arXiv subjects

Ingrid H. Stairs

Publications and source records attributed to Ingrid H. Stairs.

118 records · Page 7Linked to original sources

arXiv2004

GBT Observations of Very Low Mass Binary Millisecond Pulsars: A Search for Eclipses

We searched for eclipses of two millisecond pulsars, PSR J1807-2459 and PSR B1908+00. These pulsars are in very low mass binary systems with orbital parameters similar to those of eclipsing binaries. Observations were made with the GBT at frequencies as low as 575 MHz. No eclipses were detected in either system. Observations of well-established eclipsing binary J2051-0827 found eclipses to be substantially weaker than previously seen, with the pulsar detected throughout the eclipse region at 575 MHz and with an electron column density an order of magnitude smaller than previously measured.

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arXiv2004

Masses, Parallax, and Relativistic Timing of the PSR J1713+0747 Binary System

We report on 12 years of observations of PSR J1713+0747, a pulsar in a 68-day orbit with a white dwarf. Pulse times of arrival were measured with uncertainties as small as 200 ns. The timing data yielded measurements of the relativistic Shapiro delay, perturbations of pulsar orbital elements due to secular and annual motion of the Earth, and the pulsar's parallax, as well as pulse spin-down, astrometric, and Keplerian measurements. The observations constrain the masses of the pulsar and secondary star to be m1=1.3+-0.2 solar masses and m2=0.28+-0.03 solar masses, respectively (68% confidence). Combining the theoretical orbital period-core mass relation with the observational constraints yields a somewhat higher pulsar mass, m1=1.53-0.06+0.08 solar masses. The parallax is 0.89+-0.08 mas, corresponding to a distance of 1.1+-0.1 kpc; the precision of the parallax measurement is limited by uncertainties in the electron content of the solar wind. The transverse velocity is unusually small, 33+-3 km/s. We find significant timing noise on time scales of several years, but no more than expected by extrapolating timing noise statistics from the slow pulsar population. With the orientation of the binary orbit fully measured, we are able to improve on previous tests of equivalence principle violations.

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arXiv2004

A 20 cm Search for Pulsars in Globular Clusters with Arecibo and the GBT

We are conducting deep searches for radio pulsations at L-band (~ 20cm) towards more than 30 globular clusters using the 305m Arecibo telescope in Puerto Rico and the 100m Green Bank Telescope in West Virginia. With roughly three quarters of our search data analyzed, we have discovered 12 new millisecond pulsars, 11 of which are in binary systems, and at least three of which eclipse. We have timing solutions for several of these systems.

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arXiv2003

GBT Discovery of Two Binary Millisecond Pulsars in the Globular Cluster M30

We report the discovery of two binary millisecond pulsars in the core-collapsed globular cluster M30 using the Green Bank Telescope (GBT) at 20 cm. PSR J2140-2310A (M30A) is an eclipsing 11-ms pulsar in a 4-hr circular orbit and PSR J2140-23B (M30B) is a 13-ms pulsar in an as yet undetermined but most likely highly eccentric (e>0.5) and relativistic orbit. Timing observations of M30A with a 20-month baseline have provided precise determinations of the pulsar's position (within 4" of the optical centroid of the cluster), and spin and orbital parameters, which constrain the mass of the companion star to be m_2 >~ 0.1Msun. The position of M30A is coincident with a possible thermal X-ray point source found in archival Chandra data which is most likely due to emission from hot polar caps on the neutron star. In addition, there is a faint (V_555 ~ 23.8) star visible in archival HST F555W data that may be the companion to the pulsar. Eclipses of the pulsed radio emission from M30A by the ionized wind from the compact companion star show a frequency dependent duration (\proptoν^{-α} with α~ 0.4-0.5) and delay the pulse arrival times near eclipse ingress and egress by up to 2-3 ms. Future observations of M30 may allow both the measurement of post-Keplerian orbital parameters from M30B and the detection of new pulsars due to the effects of strong diffractive scintillation.

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arXiv2003

Heavy Neutron Stars? A Status Report on Arecibo Timing of Four Pulsar-White Dwarf Systems

Relativistic phenomena (orbital precession, Shapiro delay, and/or orbital decay) have been measured in Arecibo timing observations of four pulsar-white dwarf binaries, leading to constraints on the neutron star masses. We have detected the decay of the PSR J0751+1807 orbit due to gravitational radiation emission, the first such measurement in a binary with a low mass ratio (m_2/m_1<<1). Timing data constrains the mass of this pulsar to bet between 1.6 and 2.8 solar masses. Masses of the other pulsars are in marginal agreement with the canonical pulsar mass of 1.35 solar masses, but higher values are preferred.

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arXiv2003

Testing General Relativity with Pulsar Timing

Pulsars of very different types - isolated objects, and binaries with short- and long-period orbits, white-dwarf and neutron-star companions - provide the means to test both the predictions of general relativity and the viability of alternate theories of gravity. This article presents an overview of pulsars, then discusses the current status and future prospects of tests of equivalence principle violations and strong-field gravitational experiments.

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arXiv2003

A Young White Dwarf Companion to Pulsar 1620-26: Evidence for Early Planet Formation

The pulsar B1620-26 has two companions, one of stellar mass and one of planetary mass. We detected the stellar companion using Hubble Space Telescope observations. The color and magnitude of the stellar companion indicate that it is an undermassive white dwarf ($0.34 \pm 0.04 M_{\odot}$) of age $480\pm 140$ Myr. This places a constraint on the recent history of this triple system and supports a scenario in which the current configuration arose through a dynamical exchange interaction in the cluster core. This implies that planets may be relatively common in low-metallicity globular clusters and that planet formation is more widespread and happened earlier than previously believed.

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arXiv2002

Neutron Star Masses from Arecibo Timing Observations of Five Pulsar-White Dwarf Binary Systems

We have detected relativistic and/or kinematic post-Keplerian parameters of no fewer than five pulsar-white dwarf binary systems in long-term timing observations at Arecibo. We discuss the resulting constraints on pulsar and companion masses. The general trend is that the pulsar mass measurements are compatible with the canonical value of 1.35 solar masses, but in most cases somewhat higher masses are preferred.

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arXiv2002

Probing the Masses of the PSR J0621+1002 Binary System Through Relativistic Apsidal Motion

Orbital, spin and astrometric parameters of the millisecond pulsar PSR J0621+1002 have been determined through six years of timing observations at three radio telescopes. The chief result is a measurement of the rate of periastron advance, omega_dot = 0.0116 +/- 0.0008 deg/yr. Interpreted as a general relativistic effect, this implies the sum of the pulsar mass, m_1, and the companion mass, m_2, to be M = m_1 + m_2 = 2.81 +/- 0.30 msun. The Keplerian parameters rule out certain combinations of m_1 and m_2, as does the non-detection of Shapiro delay in the pulse arrival times. These constraints, together with the assumption that the companion is a white dwarf, lead to the 68% confidence maximum likelihood values of m_1 = 1.70(+0.32 -0.29) msun and m_2 =0.97(+0.27 - 0.15) msun and to the 95% confidence maximum likelihood values of m_1 = 1.70(+0.59 -0.63) msun and m_2 = 0.97(+0.43 -0.24) msun. The other major finding is that the pulsar experiences dramatic variability in its dispersion measure (DM), with gradients as steep as 0.013 pc cm^{-3} / yr. A structure function analysis of the DM variations uncovers spatial fluctuations in the interstellar electron density that cannot be fit to a single power law, unlike the Kolmogorov turbulent spectrum that has been seen in the direction of other pulsars. Other results from the timing analysis include the first measurements of the pulsar's proper motion, mu = 3.5 +/- 0.3 mas / yr, and of its spin-down rate, dP/dt = 4.7 x 10^{-20}, which, when corrected for kinematic biases and combined with the pulse period, P = 28.8 ms, gives a characteristic age of 1.1 x 10^{10} yr and a surface magnetic field strength of 1.2 x 10^{9} G.

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arXiv2000

On the Mass and Inclination of the PSR J2019+2425 Binary System

We report on nine years of timing observations of PSR J2019+2425, a millisecond pulsar in a wide 76.5 day orbit with a white dwarf. We measure a significant change over time of the projected semi-major axis of the orbit, x-dot/x=(1.3+-0.2)x10^-15 s^-1, where x=(a sin i)/c. We attribute this to the proper motion of the binary. This constrains the inclination angle to i<72 degrees, with a median likelihood value of 63 degrees. A similar limit on inclination angle arises from the lack of a detectable Shapiro delay signal. These limits on inclination angle, combined with a model of the evolution of the system, imply that the neutron star mass is at most 1.51 solar masses; the median likelihood value is 1.33 solar masses. In addition to these timing results, we present a polarization profile of this source. Fits of the linear polarization position angle to the rotating vector model indicate the magnetic axis is close to alignment with the rotation axis, alpha<30 degrees.

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