Showing papers by "Mallory S. E. Roberts published in 2014"
National Radio Astronomy Observatory1, University of British Columbia2, McGill University3, ASTRON4, University of Amsterdam5, University of Wisconsin-Madison6, University of Wisconsin–Milwaukee7, University of Toronto8, West Virginia University9, Western Kentucky University10, Cornell University11, Lebedev Physical Institute12, New York University13, University of New Mexico14, University of Texas at Brownsville15
TL;DR: Ransom et al. as mentioned in this paper reported precision timing and multi-wavelength observations of a unique object, the millisecond pulsar PSR J0337+1715, in orbit with two white dwarf companions.
Abstract: Precision timing and multiwavelength observations of a millisecond pulsar in a triple system show that the gravitational interactions between the bodies are strong; this allows the mass of each body to be determined accurately and means that the triple system will provide precise tests of the strong equivalence principle of general relativity. Millisecond pulsars act as high-precision celestial clocks, and astronomers can use them to test aspects of basic physics and astrophysics. A triple system containing a radio pulsar could provide measurements of the interior structures of the bodies and a test of theories of gravity, but the only previously known system with a millisecond pulsar shows only weak interactions. Scott Ransom et al. report precision timing and multiwavelength observations of a unique object, the millisecond pulsar PSR J0337+1715, in orbit with two white dwarf companions. Strong gravitational interactions are apparent in this triple system, making it possible to estimate the masses of the pulsar and the two white dwarf companions, as well as the inclinations of the orbits. The surprisingly coplanar and nearly circular orbits indicate a complex and exotic evolutionary past that differs from known stellar systems. Gravitationally bound three-body systems have been studied for hundreds of years1,2 and are common in our Galaxy3,4. They show complex orbital interactions, which can constrain the compositions, masses and interior structures of the bodies5 and test theories of gravity6, if sufficiently precise measurements are available. A triple system containing a radio pulsar could provide such measurements, but the only previously known such system, PSR B1620-26 (refs 7, 8; with a millisecond pulsar, a white dwarf, and a planetary-mass object in an orbit of several decades), shows only weak interactions. Here we report precision timing and multiwavelength observations of PSR J0337+1715, a millisecond pulsar in a hierarchical triple system with two other stars. Strong gravitational interactions are apparent and provide the masses of the pulsar (1.4378(13)
, where is the solar mass and the parentheses contain the uncertainty in the final decimal places) and the two white dwarf companions (0.19751(15)
and 0.4101(3)
), as well as the inclinations of the orbits (both about 39.2°). The unexpectedly coplanar and nearly circular orbits indicate a complex and exotic evolutionary past that differs from those of known stellar systems. The gravitational field of the outer white dwarf strongly accelerates the inner binary containing the neutron star, and the system will thus provide an ideal laboratory in which to test the strong equivalence principle of general relativity.
243 citations
University of Texas at San Antonio1, University of Texas at Brownsville2, University of New Mexico3, McGill University4, National Radio Astronomy Observatory5, ASTRON6, University of Wisconsin–Milwaukee7, Syracuse University8, Western Kentucky University9, University of Amsterdam10, University of Wisconsin-Madison11, Lebedev Physical Institute12, West Virginia University13, University of British Columbia14, Colorado State University15
TL;DR: An ongoing search for pulsars and dispersed radio emission, such as those from rotating radio transients (RRATs) and fast radio bursts, at 350 MHz using the Green Bank Telescope is described in this article.
Abstract: We describe an ongoing search for pulsars and dispersed pulses of radio emission, such as those from rotating radio transients (RRATs) and fast radio bursts, at 350 MHz using the Green Bank Telescope. With the Green Bank Ultimate Pulsar Processing Instrument, we record 100 MHz of bandwidth divided into 4096 channels every 81.92 μs. This survey will cover the entire sky visible to the Green Bank Telescope (δ > -40°, or 82% of the sky) and outside of the Galactic Plane will be sensitive enough to detect slow pulsars and low dispersion measure (<30 pc cm-3) millisecond pulsars (MSPs) with a 0.08 duty cycle down to 1.1 mJy. For pulsars with a spectral index of -1.6, we will be 2.5 times more sensitive than previous and ongoing surveys over much of our survey region. Here we describe the survey, the data analysis pipeline, initial discovery parameters for 62 pulsars, and timing solutions for 5 new pulsars. PSR J0214+5222 is an MSP in a long-period (512 days) orbit and has an optical counterpart identified in archival data. PSR J0636+5129 is an MSP in a very short-period (96 minutes) orbit with a very low mass companion (8 M J). PSR J0645+5158 is an isolated MSP with a timing residual RMS of 500 ns and has been added to pulsar timing array experiments. PSR J1434+7257 is an isolated, intermediate-period pulsar that has been partially recycled. PSR J1816+4510 is an eclipsing MSP in a short-period orbit (8.7 hr) and may have recently completed its spin-up phase.
202 citations
National Radio Astronomy Observatory1, University of British Columbia2, ASTRON3, McGill University4, University of Amsterdam5, University of Wisconsin-Madison6, University of Wisconsin–Milwaukee7, University of Toronto8, Western Kentucky University9, West Virginia University10, Cornell University11, Lebedev Physical Institute12, New York University13, University of Texas at Brownsville14, University of New Mexico15
TL;DR: In this article, a millisecond pulsar, a white dwarf, and a planetary-mass object in an orbit of a few decades was observed in a hierarchical triplesystem with two other stars.
Abstract: (with a millisecond pulsar, a white dwarf, and a planetary-mass object in an orbit of sev-eral decades), shows only weak interactions. Here we report precision timing and multi-wavelength observations of PSR J0337+1715, a millisecond pulsar in a hierarchical triplesystem with two other stars. Strong gravitational interactions are apparent and providethe masses of the pulsar (1.4378(13)M , where M is the solar mass and the parenthesescontain the uncertainty in the final decimal places) and the two white dwarf companions(0.19751(15)M and 0.4101(3)M ), as well as the inclinations of the orbits (both ˘39.2
147 citations
University of Texas at Brownsville1, University of New Mexico2, University of Texas at San Antonio3, McGill University4, National Radio Astronomy Observatory5, ASTRON6, University of Wisconsin–Milwaukee7, Syracuse University8, Western Kentucky University9, University of Amsterdam10, University of Wisconsin-Madison11, Lebedev Physical Institute12, West Virginia University13, University of British Columbia14, Colorado State University15
Abstract: We describe an ongoing search for pulsars and dispersed pulses of radio emission, such as those from rotating radio transients (RRATs) and fast radio bursts (FRBs), at 350 MHz using the Green Bank Telescope. With the Green Bank Ultimate Pulsar Processing Instrument, we record 100 MHz of bandwidth divided into 4,096 channels every 81.92 $\mu s$. This survey will cover the entire sky visible to the Green Bank Telescope ($\delta > -40^\circ$, or 82% of the sky) and outside of the Galactic Plane will be sensitive enough to detect slow pulsars and low dispersion measure ($<$30 $\mathrm{pc\,cm^{-3}}$) millisecond pulsars (MSPs) with a 0.08 duty cycle down to 1.1 mJy. For pulsars with a spectral index of $-$1.6, we will be 2.5 times more sensitive than previous and ongoing surveys over much of our survey region. Here we describe the survey, the data analysis pipeline, initial discovery parameters for 62 pulsars, and timing solutions for 5 new pulsars. PSR J0214$+$5222 is an MSP in a long-period (512 days) orbit and has an optical counterpart identified in archival data. PSR J0636$+$5129 is an MSP in a very short-period (96 minutes) orbit with a very low mass companion (8 $M_\mathrm{J}$). PSR J0645$+$5158 is an isolated MSP with a timing residual RMS of 500 ns and has been added to pulsar timing array experiments. PSR J1434$+$7257 is an isolated, intermediate-period pulsar that has been partially recycled. PSR J1816$+$4510 is an eclipsing MSP in a short-period orbit (8.7 hours) and may have recently completed its spin-up phase.
103 citations
TL;DR: In this paper, the first X-ray observations of five short orbital period (PB < 1 day), γ-ray emitting, binary millisecond pulsars (MSPs).
Abstract: We describe the first X-ray observations of five short orbital period (PB < 1 day), γ-ray emitting, binary millisecond pulsars (MSPs). Four of these—PSRs J0023+0923, J1124–3653, J1810+1744, and J2256–1024—are "black-widow" pulsars, with degenerate companions of mass 0.1 M ☉, three of which exhibit radio eclipses. The fifth source, PSR J2215+5135, is an eclipsing "redback" with a near Roche-lobe filling ~0.2 solar mass non-degenerate companion. Data were taken using the Chandra X-Ray Observatory and covered a full binary orbit for each pulsar. Two pulsars, PSRs J2215+5135 and J2256–1024, show significant orbital variability while PSR J1124–3653 shows marginal orbital variability. The lightcurves for these three pulsars have X-ray flux minima coinciding with the phases of the radio eclipses. This phenomenon is consistent with an intrabinary shock emission interpretation for the X-rays. The other two pulsars, PSRs J0023+0923 and J1810+1744, are fainter and do not demonstrate variability at a level we can detect in these data. All five spectra are fit with three separate models: a power-law model, a blackbody model, and a combined model with both power-law and blackbody components. The preferred spectral fits yield power-law indices that range from 1.3 to 3.2 and blackbody temperatures in the hundreds of eV. The spectrum for PSR J2215+5135 shows a significant hard X-ray component, with a large number of counts above 2 keV, which is additional evidence for the presence of intrabinary shock emission. This is similar to what has been detected in the low-mass X-ray binary to MSP transition object PSR J1023+0038.
101 citations
Columbia University1, University of California, Los Angeles2, Washington University in St. Louis3, Harvard University4, University of Delaware5, University College Dublin6, University of California, Santa Cruz7, University of Potsdam8, Adler Planetarium9, National University of Ireland, Galway10, Purdue University11, University of Minnesota12, University of Chicago13, Pennsylvania State University14, McGill University15, University of Iowa16, George Washington University17, DePauw University18, University of Utah19, Iowa State University20, Anderson University (South Carolina)21, Galway-Mayo Institute of Technology22, Georgia Institute of Technology23, Grand Valley State University24, California Polytechnic State University25, Cork Institute of Technology26, Argonne National Laboratory27
TL;DR: In this article, very high energy (VHE) imaging of MGRO J2019+37 obtained with the VERITAS observatory is presented, where the authors explore the unusual spectrum and morphology in the radio and X-ray bands to constrain possible emission mechanisms for this source.
Abstract: We present very high energy (VHE) imaging of MGRO J2019+37 obtained with the VERITAS observatory. The bright extended (~2°) unidentified Milagro source is located toward the rich star formation region Cygnus-X. MGRO J2019+37 is resolved into two VERITAS sources. The faint, point-like source VER J2016+371 overlaps CTB 87, a filled-center remnant (SNR) with no evidence of a supernova remnant shell at the present time. Its spectrum is well fit in the 0.65-10 TeV energy range by a power-law model with photon index 2.3 ± 0.4. VER J2019+378 is a bright extended (~1°) source that likely accounts for the bulk of the Milagro emission and is notably coincident with PSR J2021+3651 and the star formation region Sh 2–104. Its spectrum in the range 1-30 TeV is well fit with a power-law model of photon index 1.75 ± 0.3, among the hardest values measured in the VHE band, comparable to that observed near Vela-X. We explore the unusual spectrum and morphology in the radio and X-ray bands to constrain possible emission mechanisms for this source.
71 citations
TL;DR: In this article, radio eclipses, X-ray emission, and the potential for γ-ray emissions have been studied in close (Pb < 1 day) binary systems with millisecond pulsars.
Abstract: Eclipsing millisecond pulsars in close (Pb < 1 day) binary systems provide a different view of pulsar winds and shocks than do isolated pulsars. Since 2009, the numbers of these systems known in the Galactic field has increased enormously. We have been systematically studying many of these newly discovered systems at multiple wavelengths. Typically, the companion is nearly Roche-lobe filling and heated by the pulsar which drives mass loss from the companion. The pulsar wind shocks with this material just above the surface of the companion. We discuss various observational properties of this shock, including radio eclipses, orbitally modulated X-ray emission, and the potential for γ-ray emission. Redbacks, whose companions are likely non-degenerate and significantly more massive, generally have more luminous shocks than black widows which have very low mass companions. This is expected since the more massive redback companions intercept a greater fraction of the pulsar wind. We also compare these systems to accreting millisecond pulsars, which may be progenitors of black widows and in some cases can pass back and forth between redback and accretion phases.
30 citations
TL;DR: In this paper, radio eclipses, X-ray emission, and the potential for gamma-gamma$-ray emissions of millisecond pulsars have been studied at multiple wavelengths.
Abstract: Eclipsing millisecond pulsars in close ($P_b < 1$~day) binary systems provide a different view of pulsar winds and shocks than do isolated pulsars. Since 2009, the numbers of these systems known in the Galactic field has increased enormously. We have been systematically studying many of these newly discovered systems at multiple wavelengths. Typically, the companion is nearly Roche-lobe filling and heated by the pulsar which drives mass loss from the companion. The pulsar wind shocks with this material just above the surface of the companion. We discuss various observational properties of this shock, including radio eclipses, orbitally modulated X-ray emission, and the potential for $\gamma$-ray emission. Redbacks, whose companions are likely non-degenerate and significantly more massive, generally have more luminous shocks than black widows which have very low mass companions. This is expected since the more massive redback companions intercept a greater fraction of the pulsar wind. We also compare these systems to accreting millisecond pulsars, which may be progenitors of black widows and in some cases can pass back and forth between redback and accretion phases.
18 citations