Magnetar

About: Magnetar is a research topic. Over the lifetime, 2905 publications have been published within this topic receiving 106806 citations.

The allowed parameter space of a long-lived neutron star as the merger remnant of GW170817

Abstract: Limited by the sensitivities of the current gravitational wave (GW) detectors, the central remnant of the binary neutron star (NS) merger associated with GW170817 remains an open question Considering the relatively large total mass, it is generally proposed that the merger of GW170817 would lead to a shortly lived hypermassive NS or directly produce a black hole (BH) There is no clear evidence to support or rule out a long-lived NS as the merger remnant Here we utilize the GW and electromagnetic (EM) signals to comprehensively investigate the parameter space that allows a long-lived NS to survive as the merger remnant of GW170817 We find that for some stiff equations of state, the merger of GW170817 could, in principle, lead to a massive NS, which has a millisecond spin period The post-merger GW signal could hardly constrain the ellipticity of the NS If the ellipticity reaches $10^{-3}$, in order to be compatible with the multi-band EM observations, the dipole magnetic field of the NS ($B_p$) is constrained to the magnetar level of $\sim10^{14}$ G If the ellipticity is smaller than $10^{-4}$, $B_p$ is constrained to the level of $\sim10^{10}-10^{12}\,$G These conclusions weakly depend on the adoption of equations of state

SN2008am: A Super-Luminous Type IIn Supernova

Abstract: We present observations and interpretation of the Type IIn supernova SN 2008am discovered by the ROTSE Supernova Verification Project (RSVP). SN 2008am peaked at approximately -22.3 mag at a redshift of z=0.2338, giving it a peak luminosity of 3 x 10^{44}erg/s and making it one of the most luminous supernovae ever observed. The total radiated energy is ~ 2 x 10^{51} erg. Photometric observations in the ultraviolet, optical and infrared bands (J,H,Ks) constrain the SED evolution. We obtained six optical spectra of the supernova, five on the early decline from maximum light and a sixth nearly a year later plus a very late-time spectrum (~2 yr) of the host galaxy. The spectra of SN 2008am show strong Balmer-line and He I lambda 5876A emission with intermediate widths (~25A) in the first ~40 days after optical maximum. We examine a variety of models for the line wings and conclude that multiple scattering is most likely, implying that our spectra contain no specific information on the bulk flow velocity. We examine a variety of models for the ROTSE light curve subject to the rise time and the nature of the spectra, including radioactive decay, shocks in optically-thick and optically-thin circumstellar media (CSM) and a magnetar. The most successful model is one for which the CSM is optically-thick and in which diffusion of forward shock-deposited luminosity gives rise to the observed light curve. Diffusion of the shock-deposited energy from the forward shock is found to be important to account for the rising part of the light curve. Although there are differences in detail, SN 2008am appears to be closely related to other super-luminous Type IIn supernovae, SN 2006gy, SN 2006tf and perhaps SN 2008iy, that may represent the deaths of very massive LBV-type progenitors and for which the luminosity is powered by the interaction of the ejecta with a dense circumstellar medium.

Possible evidence for free precession of a strongly magnetized neutron star in the magnetar 4U 0142+61.

Abstract: broadband x rays (0.5–70 keV) with the Suzaku observatory. In hard x rays (15–40 keV), its 8.69 sec pulsations suffered slow phase modulations by � 0.7 sec, with a period of ∼15 h. When this effect is interpreted as free precession of the neutron star, the object is inferred to deviate from spherical symmetry by ∼1.6 × 10 −4 in its moments of inertia. This deformation, when ascribed to magnetic pressure, suggests a strong toroidal magnetic field, ∼10 12 T, residing inside the object. This provides one of the first observational approaches towards toroidal magnetic fields of magnetars.

3xmm j185246.6+003317: another low magnetic field magnetar

Abstract: N.R. is supported by a Ramon y Cajal fellowship and by an NWO Vidi award. N.R., D.V., and D.F.T. acknowledge support from grants AYA2012-39303, SGR 2009-811, and iLINK 2011-0303. J.A.P. acknowledges support from the grants AYA 2010-21097-C03-02 and Prometeo/2009/103.

Cosmic Ray Anisotropy as Signature for the Transition from Galactic to Extragalactic Cosmic Rays

Abstract: We constrain the energy at which the transition from Galactic to extragalactic cosmic rays occurs by computing the anisotropy at Earth of cosmic rays emitted by Galactic sources. Since the diffusion approximation starts to loose its validity for E/Z >~ 10^(16-17) eV, we propagate individual cosmic rays (CRs) using Galactic magnetic field models and taking into account both their regular and turbulent components. The turbulent field is generated on a nested grid which allows spatial resolution down to fractions of a parsec. Assuming sufficiently frequent Galactic CR sources, the dipole amplitude computed for a mostly light or intermediate primary composition exceeds the dipole bounds measured by the Auger collaboration around E ~ 10^18 eV. Therefore, a transition at the ankle or above would require a heavy composition or a rather extreme Galactic magnetic field with strength >~ 10 muG. Moreover, the fast rising proton contribution suggested by KASCADE-Grande data between 10^17 eV and 10^18 eV should be of extragalactic origin. In case heavy nuclei dominate the flux at E >~ 10^18 eV, the transition energy can be close to the ankle, if Galactic CRs are produced by sufficiently frequent transients as e.g. magnetars.