1,724,015 research outputs found
SGR 0418+5729: A SMALL INCLINATION ANGLE RESULTING IN A NOT SO LOW DIPOLE MAGNETIC FIELD?
No full textThe spin-down behaviors of SGR 0418+5729 are investigated. The pulsar spin-down model of Contopoulos and Spitkovsky is applied to SGR 0418+5729. It is shown that SGR 0418+5729 lies below the pulsar death line and its rotation-powered magnetospheric activities may therefore have stopped. The compact star is now spun down by the magnetic dipole moment perpendicular to its rotation axis. Our calculations show that under these assumptions there is the possibility of SGR 0418+5729 having a strong dipole magnetic field, if there is a small magnetic inclination angle. Its dipole magnetic field may be much higher than the characteristic magnetic field. Therefore, SGR 0418+5729 may be a normal magnetar instead of a low magnetic field magnetar.Astronomy & AstrophysicsSCI(E)10ARTICLE1null75
SGR 0418+5729,
No full textAims. We describe the so-called low magnetic field
magnetars, SGR 0418+5729, Swift J1822.3-1606, and the AXP
prototype 1E 2259+586 as massive, fast-rotating, highly magnetized white dwarfs.
Methods. We give bounds for the mass, radius, moment of inertia, and
magnetic field for these sources by requesting the stability of realistic, general
relativistic, uniformly rotating white dwarfs. We also present the theoretical expectation
of the infrared, optical, and ultraviolet emission of these objects and show their
consistency with the current available observational data.
Results. We improve the theoretical prediction of the lower limit of the
spindown rate of SGR 0418+5729; for a white dwarf close to its maximum stable mass we
obtain the very stringent interval for the spindown rate of
4.1 × 10-16 < Ṗ < 6 × 10-15,
where the upper value is the known observational limit. A lower limit has been also set
for Swift J1822.3-1606, whose spindown rate is not yet fully confirmed.
Our model provides for the source Ṗ ≥ 2.13 × 10-15 if the star
is close to its maximum stable mass. We give in addition the frequencies at which
absorption features could be present in the spectrum of these sources as the result of the
scattering of photons with the quantized electrons by the surface magnetic field
Block Card 5729 St. Clement Court
No full textThis image was produced by the Auditor's Office in Lucas County, Ohio for tax assessment purposes. Associated dates are approximate. Descriptive terms related to this photograph include: Cape Cod Style | 5729 St. Clement Court (Toledo, Ohio) | Dwelling | St. Clement Court (Toledo, Ohio) | Trilby Area (Toledo, Ohio)
GTC optical observations of SGR 0418+5729
No full textWe observed the field containing the new SGR 0418+5729 (ATel #2076, #2077) in the i'-band on 2009 September 15 with the OSIRIS camera (0.25"/pixel) mounted at the 10.4m Gran Telescopio Canarias (GTC) in the La Palma Observatory, as a part of our magnetar ToO observing program
Discovery of a new soft gamma repeater: SGR J0418+5729
No full textOn 2009 June 5, the Gamma-ray Burst Monitor (GBM) onboard the Fermi Gamma-ray Space Telescope triggered on two short and relatively dim bursts with spectral properties similar to soft gamma repeater (SGR) bursts. Independent localizations of the bursts by triangulation with the Konus-RF and with the Swift satellite confirmed their origin from the same, previously unknown, source. The subsequent discovery of X-ray pulsations with the Rossi X-ray Timing Explorer confirmed the magnetar nature of the new source, SGR J0418 + 5729. We describe here the Fermi/GBM observations, the discovery and the localization of this new SGR, and our infrared and Chandra X-ray observations. We also present a detailed temporal and spectral study of the two GBM bursts. SGR J0418 + 5729 is the second source discovered in the same region of the sky in the last year, the other one being SGR J0501 + 4516. Both sources lie in the direction of the galactic anti-center and presumably at the nearby distance of ~2 kpc (assuming they reside in the Perseus arm of our Galaxy). The near-threshold GBM detection of bursts from SGR J0418 + 5729 suggests that there may be more such "dim" SGRs throughout our Galaxy, possibly exceeding the population of "bright" SGRs. Finally, using sample statistics, we conclude that the number of observable active magnetars in our Galaxy at any given time is 10, in agreement with our earlier estimates
Is SGR 0418+5729 indeed a waning magnetar?
Get PDFSGR 0418+5729 is a transient soft gamma-ray repeater which underwent a major outburst in 2009 June, during which the emission of short bursts was observed. Its properties appeared quite typical of other sources of the same class until long-term X-ray monitoring failed to detect any period derivative. The present upper limit on P implies that the surface dipole field is Bp lsim 7.5 × 1012 G, well below those measured in other soft gamma-ray repeaters (SGRs) and in the Anomalous X-ray Pulsars (AXPs), a group of similar sources. Both SGRs and AXPs are currently believed to be powered by ultra-magnetized neutron stars (magnetars, Bp ≈ 1014-1015 G). SGR 0418+5729 hardly seems to fit in such a picture. We show that the magneto-rotational properties of SGR 0418+5729 can be reproduced if this is an aged magnetar, ≈1 Myr old, which experienced substantial field decay. The large initial toroidal component of the internal field required to match the observed properties of SGR 0418+5729 ensures that crustal fractures, and hence bursting activity, can still occur at the present time. The thermal spectrum observed during the outburst decay is compatible with the predictions of a resonant Compton scattering model (as in other SGRs/AXPs) if the field is low and the magnetospheric twist is moderate.This research was partially funded through grants AAE I/088/06/0 (R.T.), AYA 2010-21097-C03-02, GVPROMETE02009-103 (J.P.) and AYA2009-07391, SGR2009-811, TW2010005 (N.R.). N.R. also acknowledges support from a Ramon y Cajal Fellowship. P.E. acknowledges financial support from the Autonomous Region of Sardinia through a research grant under the program PO Sardegna FSE 2007-2013, L.R. 7/2007 “Promoting scientific research and innovation technology in Sardinia.
RXTE timing observations of SGR 0418+5729
Get PDFData from (publicly available) monitoring observations with RXTE of SGR 0418+5729 covering a time span of about 2 months since its discovery on June 5, 2009 (ATEL #2077,GCN #9499) have been used to construct an accurate phase-coherent timing solution. Such an analysis requires the pulse profile to be stable during the monitoring period in order to obtain reliable pulse time-of-arrivals, TOAs
Discovery of a new soft gamma repeater: SGR J0418+5729
Get PDFOn 2009 June 5, the Gamma-ray Burst Monitor (GBM) onboard the Fermi Gamma-ray Space Telescope triggered on two short and relatively dim bursts with spectral properties similar to soft gamma repeater (SGR) bursts. Independent localizations of the bursts by triangulation with the Konus-RF and with the Swift satellite confirmed their origin from the same, previously unknown, source. The subsequent discovery of X-ray pulsations with the Rossi X-ray Timing Explorer confirmed the magnetar nature of the new source, SGR J0418+5729. we describe here the Fermi/GBM observations, the discovery and the localization of this new SGR, and our infrared and Chandra X-ray observations. We also present a detailed temporal and spectral study of the two GBM bursts. SGR J0501+5729 is the second source discovered in the same region of the sky in the last year, the other one being SGR J0501+4516. Both sources lie in the direction of the galactic anti-center and presumably at the nearby distance of similar to 2 kpc (assuming they reside in the Perseus arm of our Galaxy). The near-threshold GBM detection of bursts from SGR J0418+5729 suggests that there may be more such "dim" SGRs throughout our Galaxy, possibly exceeding the population of "bright" SGRs. Finally, using sample statistics, we conclude that the number of observable active magnetars in our Galaxy at any given time is less than or similar to 10, in agreement with our earlier estimates
RXTE timing observations of SGR 0418+5729
Get PDFData from (publicly available) monitoring observations with RXTE of SGR 0418+5729 covering a time span of about 2 months since its discovery on June 5, 2009 (ATEL #2077,GCN #9499) have been used to construct an accurate phase-coherent timing solution. Such an analysis requires the pulse profile to be stable during the monitoring period in order to obtain reliable pulse time-of-arrivals, TOAs
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