111 research outputs found
An Extremely Low-mass He White Dwarf Orbiting the Millisecond Pulsar J1342+2822B in the Globular Cluster M3
No full textWe report on the discovery of the companion star to the millisecond pulsar J1342+2822B in the globular cluster M3. We exploited a combination of near-ultraviolet and optical observations acquired with the Hubble Space Telescope in order to search for the optical counterparts to the known millisecond pulsars in this cluster. At a position in excellent agreement with that of the radio pulsar J1342+2822B (M3B), we have identified a blue and faint object (m F275W ≈ 22.45) that, in the color-magnitude diagram of the cluster, is located in the region of He core white dwarfs (WDs). From the comparison of the observed magnitudes with theoretical cooling tracks we have estimated the physical properties of the companion star: It has a mass of only 0.19 ± 0.02 M o, a surface temperature of (12 ± 1) × 103 K, and a cooling age of Gyr. Its progenitor was likely a ∼0.84 M o star, and the bulk of the mass-transfer activity occurred during the subgiant branch phase. The companion mass, combined with the pulsar mass function, implies that this system is observed almost edge-on and that the neutron star (NS) has a mass of 1.1 ± 0.3 M o, in agreement with the typical values measured for recycled NSs in these compact binary systems. We have also identified a candidate counterpart to the wide and eccentric binary millisecond pulsar J1342+2822D. It is another WD with a He core and a mass of 0.22 ± 0.2 M o, implying that the system is observed at a high inclination angle and hosts a typical NS with a mass of 1.3 ± 0.3 M o. At the moment, the large uncertainty on the radio position of this millisecond pulsar prevents us from robustly concluding that the detected star is its optical counterpart
PSR J1641+3627F: A Low-mass He White Dwarf Orbiting a Possible High-mass Neutron Star in the Globular Cluster M13
No full textWe report on the discovery of the companion star to the millisecond pulsar J1631+3627F in the globular cluster M13. By means of a combination of optical and near-UV high-resolution observations obtained with the Hubble Space Telescope, we identified the counterpart at the radio source position. Its location in the color-magnitude diagrams reveals that the companion star is a faint () He-core white dwarf. We compared the observed companion magnitudes with those predicted by state-of-the-art binary evolution models and found out that it has a mass of , a radius of , and a surface temperature of K. Combining the companion mass with the pulsar mass function is not enough to determine the orbital inclination and the neutron star mass; however, the last two quantities become correlated: we found that either the system is observed at a low-inclination angle, or the neutron star is massive. In fact, assuming that binaries are randomly aligned with respect to the observer line of sight, there is a of probability that this system hosts a neutron star more massive than . In fact, the maximum and median mass of the neutron star, corresponding to orbital inclination angles of 90° and 60°, are and , respectively. On the other hand, also assuming an empirical neutron star mass probability distribution, we found that this system could host a neutron star with a mass of if orbiting with a low-inclination angle around 40°
Discovery of Three New Millisecond Pulsars in Terzan 5
No full textWe report on the discovery of three new millisecond pulsars (MSPs; namely J1748−2446aj, J1748−2446ak, and J1748−2446al) in the inner regions of the dense stellar system Terzan 5. These pulsars have been discovered thanks to a method, alternative to the classical search routines, that exploited the large set of archival observations of Terzan 5 acquired with the Green Bank Telescope over five years (from 2010 to 2015). This technique allowed the analysis of stacked power spectra obtained by combining ~206 hr of observation. J1748−2446aj has a spin period of ~2.96 ms, J1748−2446ak of ~1.89 ms (thus it is the fourth fastest pulsar in the cluster) and J1748−2446al of ~5.95 ms. All three MSPs are isolated, and currently we have timing solutions only for J1748−2446aj and J1748−2446ak. For these two systems, we evaluated the contribution to the measured spin-down rate of the acceleration due to the cluster potential field, thus estimating the intrinsic spin-down rates, which are in agreement with those typically measured for MSPs in globular clusters (GCs). Our results increase the number of pulsars known in Terzan 5 to 37, which now hosts 25% of the entire pulsar population identified, so far, in GCs
One pulsar, two white dwarfs, and a planet confirming the strong equivalence principle
No full textOn behalf of: I. Cognard, P.C.C. Freire, N. Wex, L. Guillemot, G. Desvignes, M. Kramer, G. Theureau, M. SaillenfestInternational audienceThe strong equivalence principle is a cornerstone of general relativity, tested with exquisite accuracy in the Solar system. However, tests in the strong-field regime require a compact object. Currently, PSR J0337+1715 is the unique millisecond pulsar found in a triple stellar system, orbiting two white dwarfs within an area comparable to the orbit of the Earth. This configuration offers the opportunity for a dramatic improvement over previous tests, provided that accurate and regular timing of the pulsar can be achieved. This also requires the development of a new timing model solving numerically the relativistic three-body problem with great accuracy. We report on the analysis of the high-quality dataset gathered on PSR J0337+1715 by the Nançay radiotelescope over the past 8 years. In particular, I will show how we could obtain the most stringent limit to-date on a potential violation of the strong equivalent principle in the strong field regime. I will also introduce preliminary resuts showing that the presence of a small planet in the system may explain a tiny residual signal so far unaccounted for, which if confirmed would make this system exceptionally rich
On the disruption of pulsar and x-ray binaries in globular clusters
No full textContains fulltext :
122796.pdf (Author’s version preprint ) (Open Access
One pulsar, two white dwarfs, and a planet confirming the strong equivalence principle
No full textThe strong equivalence principle is a cornerstone of general relativity,
tested with exquisite accuracy in the Solar system. However, tests in the
strong-field regime require a compact object. Currently, PSR J0337+1715 is the
unique millisecond pulsar found in a triple stellar system, orbiting two white
dwarfs within an area comparable to the orbit of the Earth. This configuration
offers the opportunity for a dramatic improvement over previous tests, provided
that accurate and regular timing of the pulsar can be achieved. This also
requires the development of a new timing model solving numerically the
relativistic three-body problem with great accuracy. We report on the analysis
of the high-quality dataset gathered on PSR J0337+1715 by the Nan{\c c}ay
radiotelescope over the past 8 years. In particular, I will show how we could
obtain the most stringent limit to-date on a potential violation of the strong
equivalent principle in the strong field regime. I will also introduce
preliminary resuts showing that the presence of a small planet in the system
may explain a tiny residual signal so far unaccounted for, which if confirmed
would make this system exceptionally rich.Comment: On behalf of: I. Cognard, P.C.C. Freire, N. Wex, L. Guillemot, G.
Desvignes, M. Kramer, G. Theureau, M. Saillenfes
Education and occupational choice in rural Jamaica
No full textAlso published in Consequences of Class and Colour: West Indian Perspective, ed. by David Lowenthal and Lambros Comitas. Garden City, NY: Anchor Press, 1973This paper seeks to describe the patterns of occupational preference in rural Jamaica. It draws upon two independent surveys for its data: 1) a study of elementary education by P.C.C. Evans in 1957, and 2) a survey of conditions affecting rural labour supply by the author in 1955. Occupational choice was investigated in both studies, and by collating their data on this topic, the correspondence of career choice amongst peasant adults and children is explored, and these aspirations related to local prospect
Experimental research related to the behaviour of the materials afferent to the liners and the pistons for production pumps under wear conditions
No full textThis paper shows the results of a serious study developed by the author under laboratory conditions and related to the behaviour of the materials for liners and pistons as components of the production pumps. Their behaviour was studied under abrasive wear conditions when the couple including the liner and the piston accommodates a translation motion.
The liners and the pistons were offered by Upetrom S.A. Ploiesti and P.C.C. Sterom S.A. Campina, two important Romanian oilfield-equipment manufacturers.
The estimation of the behaviour afferent to the said components (liners and pistons) and shown under wear conditions corresponding to certain values of temperature and specific pressure, the environment and the number of double strokes per minute is based on the determination of the mass loss per unit of time and surface as shown by the couples of liners and pistons having been studied
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/1073
An Extremely Low-mass He White Dwarf Orbiting the Millisecond Pulsar J1342+2822B in the Globular Cluster M3
No full textContains fulltext :
203019.pdf (Publisher’s version ) (Open Access)
Contains fulltext :
203019pre.pdf (Author’s version preprint ) (Open Access
Techniek en de grens van de mens: De menselijke conditie in een technologische cultuur
No full textWat betekent de alomtegenwoordige rol van techniek in onze cultuur voor mensen? Er zijn drie benaderingen van deze vraag te onderscheiden: uitwendigheid, mediatie en transhumanisme. Deze verschillen in de mate van verwevenheid die ze tussen mensen en techniek waarnemen. De mediatiebenadering blijkt het best in staat de nieuwe menselijke conditie te verhelderen: mensen geven niet meer autonoom vorm aan hun bestaan, maar alleen in verwevenheid met technologie.Technology, Policy and Managemen
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