[PPT]PowerPoint Presentation - Landing Page | The Arecibo...

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Text text text. Introduction Long-term timing of two faint millisecond pulsars at Arecibo Paulo C. C. Freire (Arecibo Observatory / West Virginia University), for the NANOGrav Collaboration The two millisecond pulsars (MSPs) described here, J1738+0333 and J1741+1351,were discovered in 2001 in a Parkes survey of the intermediate Galactic latitudes. These MSPs were amongst the faintest discovered in that survey. Both objects can be seen with the Arecibo radio telescope. The sensitivity provided by this telescope has now made these two of the most precisely timed pulsars ever: averaging the Times of Arrival of the pulses (TOAs) for 100 MHz and 1 hour, we get weighted r.m.s. residuals of 200 and 110 ns for J1738+0333 and PSR J1741+1351 respectively. These values make these objects valuable for the detection of gravitational waves. These pulsars demonstrate the capacity of the Arecibo telescope to produce useful scientific results with pulsars that are too faint to be timed with other radio telescopes. These objects are interesting studies in themselves -> NANOGrav PSR J1738+0333 is in a binary system with an orbital period of 8.5 hours. The orbital eccentricity is smaller than 0.0000001 – the orbit does not deviate from a circle by more than ~2 μm. The white dwarf companion of this pulsar has been detected at optical wavelengths. The orbital variability of its redshift allowed a measurement of its mass ratio: R = m P /M WD = 8.1 +/- 0.3. Arecibo timing carried out since 2003 has shown that the orbit appears to become shorter by (1.7 +/- 0.10) x 10 -14 s/s, i.e., the orbital period decreases by about 0.5 μs per year. The timing also allows a precise determination of the proper motion and parallax. Subtracting the kinetic effect of the pulsar's velocity and the Galactic potential, we obtain the orbital decay due to the emission of gravitational waves: -(2.5 +/- 0.10) x 10 -14 s/s. Above : Mass-mass diagram for the PSR J1738+0333 binary system. The component masses are more likely to be located at the intersection of the regions limited by the mass ratio measurement (R, with +/- 1 σ) and the relativistic orbital decay (calculated assuming GR applies, also +/- 1 σ). Note that the pulsar mass is similar to the masses derived for neutron stars in double neutron star systems (green bar). An independent determination of mass of the companion of PSR J1738+0333 (which is, unfortunately, not possible to determine from the Shapiro delay, given the low orbital inclination i) could make this one of the best laboratories for testing gravitational theories: the system would then impose very strong constraints on the emission of dipolar gravitational waves, which are predicted by alternative theories of gravitation. Left : Companion mass – cos i plot for PSR J1741+1351. The contours include 99.7, 95.4 and 68.3 % of all probability, the constraints are derived from a measurement of the Shapiro delay for this 16.3-day binary system. The companion appears to have a mass of 0.27 +/- 0.02 M (1 -σ) and the pulsar a mass of 1.55 +/- 0.15 M (1-σ). Above : Pulse profiles for the two MSPs. The presence of sharp features allows for precise timing.

Transcript of [PPT]PowerPoint Presentation - Landing Page | The Arecibo...

Text text text.

Introduction

Long-term timing of two faint millisecond pulsars at AreciboPaulo C. C. Freire (Arecibo Observatory / West Virginia University),

for the NANOGrav Collaboration

•The two millisecond pulsars (MSPs) described here, J1738+0333 and J1741+1351,were discovered in 2001 in a Parkes survey of the intermediate Galactic latitudes. These MSPs were amongst the faintest discovered in that survey.•Both objects can be seen with the Arecibo radio telescope. The sensitivity provided by this telescope has now made these two of the most precisely timed pulsars ever: averaging the Times of Arrival of the pulses (TOAs) for 100 MHz and 1 hour, we get weighted r.m.s. residuals of 200 and 110 ns for J1738+0333 and PSR J1741+1351 respectively. These values make these objects valuable for the detection of gravitational waves.•These pulsars demonstrate the capacity of the Arecibo telescope to produce useful scientific results with pulsars that are too faint to be timed with other radio telescopes. These objects are interesting studies in themselves ->

NANOGrav

• PSR J1738+0333 is in a binary system with an orbital period of 8.5 hours. The orbital eccentricity is smaller than 0.0000001 – the orbit does not deviate from a circle by more than ~2 μm.• The white dwarf companion of this pulsar has been detected at optical wavelengths. The orbital variability of its redshift allowed a measurement of its mass ratio:

R = mP/MWD = 8.1 +/- 0.3.•Arecibo timing carried out since 2003 has shown that the orbit appears to become shorter by (1.7 +/- 0.10) x 10-14 s/s, i.e., the orbital period decreases by about 0.5 μs per year.•The timing also allows a precise determination of the proper motion and parallax. Subtracting the kinetic effect of the pulsar's velocity and the Galactic potential, we obtain the orbital decay due to the emission of gravitational waves: -(2.5 +/- 0.10) x 10-14 s/s.

•Above : Mass-mass diagram for the PSR J1738+0333 binary system. The component masses are more likely to be located at the intersection of the regions limited by the mass ratio measurement (R, with +/- 1 σ) and the relativistic orbital decay (calculated assuming GR applies, also +/- 1 σ). Note that the pulsar mass is similar to the masses derived for neutron stars in double neutron star systems (green bar).•An independent determination of mass of the companion of PSR J1738+0333 (which is, unfortunately, not possible to determine from the Shapiro delay, given the low orbital inclination i) could make this one of the best laboratories for testing gravitational theories: the system would then impose very strong constraints on the emission of dipolar gravitational waves, which are predicted by alternative theories of gravitation.•Left : Companion mass – cos i plot for PSR J1741+1351. The contours include 99.7, 95.4 and 68.3 % of all probability, the constraints are derived from a measurement of the Shapiro delay for this 16.3-day binary system. The companion appears to have a mass of 0.27 +/- 0.02 M⊙ (1 -σ) and the pulsar a mass of 1.55 +/- 0.15 M⊙ (1-σ).

•Above : Pulse profiles for the two MSPs. The presence of sharp features allows for precise timing.