scholarly journals The Relativistic Binary Programme on MeerKAT: Science objectives and first results

2021 ◽  
Author(s):  
M Kramer ◽  
I H Stairs ◽  
V Venkatraman Krishnan ◽  
P C C Freire ◽  
F Abbate ◽  
...  
Keyword(s):  
Relativistic Effects ◽  
Position Angle ◽  
Vector Model ◽  
High Time Resolution ◽  
Orbital Inclination ◽  
Priority List ◽  
Binary Pulsars ◽  
First Results ◽  
Phase Resolution ◽  
Order Of Magnitude

Abstract We describe the ongoing Relativistic Binary programme (RelBin), a part of the MeerTime large survey project with the MeerKAT radio telescope. RelBin is primarily focused on observations of relativistic effects in binary pulsars to enable measurements of neutron star masses and tests of theories of gravity. We selected 25 pulsars as an initial high priority list of targets based on their characteristics and observational history with other telescopes. In this paper, we provide an outline of the programme, present polarisation calibrated pulse profiles for all selected pulsars as a reference catalogue along with updated dispersion measures. We report Faraday rotation measures for 24 pulsars, twelve of which have been measured for the first time. More than a third of our selected pulsars show a flat position angle swing confirming earlier observations. We demonstrate the ability of the Rotating Vector Model (RVM), fitted here to seven binary pulsars, including the Double Pulsar (PSR J0737−3039A), to obtain information about the orbital inclination angle. We present a high time resolution light curve of the eclipse of PSR J0737−3039A by the companion’s magnetosphere, a high-phase resolution position angle swing for PSR J1141−6545, an improved detection of the Shapiro delay of PSR J1811−2405, and pulse scattering measurements for PSRs J1227−6208, J1757−1854, and J1811−1736. Finally, we demonstrate that timing observations with MeerKAT improve on existing data sets by a factor of, typically, 2–3, sometimes by an order of magnitude.

scholarly journals Rotating vector model for magnetars

2021 ◽  
Vol 502 (1) ◽  
pp. 1549-1556
Author(s):  
H Tong ◽  
P F Wang ◽  
H G Wang ◽  
Z Yan
Keyword(s):  
Magnetic Field ◽  
Magnitude Estimation ◽  
Position Angle ◽  
Vector Model ◽  
Line Of Sight ◽  
Estimation Formula ◽  
Emission Point ◽  
Order Of Magnitude ◽  
Field Geometry ◽  
The Magnetic Field

ABSTRACT The modification of the rotating vector model in the case of magnetars are calculated. Magnetars may have twisted magnetic field compared with normal pulsars. The polarization position angle of magnetars will change in the case of a twisted magnetic field. For a twisted dipole field, we found that the position angle will change both vertically and horizontally. During the untwisting process of the magnetar magnetosphere, the modifications of the position angle will evolve with time monotonously. This may explain the evolution of the position angle in magnetar PSR J1622-4950 and XTE J1810-197. The relation between the emission point and the line of sight will also change. We suggest every magnetospheric models of magnetars also calculate the corresponding changes of position angle in their models. Order of magnitude estimation formula for doing this is given. This opens the possibility to extract the magnetic field geometry of magnetars from their radio polarization observations.

scholarly journals On the 2PN Periastron Precession of the Double Pulsar PSR J0737–3039A/B

Universe ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 443
Author(s):  
Lorenzo Iorio
Keyword(s):  
General Relativity ◽  
Present Author ◽  
Moment Of Inertia ◽  
The Other ◽  
Orbital Elements ◽  
Binary Pulsars ◽  
Orbital Phase ◽  
Order Of Magnitude ◽  
General Relativistic ◽  
The Moment

One of the post-Keplerian (PK) parameters determined in timing analyses of several binary pulsars is the fractional periastron advance per orbit kPK. Along with other PK parameters, it is used in testing general relativity once it is translated into the periastron precession ω˙PK. It was recently remarked that the periastron ω of PSR J0737–3039A/B may be used to measure/constrain the moment of inertia of A through the extraction of the general relativistic Lense–Thirring precession ω˙LT,A≃−0.00060∘yr−1 from the experimentally determined periastron rate ω˙obs provided that the other post-Newtonian (PN) contributions to ω˙exp can be accurately modeled. Among them, the 2PN seems to be of the same order of magnitude of ω˙LT,A. An analytical expression of the total 2PN periastron precession ω˙2PN in terms of the osculating Keplerian orbital elements, valid not only for binary pulsars, is provided, thereby elucidating the subtleties implied in correctly calculating it from k1PN+k2PN and correcting some past errors by the present author. The formula for ω˙2PN is demonstrated to be equivalent to that obtainable from k1PN+k2PN by Damour and Schäfer expressed in the Damour–Deruelle (DD) parameterization. ω˙2PN actually depends on the initial orbital phase, hidden in the DD picture, so that −0.00080∘yr−1≤ω˙2PN≤−0.00045∘yr−1. A recently released prediction of ω˙2PN for PSR J0737–3039A/B is discussed.

scholarly journals An Ion Source for the HVEE 14C Isotope Ratio Mass Spectrometer for Biomedical Applications

Radiocarbon ◽  
1997 ◽  
Vol 40 (1) ◽  
pp. 283-288 ◽  
Author(s):  
Dirk J. W. Mous ◽  
Wim Fokker ◽  
Rein Van Den Broek ◽  
Ron Koopmans ◽  
Christopher Bronk Ramsey ◽  
...  
Keyword(s):  
Biomedical Research ◽  
Biomedical Applications ◽  
Ion Source ◽  
User Friendliness ◽  
The Past ◽  
Widespread Acceptance ◽  
First Results ◽  
Order Of Magnitude ◽  
Isotope Ratio Mass Spectrometer ◽  
Near Future

During the past two decades, accelerator mass spectrometry (AMS) has allowed major developments in many areas of geosciences and archaeology. In the near future, AMS should realize a similar potential in the field of biomedical research, leading ultimately to clinical applications. For such applications, the required instrument differs significantly from that presently used in the field of 14C dating. Whereas the needed accuracy and sensitivity is more than an order of magnitude less demanding than that for present state-of-the-art 14C instrumentation, the widespread acceptance of 14C AMS in biomedical research will require AMS spectrometers that are small, simple to operate and capable of handling CO2 samples. In order to satisfy these demands, HVEE has developed a compact 14C AMS spectrometer dedicated to biomedical research. The instrument consists of a compact accelerator with a footprint of 2.25 × 1.25 m and an ion source that features direct CO2 acceptance and optimal user friendliness. Having previously described the layout and design of the accelerator, we here discuss progress on the accelerator and present the design and first results of the CO2 ion source.

scholarly journals The S2 Baseband Processing System for Phase-coherent Pulsar Observations

1996 ◽  
Vol 160 ◽  
pp. 21-22
Author(s):  
R. Wietfeldt ◽  
W. Van Straten ◽  
D. Del Rizzo ◽  
N. Bartel ◽  
W. Cannon ◽  
...  
Keyword(s):  
High Speed ◽  
Processing System ◽  
High Time Resolution ◽  
Data Sets ◽  
Future Developments ◽  
Huge Data ◽  
Pulse Timing ◽  
First Results ◽  
Vela Pulsar ◽  
Baseband Processing

AbstractThe phase-coherent recording of pulsar data and subsequent software dispersion removal provide a flexible way to reach the limits of high time resolution, useful for more precise pulse timing and the study of fast signal fluctuations within a pulse. Because of the huge data rate and lack of adequate recording and computing capabilities, this technique has been used mostly only for small pulsar data sets. In recent years, however, the development of very capable, reasonably inexpensive high-speed recording systems and computers has made feasible the notion of pulsar baseband recording and subsequent processing with a workstation/computer. In this paper we discuss the development of a phase-coherent baseband processing system for radio pulsar observations. This system is based on the S2 VLBI recorder developed at ISTS/York University in Toronto, Canada. We present preliminary first results for data from the Vela pulsar, obtained at Parkes, Australia, and processed at ISTS/York University, and discuss plans for future developments.

scholarly journals Simultaneous Five Color (UBVRI) Polarimetry of VV Puppis

1987 ◽  
Vol 93 ◽  
pp. 203-203
Author(s):  
V. Piirola ◽  
A. Reiz ◽  
G.V. Coyne
Keyword(s):  
Circular Polarization ◽  
Linear Polarization ◽  
Wavelength Dependence ◽  
Position Angle ◽  
Orbital Inclination ◽  
V Band ◽  
Highly Active ◽  
Phase Interval ◽  
In The Beginning ◽  
Bright Phase

AbstractObservations of linear and circular polarization in five colour bands during a highly active state of VV Puppis in January 86 are reported. A strong linear polarization pulse with the maximum in the blue, PB ≈ 22%, is observed at the end of the bright phase when the active pole is at the limb and a weaker secondary pulse, PB ≈ 7%, is seen in the beginning of the bright phase, when the active pole reappears. Strong positive circular polarization is also observed in the blue and the ultraviolet, РU ≈ PB ≈ 18%, PV ≈ 10% during the bright phase. The circular polarization reverses the sign in the B and V bands during the faint phase and a negative polarization hump is seen when the active pole crosses the limb. The circular polarization in the V band reaches the value PV ≈ −10% at the hump, after which it remains near PV ≈ −5% during the faint phase. This is probably due to radiation coming from the second, less active pole and accretion thus takes place onto both poles. The wavelength dependences of the positive and negative parts of the circular polarization curve are different and no polarization reversal is seen in the U band. The position angle of the linear polarization is well determined during a large portion of the cycle, especially in the V band, thanks to the activity from both poles. A best fit to the position angle curve, taking into account also the duration of the positive circular polarization phase interval ΔΦ = 0.40 (in the V band), yields the values of orbital inclination i = 78° ± 2° and the colatitude of the active magnetic pole ß = 146° ± 2°. The relatively good fit to the position angle data indicates that the simple dipole model is nearly correct in the case of VV Puppis. Some wavelength dependence is, however, seen in the position angle curves, especially in the I band where the slope Δθ/ΔΦ at the main pulse is considerably smaller than in the other bands. The shape of the position angle curves changes also in the blue and the ultraviolet around the middle of the bright phase. This is probably due to optical thickness effects as the side of the accretion column which is toward the observer changes near this phase.

scholarly journals 100 GHz Room-Temperature Laboratory Emission Spectrometer

2017 ◽  
Vol 13 (S332) ◽  
pp. 332-345 ◽  
Author(s):  
Nadine Wehres ◽  
Bettina Heyne ◽  
Frank Lewen ◽  
Marius Hermanns ◽  
Bernhard Schmidt ◽  
...  
Keyword(s):  
Room Temperature ◽  
Time Integration ◽  
Absolute Intensity ◽  
Fast Response ◽  
High Resolution Spectroscopy ◽  
Recording Time ◽  
Intensity Measurements ◽  
First Results ◽  
Long Time ◽  
Order Of Magnitude

AbstractWe present first results of a new heterodyne spectrometer dedicated to high-resolution spectroscopy of molecules of astrophysical importance. The spectrometer, based on a room-temperature heterodyne receiver, is sensitive to frequencies between 75 and 110 GHz with an instantaneous bandwidth of currently 2.5 GHz in a single sideband. The system performance, in particular the sensitivity and stability, is evaluated. Proof of concept of this spectrometer is demonstrated by recording the emission spectrum of methyl cyanide, CH3CN. Compared to state-of-the-art radio telescope receivers the instrument is less sensitive by about one order of magnitude. Nevertheless, the capability for absolute intensity measurements can be exploited in various experiments, in particular for the interpretation of the ever richer spectra in the ALMA era. The ease of operation at room-temperature allows for long time integration, the fast response time for integration in chirped pulse instruments or for recording time dependent signals. Future prospects as well as limitations of the receiver for the spectroscopy of complex organic molecules (COMs) are discussed.

scholarly journals Cosmic ray feedback in the FIRE simulations: constraining cosmic ray propagation with GeV γ-ray emission

2019 ◽  
Vol 488 (3) ◽  
pp. 3716-3744 ◽  
Author(s):  
T K Chan ◽  
D Kereš ◽  
P F Hopkins ◽  
E Quataert ◽  
K-Y Su ◽  
...  
Keyword(s):  
Transport Coefficients ◽  
Cosmic Ray ◽  
Starburst Galaxies ◽  
Secondary Importance ◽  
Star Forming ◽  
First Results ◽  
Order Of Magnitude ◽  
Γ Ray ◽  
Field Lines ◽  
Formation Efficiency

ABSTRACT We present the implementation and the first results of cosmic ray (CR) feedback in the Feedback In Realistic Environments (FIRE) simulations. We investigate CR feedback in non-cosmological simulations of dwarf, sub-L⋆ starburst, and L⋆ galaxies with different propagation models, including advection, isotropic, and anisotropic diffusion, and streaming along field lines with different transport coefficients. We simulate CR diffusion and streaming simultaneously in galaxies with high resolution, using a two-moment method. We forward-model and compare to observations of γ-ray emission from nearby and starburst galaxies. We reproduce the γ-ray observations of dwarf and L⋆ galaxies with constant isotropic diffusion coefficient $\kappa \sim 3\times 10^{29}\, {\rm cm^{2}\, s^{-1}}$. Advection-only and streaming-only models produce order of magnitude too large γ-ray luminosities in dwarf and L⋆ galaxies. We show that in models that match the γ-ray observations, most CRs escape low-gas-density galaxies (e.g. dwarfs) before significant collisional losses, while starburst galaxies are CR proton calorimeters. While adiabatic losses can be significant, they occur only after CRs escape galaxies, so they are only of secondary importance for γ-ray emissivities. Models where CRs are ‘trapped’ in the star-forming disc have lower star formation efficiency, but these models are ruled out by γ-ray observations. For models with constant κ that match the γ-ray observations, CRs form extended haloes with scale heights of several kpc to several tens of kpc.

scholarly journals The discovery of two mildly recycled binary pulsars in the Northern High Time Resolution Universe pulsar survey

2017 ◽  
Vol 470 (4) ◽  
pp. 4421-4433 ◽  
Author(s):  
M. Berezina ◽  
D. J. Champion ◽  
P. C. C. Freire ◽  
T. M. Tauris ◽  
M. Kramer ◽  
...  
Keyword(s):  
Time Resolution ◽  
High Time ◽  
High Time Resolution ◽  
Binary Pulsars

scholarly journals Manchester Ice Nucleus Counter (MINC) measurements from the 2007 International workshop on Comparing Ice nucleation Measuring Systems (ICIS-2007)

2011 ◽  
Vol 11 (1) ◽  
pp. 53-65 ◽  
Author(s):  
H. M. Jones ◽  
M. J. Flynn ◽  
P. J. DeMott ◽  
O. Möhler
Keyword(s):  
International Workshop ◽  
Diffusion Chamber ◽  
Ice Nucleation ◽  
Concentric Cylinder ◽  
Measuring Systems ◽  
Colorado State University ◽  
Ice Nuclei ◽  
Nucleus Counter ◽  
First Results ◽  
Order Of Magnitude

Abstract. An ice nucleus counter was developed and constructed to enable investigation of potential ice nucleating materials. The Manchester Ice Nucleus Chamber (MINC) is a concentric-cylinder continuous flow diffusion chamber (CFDC). A full explanation of the MINC instrument is given here, along with first results and a comparison to an established instrument of similar design (Colorado State University CFDC) during sampling of common ice nucleating aerosols at the 2007 International workshop on Comparing Ice nucleation Measuring Systems (ICIS-2007). MINC and CSU-CFDC detected the onset of ice nucleation under similar conditions of temperature and supersaturation for several different types of ice nuclei. Comparisons of the ratio of ice nuclei to total aerosol concentrations as a function of supersaturation with respect to water (SSw) showed agreement within one order of magnitude. Possible reasons for differences between the two instruments relating to differences in their design are discussed, along with suggestions to future improvements to the current design.

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