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Chandra Proper Motions and Milliarcsecond Astrometry of Nineteen Pulsars

Jack T. Dinsmore, Roger W. Romani

Abstract

We present X-ray proper motion (PM) measurements of 19 pulsars using new and archival data from the Chandra X-ray Observatory, including pulsar wind trails and X-ray filaments. Precise X-ray PMs are often limited by uncertainties in aligning observations to a common reference frame. Our analysis uses unresolved X-ray flux from stars in the Gaia catalog in addition to X-ray bright point sources for alignment, improving uncertainties. We obtain absolute positions referenced to Gaia with typical astrometric precision $\sim$10 mas and PM statistical uncertainties down to 1.3 mas yr$^{-1}$, the most precise X-ray PM achieved to date. With our improved frame alignment, PM accuracies are now limited by the pulsar flux in most cases. These results reveal a new X-ray filament and illuminate the wind nebula structures and origins of several of these pulsars.

Chandra Proper Motions and Milliarcsecond Astrometry of Nineteen Pulsars

Abstract

We present X-ray proper motion (PM) measurements of 19 pulsars using new and archival data from the Chandra X-ray Observatory, including pulsar wind trails and X-ray filaments. Precise X-ray PMs are often limited by uncertainties in aligning observations to a common reference frame. Our analysis uses unresolved X-ray flux from stars in the Gaia catalog in addition to X-ray bright point sources for alignment, improving uncertainties. We obtain absolute positions referenced to Gaia with typical astrometric precision 10 mas and PM statistical uncertainties down to 1.3 mas yr, the most precise X-ray PM achieved to date. With our improved frame alignment, PM accuracies are now limited by the pulsar flux in most cases. These results reveal a new X-ray filament and illuminate the wind nebula structures and origins of several of these pulsars.
Paper Structure (14 sections, 2 equations, 4 figures, 3 tables)

This paper contains 14 sections, 2 equations, 4 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Methods
  3. Data Preparation
  4. Uncertainty Improvement from Gaia PSs
  5. Fit Method
  6. Pulsar Birth Sites
  7. Results
  8. Individual Sources
  9. Review of systematic Uncertainties
  10. PWN Fluctuations
  11. Field PS Mis-modeling
  12. Spacecraft Roll Error
  13. Discussion & Conclusions
  14. Observations

Figures (4)

  • Figure 1: Estimated frame alignment precision for our pulsar fields. Histogram bar numbers indicate the cumulative number of PSs included in the fit, and redder colors correspond to X-ray faint, Gaia-selected PSs. The pulsar astrometric precision is marked with a star. Whenever this star lies above the blue portion of the bars, Gaia PSs are major contributors to the final PM precision.
  • Figure 2: Chandra images of the pulsars considered in this work. Our best-fit proper motions are shown as white arrows, scaled to 1 kyr of motion, with the arrow tip enclosed by 68% confidence intervals. The directions to the Galactic plane and potential birth sites are marked in green and blue respectively. Blue arcs show the angular extent of the birth site. A blue circle indicates that the pulsar is inside the birth site.
  • Figure 3: Locations and tracks of the pulsars considered in this work, in Galactic coordinates. Tracks are determined by propagating the observed proper motion through the Galactic potential and terminating at the spin-down age. 68% confidence intervals represent combined proper motion, radial velocity, and 30% distance uncertainties. SNRs and OB associations within 3 kpc of the Sun are also shown. When a pulsar track intersects with an SNR or OB track, the association is marked with the pulsar's color and the size is shown.
  • Figure 4: Distribution of Chandra frame-frame pointing offsets measured by our method. The blue band indicates uncertainties.