24 research outputs found
Changes in intima media thickness, ankle brachial index and flow mediated dilation in pre hypertensive individuals
Introduction: Prehypertension (PH) is a state being on the frontier between the physiological referent arterial pressure values and pathological ones. The opinion concerned with its treatment is contradictory. Vascular alteration is an object of interest.Material and methods: Â Intima Media Thickness (IMT), Ankle Brachial Index (ABI) and Flow Mediated Dilation (FMD) indices were examined in 103 individuals with PH and 45 normotensives. Anthropometric and clinical chemical methods were also applied. The statistical processing was carried out by ĂĆS Excel 2000 and SPSS 11.0.Results: The pre hypertensives` metabolic profile was unfavorable, they are overweight and have bigger waist size, reflecting in higher cardiovascular risk. The percentage of FMD is reduced as an expression of endothelial function. Structural vascular alterations are not registered - ITM and ABI values are of no significant difference in the two followed up groups.Conclusion: The therapeutic approach in prehypertensives should be directed to reestablishment of the endothelial function.
The Einstein@Home Search for Radio Pulsars and PSR J2007+2722
Einstein@Home aggregates the computer power of hundreds of thousands of volunteers from 193 countries, to search for new neutron stars using data from electromagnetic and gravitational-wave detectors. This paper presents a detailed description of the search for new radio pulsars using Pulsar ALFA survey data from the Arecibo Observatory. The enormous computing power allows this search to cover a new region of parameter space; it can detect pulsars in binary systems with orbital periods as short as 11 minutes. We also describe the first Einstein@Home discovery, the 40.8 Hz isolated pulsar PSR J2007+2722, and provide a full timing model. PSR J2007+2722\u27s pulse profile is remarkably wide with emission over almost the entire spin period. This neutron star is most likely a disrupted recycled pulsar, about as old as its characteristic spin-down age of 404 Myr. However, there is a small chance that it was born recently, with a low magnetic field. If so, upper limits on the X-ray flux suggest but cannot prove that PSR J2007+2722 is at least ~100 kyr old. In the future, we expect that the massive computing power provided by volunteers should enable many additional radio pulsar discoveries
Arecibo Pulsar Survey Using ALFA: Probing Radio Pulsar Intermittency and Transients
We present radio transient search algorithms, results, and statistics from the ongoing Arecibo Pulsar ALFA (PALFA) survey of the Galactic plane. We have discovered seven objects through a search for isolated dispersed pulses. All of these objects are Galactic and have measured periods between 0.4 and 4.7 s. One of the new discoveries has a duty cycle of 0.01%, smaller than that of any other radio pulsar. We discuss the impact of selection effects on the detectability and classification of intermittent sources, and compare the efficiencies of periodicity and single-pulse (SP) searches for various pulsar classes. For some cases we find that the apparent intermittency is likely to be caused by off-axis detection or a short time window that selects only a few bright pulses and favors detection with our SP algorithm. In other cases, the intermittency appears to be intrinsic to the source. No transients were found with DMs large enough to require that they originate from sources outside our Galaxy. Accounting for the on-axis gain of the ALFA system, as well as the low gain but large solid-angle coverage of far-out sidelobes, we use the results of the survey so far to place limits on the amplitudes and event rates of transients of arbitrary origin
Galactic Center Pulsars with the ngVLA
Pulsars in the Galactic Center (GC) are important probes of General
Relativity, star formation, stellar dynamics, stellar evolution, and the
interstellar medium. Despite years of searching, only a handful of pulsars in
the central 0.5 deg are known. The high-frequency sensitivity of ngVLA will
open a new window for discovery and characterization of pulsars in the GC. A
pulsar in orbit around the GC black hole, Sgr A*, will provide an unprecedented
probe of black hole physics and General Relativity.Comment: To be published in the ASP Monograph Series, "Science with a
Next-Generation VLA", ed. E. J. Murphy (ASP, San Francisco, CA
Two Millisecond Pulsars Discovered by the PALFA Survey and a Shapiro Delay Measurement
We present two millisecond pulsar discoveries from the PALFA survey of the Galactic plane with the Arecibo telescope. PSR J1955+2527 is an isolated pulsar with a period of 4.87 ms, and PSR J1949+3106 has a period of 13.14 ms and is in a 1.9 day binary system with a massive companion. Their timing solutions, based on 4 years of timing measurements with the Arecibo, Green Bank, Nançay, and Jodrell Bank telescopes, allow precise determination of spin and astrometric parameters, including precise determinations of their proper motions. For PSR J1949+3106, we can clearly detect the Shapiro delay. From this we measure the pulsar mass to be 1.47+0.43 â 0.31 M â, the companion mass to be 0.85+0.14 â 0.11 M â, and the orbital inclination to be i = 79.9â1.9 + 1.6 deg, where uncertainties correspond to ±1Ï confidence levels. With continued timing, we expect to also be able to detect the advance of periastron for the J1949+3106 system. This effect, combined with the Shapiro delay, will eventually provide very precise mass measurements for this system and a test of general relativity
AN ECCENTRIC BINARY MILLISECOND PULSAR with A HELIUM WHITE DWARF COMPANION in the GALACTIC FIELD
Low-mass white dwarfs (LMWDs) are believed to be exclusive products of binary evolution, as the universe is not old enough to produce them from single stars. Because of the strong tidal forces operating during the binary interaction phase, the remnant systems observed today are expected to have negligible eccentricities. Here, we report on the first unambiguous identification of an LMWD in an eccentric (e = 0.13) orbit around the millisecond pulsar PSR J2234+0511, which directly contradicts this picture. We use our spectra and radio-timing solution (derived elsewhere) to infer the WD temperature (Teff = 8600 ñ190 K), and peculiar systemic velocity relative to the local standard of rest ( km s-1). We also place model-independent constraints on the WD radius ( ) and surface gravity ( dex). The WD and kinematic properties are consistent with the expectations for low-mass X-ray binary evolution and disfavor a dynamic three-body formation channel. In the case of the high eccentricity being the result of a spontaneous phase transition, we infer a mass of ĂąËÂŒ1.60 M o for the pulsar progenitor, which is too low for the quark-nova mechanism proposed by Jiang et al., and too high for the scenario of Freire & Tauris, in which a WD collapses into a neutron star via a rotationally delayed accretion-induced collapse. We find that eccentricity pumping via interaction with a circumbinary disk is consistent with our inferred parameters. Finally, we report tentative evidence for pulsations that, if confirmed, would transform the star into an unprecedented laboratory for WD physics
Discovery and Timing of Millisecond Pulsars with the Arecibo 327 MHz Drift-Scan Survey
We present the discovery and timing solutions of four millisecond pulsars
(MSPs) discovered in the Arecibo 327 MHz Drift-Scan Pulsar Survey. Three of
these pulsars are in binary systems, consisting of a redback (PSR J2055+1545),
a black widow (PSR J1630+3550), and a neutron star-white dwarf binary (PSR
J2116+1345). The fourth MSP, PSR J2212+2450, is isolated. We present the
multi-year timing solutions as well as polarization properties across a range
of radio frequencies for each pulsar. We perform a multi-wavelength search for
emission from these systems and find an optical counterpart for PSR J2055+1545
in Gaia DR3, as well as a gamma-ray counterpart for PSR J2116+1345 with the
Fermi-LAT telescope. Despite the close co-location of PSR J2055+1545 with a
Fermi source, we are unable to detect gamma-ray pulsations, likely due to the
large orbital variability of the system. This work presents the first two
binaries found by this survey with orbital periods shorter than a day; we
expect to find more in the 40% of the survey data which have yet to be
searched.Comment: 20 pages, 11 figures, 4 tables. Submitted to Ap
Discovery, Timing, and Multiwavelength Observations of the Black Widow Millisecond Pulsar PSR J1555-2908
We report the discovery of PSR J1555-2908, a 1.79 ms radio and gamma-ray pulsar in a 5.6 hr binary system with a minimum companion mass of 0.052 M â. This fast and energetic ( Ä=3Ă1035 erg s-1) millisecond pulsar was first detected as a gamma-ray point source in Fermi Large Area Telescope (LAT) sky survey observations. Guided by a steep-spectrum radio point source in the Fermi error region, we performed a search at 820 MHz with the Green Bank Telescope that first discovered the pulsations. The initial radio pulse timing observations provided enough information to seed a search for gamma-ray pulsations in the LAT data, from which we derive a timing solution valid for the full Fermi mission. In addition to the discovery and timing of radio and gamma-ray pulsations, we searched for X-ray pulsations using NICER but no significant pulsations were detected. We also obtained time-series r-band photometry that indicates strong heating of the companion star by the pulsar wind. Material blown off the heated companion eclipses the 820 MHz radio pulse during inferior conjunction of the companion for â10% of the orbit, which is twice the angle subtended by its Roche lobe in an edge-on system. © 2022. The Author(s). Published by the American Astronomical Society
Discovery, Timing, and Multiwavelength Observations of the Black Widow Millisecond Pulsar PSR J1555-2908
We report the discovery of PSR J1555-2908, a 1.79 ms radio and gamma-ray
pulsar in a 5.6 hr binary system with a minimum companion mass of 0.052
. This fast and energetic ( erg/s)
millisecond pulsar was first detected as a gamma-ray point source in Fermi LAT
sky survey observations. Guided by a steep spectrum radio point source in the
Fermi error region, we performed a search at 820 MHz with the Green Bank
Telescope that first discovered the pulsations. The initial radio pulse timing
observations provided enough information to seed a search for gamma-ray
pulsations in the LAT data, from which we derive a timing solution valid for
the full Fermi mission. In addition to the radio and gamma-ray pulsation
discovery and timing, we searched for X-ray pulsations using NICER but no
significant pulsations were detected. We also obtained time-series r-band
photometry that indicates strong heating of the companion star by the pulsar
wind. Material blown off the heated companion eclipses the 820 MHz radio pulse
during inferior conjunction of the companion for ~10% of the orbit, which is
twice the angle subtended by its Roche lobe in an edge-on system.Comment: 15 pages, 6 figures, accepted by Ap