Soft gamma repeaters (SGRs) and anomalous X-ray pulsars are thought to be neutron stars with strong magnetic fields, called magnetars, which emit intermittent bursts of hard X-rays and soft gamma rays. Three highly energetic bursts, known as giant flares, have been observed originating from three different SGRs, the latest and most energetic of which occurred on December 27, 2004, from the SGR with the largest estimated magnetic field, SGR 1806-20. Modulations in the X-ray tails of giant flares may be caused by global seismic oscillations. Non-radial oscillations of the dense neutron star matter could emit gravitational waves powered by the magnetar's magnetic energy reservoir. This analysis searched for long-duration transient gravitational waves associated with three magnetar bursts that occurred during LIGO's sixth science run, from July 7, 2009 to October 20, 2010. The search results were consistent with the calculated background, and 90% confidence upper limits on the possible undetected gravitational wave energy were found.

The ultra-strong magnetic fields of magnetars have profound implications for their radiative phenomena. We study the dynamics of strong magnetic fields inside and outside magnetars. Inside the magnetar, the strong magnetic stress can break the crust and trigger plastic failures. The interaction between magnetic fields and plastic failures is studied in two scenarios: 1. Internal Hall waves launched from the core-crust interface can initiate plastic failures and lead to X-ray outbursts. 2. External Alfven waves produced by giant flares can also initiate crustal plastic failures which dissipate the waves and give rise to delayed thermal afterglow. The crustal dissipation of Alfven waves competes with the magnetospheric dissipation outside the magnetar. Using a high order simulation of Force-Free Electrodynamics (FFE), we found that the magnetospheric dissipation of Alfven waves is generally slow and most wave energy will dissipate inside the magnetar.

Supernova explosions are among the most energetic events known in the universe, leaving supernova remnants (SNRs) as their relics. The cores of massive stars collapse to form neutron stars, among the most compact and strongest magnets in the cosmos. The thesis studies a sample of such magnetic "beauties" in X-rays, the magnetars and high-magnetic field pulsars (HBPs), with the motivation to understand their evolutionary links. We also address the connection between these sources by investigating their environs through their securely associated SNRs. Magnetars have ultra-high magnetic fields B ~ 10^{14} - 10^{15} Gauss (G) and include the soft-gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs). The HBPs have magnetic fields B ~ 10^{13} - 10^{14} G, intermediate between the classical rotation-powered pulsars (B ~ 10^{12} G) and magnetars. We focussed on two HBPs: J1119-6127 and J1846-0258, with similar spin-properties and associated with the SNRs G292.2-0.5 and Kes 75, respectively. In our studies, magnetar-like behavior was discovered from the Crab-like pulsar J1846-0258, clearly establishing a connection between the HBPs and magnetars for the first time, while no such behavior has been observed from PSR J1119-6127 so far. J1119-6127's overall X-ray properties together with its compact pulsar wind nebula resemble more the classical rotation-powered pulsars. We studied two magnetars, one from each sub-class: SGR 0501+4516 and AXP 1E 1841-045. The spectral and statistical analysis of the bursts and the persistent X-ray emission properties observed from them were found consistent with the magnetar model predictions as well as those seen in other SGRs. Finally, we probed the environment of these stellar magnets by performing a detailed X-ray imaging and spatially resolved spectroscopic study of two SNRs: G292.2-0.5 and Kes 73 associated with J1119-6127 and 1E 1841-045, respectively. We found that both SNRs point to very massive progenitors (>~25 solar masses), further supporting the growing evidence for magnetars originating from massive progenitors using other multiwavelength studies.

Supernova explosions are among the most energetic events known in the universe, leaving supernova remnants (SNRs) as their relics. The cores of massive stars collapse to form neutron stars, among the most compact and strongest magnets in the cosmos. The thesis studies a sample of such magnetic "beauties" in X-rays, the magnetars and high-magnetic field pulsars (HBPs), with the motivation to understand their evolutionary links. We also address the connection between these sources by investigating their environs through their securely associated SNRs. Magnetars have ultra-high magnetic fields B ~ 10^{14} - 10^{15} Gauss (G) and include the soft-gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs). The HBPs have magnetic fields B ~ 10^{13} - 10^{14} G, intermediate between the classical rotation-powered pulsars (B ~ 10^{12} G) and magnetars. We focussed on two HBPs: J1119-6127 and J1846-0258, with similar spin-properties and associated with the SNRs G292.2-0.5 and Kes 75, respectively. In our studies, magnetar-like behavior was discovered from the Crab-like pulsar J1846-0258, clearly establishing a connection between the HBPs and magnetars for the first time, while no such behavior has been observed from PSR J1119-6127 so far. J1119-6127's overall X-ray properties together with its compact pulsar wind nebula resemble more the classical rotation-powered pulsars. We studied two magnetars, one from each sub-class: SGR 0501+4516 and AXP 1E 1841-045. The spectral and statistical analysis of the bursts and the persistent X-ray emission properties observed from them were found consistent with the magnetar model predictions as well as those seen in other SGRs. Finally, we probed the environment of these stellar magnets by performing a detailed X-ray imaging and spatially resolved spectroscopic study of two SNRs: G292.2-0.5 and Kes 73 associated with J1119-6127 and 1E 1841-045, respectively. We found that both SNRs point to very massive progenitors (>~25 solar masses), further supporting the growing evidence for magnetars originating from massive progenitors using other multiwavelength studies.

Multi-messenger astronomy began when a massive star underwent core collapse in a neighboring dwarf galaxy, whose light and neutrinos reached Earth in 1987. Supernova 1987A was observed optically but was also observed through roughly two dozen neutrinos. Modern instruments have the ability to measure electromagnetic signatures in more wavelengths and detect many more neutrinos from a nearby core-collapse supernova, providing insight into an astrophysical phenomena that is not yet fully understood. In this dissertation, we discuss predictions for future core-collapse supernova signals and the nuclear and particle interactions that produce them. We focus on several different aspects related to both typical and rare supernovae. The diffuse supernova neutrino background (DSNB) - the isotropic background of ~10 MeV neutrinos from all past supernovae - is one such signal that does not rely on a local event for neutrino detection. We update several aspects of theoretical DSNB modeling by (i) using simulation data to better understand neutrino emission spectra as a function of time, (ii) collating recent star formation rate measurements to infer the rate of core collapse in the cosmos, and (iii) performing a signal vs. background analysis of state-of-the-art neutrino experiments. We find that the DSNB is likely to be detected in the next two decades, but large uncertainty on the average neutrino emission spectra combined with unclear treatment of background events prevents a precise timeline. We also discuss the signatures from rare supernovae driven by magnetorotational engines called protomagnetars. We find that outflows from these central engines can produce pions through inelastic np interactions, resulting in ~0.1 - 10 GeV neutrinos that are detectable for galactic supernovae. We also find that these outflows can synthesize heavier nuclei than traditional supernovae through the `weak r-process.' We compare the nucleosynthesis in supernova outflows to that in compact object mergers and find that mergers are more conducive for creating the heaviest nuclei. We also predict the detection rates of another kind of transient called kilonovae that are powered by the decay of unstable nuclei. Finally, these protomagnetar systems may be able to accelerate nuclei in relativistic jets. If these jets are beamed toward us, the gamma ray lines from the decays of unstable nuclei can be boosted to high energies and are detectable from extragalactic distances. / Doctor of Philosophy / Supernovae are one of the most well studied astronomical phenomena because of how broadly they connect to different fields of physics. This kind of event can be bright enough to be seen visually and has been observed and documented for centuries. Its name derives from nova stella - Latin for `new star' - but supernovae occur as the final stages of a star's life. Core-collapse supernovae are an important subclass that occur for stars several times more massive than our own sun. There is a long history of core-collapse supernova observation - from the naked eye to modern optical telescopes - but only one has ever been observed using a particle other than light. SN1987A was a nearby core-collapse supernova that occurred in 1987 and emitted a large burst of rarely interacting particles known as neutrinos along with its usual optical emission. Only two dozen neutrinos were detected during this event, but nearby core-collapse supernovae are rare and astronomers have been eager for another one. With today's modern neutrino detectors, a nearby core-collapse supernova would yield thousands of neutrino events which would help astronomers learn about the internal physics occurring during the collapse, which an optical signal cannot do. In this dissertation, we study the ways in which light and neutrinos can teach us more about core-collapse supernovae. We cover another way to observe supernova neutrinos without waiting for one nearby to occur by predicting the signal from the `diffuse supernova neutrino background.' This is a background of supernova neutrinos that constantly surrounds us, but interacts extremely infrequently, so kiloton-mass detectors are needed to detect this background. Measuring this will also shed light on how stars evolve over a galaxy's history. There are additional subclasses of core-collapse supernovae that give rise to the usual optical and neutrino signal but may also populate the universe with heavy elements, produce higher energy light, and emit higher energy neutrinos. This class is even rarer but are systematically more energetic and are powered internally by objects called `protomagnetars.' We study models of these rare, energetic supernovae and make predictions for each of these signals - heavy elements, high energy light, and high energy neutrinos - to help answer outstanding questions in astrophysics and make predictions for events not yet seen.

The merger of a neutron star (NS) binary may result in the formation of a rapidly spinning magnetar. The magnetar can potentially survive for seconds or longer as a supramassive NS before collapsing to a black hole if, indeed, it collapses at all. During this process, a fraction of the magnetar's rotational energy of similar to 10(53) erg is transferred via magnetic spin-down to the surrounding ejecta. The resulting interaction between the ejecta and the surrounding circumburst medium powers a year-long or greater synchrotron radio transient. We present a search for radio emission with the Very Large Array following nine short-duration gamma-ray bursts (GRBs) at rest-frame times of approximate to 1.3-7.6 yr after the bursts, focusing on those events that exhibit early-time excess X-ray emission that may signify the presence of magnetars. We place upper limits of less than or similar to 18-32 mu Jy on the 6.0 GHz radio emission, corresponding to spectral luminosities of less than or similar to(0.05-8.3) x 10(39) erg s(-1). Comparing these limits to the predicted radio emission from a long-lived remnant and incorporating measurements of the circumburst densities from broadband modeling of short GRB afterglows, we rule out a stable magnetar with an energy of 10(53) erg for half of the events in our sample. A supramassive remnant that injects a lower rotational energy of 10(52) erg is ruled out for a single event, GRB 050724A. This study represents the deepest and most extensive search for long-term radio emission following short GRBs to date, and thus the most stringent limits placed on the physical properties of magnetars associated with short GRBs from radio observations.

No description available.

In this thesis, the recently discovered Soft Gamma Ray Repeaters SGR J1833-0832, SWIFT J1822.3-1606 and SWIFT J1834.9-0846 are analysed using the archival Swift, RXTE, Chandra and XMM-Newton observations. The period fluctuations and timing noise properties of these sources are investigated. Spectral characteristics and long term frequency evolution of these sources are presented. Investigation for timing noise structure of these magnetars has shown a correlation between first frequency derivative of the spin frequency and torque noise strength.

This thesis is composed of three published articles. Each chapter is devoted to an article. In the first part the origin of some of the single radio pulsars with relatively low magnetic fields (B &lt / 1e12 G) and with characteristic ages (tau) less than 1e7 years is questioned. We proposed that such pulsars might occur as a result of the disruption of high-mass X-ray binary systems after a second supernova explosion. In these binaries, mass accretion on to the surface of X-ray pulsars may lead to the decrease in the magnetic field from its value at birth (B similar to 1e12 &ndash / 1e13 G) down to B &lt / 1e12 G similar to the processes in low-mass X-ray binaries. In the second part we put together many observational data of SGRs and AXPs and analyzed them with the main purpose of the removal of contradiction between the real age (t) of these objects and their characteristic times of period change (tau). SGRs and AXPs are neutron stars that undergo star-quakes. Magnetic activity increases from time to time. We suggest that as a result of these processes plasma is ejected from the NS and propeller mechanism starts to work. Due to propeller effect dP/dt increases, tau decreases. Indeed, high dP/dt values are observed in SGRs and in half of the AXPs. Then, for a long time NS looses its activity, its dP/dt decreases, tau increases and rapid cooling begins. It seems that there is a possible transition between each NS stage (AXP,SGR,dim). This transient cycle may be repeated once or several times until the spin period of the neutron star becomes P &gt / 10 - 12 s. Observational data and mainly the data of AXP 1E 1048-5937 and DRQNS RX J1308.8+2127 support this idea. In the third part dependence of the X-ray luminosity (Lx) of young single pulsars, due to ejection of relativistic particles, on electric field intensity, rate of rotational energy loss (dE/dt), magnetic field, period and some other parameters of neutron stars are discussed. Influence of the magnetic field and effects of some other parameters of neutron stars on the Lx - dE/dt and the Lx - tau(characteristic time) relations are considered. Evolutionary factors also play an important role in our considerations. Only the pulsars whose X-ray luminosity in the 2 &ndash / 10 keV energy band is greater than 1033 erg/s have pulsar wind nebula around them. The pulsars from which gamma-ray radiation has been observed have low X-ray luminosity in general.

Submitted by Biblioteca do Instituto de Física (bif@ndc.uff.br) on 2017-06-09T18:45:03Z No. of bitstreams: 1 Dissertação .pdf: 8597580 bytes, checksum: bb76dda18d3a914f374ff1ebfea47fe1 (MD5) / Made available in DSpace on 2017-06-09T18:45:03Z (GMT). No. of bitstreams: 1 Dissertação .pdf: 8597580 bytes, checksum: bb76dda18d3a914f374ff1ebfea47fe1 (MD5) / Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Estrelas de nêutrons se manifestam como diferentes tipos de classes de fontes astrofísicas, que estão associadas a distintas fenomenologias. Aqui focaremos nossas atenções aos magnetares (ou estrelas de nêutrons altamente magnetizadas) que estão associados aos Soft Gamma Repeaters e os Anomalous X-ray pulsars. O campo magnético na superfície desses objetos atingem valores maiores que 1015G. No âmbito de campos magnéticos tão intensos, efeitos relativísticos começam a serem determinantes para a definição da estrutura desses objetos e somos tentados a nos questionarmos de que forma esses campos magnéticos tão intensos modificam a estrutura e a evolução dessas estrelas. Neste trabalho realizaremos um estudo a respeitos de duas soluções das equações de Einstein-Maxwell (a solução de Bonnor que é uma solução analítica e a solução completa das equações de Einstein-Maxwell encontrada por métodos numéricos) e que descrevem o espaço-tempo exterior a um objeto compacto massivo e com campo magnético dipolar. Para isto revisaremos estas duas soluções e em seguida descreveremos as equações das geodésicas geradas por tais soluções. Nossos estudos mostram que, apesar da solução de Bonnor não satisfazer as equações de Maxwell, as órbitas geradas por esta solução são as mesmas descritas pela solução numérica. Também mostraremos que a inserção de campos magnéticos que assumem valores de até 1017G no centro da estrela não modificam tanto as órbitas das partículas massivas e dos fótons descritas ao redor dessa estrela, e assim a utilização da solução de Schwarzschild para a descrição das órbitas ao redor desse objeto é uma aproximação razoável. / Neutron stars manifest themselves as different classes of astrophysical sources that are associated to distinct phenomenology. Here we focus ours attention on magnetars (or strongly magnetized neutron stars) that are associated to Soft Gamma Repeaters and Anomalous Xray Pulsars. The magnetic field on surface these objects, reaches values greater than 1015. Under intense magnetic fields, relativistic effects begin to be decisive for the definition of the structure and evolution of these objects and are tempted to question ourselves how these strengths fields affect the structure of these stars. In this work we will conduct a study to respect the two solutions of Einstein-Maxwell’s equations (the Bonnor solution which is an analytical solution and a complete solution of the Einstein -Maxwell equations found by numerical methods) that have been found in the literature which describe the spacetime exterior a massive compact object wich possess a magnetic field that a character dipole. For this we revised this two solutions, and then describe the geodesic equations generated by such solutions. Our studies show that, despite the Bonnor solution does not satisfy Maxwell’s equations, the orbits generated by this solution are the same as described by numerical solution. Also show that the inclusion of magnetic fields that assumes values of up to 1017G in the center of the star does not modify the orbits of the massive particles and the photons which are described around this star, and so the use of Schwarzschild solution for the description of the orbits around this object is a reasonable approximation.