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Many physically motivated extensions to general relativity (GR) predict substantial deviations in the properties of spacetime surrounding massive neutron stars. We report the measurement of a 2.01 ± 0.04 solar mass (M⊙) pulsar in a 2.46-hour orbit with a 0.172 ± 0.003 M⊙ white dwarf. The high pulsar mass and the compact orbit make this system a sensitive(More)
Radio pulsars with millisecond spin periods are thought to have been spun up by the transfer of matter and angular momentum from a low-mass companion star during an x-ray-emitting phase. The spin periods of the neutron stars in several such low-mass x-ray binary (LMXB) systems have been shown to be in the millisecond regime, but no radio pulsations have(More)
We analyse the stochastic properties of the 49 pulsars that comprise the first International Pulsar Timing Array (IPTA) data release. We use Bayesian methodology, performing model selection to determine the optimal description of the stochastic signals present in each pulsar. In addition to spin-noise and dispersion-measure (DM) variations, these models can(More)
A survey of weak Mg ii absorbers at redshift z = 1.78 ABSTRACT The exact nature of weak Mg ii absorbers (those with W r (2796) < 0.3 ˚ A) is a matter of debate, but most are likely related to areas of local star formation or supernovae activity outside of giant galaxies. Using 18 QSO spectra obtained with the UltraViolet Echelle Spectrograph (UVES) on the(More)
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. ABSTRACT We have made extensive observations of 35 distant slow(More)
Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the(More)
We consider the evolution of strong (W r (2796) > 0.3 ˚ A) Mg ii absorbers, most of which are closely related to luminous galaxies. Using 20 high resolution quasar spectra from the VLT/UVES public archive, we examine 33 strong Mg ii absorbers in the redshift range 0.3 < z < 2.5. We compare and supplement this sample with 23 strong Mg ii absorbers at 0.4 < z(More)
We present the results of a survey of the analogs of weak Mgii absorbers (rest– frame equivalent width W r (2796) < 0.3 ˚ A) at 0 < z < 0.3. Our sample consisted of 25 HST/STIS echelle quasar spectra (R = 45, 000) which covered Siii 1260 and Cii 1335 over this redshift range. Using those similar transitions as tracers of Mg ii facilitates a much larger(More)