs. We find that the rotation of all pulsars in this dataset is affected by small step changes in nu and $ Among them, we find three new glitches that have not been reported before: two glitches in PSR J1048$-$5832 with relative sizes of $ $ and $ $, and one glitch in the Vela pulsar with a size of $ $. We also report new decay terms on the 2021 Vela giant glitch, and on the 2022 giant glitches in PSR J0742$-$2822 and PSR J1740$-$3015, respectively. In addition, we find that the red noise contribution significantly diminished in PSR J0742$-$2822 after its giant glitch in 2022. Our results highlight the importance of high-cadence monitoring with an exhaustive analysis of the residuals to better characterise the distribution of glitch sizes and to deepen our understanding of the mechanisms behind glitches, red noise, and timing irregularities.

A phase-resolved Fermi-LAT analysis of the mode-changing pulsar PSR J2021+4026 shows hints of a multipolar magnetosphere

Context. The radio-quiet γ-ray pulsar PSR J2021+4026 is a peculiar Fermi-LAT pulsar showing repeated and quasi-periodic mode changes. Its γ-ray flux shows repeated variations between two states at intervals of ∼3.5 years. These events occur over timescales < 100 days and are correlated with sudden changes in the spin-down rate. Multiwavelength observations also revealed an X-ray phase shift relative to the γ-ray profile for one of the events. PSR J2021+4026 is currently the only known isolated γ-ray pulsar showing significant variability, and thus it has been the object of thorough investigations. Aims. The goal of our work is to study the mode changes of PSR J2021+4026 with improved detail. By accurately characterizing variations in the γ-ray spectrum and pulse profile, we aim to relate the Fermi-LAT observations to theoretical models. We also aim to interpret the mode changes in terms of variations in the structure of a multipolar dissipative magnetosphere. Methods. We continually monitored the rotational evolution and the γ-ray flux of PSR J2021+4026 using more than 13 years of Fermi-LAT data with a binned likelihood approach. We investigated the features of the phase-resolved spectrum and pulse profile, and from these we inferred the macroscopic conductivity, the electric field parallel to the magnetic field, and the curvature radiation cutoff energy. These physical quantities are related to the spin-down rate and the γ-ray flux and therefore are relevant to the theoretical interpretation of the mode changes. We introduced a simple magnetosphere model that combines a dipole field with a strong quadrupole component. We simulated magnetic field configurations to determine the positions of the polar caps for different sets of parameters. Results. We clearly detect the previous mode changes and confirm a more recent mode change that occurred around June 2020. We provide a full set of best-fit parameters for the phase-resolved γ-ray spectrum and the pulse profile obtained in five distinct time intervals. We computed the relative variations in the best-fit parameters, finding typical flux changes between 13% and 20%. Correlations appear between the γ-ray flux and the spectral parameters, as the peak of the spectrum shifts by ∼10% toward lower energies when the flux decreases. The analysis of the pulse profile reveals that the pulsed fraction of the light curve is larger when the flux is low. Finally, the magnetosphere simulations show that some configurations could explain the observed multiwavelength variability. However, self-consistent models are required to reproduce the observed magnitudes of the mode changes.

High-cadence Timing of Binary Pulsars with CHIME

We performed near-daily observations of the binary pulsars PSR J0218+4232, PSR J1518+4904, and PSR J2023+2853 with the Canadian Hydrogen Intensity Mapping Experiment (CHIME). For the first time, we detected the Shapiro time delay in all three pulsar binary systems, using only 2–4 yr of CHIME/Pulsar timing data. We measured the pulsar masses to be 1.49−0.20+0.23 M ⊙, 1.470−0.034+0.030 M ⊙, and 1.50−0.38+0.49 M ⊙, respectively. The companion mass to PSR J0218+4232 was found to be 0.179−0.016+0.018 M ⊙. We constrained the mass of the neutron star companion of PSR J1518+4904 to be 1.248−0.029+0.035 M ⊙, using the observed apsidal motion as a constraint on the mass estimation. The binary companion to PSR J2023+2853 was found to have a mass of 0.93−0.14+0.17 M ⊙; in the context of the near-circular orbit, this mass estimate suggests that the companion to PSR J2023+2853 is likely a high-mass white dwarf. By comparing the timing model obtained for PSR J0218+4232 with previous observations, we found a significant change in the observed orbital period of the system of Pḃ=0.14(2)×10−12 ; we determined that this variation arises from “Shklovskii acceleration” due to the relative motion of the binary system, and used this measurement to estimate a distance of d = (6.7 ± 1.0) kpc to PSR J0218+4232. This work demonstrates the capability of high-cadence observations, enabled by the CHIME/Pulsar system, to detect and refine general-relativistic effects of binary pulsars over short observing timescales.

Possible GeV gamma-ray emission from the pulsar wind nebula in CTA 1

ABSTRACT We report a detection of GeV γ-ray emission potentially originating from the pulsar wind nebula in CTA 1 by analysing about 15 yr of Fermi Large Area Telescope data. By selecting an energy range from 50 GeV to 1 TeV to remove contamination from the γ-ray pulsar PSR J0007+7303, we have discovered an extended γ-ray source with a test statistic value of ∼44.94 in the region of CTA 1. The obtained flux is measured to be 6.71 ± 2.60 × 10−12 erg cm−2 s−1 with a spectral index of 1.61 ± 0.36, which allows for a smooth connection with the flux in the TeV band. CTA 1 is also considered to be associated with 1LHAASO J0007+7303u, which is an ultra-high-energy source listed in the recently published catalogue of the Large High Altitude Air Shower Observatory. We assume that the radiation originates from the pulsar wind nebula and that its multiwavelength spectral energy distribution can be explained well with a time-dependent one-zone model.

A Relativistic Double Neutron Star Binary PSR J1846-0513

We report the timing analysis of PSR J1846−0513, a pulsar discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in Commensal Radio Astronomy FAST Survey. The pulsar possesses a spin period of 23.36 ms and a spin-down rate ( Ṗ ) of 1.0106(3) × 10−18 s s−1, and it is located in an eccentric orbit (e ∼0.208) with an orbital period of 0.61 days. The characteristic age and surface magnetic field of the pulsar are found to be 366.62 Myr and 4.9178 × 109 G, respectively, indicating that it is a recycled pulsar. Using over two years of timing data, we measure the periastron advance ω̇ = 0.8956(8) deg yr−1. By assuming that this effect is purely relativistic, we have estimated the total mass M = 2.6287(35)M ⊙ and obtained an upper limit for the pulsar mass and a lower limit for the companion’s mass. Our results indicate that this is a double neutron star system.

Energy-dependent Analyses of the Gamma-Ray Emission from HESS J1857+026 with Fermi-LAT

We report the discovery of the energy-dependent morphology of the GeV gamma-ray emission from HESS J1857+026 with more than 13 yr of Fermi Large Area Telescope data. The GeV gamma-ray emission from this region is composed of two extended components. The hard component with an index of 1.74 ± 0.07 in the energy range of 0.5–500 GeV is spatially coincident with HESS J1857+026, and its 68% containment radius varies from ∼0.°44 below 40 GeV to ∼0.°30 above 140 GeV. The hard GeV gamma-ray spectrum and the energy-dependent morphology of HESS J1857+026 make it favor a pulsar wind nebula origin, which is associated with the energetic pulsar PSR J1856+0245. The soft component with an index of 2.70 ± 0.16 and another extended gamma-ray source detected in this region, 4FGL J1857.9+0313e, with an index of 2.55 ± 0.07, are spatially coincident with two molecular clumps in the northeast and southwest of HESS J1857+026, which favors the hadronic process, and the protons could be accelerated by the hypothetical supernova remnant associated with PSR J1856+0245.

A 3D diffusive and advective model of electron transport applied to the pulsar wind nebula HESS J1825 − 137

ABSTRACT HESS J1825 − 137 is one of the most powerful and luminous TeV gamma-ray pulsar wind nebulae, making it an excellent laboratory to study particle transportation around pulsars. We present a model of the (diffusive and advective) transport and radiative losses of electrons from the pulsar PSR J1826 − 1334 powering HESS J1825 − 137 using interstellar medium gas (ISM) data, soft photon fields, and a spatially varying magnetic field. We find that for the characteristic age of $21\, \mathrm{k}\mathrm{yr}$, PSR J1826 − 1334 is unable to meet the energy requirements to match the observed X-ray and gamma-ray emission. An older age of $40\, \mathrm{k}\mathrm{yr}$, together with an electron conversion efficiency of 0.14 and advective flow of v = 0.002c, can reproduce the observed multiwavelength emission towards HESS J1825 − 137. A turbulent ISM with magnetic field of $B=20 \,{\rm to}\, 60 \,\mathrm{\mu }{\rm G}$ to the north of HESS J1825 − 137 (as suggested by ISM observations) is required to prevent significant gamma-ray contamination towards the northern $\mathrm{T}\mathrm{e\mathrm{V}}$ source HESS J1826 − 130.

An investigation of the state changes of PSR J2021+4026 and the Vela pulsar

ABSTRACT We report on long-term evolution of gamma-ray flux and spin-down rate of two bright gamma-ray pulsars, PSR J2021+4026 and Vela (PSR J0835−4510). PSR J2021+4026 shows repeated state changes in gamma-ray flux and spin-down rate. We report two new state changes, a first one from a low gamma-ray flux to a high flux that occurred around MJD 58910, and a second one from high to low flux that occurred around MJD 59510. We find that the flux changes associated with these two state changes are smaller than those determined in the previous events, and the waiting time of the new state change from the high gamma-ray flux to low gamma-ray flux is significantly shorter than previous events. Since the waiting time-scale of the quasi-periodic state changes of PSR J2021+4026 is similar to the waiting time-scale of the glitch events of the Vela pulsar, we search for the state change of the gamma-ray emission of the Vela pulsar to investigate the possibility that the glitching process is the trigger of the state change of PSR J2021+4026. For the Vela pulsar, the flux of the radio pulses briefly decreased around the 2016 glitch, suggesting that the glitch may have affected the structure of the magnetosphere. Nevertheless, we could not find any significant change of the gamma-ray emission properties using 15 yr of Fermi-LAT data. Overall, it seems inconclusive that a glitch-like process similar to that occurred to the Vela pulsar triggers the structure change of the global magnetosphere and causes state changes of PSR J2021+4026. Further and deep investigations to clarify the mechanism of the mode change for PSR J2021+4026 are required.

Discovery of a one-sided radio filament of PSR J0538+2817 in S147: escape of relativistic PWN leptons into surrounding supernova remnant?

ABSTRACT We report the discovery of a faint radio filament near PSR J0538+2817 in the NVSS, CGPS, and the Rapid ASKAP Continuum Survey data. This pulsar is plausibly associated with the supernova that gave rise to the Spaghetti nebula (Simeis 147). The structure is one-sided and appears to be almost aligned (within 17 degrees) with the direction of the pulsar’s proper motion, but in contrast to the known cases of pulsar radio tails, it is located ahead of the pulsar. At the same time, this direction is also approximately (within 5 degrees) perpendicular to the axis of the extended non-thermal X-ray emission around the pulsar. No X-ray or optical emission is detected from the filament region, although the end point of the radio filament appears to be adjacent to a filament of Hα emission. We speculate that this structure might represent a filament connecting pulsar wind nebula (PWN) with the ambient interstellar medium filled with relativistic electrons escaping the pulsar nebula, i.e. a radio analogue of X-ray filaments of Guitar and Lighthouse PWNs and filaments of non-thermal radio emission in the Galactic Centre.

X-Ray Properties of PSR J1811-1925 by NuSTAR

We analyzed the spectral properties and pulse profile of PSR J1811–1925, a pulsar located in the center of composite supernova remnant (SNR) G11.2–0.3, by using high timing resolution archival data from the Nuclear Spectroscopic Telescope Array Mission (NuSTAR). Analysis of archival Chandra data over different regions rules out the SNR shell as the site of the hard X-ray emission while spectral analysis indicates that the NuSTAR photons originate in the pulsar and its nebula. The pulse profile exhibits a broad single peak up to 35 keV. The jointed spectrum by combining NuSTAR and Chandra can be well fitted by a power-law model with a photon index of Γ = 1.58 ± 0.04. The integrated flux of jointed spectrum over 1–10 keV is 3.36 × 10−12 erg cm−2 s−1. The spectrum of pulsar having photon index Γ = 1.33 ± 0.06 and a 1–10 keV flux of 0.91 × 10−12 erg cm−2 s−1. We also performed the phase-resolved spectral analysis by splitting the whole pulse-on phase into five phase bins. The photon indices of the bins are all around 1.4, indicating that the photon index does not evolve with the phase.

The FAST Galactic Plane Pulsar Snapshot Survey – III. Timing results of 30 newly discovered pulsars

ABSTRACT Timing observations are crucial for determining the basic parameters of newly discovered pulsars. Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST) with the L-band 19-beam receiver covering the frequency range of 1.0–1.5 GHz, the FAST Galactic Plane Pulsar Snapshot (GPPS) Survey has discovered more than 600 faint pulsars with flux densities of only a few or a few tens of μJy at 1.25 GHz. To obtain accurate position, spin parameters and dispersion measure of a pulsar, and to calculate derived parameters such as the characteristic age and surface magnetic field, we collect available FAST pulsar data obtained either through targeted follow-up observations or through coincidental survey observations with one of the 19 beams of the receiver. From these data we obtain time of arrival (TOA) measurements for 30 newly discovered pulsars as well as for 13 known pulsars. We demonstrate that the TOA measurements acquired by the FAST from any beams of the receiver in any observation mode (e.g. the tracking mode or the snapshot mode) can be combined to get timing solutions. We update the ephemerides of 13 previously known pulsars and obtain the first phase-coherent timing results for 30 isolated pulsars discovered in the FAST GPPS Survey. Notably, PSR J1904+0853 is an isolated millisecond pulsar, PSR J1906+0757 is a disrupted recycled pulsar, and PSR J1856+0211 has a long period of 9.89 s that can constrain pulsar death lines. Based on these timing solutions, all available FAST data have been added together to obtain the best pulse profiles for these pulsars.

Multiwavelength observations of PSR J2021+4026 across a mode change reveal a phase shift in its X-ray emission

Context. We have investigated the multiwavelength emission of PSR J2021+4026, the only isolated γ-ray pulsar known to be variable, which in October 2011 underwent a simultaneous change in γ-ray flux and spin-down rate, followed by a second mode change in February 2018. Multiwavelength monitoring is crucial to understand the physics behind these events and how they may have affected the structure of the magnetosphere. Aims. The monitoring of pulse profile alignment is a powerful diagnostic tool for constraining magnetospheric reconfiguration. We aim to investigate timing or flux changes related to the variability of PSR J2021+4026 via multiwavelength observations, including γ-ray observations from Fermi-LAT, X-ray observations from XMM-Newton, and a deep optical observation with the Gran Telescopio Canarias. Methods. We performed a detailed comparison of the timing features of the pulsar in γ and X-rays and searched for any change in phase lag between the phaseogram peaks in these two energy bands. Although previous observations did not detect a counterpart in visible light, we also searched for optical emission that might have increased due to the mode change, making this pulsar detectable in the optical. Results. We have found a change in the γ-to X-ray pulse profile alignment by 0.21 ± 0.02 in phase, which indicates that the first mode change affected different regions of the pulsar magnetosphere. No optical counterpart was detected down to g′ = 26.1 and r′ = 25.3. Conclusions. We suggest that the observed phase shift could be related to a reconfiguration of the connection between the quadrupole magnetic field near the stellar surface and the dipole field that dominates at larger distances. This is consistent with the picture of X-ray emission coming from the heated polar cap and with the simultaneous flux and frequency derivative change observed during the mode changes.

A NICER View on the 2020 Magnetar-like Outburst of PSR J1846−0258

We report on our monitoring of the strong-field magnetar-like pulsar PSR J1846−0258 with the Neutron Star Interior Composition Explorer (NICER) and the timing and spectral evolution during its outburst in 2020 August. Phase-coherent timing solutions were maintained from 2017 March through 2021 November, including a coherent solution throughout the outburst. We detected a large spin-up glitch of magnitude Δν/ν = 3 × 10−6 at the start of the outburst and observed an increase in pulsed flux that reached a factor of more than 10 times the quiescent level, a behavior similar to that of the 2006 outburst. Our monitoring observations in 2020 June and July indicate that the flux was rising prior to the Swift announcement of the outburst on 2020 August 1. We also observed several sharp rises in the pulsed flux following the outburst and the flux reached quiescent level by 2020 November. The pulse profile was observed to change shape during the outburst, returning to the preoutburst shape by 2021. Spectral analysis of the pulsed emission of NICER data shows that the flux increases result entirely from a new blackbody component that gradually fades away while the power law remains nearly constant at its quiescent level throughout the outburst. Joint spectral analysis of NICER and simultaneous NuSTAR data confirms this picture. We discuss the interpretation of the magnetar-like outburst and origin of the transient thermal component in the context of both a pulsar-like and a magnetar-like model.

A renewed search for radio emission from the variable γ-ray pulsar PSR J2021+4026

ABSTRACT We undertake the first targeted search at 1.5 GHz for radio emission from the variable γ-ray pulsar PSR J2021+4026. This radio-quiet pulsar assumes one of two stable γ-ray emission states, between which it transitions on a time-scale of years. These transitions, in both γ-ray flux and pulse profile shape, are accompanied by contemporaneous changes to the pulsar’s spin-down rate. A number of radio pulsars are known to exhibit similar correlated variability, which in some cases involves an emission state in which the radio emission ceases to be detectable. In this paper, we perform a search for radio emission from PSR J2021+4026, using archival radio observations recorded when the pulsar was in each of its emission/spin-down states. Using improved techniques, we search for periodic radio emission as well as single pulse phenomena such as giant radio pulses and RRAT-like emission. Our search reveals no evidence of radio emission from PSR J2021+4026. We estimate that the flux density for periodic emission from PSR J2021+4026 does not exceed 0.2 mJy at this frequency. We also estimate single-pulse flux limits for RRAT-like bursts and giant radio pulses to be 0.3 and 100 Jy, respectively. We discuss the transitioning behaviour of PSR J2021+4026 in the context of pulsar glitches, intermittent pulsars and the increasingly common emission-rotation correlation observed in radio pulsars.

HESS J1809−193: A halo of escaped electrons around a pulsar wind nebula?

Context. HESS J1809−193 is an unassociated very-high-energy γ-ray source located on the Galactic plane. While it has been connected to the nebula of the energetic pulsar PSR J1809−1917, supernova remnants and molecular clouds present in the vicinity also constitute possible associations. Recently, the detection of γ-ray emission up to energies of ∼100 TeV with the HAWC observatory has led to renewed interest in HESS J1809−193. Aims. We aim to understand the origin of the γ-ray emission of HESS J1809−193. Methods. We analysed 93.2 h of data taken on HESS J1809−193 above 0.27 TeV with the High Energy Stereoscopic System (H.E.S.S.), using a multi-component, three-dimensional likelihood analysis. In addition, we provide a new analysis of 12.5 yr of Fermi-LAT data above 1 GeV within the region of HESS J1809−193. The obtained results are interpreted in a time-dependent modelling framework. Results. For the first time, we were able to resolve the emission detected with H.E.S.S. into two components: an extended component (modelled as an elongated Gaussian with a 1-σ semi-major and semi-minor axis of ∼0.62° and ∼0.35°, respectively) that exhibits a spectral cutoff at ∼13 TeV, and a compact component (modelled as a symmetric Gaussian with a 1-σ radius of ∼0.1°) that is located close to PSR J1809−1917 and shows no clear spectral cutoff. The Fermi-LAT analysis also revealed extended γ-ray emission, on scales similar to that of the extended H.E.S.S. component. Conclusions. Our modelling indicates that based on its spectrum and spatial extent, the extended H.E.S.S. component is likely caused by inverse Compton emission from old electrons that form a halo around the pulsar wind nebula. The compact component could be connected to either the pulsar wind nebula or the supernova remnant and molecular clouds. Due to its comparatively steep spectrum, modelling the Fermi-LAT emission together with the H.E.S.S. components is not straightforward.

First results of the glitching pulsar monitoring programme at the Argentine Institute of Radioastronomy

ABSTRACT We report here on the first results of a systematic monitoring of southern glitching pulsars at the Argentine Institute of Radioastronomy that started in the year 2019. We detected a major glitch in the Vela pulsar (PSR J0835 − 4510) and two small glitches in PSR J1048 − 5832. For each glitch, we present the measurement of glitch parameters by fitting timing residuals. We then make an individual pulse study of Vela in observations before and after the glitch. We selected 6 days of observations around the major glitch on 2021 July 22 and study their statistical properties with machine learning techniques. We use variational autoencoder (VAE) reconstruction of the pulses to separate them clearly from the noise. We perform a study with self-organizing map (SOM) clustering techniques to search for unusual behaviour of the clusters during the days around the glitch not finding notable qualitative changes. We have also detected and confirmed recent glitches in PSR J0742 − 2822 and PSR J1740 − 3015.