John M. Sarkissian

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On 4 July 2005, many observatories around the world and in space observed the collision of Deep Impact with comet 9P/Tempel 1 or its aftermath. This was an unprecedented coordinated observational campaign. These data show that (i) there was new material after impact that was compositionally different from that seen before impact; (ii) the ratio of dust mass(More)
Anomalous X-ray pulsars (AXPs) are slowly rotating neutron stars with very bright and highly variable X-ray emission that are believed to be powered by ultra-strong magnetic fields of >10(14) G, according to the 'magnetar' model. The radio pulsations that have been observed from more than 1,700 neutron stars with weaker magnetic fields have never been(More)
Analysis of ten years of high-precision timing data on the millisecond pulsar PSR J0437−4715 has resulted in a model-independent kinematic distance based on an apparent orbital period derivative, ˙ P b , determined at the 1.5% level of precision (D k = 157.0±2.4 pc), making it one of the most accurate stellar distance estimates published to date. The(More)
A new technique of reduction clitoroplasty is presented. The procedure consists of a subtotal resection of the shaft of the clitoris with preservation of the dorsal neurovascular bundle of the glans. The purpose is to preserve erogenous glans clitoris and the erection of the crura. The anatomical results in 8 patients were excellent; partial necrosis(More)
We present radio observations of comet 9P/Tempel 1 associated with the Deep Impact spacecraft collision of 2005 July 4. Weak 18-cm OH emission was detected with the Parkes 64-m telescope, in data averaged over July 4 to 6, at a level of 12 ± 3 mJy km/s, corresponding to OH production rate 2.8 × 10 28 molecules/second (Despois et al. inversion model, or 1.0(More)
The merger of close binary systems containing two neutron stars should produce a burst of gravitational waves, as predicted by the theory of general relativity. A reliable estimate of the double-neutron-star merger rate in the Galaxy is crucial in order to predict whether current gravity wave detectors will be successful in detecting such bursts. Present(More)
The double pulsar system PSR J0737-3039A/B is unique in that both neutron stars are detectable as radio pulsars. They are also known to have much higher mean orbital velocities and accelerations than those of other binary pulsars. The system is therefore a good candidate for testing Einstein's theory of general relativity and alternative theories of gravity(More)
Using a statistically rigorous analysis method, we place limits on the existence of an isotropic stochastic gravitational wave background using pulsar timing observations. We consider backgrounds whose characteristic strain spectra may be described as a power-law dependence with frequency. Such backgrounds include an astrophysical background produced by(More)
A 'pulsar timing array' (PTA), in which observations of a large sample of pulsars spread across the celestial sphere are combined, allows investigation of 'global' phenomena such as a background of gravitational waves or instabilities in atomic timescales that produce correlated timing residuals in the pulsars of the array. The Parkes Pulsar Timing Array(More)
Binary pulsars provide an excellent system for testing general relativity because of their intrinsic rotational stability and the precision with which radio observations can be used to determine their orbital dynamics. Measurements of the rate of orbital decay of two pulsars have been shown to be consistent with the emission of gravitational waves as(More)