In this work, we introduce the use of the differential geometry Frenet-Serret equations to describe a magnetic line in a pulsar magnetosphere. These equations, which need to be solved numerically, fix the magnetic line in terms of their tangent, normal, and binormal vectors at each position, given assumptions on the radius of curvature and torsion. Once the representation of the magnetic line is defined, we provide the relevant set of transformations between reference frames; the ultimate aim is to express the map of the emission directions in the star co-rotating frame. In this frame, an emission map can be directly read as a light curve seen by observers located at a certain fixed angle with respect to the rotational axis. We provide a detailed step-by-step numerical recipe to obtain the emission map for a given emission process, and give a set of simplified benchmark tests. Key to our approach is that it offers a setting to achieve an effective description of the system's geometry {\it together} with the radiation spectrum. This allows to compute multi-frequency light curves produced by a specific radiation process (and not just geometry) in the pulsar magnetosphere, and intimately relates with averaged observables such as the spectral energy distribution.
We present here a simple, systematic method for determining the correct global rotation count of a radio pulsar; an essential step for the derivation of an accurate phase-coherent ephemeris. We then build on this method by developing a new algorithm for determining the global rotational count for pulsars with sparse timing data sets. This makes it possible to obtain phase-coherent ephemerides for pulsars for which this has been impossible until now. As an example, we do this for PSR J0024-7205aa, an extremely faint MSP recently discovered in the globular cluster 47 Tucanae. This algorithm has …
This paper describes a new technique for determining the optimal period of a pulsar and consequently its light curve. The implemented technique makes use of the Principal Component Analysis (PCA) applied to the so-called waterfall diagram, which is a bidimensional representation of the pulsar acquired data. In this context we have developed the python package pywpf to easily retrieve the period with the presented method. We applied this technique to sets of data of the brightest pulsars in visible light that we obtained with the fast photon counter Iqueye. Our results are compared with those o…
The earthward journey of ultra high energy electrons ($\sim 600$ TeV) produced in the Pulsar atmosphere by Landau damping of magneto-centrifugally excited Langmuir waves (drawing energy form the rotational slowdown) on primary electrons, is charted. It is shown, that just as they escape the light cylinder zone, the ultra-high energy particles, interacting with the medium of the Crab nebula, rapidly loose their energy via the quantum synchrotron process, producing highly energetic gamma rays ~ $\sim 0.6$PeV. Interacting with the cosmic background radiation in the interstellar medium, only a tin…
It is now known that the emission from radio pulsars can vary over a wide range of timescales, from fractions of seconds to decades. However, it is not yet known if long- and short-term emission variability are caused by the same physical processes. It has been observed that long-term emission variability is often correlated with rotational changes in the pulsar. We do not yet know if the same is true of short-term emission variability, as the rotational changes involved cannot be directly measured over such short timescales. To remedy this, we propose a continuous pulsar monitoring technique …
It is generally accepted that the pulsar magnetic field converts most of its rotational energy losses into radiation. In this paper, we propose an alternative emission mechanism, in which neither the pulsar rotational energy nor its magnetic field is involved. The emission mechanism proposed here is based on the hypothesis that the pulsar matter is stable only when moving with respect to the ambient medium at a velocity exceeding some threshold value. A decrease in velocity below this threshold value leads to the decay of matter with the emission of electromagnetic radiation. It is shown that …
Plasma-filled pulsar magnetospheres contain thin current sheets wherein the charged particles are accelerated by magnetic reconnections to travel at ultra-relativistic speeds. On the other hand, the plasma frequency of the more regular force-free regions of the magnetosphere rests almost precisely on the upper limit of radio frequencies, with the cyclotron frequency being far higher due to the strong magnetic field. This combination produces a peculiar situation, whereby radio-frequency waves can travel at subluminal speeds without becoming evanescent. The conditions are thus conducive to Cere…
To look for possible phenomenological connections between pulsar's timing properties and emissions from pulsar wind nebulae and their pulsars, we studied the power-law component of the X-ray emissions from 35 pulsar wind nebulae which have a detected pulsar in X-rays. Our major results are in the following: (1) The power-law component of the X-ray luminosities, in the energy range from 0.5 keV to 8 keV, of the nebulae and of the pulsar both show a strong correlation with the pulsar spin-down power ($\dot{E}$), consistent with earlier studies. However, equally significant correlations with the …
Since its launch in 2008, the Fermi Large Area Telescope (LAT) has detected over 200 -ray pulsars above 100 MeV. This population of pulsars is characterised by a rich diversity of light curve morphologies. Researchers have been using both the radio and -ray light curves to constrain the inclination and observer angles for each of these pulsars. At first, this was done using a by-eye technique and later via statistical approaches. We have also developed two novel statistical approaches that place the radio and -ray data on equal footing despite their disparate relative flux errors. We chose ele…
Highly extended gamma-ray emission around the Geminga pulsar was discovered by Milagro and verified by HAWC. Despite many observations with Imaging Atmospheric Cherenkov Telescopes (IACTs), detection of gamma-ray emission on angular scales exceeding the IACT field-of-view has proven challenging. Recent developments in analysis techniques have enabled the detection of significant emission around Geminga in archival data with H.E.S.S.. In 2019, further data on the Geminga region were obtained with an adapted observation strategy. Following the announcement of the detection of significant TeV emi…
On the Difference Between Pulsar Radio Emission Beams from the Two Poles
Guangzhou University（广州大学）；National Astronomical Data Centre, the Great Bay Area, Higher Education Mega Centre（粤港澳大湾区高等教育超算中心国家天文数据中心）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；School of Astronomy, University of Chinese Academy of Sciences（中国科学院大学天文学院）
Constraints on the internal physics of neutron stars from the observational data of several young pulsars: the role of a power-law decaying dipole magnetic field
We study the gamma-ray spectra of 30 globular clusters (GCs) thus far detected with the Fermi Gamma-ray Space Telescope. Presuming that gamma-ray emission of a GC comes from millisecond pulsars (MSPs) contained in, a model that generates spectra for the GCs is built based on the gamma-ray properties of the detected MSP sample. We fit the GCs' spectra with the model, and for 27 of them, their emission can be explained with arising from MSPs. The spectra of the other three, NGC 7078, 2MS-GC01, and Terzan 1, can not be fit with our model, indicating that MSPs' emission should not be the dominant …
Context: The Crab pulsar is a bright $γ$-ray source detected at photon energies up to $\sim$1 TeV. Its phase-averaged and phase-resolved $γ$-ray spectra below 10 GeV exhibit exponential cutoffs while those above 10 GeV apparently follow simple power-laws. Aims: We re-visit the $γ$-ray properties of the Crab pulsar with 10-year \emph{Fermi} Large Area Telescope (LAT) data in the range of 60 MeV--500 GeV. With the phase-resolved spectra, we investigate the origins and mechanisms responsible for the emissions. Methods: The phaseograms are reconstructed for different energy bands and further analy…
The first detected gravitational wave GW170817 from a binary neutron star merger is associated with an important optical transient AT 2017gfo, which is a direct observation of kilonova. Recent observations suggest that the remnant compact object of the binary neutron star merger associated with GW170817/GRB 170817A may be a stable long-lived magnetized neutron star. In this situation, there would be a pulsar wind nebula (PWN) embedded inside the dynamic ejecta. The PWN emission may be absorbed by the ejecta or leak out of the system. We study the effect of the PWN emission on the observed ligh…
Main and interpulse interaction in PSRs J1842+0358 and J1926+0737: evidence for interpole communication
ASTRON, the Netherlands Institute for Radio Astronomy（荷兰射电天文研究所）；Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester（曼彻斯特大学物理与天文学系乔德雷尔银行天体物理学中心）
In the canonical model of a pulsar, rotational energy is transmitted through the surrounding plasma via two electrical circuits, each connecting to the star over a small region known as a "polar cap." For a dipole-magnetized star, the polar caps coincide with the magnetic poles (hence the name), but in general, they can occur at any place and take any shape. In light of their crucial importance to most models of pulsar emission (from radio to X-ray to wind), we develop a general technique for determining polar cap properties. We consider a perfectly conducting star surrounded by a force-free m…
Rotating Radio Transients (RRATs) represent a relatively new class of pulsar, primarily characterised by their sporadic bursting emission of single pulses on time scales of minutes to hours. In addition to the difficulty involved in detecting these objects, low-frequency ($<$300 MHz) observations of RRATs are sparse, which makes understanding their broadband emission properties in the context of the normal pulsar population problematic. Here, we present the simultaneous detection of RRAT J2325-0530 using the Murchison Widefield Array (154 MHz) and Parkes radio telescope (1.4 GHz). On a single-…
