Publications (3)0 Total impact
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Article: A parallax distance and mass estimate for the transitional millisecond pulsar system J1023+0038
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ABSTRACT: The recently discovered transitional millisecond pulsar system J1023+0038 exposes a crucial evolutionary phase of recycled neutron stars for multiwavelength study. The system, comprising the neutron star itself, its stellar companion, and the surrounding medium, is visible across the electromagnetic spectrum from the radio to X-ray/gamma-ray regimes and offers insight into the recycling phase of millisecond pulsar evolution. Here, we report on multiple-epoch astrometric observations with the Very Long Baseline Array (VLBA) which give a system parallax of 0.731 +/- 0.022 milliarcseconds (mas) and a proper motion of 17.98 +/- 0.05 mas/yr. By combining our results with previous optical observations, we are able to use the parallax distance of 1368+42-39 pc to estimate the mass of the pulsar as 1.71 +/- 0.16 solar masses, and we are also able to measure the 3D space velocity of the system as 126 +/- 5 km/s. Despite the precise nature of the VLBA measurements, the remaining ~3% distance uncertainty dominates the 0.16 solar mass error on our mass estimate.07/2012; -
Article: Discovery of the Optical/Ultraviolet/Gamma-ray Counterpart to the Eclipsing Millisecond Pulsar J1816+4510
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ABSTRACT: The energetic, eclipsing millisecond pulsar J1816+4510 was recently discovered in a low-frequency radio survey with the Green Bank Telescope. With an orbital period of 8.7 hr and minimum companion mass of 0.16 Msun it appears to belong to an increasingly important class of pulsars that are ablating their low-mass companions. We report the discovery of the gamma-ray counterpart to this pulsar, and present a likely optical/ultraviolet counterpart as well. Using the radio ephemeris we detect pulsations in the unclassified gamma-ray source 2FGL J1816.5+4511, implying an efficiency of ~25% in converting the pulsar's spin-down luminosity into gamma-rays and adding PSR J1816+4510 to the large number of millisecond pulsars detected by Fermi. The likely optical/UV counterpart was identified through position coincidence (<0.1") and unusual colors. Assuming that it is the companion, with R=18.27+/-0.03 mag and effective temperature >15,000 K it would be among the brightest and hottest of low-mass pulsar companions, and appears qualitatively different from other eclipsing pulsar systems. In particular, current data suggest that it is a factor of two larger than most white dwarfs of its mass, but a factor of four smaller than its Roche lobe. We discuss possible reasons for its high temperature and odd size, and suggest that it recently underwent a violent episode of mass loss. Regardless of origin, its brightness and the relative unimportance of irradiation make it an ideal target for a mass, and hence a neutron star mass, determination.05/2012; -
Article: Timing Derived Properties Of The First Discoveries From The GBT 350-MHz Pulsar Survey
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ABSTRACT: The GBT 350-MHz pulsar drift-scan survey took advantage of the track refurbishing to search the sky for radio pulsars during the northern summer of 2007. Data were taken between declinations of -21 and 38 degrees and a total of 1491 hours of data was accumulated. The flux limit, given an integration time of 140 seconds, is about 2 mJy (eight sigma detection), making this one of the most sensitive large-scale pulsar surveys ever undertaken. In our on-going analysis 25 new pulsars have been discovered. These include five millisecond pulsars (MSPs), two mildly recycled pulsars, and one rotating radio transient. The MSPs include the first radio pulsar binary system that shows evidence for recent accretion, providing a crucial missing link between radio MSPs and LMXBs. We present the timing-derived properties of the first discoveries from this survey.12/2009; 42:464.
