1,721,070 research outputs found
Discovery of short-period binary millisecond pulsars in four globular clusters
No full textWe report the discovery, using the Parkes radio telescope, of binary millisecond pulsars in four clusters for which no associated pulsars were previously known. The four pulsars have pulse periods lying between 3 and 6 ms. All are in circular orbits with low-mass companions and have orbital periods of a few days or less. One is in a 1.7 hr orbit with a companion of planetary mass. Another is eclipsed by a wind from its companion for 40% of the binary period despite being in a relatively wide orbit. These discoveries result from the use of improved technologies and prove that many millisecond pulsars remain to be found in globular clusters
Three binary millisecond pulsars in NGC 6266
No full textWe present rotational and astrometric parameters of three millisecond pulsars located near the center of the globular cluster NGC 6266 (M62), resulting from timing observations with the Parkes radio telescope. Their accelerations toward the cluster center yield values of the cluster central density and mass-to-light ratio consistent with those derived from optical data. The three pulsars are in binary systems. One (spin period P = 5.24 ms) is in a 3.5 day orbit around a companion of minimum mass 0.2 M-circle dot. The other two millisecond pulsars (P = 3.59 and 3.81 ms) have shorter orbital periods (3.4 and 5.0 hr) and lighter companions (minimum masses of 0.12 and 0.07 M-circle dot, respectively). The pulsar in the closest system is the fifth member of an emerging class of millisecond pulsars displaying irregular radio eclipses and having a relatively massive companion. This system is a good candidate for optical identification of the companion star. The lack of known isolated pulsars in NGC 6266 is also discussed
The 69 millisecond radio pulsar near the supernova remnant RCW 103
No full textWe report the detection of the radio pulsar counterpart to the 69 ms X-ray pulsar discovered near the supernova remnant RCW 103 (G332.4-0.4). Our detection confirms that the pulsations arise from a rotation-powered neutron star, which we name PSR J1617-5055. The observed barycentric period derivative confirms that the pulsar has a characteristic age of only 8 kyr, the sixth youngest of all known pulsars. The unusual apparent youth of the pulsar and its proximity to a young remnant require that an association be considered. Although the respective ages and distances are consistent within substantial uncertainties, the large inferred pulsar transverse velocity is difficult to explain given the observed pulsar velocity distribution, the absence of evidence for a pulsar wind nebula, and the symmetry of the remnant. Rather, we argue that the objects are likely superposed on the sky; this is reasonable given the complex area. Without an association, the question of where is the supernova remnant left behind following the birth of PSR J1617-5055 remains open. We also discuss a possible association between PSR J1617-5055 and the gamma-ray source 2CG 333+01. Although an association is energetically plausible, it is unlikely given that EGRET did not detect 2CG 333+01
An eclipsing millisecond pulsar with a possible main-sequence companion in NGC 6397
No full textWe present the results of 1 yr of pulse timing observations of PSR J1740-5340, an eclipsing millisecond pulsar located in the globular cluster NGC 6397. We have obtained detailed orbital parameters and a precise position for the pulsar. The radio pulsar signal shows frequent interactions with the atmosphere of the companion and suffers significant and strongly variable delays and intensity variations over a wide range of orbital phases. These characteristics and the binary parameters indicate that the companion may be a bloated main-sequence star or the remnant (still overflowing its Roche lobe) of the star that spun up the pulsar. In both cases, this would be the first binary millisecond pulsar system known with such a companion
Timing of Millisecond Pulsars in NGC 6752. II. Proper Motions of the Pulsars in the Cluster Outskirts
No full textExploiting a 5 year span of data, we present improved timing solutions for the five millisecond pulsars known in the globular cluster NGC 6752. These include proper-motion determinations for the two outermost pulsars in the cluster, PSR J1910-5959Aand PSR J1910-5959C. The values of the proper motions are in agreement with each other within current luncertainties, but they do not match (at the 4 sigma and 2 sigma levels, respectively) the value of the proper motion of the entire globular cluster derived in the optical band. The implications of these results for the clustermembership of the two pulsars are investigated. Prospects for the detection of the Shapiro delay in the binary system J1910-5959A are also discussed
Further results from the timing of the millisecond pulsars in 47 Tucanae
No full textWe have been observing the millisecond pulsars in the globular cluster 47 Tucanae (47 Tuc) at the Parkes radio telescope since 1999 August with threefold higher time-resolution than hitherto possible. We present the results in this paper, including: improved 1400-MHz pulse profiles; one new timing solution, for PSR J0024-7204S, which imposes stringent constraints on the acceleration model for 47 Tucanae and implies a projected mass-to-light ratio >1.4 M-circle dot/L-circle dot at the centre of the cluster; refined estimates for the five previously determined proper motions; and newly determined proper motions for six pulsars. We have detected, for the first time, relative motions between the pulsars. We have detected a second period derivative for the pulsar in the PSR J0024-7204H binary system, which could indicate the presence of a third nearby object, and improved measurement of the rate of advance of periastron of this pulsar, which yields a total system mass of 1.61+/-0.04 M-circle dot. We also have determined upper limits for the masses of any hypothetical planets orbiting the pulsars in 47 Tuc. PSR J0023-7203J shows variations of dispersion measure (DM) as a function of orbital phase with a total column density at superior conjunction of about 1.7x10(16) cm(-2), 10 times smaller than observed for a similar system in the Galaxy. We interpret the small value as being due to a smaller inclination of the orbit of PSR J0023-7203J. We find that the DM variation with orbital phase changes with time, and we detect material at more than 90degrees (in orbital phase) from the companion. PSR J0024-7204O also shows variations of DM with orbital phase, but these are restricted to phases near the eclipse. This binary system displays significant monotonic variation of its orbital period: (P)over dot(b)=(9+/-1)x10(-12). This is probably due to spin-orbit coupling; this effect seems to be significantly smaller for PSR J0023-7203J
Discovery of two high magnetic field radio pulsars
No full textWe report the discovery of two young isolated radio pulsars with very high inferred magnetic fields. PSR J1119-6127 has period P = 0.407 s, and the largest period derivative known among radio pulsars, P = 4.0 x 10(-12). Under standard assumptions these parameters imply a characteristic spin-down age of only tau(c) = 1.6 kyr and a surface dipole magnetic field strength of B = 4.1 x 10(13) G. We have measured a stationary period second derivative for this pulsar, resulting in a braking index of n = 2.91 +/- 0.05. We have also observed a glitch in the rotation of the pulsar, with fractional period change Delta P/P = -4.4 x 10(-9). Archival radio imaging data suggest the presence of a previously uncataloged supernova remnant centered on the pulsar. The second pulsar, PSR J1814-1744 has P = 3.975 s and P = 7.4 x 10(-13). These parameters imply tau(c) = 85 kyr, and B = 5.5 x 1013 G, the largest of any known radio pulsar. Both PSR J1119-6127 and PSR J1814-1744 show apparently normal radio emission in a regime of magnetic field strength where some models predict that no emission should occur. Also, PSR J1814-1744 has spin parameters similar to the anomalous X-ray pulsar (AXP) 1E 2259 + 586, but shows no discernible X-ray emission. If AXPs are isolated, high magnetic field neutron stars ("magnetars"), these results suggest that their unusual attributes are unlikely to be merely a consequence of their very high inferred magnetic fields
Timing of millisecond pulsars in NGC 6752: Evidence for a high mass-to-light ratio in the cluster core
No full textUsing pulse timing observations, we have obtained precise parameters, including positions with similar to20 mas accuracy, of five millisecond pulsars in NGC 6752. Three of them, located relatively close to the cluster center, have line-of-sight accelerations larger than the maximum value predicted by the central mass density derived from optical observation, providing dynamical evidence for a central mass-to-light ratio greater than or similar to10, much higher than for any other globular cluster. It is likely that the other two millisecond pulsars have been ejected out of the core to their present locations at 1.4 and 3.3 half-mass radii, respectively, suggesting unusual nonthermal dynamics in the cluster core
Radio pulsars in the Magellanic Clouds
No full textWe report the results of a survey of the Small Magellanic Cloud (SMC) for radio pulsars conducted with the 20 cm multibeam receiver of the Parkes 64 m telescope. This survey targeted a more complete region of the SMC than a previous pulsar search and had an improvement in sensitivity by a factor of about 2 for most pulsar periods. This survey is much more sensitive to fast young pulsars (with P less than or similar to 100 ms) and is the first survey of the SMC with any sensitivity to millisecond pulsars. Two new pulsars were discovered in the survey, one of which is located within the SMC. The number of pulsars found in the survey is consistent with the expected number derived using several methods. We also report the serendipitous discovery of a new pulsar in the 30 Doradus region of the Large Magellanic Cloud (LMC). These discoveries bring the total number of rotation-powered pulsars currently known in the Magellanic Clouds to eight. We have also made refined timing measurements for the new discoveries as well as for three previously known LMC pulsars. The age distribution of luminous Magellanic Cloud pulsars supports the conjecture that pulsars younger than about 5 Myr are more luminous on average than older pulsars
Detection of ionized gas in the globular cluster 47 Tucanae
No full textWe report the detection of ionized intracluster gas in the globular cluster 47 Tucanae. Pulsars in this cluster with a negative period derivative, which must lie in the distant half of the cluster, have significantly higher measured integrated electron column densities than the pulsars with a positive period derivative. We derive the plasma density within the central few parsecs of the cluster using two different methods that yield consistent values. Our best estimate of n(e) = 0.067 +/- 0.015 cm(-3) is about 100 times the free electron density of the interstellar medium in the vicinity of 47 Tucanae, and the ionized gas is probably the dominant component of the intracluster medium
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