Variation of Gravitational Delay in Pulsar Timing Observations due to Proper Motion of Foreground Stars and Measurement of Stellar Mass

1995 ◽  
Vol 448 ◽  
pp. 271 ◽  
Author(s):  
Kouji Ohnishi ◽  
Mizuhiko Hosokawa ◽  
Toshio Fukushima ◽  
Mine Takeuti
Keyword(s):  
Proper Motion ◽  
Stellar Mass ◽  
Pulsar Timing

scholarly journals Characterizing Blue Straggler Star Populations in Globular Clusters using HST Photometric Survey Data

2015 ◽  
Vol 11 (A29B) ◽  
pp. 149-150
Author(s):  
Mirko Simunovic ◽  
Thomas H. Puzia
Keyword(s):  
Detailed Analysis ◽  
Survey Data ◽  
Proper Motion ◽  
Globular Clusters ◽  
Stellar Mass ◽  
Evolutionary Models ◽  
Early Results ◽  
Blue Straggler ◽  
Age Estimates

AbstractWe present early results from a detailed analysis of the BSS population in Galactic GCs based on HST data. Using proper motion cleaning of the color-magnitude diagrams we construct a large catalog of BSSs and study some population properties. Stellar evolutionary models are used to find stellar mass and age estimates for the BSS populations in order to establish constraints related to the dynamical interactions in which they may have formed.

scholarly journals Timing of young radio pulsars – I. Timing noise, periodic modulation, and proper motion

2019 ◽  
Vol 489 (3) ◽  
pp. 3810-3826 ◽  
Author(s):  
A Parthasarathy ◽  
R M Shannon ◽  
S Johnston ◽  
L Lentati ◽  
M Bailes ◽  
...  
Keyword(s):  
Bayesian Inference ◽  
Plasma Physics ◽  
Proper Motion ◽  
Noise Amplitude ◽  
Periodic Modulation ◽  
Proper Motions ◽  
Radio Pulsars ◽  
Arrival Times ◽  
Pulsar Timing ◽  
Timing Noise

ABSTRACT The smooth spin-down of young pulsars is perturbed by two non-deterministic phenomenon, glitches, and timing noise. Although the timing noise provides insights into nuclear and plasma physics at extreme densities, it acts as a barrier to high-precision pulsar timing experiments. An improved methodology based on the Bayesian inference is developed to simultaneously model the stochastic and deterministic parameters for a sample of 85 high-$\dot{E}$ radio pulsars observed for ∼10 yr with the 64-m Parkes radio telescope. Timing noise is known to be a red process and we develop a parametrization based on the red-noise amplitude (Ared) and spectral index (β). We measure the median Ared to be $-10.4^{+1.8}_{-1.7}$ yr3/2 and β to be $-5.2^{+3.0}_{-3.8}$ and show that the strength of timing noise scales proportionally to $\nu ^{1}|\dot{\nu }|^{-0.6\pm 0.1}$, where ν is the spin frequency of the pulsar and $\dot{\nu }$ is its spin-down rate. Finally, we measure significant braking indices for 19 pulsars and proper motions for 2 pulsars, and discuss the presence of periodic modulation in the arrival times of 5 pulsars.

Radial Velocity Studies of the Internal Kinematics of Open Clusters

1984 ◽  
Vol 88 ◽  
pp. 249-256
Author(s):  
Robert D. Mathieu
Keyword(s):  
Radial Velocity ◽  
Proper Motion ◽  
Globular Clusters ◽  
Cluster Structure ◽  
Relaxation Times ◽  
Stellar Mass ◽  
Open Clusters ◽  
Radial Velocities ◽  
Order Of Magnitude ◽  
Motion Studies

The internal kinematics of open clusters are a particularly challenging subject for study with radial velocities. Our present sitate of knowledge concerning the structure and kinematics of open clusters has recently been reviewed (Mathieu 1985), so I will only summarize here several of the essential concerns. The most basic goal is to measure a central or global velocity dispersion. Comparison of such measured dispersions with dynamical models fit to the cluster structure is a direct test of our understanding of the dynamics of open clusters. Far more difficult but of great importance to our understanding of cluster dynamics is the observation of assorted differential effects in these clusters. Open clusters provide a unique opportunity to study velocity distributions as a function of stellar mass. Radial velocity studies of nearby clusters can in themselves span a factor 2 in stellar mass; when combined with proper-motion studies which include the earlier stars inaccessible to high-precision radial velocities, a mass spectrum of up to an order of magnitude can be studied. Also, as with globular clusters, anisotropie velocity distributions are to be expected in the halos of those open clusters which are more than a few relaxation times old. Proper-motion studies (Jones 1970, 1971; van Leeuwen 1983) have found that anisotropy exists to within 1 pc of the centers of the Pleiades and Praesepe, much nearer the center than has so far been found in globular clusters. Independent confirmation of these findings as well as an increase in the sample of clusters studied would be of real value. And finally, the very youngest open clusters allow us to study the state of clusters at formation and indeed the star-formation process itself.

scholarly journals New timing measurement results of 16 pulsars

2020 ◽  
Vol 72 (4) ◽  
Author(s):  
Jie Liu ◽  
Zhen Yan ◽  
Zhi-Qiang Shen ◽  
Zhi-Peng Huang ◽  
Ru-Shuang Zhao ◽  
...  
Keyword(s):  
Proper Motion ◽  
Observation Data ◽  
Independent Manner ◽  
Long Baseline ◽  
Pulsar Timing ◽  
Measurement Results ◽  
Fast Development ◽  
Period Derivative ◽  
Timing Properties ◽  
Model Independent

Abstract A pulsar’s position, proper motion, and parallax are important parameters in timing equations. It is challenging to fit astrometric parameters accurately through pulsar timing, especially for pulsars that show irregular timing properties. With the fast development of related techniques, it is possible to measure astrometric parameters of more and more pulsars in a model-independent manner with very-long-baseline interferometry (VLBI). In this work we select 16 normal pulsars, whose parallax and proper motion have not been successfully fitted with timing observations or show obvious differences from the corresponding latest VLBI solutions, and do further studies on their timing properties. After updating the astrometric parameters in pulsar ephemerides with the latest VLBI measurements, we derive the latest rotation solutions of these pulsars with observation data in the S and C bands obtained from the Shanghai Tian Ma Radio Telescope. Compared with the spin frequency ν inferred from previous rotation solutions, the newly fitted ν show differences larger than 10−9 Hz for most pulsars. The contribution of the Shklovsky effect to the period derivative $\dot{P}$ can be properly removed by taking advantage of the accurate proper motion and distance of target pulsars measured by VLBI astrometry. This further leads to a precise estimate of the intrinsic characteristic age τc. The differences between the newly measured τc and corresponding previous results are as large as 2% for some pulsars. VLBI astrometric parameter solutions also lead to better measurements of timing irregularities. For PSR B0154+61, the glitch epoch (MJD 58279.5) measured with a previous ephemeris is about 13 d later than the result (MJD 58266.4) obtained with VLBI astrometric parameter solutions.

scholarly journals Macho Detection by Pulsar Timing Observation

1996 ◽  
Vol 160 ◽  
pp. 125-126 ◽  
Author(s):  
Kouji Ohnishi ◽  
Mizuhiko Hosokawa ◽  
Toshio Fukushima ◽  
Mine Takeuti
Keyword(s):  
Dark Matter ◽  
Galactic Halo ◽  
Mass Measurement ◽  
Relativistic Effects ◽  
Stellar Mass ◽  
Actual Measurement ◽  
Pulsar Timing ◽  
General Relativistic ◽  
Gravitational Deflection

The magnitudes of some general relativistic effects depend on the mass of gravitating objects; therefore, these effects can be used for the stellar mass measurement. Several methods have been proposed; for example, the microlensing effect (Paczyński 1986), and the parallactic variation of gravitational deflection of the light from the source (Hosokawa et al. 1993).Recently some candidates for MACHOs – a kind of dark matter candidates in the Galactic halo – have been discovered by their microlensing effect, and their masses were estimated to be of the order of 0.1Mʘ, under many assumptions. Actual measurement of MACHO masses are important in specifying what kind of object the MACHO is.

scholarly journals Multiplicity of Solar-Type Stars

1977 ◽  
Vol 33 ◽  
pp. 47-51
Author(s):  
Helmut A. Abt
Keyword(s):  
Proper Motion ◽  
Stellar Mass ◽  
Spectroscopic Binaries ◽  
Cube Root ◽  
Bright Field ◽  
Mass Distributions ◽  
Root Relation ◽  
Median Period ◽  
Solar Type

AbstractA systematic search for binaries in a sample of 123 bright field stars of types F3-G2 IV or V is described. Combination of the results for 25 newly discovered spectroscopic binaries with those of 21 spectroscopic, 23 visual, and 25 common-proper-motion pairs previously known brings to 88 the total number of companions identified in the sample. The distribution of the 88 periods shows a single maximum; the median period is 14 years.The frequencies of singles: doubles: triples: quadruples are found to be 42: 46: 9: 2. Less than half of the stars are thus observed to be single. Estimates of the completeness of this search lead to a determination of the number of systems missed and to a determination of their secondary masses.Analysis of the secondary-mass distributions, observed and predicted from completeness estimates, indicates the existence of two types of binaries.For systems with periods less than about 100 years, the distribution of secondaries varies with the cube-root of the secondary mass. These systems must be the result of fission. Two-thirds of their primaries have companions of stellar mass. Extrapolation of the cube-root relation implies that the remaining one-third of the primaries have non-stellar secondaries, i.e., close companions whose masses are less than 0.07 solar masses.For systems with periods larger than roughly 100 years the distribution of secondaries follows that given by the van Rhijn function. They must be the result of condensations that contracted separately but are bound gravitationally. Roughly three-fourths of all primaries in the sample have such distant companions, all of which are likely to be themselves close fission-systems. Evidently single stars are rare among solar-type dwarfs.

Large-scale Motion of Solar Filaments

2000 ◽  
Vol 179 ◽  
pp. 205-208
Author(s):  
Pavel Ambrož ◽  
Alfred Schroll
Keyword(s):  
Magnetic Flux ◽  
Proper Motion ◽  
Time Scale ◽  
Large Scale ◽  
Accuracy Of Measurements ◽  
Solar Filaments ◽  
General Movement ◽  
Scale Motion ◽  
Velocity Scatter

AbstractPrecise measurements of heliographic position of solar filaments were used for determination of the proper motion of solar filaments on the time-scale of days. The filaments have a tendency to make a shaking or waving of the external structure and to make a general movement of whole filament body, coinciding with the transport of the magnetic flux in the photosphere. The velocity scatter of individual measured points is about one order higher than the accuracy of measurements.

Status of “AGK4” Project

1978 ◽  
Vol 48 ◽  
pp. 527-533
Author(s):  
Chr. de Vegt
Keyword(s):  
Northern Hemisphere ◽  
Proper Motion ◽  
The Mean ◽  
Spectral Bandpass

The present accuracy limit for the majority of fainter stars on the northern hemisphere is set by the AGK2/3-catalogue, recently completely finished, but it should be noted that its epoch is much earlier (1960). Furtheron the AGK3-catalogue is a direct repetition of the AGK2, the plates have been taken with the same astrograph in a broad blue spectral bandpass and measured visually with the same equipment, therefore virtually an instrumental standard of 1930 is realized again. Figure 1 shows the mean errors of the AGK2/3 catalogue positions as a function of magnitude. The best accuracy for the AGK2/3 data is obtained for the stars of about ninth magnitude: 017 (AGK2) and 020 (AGK3) but decreases for the faint stars with mpg11 to 019 (AGK2) and Pg 027 (AGK3). Here the AGK3 data are even less accurate. With increasing distance to the catalogue epochs, the accuracy of positions decreases due to the proper motion errors. In the upper part of figure 2 the dependence of the AGK2/3 catalogue accuracy on time is shown for the faint stars separately and an averaged value.

Status of the Lick Proper Motion Program

1978 ◽  
Vol 48 ◽  
pp. 387-388
Author(s):  
A. R. Klemola
Keyword(s):  
Proper Motion ◽  
The Future

Second-epoch photographs have now been obtained for nearly 850 of the 1246 fields of the proper motion program with centers at declination -20° and northwards. For the sky at 0° and northward only 130 fields remain to be taken in the next year or two. The 270 southern fields with centers at -5° to -20° remain for the future.

Gravitational Waves

2018 ◽  
Author(s):  
Michele Maggiore
Keyword(s):  
Black Hole ◽  
Perturbation Theory ◽  
Gravitational Waves ◽  
Transfer Functions ◽  
Normal Modes ◽  
Cosmological Perturbation ◽  
Tests Of General Relativity ◽  
Pulsar Timing ◽  
Tensor Perturbations ◽  
Stochastic Backgrounds

A comprehensive and detailed account of the physics of gravitational waves and their role in astrophysics and cosmology. The part on astrophysical sources of gravitational waves includes chapters on GWs from supernovae, neutron stars (neutron star normal modes, CFS instability, r-modes), black-hole perturbation theory (Regge-Wheeler and Zerilli equations, Teukoslky equation for rotating BHs, quasi-normal modes) coalescing compact binaries (effective one-body formalism, numerical relativity), discovery of gravitational waves at the advanced LIGO interferometers (discoveries of GW150914, GW151226, tests of general relativity, astrophysical implications), supermassive black holes (supermassive black-hole binaries, EMRI, relevance for LISA and pulsar timing arrays). The part on gravitational waves and cosmology include discussions of FRW cosmology, cosmological perturbation theory (helicity decomposition, scalar and tensor perturbations, Bardeen variables, power spectra, transfer functions for scalar and tensor modes), the effects of GWs on the Cosmic Microwave Background (ISW effect, CMB polarization, E and B modes), inflation (amplification of vacuum fluctuations, quantum fields in curved space, generation of scalar and tensor perturbations, Mukhanov-Sasaki equation,reheating, preheating), stochastic backgrounds of cosmological origin (phase transitions, cosmic strings, alternatives to inflation, bounds on primordial GWs) and search of stochastic backgrounds with Pulsar Timing Arrays (PTA).

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