Search

Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances (1-8). Previous follow-up observations have failed to find additional bursts at [...]

Asymmetry is required by most numerical simulations of stellar core-collapse explosions, but the form it takes differs significantly among models. The spatial distribution of radioactive [sup.44]Ti, synthesized in an exploding star near the boundary between material falling back onto the collapsing core and that ejected into the surrounding medium (1), directly probes the explosion asymmetries. Cassiopeia A is a young (2), nearby (3), core-collapse (4) remnant from which [sup.44]Ti emission has previously been detected (5-8) but not imaged. Asymmetries in the explosion have been indirectly inferred from a high ratio of observed [sup.44]Ti emission to estimated [sup.56]Ni emission (9), from optical light echoes (10), and from jet-like features seen in the X-ray (11) and optical (12) ejecta. Here we report spatial maps and spectral properties of the [sup.44]Ti in Cassiopeia A. This may explain the unexpected lack of correlation between the [sup.44]Ti and iron X-ray emission, the latter being visible only in shock-heated material. The observed spatial distribution rules out symmetric explosions even with a high level of convective mixing, as well as highly asymmetric bipolar explosions resulting from a fast-rotating progenitor. Instead, these observations provide strong evidence for the development of low-mode convective instabilities in core-collapse supernovae., Titanium-44 is produced in Si burning in the innermost regions of the material ejected in core-collapse supernovae, in the same processes that produce Fe and [56.sup]Ni (ref. 13). The decay [...]

Gravitationally bound three-body systems have been studied for hundreds of years (1,2) and are common in our Galaxy (3,4). They show complex orbital interactions, which can constrain the compositions, masses and interior structures of the bodies (5) and test theories of gravity (6), 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 ahierarchical triple system with two other stars. Strong gravitational interactions are apparent and provide the masses of the pulsar (1.4378(13)[M.sub.[dot in a circle]], where [M.sub.[dot in a circle]] is the solar mass and the parentheses contain the uncertainty in the final decimal places) and the two white dwarf companions (0.19751(15)[M.sub.[dot in a circle]] and 0.4101(3)[M.sub.[dot in a circle]]), 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., Millisecond pulsars (MSPs) are neutron stars that rotate hundreds of times per second and emit beams of radio waves much as a lighthouse emits light. They are thought to form [...]

Magnetars are neutron stars with X-ray and soft γ-ray outbursts thought to be powered by intense internal magnetic fields (1). Like conventional neutron stars in the form of radio pulsars, [...]

We have detected an x-ray nebula around the binary millisecond pulsar B1957+20. A narrow tail corresponding to the shocked pulsar wind, is seen interior to the known Hα bow shock [...]

Misalignment of the angular momentum of the pulsar PSR J0045 - 7319 that is revolving around a B star provides evidence for birth kicks to neutron stars by supernova explosions that form the stars. Radio studies of the pulsar shows that the B star's spin axis is inclined at between a 25 and 41 degree angle rather than the 44 plus or minus 5 degrees expected for the orbital angular momentum vector. Angular momenta of the system were aligned before the supernova explosion due to tidal effects and mass transfer or primordial effects. Misalignment after the explosion is probably due to the kick velocity of the neutron star induced by the explosion.

The pulsar PSR J0437-4715 was first recorded on Feb 13, 1992, and confirmed on Jul 11 as possibly the closest pulsar to the Earth during a survey for millisecond pulsars in the southern sky. A possible optical companion has been determined because of no other stars are close to the radio signal. This pulsar can be used to confirm or deny the theory that millisecond pulsars generate gamma rays and contribute to the galactic gamma ray background.

PSR1706-44 is the fourth radio pulsar to be identified as a source of pulsed gamma-radiation. PSR1706-44's gamma rays, measured at more than 100 MeV in energy and with a pulse period of 102 minutes, are emitted as one broad peak rather than as two narrow peaks as with the other three radio pulsars. The geometry of the magnetic and rotation axes and the line of sight probably accounts for this difference. Further research on gamma-radiation emissions from these pulsars is needed since such radiation comprises at least 1% of total neutron-star spin-down energy.