Two New Black Widow Millisecond Pulsars in M28 Douglas, Andrew; Padmanabh, Prajwal V.; Ransom, Scott M. ...
The Astrophysical journal,
03/2022, Letnik:
927, Številka:
1
Journal Article
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Abstract
We report the discovery of two Black Widow millisecond pulsars in the globular cluster (GC) M28 with the MeerKAT telescope. PSR J1824−2452M (M28M) is a 4.78 ms pulsar in a 5.82 hr orbit, and ...PSR J1824−2452N (M28N) is a 3.35 ms pulsar in a 4.76 hr orbit. Both pulsars have dispersion measures near 119.30 pc cm
−3
and have low-mass companion stars (∼0.01–0.03
M
⊙
) that do not cause strong radio eclipses or orbital variations. Including these systems, there are now five known black widow pulsars in M28. The pulsar searches were conducted as a part of an initial phase of MeerKAT’s GC census (within the TRAPUM Large Survey Project). These faint discoveries demonstrate the advantages of MeerKAT’s survey sensitivity over previous searches, and we expect to find additional pulsars in continued searches of this cluster.
Timing stability of three black widow pulsars Bak Nielsen, Ann-Sofie; Janssen, Gemma H; Shaifullah, Golam ...
Monthly notices of the Royal Astronomical Society,
2020, Letnik:
494, Številka:
2
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ABSTRACT
We study the timing stability of three black widow pulsars (BWPs), both in terms of their long-term spin evolution and their shorter term orbital stability. The erratic timing behaviour and ...radio eclipses of the first two BWP systems discovered (PSRs B1957+20 and J2051−0827) were assumed to be representative for this class of pulsars. With several new black widow systems added to this population in the last decade, there are now several systems known that do not show these typical orbital variations or radio eclipses. We present timing solutions using 7–8 yr of observations from four of the European Pulsar Timing Array telescopes for PSRs J0023+0923, J2214+3000, and J2234+0944, and confirm that two of these systems do not show any significant orbital variability over our observing time span, both in terms of secular or orbital parameters. The third pulsar PSR J0023+0923 shows orbital variability and we discuss the implications for the timing solution. Our results from the long-term timing of these pulsars provide several new or improved parameters compared to earlier works. We discuss our results regarding the stability of these pulsars, and the stability of the class of BWPs in general, in the context of the binary parameters, and discuss the potential of the Roche lobe filling factor of the companion star being an indicator for stability of these systems.
Abstract
We report on the first pulsar and transient survey of the Galactic Center (GC) with the Atacama Large Millimeter/submillimeter Array (ALMA). The observations were conducted during the Global ...Millimeter VLBI Array campaign in 2017 and 2018. We carry out searches using time series of both total intensity and other polarization components in the form of Stokes parameters. We incorporate acceleration and its derivative in the pulsar search, and also search in segments of the entire observation to compensate for potential orbital motion of the pulsar. While no new pulsar is found, our observations yield the polarization profile of the GC magnetar PSR J1745−2900 at millimeter wavelength for the first time, which turns out to be nearly 100% linearly polarized. Additionally, we estimate the survey sensitivity placed by both system and red noise, and evaluate its capability of finding pulsars in orbital motion with either Sgr A* or a binary companion. We show that the survey is sensitive to only the most luminous pulsars in the known population and future observations with ALMA in Band-1 will deliver significantly deeper survey sensitivity on the GC pulsar population.
Abstract
We present the first detection of pulsations from a neutron star in the submillimeter range. The source is the magnetar XTE J1810−197, observed with the James Clerk Maxwell Telescope on 2020 ...February 27, 2020 July 9, and 2021 May 15. XTE J1810−197 is detected at 353 GHz (
λ
= 0.85 mm) in the three epochs, but not detected in the simultaneously observed band at 666 GHz (
λ
= 0.45 mm). We measure an averaged flux density at 353 GHz of 6.7 ± 1.0, 4.0 ± 0.6, and 1.3 ± 0.3 mJy, and set 3
σ
flux density upper limits at 666 GHz of 11.3, 4.7, and 4.3 mJy, at each of the three observing epochs, respectively. Combining close-in-time observations with the Effelsberg 100 m and IRAM 30 m telescopes covering noncontiguously from 6 to 225 GHz (5.0 cm >
λ
> 1.33 mm), we investigate the spectral shape and frequency range of a potential spectral turn-up predicted by some pulsar radio emission models. The results demonstrate that the beamed radio emission from neutron stars can extend into the submillimeter regime, but are inconclusive on the existence and location of a potential spectral turn-up within the covered frequency range. The observed properties of the submillimeter emission resemble those of longer wavelengths and support a coherent mechanism for the production of pulsations at 353 GHz.
New Very Large Array (VLA) detections of the variable radio continuum source VLA J181335.1−174957, associated with the energetic X-ray pulsar PSR J1813−1749 and the TeV source HESS J1813-178, are ...presented. The radio source has a right circular polarization of ∼50% and a negative spectral index of −1.3 0.1, which show that it is nonthermal. The radio pulses of the pulsar are not detected from additional Effelsberg observations at 1.4 GHz made within one week of a VLA detection. This result would appear to support the idea that the continuum radio emission detected with the VLA does not trace the time-averaged emission pulses, as had previously been suggested. We discuss other possible origins for the radio source, such as a pulsar wind, magnetospheric emission, and a low-mass star companion. However, observations made at higher frequencies by Camilo et al. show that the VLA source is in fact the time-averaged pulsed emission and that the detection of the pulses had not been achieved because this is the most scattered pulsar known.
ABSTRACT
Propagation effects are one of the main sources of noise in high-precision pulsar timing. For pulsars below an ecliptic latitude of 5°, the ionized plasma in the solar wind can introduce ...dispersive delays of order $100\, \mu \mathrm{s}$ around solar conjunction at an observing frequency of 300 MHz. A common approach to mitigate this assumes a spherical solar wind with a time-constant amplitude. However, this has been shown to be insufficient to describe the solar wind. We present a linear, Gaussian-process piecewise Bayesian approach to fit a spherical solar wind of time-variable amplitude, which has been implemented in the pulsar software run_enterprise. Through simulations, we find that the current EPTA+InPTA data combination is not sensitive to such variations; however, solar wind variations will become important in the near future with the addition of new InPTA data and data collected with the low-frequency LOFAR telescope. We also compare our results for different high-precision timing data sets (EPTA+InPTA, PPTA, and LOFAR) of 3 ms pulsars (J0030+0451, J1022+1001, J2145−0450), and find that the solar-wind amplitudes are generally consistent for any individual pulsar, but they can vary from pulsar to pulsar. Finally, we compare our results with those of an independent method on the same LOFAR data of the three millisecond pulsars. We find that differences between the results of the two methods can be mainly attributed to the modelling of dispersion variations in the interstellar medium, rather than the solar wind modelling.
We have resolved the scatter-broadened image of PSR B0329+54 and detected a substructure within it. These results are not influenced by any extended structure of a source but instead are directly ...attributed to the interstellar medium. We obtained these results at 324 MHz with the ground-space interferometer RadioAstron, which included the Space Radio Telescope, ground-based Westerbork Synthesis Radio Telescope and 64-m Kalyazin Radio Telescope on baseline projections up to 330 000 km in 2013 November 22 and 2014 January 1 to 2. At short 15 000 to 35 000 km ground-space baseline projections, the visibility amplitude decreases with baseline length, providing a direct measurement of the size of the scattering disc of 4.8 plus or minus 0.8 mas. At longer baselines, no visibility detections from the scattering disc would be expected. However, significant detections were obtained with visibility amplitudes of 3 to 5 per cent of the maximum scattered around a mean and approximately constant up to 330 000 km. These visibilities reflect a substructure from scattering in the interstellar medium and offer a new probe of ionized interstellar material. The size of the diffraction spot near Earth is 17 000 plus or minus 3 000 km. With the assumption of turbulent irregularities in the plasma of the interstellar medium, we estimate that the effective scattering screen is located 0.6 plus or minus 0.1 of the distance from the Earth towards the pulsar.
We report on the first detection of pulsed radio emission from a radio pulsar with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope. The detection was made in the Band-3 frequency ...range (85-101 GHz) using ALMA in the phased-array mode developed for VLBI observations. A software pipeline has been implemented to enable a regular pulsar observing mode in the future. We describe the pipeline and demonstrate the capability of ALMA to perform pulsar timing and searching. We also measure the flux density and polarization properties of the Vela pulsar (PSR J0835-4510) at millimeter wavelengths, providing the first polarimetric study of any ordinary pulsar at frequencies above 32 GHz. Finally, we discuss the lessons learned from the Vela observations for future pulsar studies with ALMA, particularly for searches near the supermassive black hole in the Galactic center, and the potential of using pulsars for polarization calibration of ALMA.
The overview of a Phased Array Feed (PAF) system and the early results with it on the 100 m diameter telescope at Effelsberg are presented in the paper.
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