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Upper Limits on Pulsed Radio Emission from Unseen Compact Objects in Six Galactic Stellar Binaries

Melanie Ficarra, Fronefield Crawford, T. Joseph W. Lazio

Abstract

We have conducted a search for radio pulsars in six Galactic stellar binary systems having unseen primary stars. All six systems have estimated primary masses in the range that could be consistent with neutron stars. We used the Green Bank Telescope at a center frequency of 350 MHz to search for dispersed periodicities and single pulses across a range of possible dispersion measures (DMs) and binary accelerations. No astrophysical signals were detected in our search. The estimated 400-MHz luminosity upper limits from the search are comparable to or smaller than the lowest values observed for almost all the known Galactic binary pulsars having cataloged 400 MHz radio luminosities. This implies that the systems we observed either do not harbor radio-emitting pulsars, contain pulsars that do not beam in our direction, or contain pulsars with luminosities that are significantly lower than this subset of the known Galactic binary pulsar population.

Upper Limits on Pulsed Radio Emission from Unseen Compact Objects in Six Galactic Stellar Binaries

Abstract

We have conducted a search for radio pulsars in six Galactic stellar binary systems having unseen primary stars. All six systems have estimated primary masses in the range that could be consistent with neutron stars. We used the Green Bank Telescope at a center frequency of 350 MHz to search for dispersed periodicities and single pulses across a range of possible dispersion measures (DMs) and binary accelerations. No astrophysical signals were detected in our search. The estimated 400-MHz luminosity upper limits from the search are comparable to or smaller than the lowest values observed for almost all the known Galactic binary pulsars having cataloged 400 MHz radio luminosities. This implies that the systems we observed either do not harbor radio-emitting pulsars, contain pulsars that do not beam in our direction, or contain pulsars with luminosities that are significantly lower than this subset of the known Galactic binary pulsar population.
Paper Structure (18 sections, 2 equations, 1 figure)

This paper contains 18 sections, 2 equations, 1 figure.

Table of Contents

  1. Introduction and Background
  2. 2XMM J125556.57+565846.4
  3. SDSS J022932.28+713002.7
  4. TON S 183
  5. HE 0929$-$0424
  6. PG 1232$-$136
  7. BPS BS 16981$-$0016
  8. Observations
  9. Prior Observations and Analysis of Some of the Targets
  10. Data Analysis and Results
  11. Periodicity Search
  12. Single Pulse Search
  13. Discussion
  14. Expected Dispersion Smearing, Scattering, and Scintillation Effects
  15. Sensitivity Limits
  16. ...and 3 more sections

Figures (1)

  • Figure 1: Estimated 400-MHz luminosity limits vs. spin period for our six targets, plotted as differently colored curves. The population of known Galactic binary radio pulsars with measured 400-MHz luminosities from the ATNF catalog mht+05 is plotted as red dots. For the calculation of the sensitivity curves, we used the estimated DM for each source, derived from its distance and the NE2001 Galactic electron model cl02 (see Table \ref{['tbl-2']}). We also used the NE2001 model to estimate the scattering times for these targets at their estimated distances (see Table \ref{['tbl-2']}). The calculated sensitivity limits assumed an intrinsic width corresponding to a pulsed duty cycle of 5%, with the sampling time, DM smearing time within channels, and scattering time added to this width in quadrature to obtain an effective pulse width. For all but two of the targets, the searches were sensitive to the lowest luminosities observed for this set of Galactic binary radio pulsars. The searches of the other two targets would be sensitive to most of these systems.