Abstract We report two phenomena detected in PSR J0344−0901 from two observations conducted at frequencies centered at 1.25 GHz using the Five-hundred-meter Aperture Spherical Radio Telescope. The ...first phenomenon manifests as the pulse emission shifting to later longitudinal phases and then gradually returning to its original location. The event lasts for about 216 pulse periods, with an average shift of about 0.°7 measured at the peak of the integrated profile. Changes in the polarization position angle (PPA) are detected around the trailing edge of the profile, together with an increase in the profile width. The second phenomenon is characterized by the apparent movement of subpulses, which results in different subpulse track patterns across the profile window. For the first time in this pulsar, we identify four emission modes, each with unique subpulse movement, and determine the pattern periods for three of them. Pulse nulling was not detected. Modeling of the changes in the PPA using the rotating vector model gives an inclination angle of 75.°12 ± 3.°80 and an impact parameter of −3.°17 ± 5.°32 for this pulsar. We speculate that the subpulse movement may be related to the shifting of the pulse emission.
Conservation of magnetic flux is associated with regions of the powerful magnetic fields (
B
∽ 10
13
G) near neutron stars' surface. The vector potential generated by moving electric charge
Q
is ...uniformly distributed within a Neutron star's surface (radius
R
). The evolution of the magnetic field of isolated neutron stars is studied and based on magnetic flux conservation; the multipolar magnetic fields for (
l
= 1;
l
= 2;
l
= 3;
l
= 4) have calculated. We developed the field line equations and simulated the magnetic field line geometry for the interaction between neutron stars’ dipole–multipolar magnetic fields using the MATLAB software program.
We investigate properties of the emission region as revealed by drifting subpulses of opposite drift directions at different parts of a pulse profile by using the rotating carousel model in an ...obliquely rotating pulsar magnetosphere of multiple emission states. Subpulse emission is assumed coming from
m
discrete emission areas that are distributed around the magnetic axis on a rotating carousel. The flow rate of the emission areas is determined by the
E
×
B
drift in an emission state, designated by the parameter
y
, in which
E
and the associated flow rate are dependent on
y
. In this model, subpulses appear to drift in an emission state if a relative speed exists between the plasma flow and corotation, and the diversity in the drift rates and directions corresponds to the relative speed being different in different parts of a profile. We apply the model to three pulsars that exhibit drifting subpulses of opposite drift directions to identify the emission states and the values of
m
. Our results show that different drifting subpulses correspond to particular values of
m
and
y
, and the latter implies that different emission states can coexist and operate concurrently in an emission region. We find that
m
does not show clear dependency on either the obliquity angle or emission state. We demonstrate that subpulse arrangement may vary across an emission region meaning that it is not always uniform on a carousel. We discuss drifting subpulses of opposite drift directions and subpulse drift-rate switching in terms of different emission states in our model, and speculate that they may be two manifestations of the same underlying mechanism.
Abstract
We report on the pulse-to-pulse energy distribution and longitude-resolved modulation properties of PSR J1631+1252 discovered by the Five-hundred-meter Aperture Spherical radio Telescope. ...Our analysis made use of the data acquired at 1250 MHz from the follow-up timing observations that lasted over a year. PSR J1631+1252 has a rotational period of ∼0.310 s, and a dispersion measure of ∼32.73 pc cm
−3
. The energy distribution is well described by a lognormal distribution, the parameters of which do not vary with time. We show that large modulation occurs across the bridge emission of the pulse profile, with sporadic bright bursts at the leading emission region. The fluctuation spectral analysis reveals the existence of subpulse drifting in the leading component with vertical spacing between the drift bands of 3.28 ± 0.08 pulse periods between consecutive drift bands. Possible physical mechanisms for subpulse drifting are discussed.
ABSTRACT
The study of polarization and micro-structure is very important for understanding the radiation mechanism of Rotating Radio Transients (RRATs). Due to the limitations of telescope ...sensitivity and time resolution, studies of the polarization and micro-structure of RRATs have been rare in the past. In this work, we report on a high-time resolution and full polarization observation of RRAT J0139+3336 with the Five-hundred-meter Aperture Spherical Radio Telescope (FAST). A total of 96 burst pulses were detected in the 3-h observation. The degrees of linear and circular polarization and the shape of the polarization position angle (PPA) of the single pulses vary significantly. The average profile displays a small degree of linear and circular polarization, and the PPA exhibits a remarkably smooth and steep S-shaped curve, which are also characteristics of pulsars. The circular polarization in some single pulses demonstrates a clear sign change. We discuss the geometric structure of the emission beam based on the results from fitting the RVM model to the changes in the PPA. Using an autocorrelation analysis, the quasi-periodic micro-structure in the single pulse emission is detected with a median period of about 0.91 ms. We show that the position of RRAT J0139+3336 on the P–Pμ diagram falls in the normal pulsar (NP) region . The radio emission of RRAT J0139+3336 shows unique properties, such as the sign change in the circular polarization and quasi-periodicity in the micro-structure, which will provide important clues to the emission mechanism of RRATs.
Abstract
We report on the variation in the single-pulse emission from PSR J1900+4221 (CRAFTS 19C10) observed at frequency centered at 1.25 GHz using the Five-hundred-meter Aperture Spherical radio ...Telescope. The integrated pulse profile shows two distinct components, referred to here as the leading and trailing components, with the latter component also containing a third weak component. The single-pulse sequence reveals different emissions demonstrating as nulling, regular, and bright pulses, each with a particular abundance and duration distribution. There also exists pulses that follow a log-normal distribution suggesting the possibility of another emission, in which the pulsar is radiating weakly. Changes in the profile shape are seen across different emissions. We examine the emission variations in the leading and trailing components collectively and separately, and find moderate correlation between the two components. The inclination angle is estimated to be about 7° based on pulse-width, and we discuss that nulling in this pulsar does not seem to show correlation with age and rotation period.
ABSTRACT
The follow-up timing observations were carried out for 24 pulsars discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in Commensal Radio Astronomy FAST Survey. ...We report their phase-connected timing ephemeris, polarization pulse profiles, and Faraday rotation measurements. With their spin periods spanning from 2.995 ms to 4.34 s, their period derivatives were determined to spread between 7.996(8) × 10−21 and 9.83(3) × 10−15 s s−1, which imply that they have characteristic ages from 1.97 × 106 to 5.93 × 109 yr. It is inferred that PSRs J0211+4235 and J0518+2431 are beyond the ‘traditional death line’. PSR J0211+4235 is beyond the ‘death valley’. The death line model of Zhang et al. also cannot explain the radio presence of PSR J0211+4235. This suggests that radiation theory needs to be improved. Besides, ten of the 22 canonical pulsars show nulling phenomena. Moreover, PSR J1617+1123 exhibits variation of emission and J0540+4542 shows subpulse drifting. The DM of five pulsars is larger than the estimated by the YMW16 electron density model, which could suggest that electron density models need updates for higher Galactic latitude regions. PSRs J0447+2447 and J1928−0548 are isolated millisecond pulsars. With their flux densities spanning from 5(1)–553(106) μJy, some of these new pulsars found by FAST are distant, dim, and low-$\dot{E}$ ones and are suitable for testing pulsar emission theories.
Aim
Pneumonia is the leading infectious cause of death among children under five globally. Many pneumonia deaths result from inappropriate treatment due to misdiagnosis of signs and symptoms. This ...study aims to identify whether health extension workers (HEWs) in Ethiopia, using an automated multimodal device (Masimo Rad‐G), adhere to required guidelines while assessing and classifying under five children with cough or difficulty breathing and to understand device acceptability.
Methods
A cross‐sectional study was conducted in three districts of Southern Nations, Nationalities, and Peoples' Region, Ethiopia. Between September and December 2018, 133 HEWs were directly observed using Rad‐G while conducting 599 sick child consultations. Usability was measured as adherence to the World Health Organization requirements to assess fast breathing and device manufacturer instructions for use. Acceptability was assessed using semi‐structured interviews with HEWs, first‐level health facility workers and caregivers.
Results
Adherence using the Rad‐G routinely for 2 months was 85.3% (95% CI 80.2, 89.3). Health workers and caregivers stated a preference for Rad‐G. Users highlighted a number of device design issues.
Conclusion
While demonstrating high levels of acceptability and usability, the device modifications to consider include better probe fit, improved user interface with exclusive age categories and simplified classification outcomes.
We report two phenomena detected in PSR J0344\(-\)0901 from two observations conducted at frequency centered at 1.25 GHz using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The ...first phenomenon manifests as shifting in the pulse emission to later longitudinal phases and then gradually returns to its original location. The event lasts for about 216 pulse periods, with an average shift of about \(0.7^\circ\) measured at the peak of the integrated profile. Changes in the polarization position angle (PPA) are detected around the trailing edge of the profile, together with an increase in the profile width. The second phenomenon is characterized by the apparent movement of subpulses, which results in different subpulse track patterns across the profile window. For the first time in this pulsar, we identify four emission modes, each with unique subpulse movement, and determine the pattern periods for three of the emission modes. Pulse nulling was not detected. Modeling of the changes in the PPA using the rotating vector model gives an inclination angle of \(75.12^\circ \pm 3.80^\circ\) and an impact parameter of \(-3.17^\circ \pm 5.32^\circ\) for this pulsar. We speculate that the subpulse movement may be related to the shifting of the pulse emission.
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