Enriched Old Stars
نویسندگان
چکیده
منابع مشابه
Magnetically Accreting Isolated Old Neutron Stars
Previous work on the emission from isolated old neutron stars (IONSs) accreting from the interstellar medium (ISM) has focused on gravitational captureÈi.e., Bondi accretion. We propose a new class of sources that accrete via magnetic interaction with the ISM. While for the Bondi mechanism the accretion rate decreases with increasing neutron star velocity, in magnetic accretors (MAGACs) M0 Bond...
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Old neutron stars (ONSs) which have radiated away their internal and rotational energy may still shine if accreting the interstellar medium. Despite their large number, only two promising candidates have been detected so far and rather stringent limits on their observability follow from the analysis of ROSAT surveys. This contrasts with optimistic theoretical estimates that predicted a large nu...
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We report the results of a coherent study of three chemically anomalous metal-poor ([Fe/H] ∼ –2) stars. These objects exhibit unusually low abundances of Mg, Si, Ca (α-elements) and Sr, Y, and Ba (neutron-capture elements). Our analyses confirm and expand upon earlier reports of atypical abundances in BD+80 245, G4-36, and CS22966-043. We also find that the latter two stars exhibit enhanced abu...
متن کاملSpin and Magnetism in Old Neutron Stars
The thermal, spin and magnetic evolution of neutron stars in the old low mass binaries is first explored. Recycled to very short periods via accretion torques, the neutron stars lose their magnetism progressively. If accretion proceeds undisturbed for 100 Myrs these stars can rotate close to break up with periods far below the minimum observed of 1.558 ms. We investigate their histories using p...
متن کاملHigh energy gamma rays from old accreting neutron stars
We consider a magnetized neutron star with accretion from a companion star or a gas cloud around it, as a possible source of gamma rays with energy between 100 MeV and 10 − 10 eV . The flow of the accreting plasma is terminated by a shock at the Alfvén surface. Such a shock is the site for the acceleration of particles up to energies of ∼ 10 − 10 eV ; gamma photons are produced in the inelastic...
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ژورنال
عنوان ژورنال: Science
سال: 2013
ISSN: 0036-8075,1095-9203
DOI: 10.1126/science.342.6159.671-a