Pulsar

Résumé

thumb|Vue artistique d'un pulsar tirant de la matière d'une étoile proche. Un pulsar est un objet astronomique produisant un signal périodique allant de l'ordre de la milliseconde à quelques dizaines de secondes. Ce serait une étoile à neutrons tournant très rapidement sur elle-même (période typique de l'ordre de la seconde, voire beaucoup moins pour les pulsars milliseconde) et émettant un fort rayonnement électromagnétique dans la direction de son axe magnétique. Terminologie Attesté dès , le substantif masculin pulsar ( ) a été emprunté à l'anglais en, un mot-valise de même sens, créé à partir de la locution en (proprement « étoile pulsante »), composée de en (« vibrant ») et en (« étoile »). Le néologisme a d'abord été attribué à l'astronome et astrophysicien américain en qui l'aurait proposé dès , mais il s'avère qu'il est apparu antérieurement

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Cours associés (11)

Cosmology is the study of the structure and evolution of the universe as a whole. This course describes the principal themes of cosmology, as seen from the point of view of observations.

We present the role of particle physics in cosmology and in the description of astrophysical phenomena. We also present the methods and technologies for the observation of cosmic particles.

Introduce the students to general relativity and its classical tests.

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Séances de cours associées (16)

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Constraining the production of cosmic rays by pulsars

Mikhail Ivanov

One of the possible sources of hadronic cosmic rays (CRs) are newborn pulsars. If this is indeed the case, they should feature diffusive gamma-ray halos produced by interactions of CRs with interstellar gas. In this paper we try to identify extended gamma-ray emission around young pulsars, making use of the 7-year Fermi-LAT data. For this purpose we select and analyze a set of eight pulsars that are most likely to possess detectable gamma-ray halos. We find extended emission that might be interpreted as a gamma-ray halo only in the case of PSR J0007 + 7303. Its luminosity accords with the total energy of injected cosmic rays similar to 10(50) erg, although other interpretations of this source are possible. Irrespectively of the nature of this source, we put bounds on the luminosity of gamma-ray halos which suggest that pulsars' contribution to the overall energy budget of galactic CRs is subdominant in the GeV-TeV range.

Amer Physical Soc2016

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Gravitational radiation in Horava gravity

Diego Blas Temino, Hillary Sanctuary

We study the radiation of gravitational waves by self-gravitating binary systems in the low-energy limit of Horava gravity. We find that the predictions for the energy-loss formula of general relativity are modified already for Newtonian sources: the quadrupole contribution is altered, in part due to the different speed of propagation of the tensor modes; furthermore, there is a monopole contribution stemming from an extra scalar degree of freedom. A dipole contribution only appears at higher post-Newtonian order. We use these findings to constrain the low-energy action of Horava gravity by comparing them with the radiation damping observed for binary pulsars. Even if this comparison is not completely appropriate-since compact objects cannot be described within the post-Newtonian approximation-it represents an order of magnitude estimate. In the limit where the post-Newtonian metric coincides with that of general relativity, our energy-loss formula provides the strongest constraints for Horava gravity at low-energies.

2011

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Secular effects of ultralight dark matter on binary pulsars

Diego Blas Temino, Sergey Sibiryakov

Dark matter (DM) can consist of very light bosons behaving as a classical scalar field that experiences coherent oscillations. The presence of this DM field would perturb the dynamics of celestial bodies, either because the (oscillating) DM stress tensor modifies the gravitational potentials of the galaxy or if DM is directly coupled to the constituents of the body. We study secular variations of the orbital parameters of binary systems induced by such perturbations. Two classes of effects are identified. Effects of the first class appear if the frequency of DM oscillations is in resonance with the orbital motion; these exist for general DM couplings including the case of purely gravitational interaction. Effects of the second class arise if DM is coupled quadratically to the masses of the binary system members and do not require any resonant condition. The exquisite precision of binary pulsar timing can be used to constrain these effects. Current observations are not sensitive to oscillations in the galactic gravitational field, though a discovery of pulsars in regions of high DM density may improve the situation. For DM with direct coupling to ordinary matter, the current timing data are already competitive with other existing constraints in the range of DM masses similar to 10(-22)-10(-18) eV. Future observations are expected to increase the sensitivity and probe new regions of parameters.

AMER PHYSICAL SOC2020

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