4,606 research outputs found
Contrasting neutron star heating mechanisms with Hubble Space Telescope observations
No full textTesis (Magíster en Física)--Pontificia Universidad Católica de Chile, 2018Si las estrellas de neutrones se enfriaran pasivamente, se esperaría que se vuelvan
indetectables en un tiempo menor a 107 años, al alcanzar bajas temperaturas
T < 104 K. Sin embargo, radiación del tipo ultravioleta, que implica temperaturas
superficiales T ∼ 105 K, fue detectada desde los pulsares de Giga años PSR J0437-
4715 y PSR J2124-3358 y también desde el pulsar B0950+08 cuya edad es ∼ 107
años. Esta discrepancia puede ser explicada por un grupo de mecanismos de
calentamiento propuestos en la literatura.
Usando el código de Petrovich y Reisenegger se calcularon curvas de evolución
térmica considerando diferentes mecanismos de calentamiento. Estas fueron contrastadas con las temperaturas inferidas a partir de las observaciones de los pulsares para determinar cuál es la principal fuente de emisión térmica de las estrellas
de neutrones.
Encontramos que el calentamiento rotoquímico, reacciones nucleares en las capas
profundas de la corteza y el calor liberado por la fricción de vórtices superfluidos pueden mantener la estrella lo suficientemente caliente más allá del tiempo
estándar de enfriamiento pasivo y explicar las observaciones.Si las estrellas de neutrones se enfriaran pasivamente, se esperaría que se vuelvan
indetectables en un tiempo menor a 107 años, al alcanzar bajas temperaturas
T < 104 K. Sin embargo, radiación del tipo ultravioleta, que implica temperaturas
superficiales T ∼ 105 K, fue detectada desde los pulsares de Giga años PSR J0437-
4715 y PSR J2124-3358 y también desde el pulsar B0950+08 cuya edad es ∼ 107
años. Esta discrepancia puede ser explicada por un grupo de mecanismos de
calentamiento propuestos en la literatura.
Usando el código de Petrovich y Reisenegger se calcularon curvas de evolución
térmica considerando diferentes mecanismos de calentamiento. Estas fueron contrastadas con las temperaturas inferidas a partir de las observaciones de los pulsares para determinar cuál es la principal fuente de emisión térmica de las estrellas
de neutrones.
Encontramos que el calentamiento rotoquímico, reacciones nucleares en las capas
profundas de la corteza y el calor liberado por la fricción de vórtices superfluidos pueden mantener la estrella lo suficientemente caliente más allá del tiempo
estándar de enfriamiento pasivo y explicar las observaciones.2020-08-0
Rotochemical heating of neutron stars
No full textThe electrostatic potential that keeps approximate charge neutrality in neutron star matter is self-consistently introduced into the formalism for "rotochemical heating" presented in a previous paper by Fernandez and Reisenegger. Although the new formalism is more rigorous, we show that its observable consequences are indistinguishable from those of the previous one, leaving the conclusions of the previous paper unchanged
Stylos kai edraiōma tēs ekklēsias, sive, Dissertatio de iustificatione hominis
No full textquam ... sub praesidio ... Ioh. Henrici Heideggeri ... placido eruditorum examini subiicit Andreas Steinerus, Vitod. author & respondens, ad diem Octobris loco horisque solitisDiss. Hohe Schule Zürich, 167
Author: Andreas Johannis Prytz
No full textAn edition of the consecration sermons in Gothenburg Cathedral 1633 by Superintendent Andreas Johannis Prytz, with introductory comments. The first sermon deals with the need for Church buildings, the second with the consecration of a new Church
We must combine conservation of nature with benefits to society. Interview by Gaby Allheilig with Andreas Heinimann on IPBES' Global Assessment Report on Biodiversity and Ecosystem Services
No full textOn 6 May 2019, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) presented its report on the state of biodiversity and ecosystem services worldwide. The first such assessment since 2005, it concludes that biodiversity and ecosystem loss has reached the point where it threatens human well-being. The researchers involved recommend several urgent measures to political decision-makers. Andreas Heinimann of CDE was the one Swiss scientist who worked as a lead author on a chapter of the report
To athanaton tēs psychēs, sive, Dissertatio de animae immortalitate, ex naturae & sanae rationis lumine demonstrata
No full textquam ... sub praesidio ... Iohannis Lavateri ... publicae ac placidae disquisitioni submittit Andreas Steinerus, Vitod. author & respondens ...Dedikation an Johannes Lavater, Jacob Meyer, Joh. Jacob Schaedler und Jacob Hegner auf dem Titelbl. versoDiss. Hohe Schule Zürich, 167
Internal heating of old neutron stars: contrasting different mechanisms
No full textContext. The standard cooling models of neutron stars predict
temperatures of T < 104 K for ages
t > 107 yr. However, the likely
thermal emission detected from the millisecond pulsar J0437-4715, of spin-down age
ts ~ 7 × 109 yr, implies a temperature
T ~ 105 K. Thus, a heating mechanism needs to be added to
the cooling models in order to obtain agreement between theory and observation.
Aims. Several internal heating mechanisms could be operating in neutron
stars, such as magnetic field decay, dark matter accretion, crust cracking, superfluid
vortex creep, and non-equilibrium reactions (“rotochemical heating”). We study these
mechanisms to establish which could be the dominant source of thermal emission from old
pulsars.
Methods. We show by simple estimates that magnetic field decay, dark
matter accretion, and crust cracking are unlikely to have a significant heating effect on
old neutron stars. The thermal evolution for the other mechanisms is computed with the
code of Fernández and Reisenegger. Given the dependence of the heating mechanisms on the
spin-down parameters, we study the thermal evolution for two types of pulsars: young,
slowly rotating “classical” pulsars and old, fast rotating millisecond pulsars.
Results. We find that magnetic field decay, dark matter accretion, and
crust cracking do not produce any detectable heating of old pulsars. Rotochemical heating
and vortex creep can be important both for classical pulsars and millisecond pulsars. More
restrictive upper limits on the surface temperatures of classical pulsars could rule out
vortex creep as the main source of thermal emission. Rotochemical heating in classical
pulsars is driven by the chemical imbalance built up during their early spin-down, and is
therefore strongly sensitive to their initial rotation period
Family Virtues and Social Critique: Andreas Latzko’s Anti-War Prose (1917-1918)
No full textBetween 1917 and 1918, the Austro-Hungarian author Andreas Latzko (1876-1943) wrote three separate publications against the Great War: Menschen im Krieg (1917), Friedensgericht (1918), and Der letzte Mann (published 1919). Literary historians tend to bypass these works, and the few who note them chiefly focus on the best-selling novella cycle Menschen im Krieg (1917). It is usually presented as an example of expressionist political prose, or as a mixture of social satire and aesthetic shock-tactics that chiefly remains indebted to realist traditions, albeit with occasional incursions into expressionistic styles..
Chemical Equilibrium and Stable Stratification of a Multicomponent Fluid: Thermodynamics and Application to Neutron Stars
No full textShort laws for finite groups and residual finiteness growth
No full text We prove that for every n ∈ N n \in \mathbb {N} and δ > 0 \delta >0 there exists a word w n ∈ F 2 w_n \in F_2 of length O ( n 2 / 3 log ( n ) 3 + δ ) O(n^{2/3} \log (n)^{3+\delta }) which is a law for every finite group of order at most n n . This improves upon the main result of Andreas Thom [Israel J. Math. 219 (2017), pp. 469–478] by the second named author. As an application we prove a new lower bound on the residual finiteness growth of non-abelian free groups. </p
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