Comparing supernova remnants around strongly magnetized and canonical pulsars

The origin of the strong magnetic fields measured in magnetars is one of the main uncertainties in the neutron star field. On the other hand, the recent discovery of a large number of such strongly magnetized neutron stars, is calling for more investigation on their formation. The first proposed model for the formation of such strong magnetic fields in magnetars was through alpha-dynamo effects on the rapidly rotating core of a massive star. Other scenarios involve highly magnetic massive progenitors that conserve their strong magnetic moment into the core after the explosion, or a common envelope phase of a massive binary system. In this work, we do a complete re-analysis of the archival X-ray emission of the Supernova Remnants (SNR) surrounding magnetars, and compare our results with all other bright X-ray emitting SNRs, which are associated with Compact Central Objects (CCOs; which are proposed to have magnetar-like B-fields buried in the crust by strong accretion soon after their formation), high-B pulsars and normal pulsars. We find that emission lines in SNRs hosting highly magnetic neutron stars do not differ significantly in elements or ionization state from those observed in other SNRs, neither averaging on the whole remnants, nor studying different parts of their total spatial extent. Furthermore, we find no significant evidence that the total X-ray luminosities of SNRs hosting magnetars, are on average larger than that of typical young X-ray SNRs. Although biased by a small number of objects, we found that for a similar age, there is the same percentage of magnetars showing a detectable SNR than for the normal pulsar population.Comment: 16 pages, 5 figures, Accepted for publication in MNRA

The effects of magnetic field, age, and intrinsic luminosity on Crab-like pulsar wind nebulae

We investigate the time-dependent behavior of Crab-like pulsar wind nebulae (PWNe) generating a set of models using 4 different initial spin-down luminosities ($L_0 =\{1,0.1,0.01,0.001\} \times L_{0, {\rm Crab}}$), 8 values of magnetic fraction ($\eta =$ 0.001, 0.01, 0.03, 0.1, 0.5, 0.9, 0.99, and 0.999, i.e., from fully particle dominated to fully magnetically dominated nebulae), and 3 distinctive ages: 940, 3000, and 9000 years. We find that the self-synchrotron Compton (SSC) contribution is irrelevant for $L_{SD}$=0.1, 1, and 10% of the Crab power, disregarding the age and the magnetic fraction. SSC only becomes relevant for highly energetic ($\sim 70$ of the Crab), particle dominated nebulae at low ages (of less than a few kyr), located in a FIR background with relatively low energy density. Since no pulsar other than Crab is known to have these features, these results clarify why the Crab Nebula, and only it, is SSC dominated. No young PWN would be detectable at TeV energies if the pulsar's spin-down power is 0.1% Crab or lower. For 1% of the Crab spin-down, only particle dominated nebulae can be detected by H.E.S.S.-like telescopes when young enough (with details depending on the precise injection and environmental parameters). Above 10% of the Crab's power, all PWNe are detectable by H.E.S.S.-like telescopes if they are particle dominated, no matter the age. The impact of the magnetic fraction on the final SED is varied and important, generating order of magnitude variations in the luminosity output for systems that are otherwise the same (equal $P$, $\dot P$, injection, and environment).Comment: Accepted for publication in MNRA

Is there room for highly magnetized pulsar wind nebulae among those non-detected at TeV?

We make a time-dependent characterization of pulsar wind nebulae (PWNe) surrounding some of the highest spin-down pulsars that have not yet been detected at TeV. Our aim is assessing their possible level of magnetization. We analyze the nebulae driven by J2022+3842 in G76.9+1.0, J0540-6919 in N158A (the Crab twin), J1400--6325 in G310.6--1.6, and J1124--5916 in G292.0+0.18, none of which have been found at TeV energies. For comparison we refer to published models of G54.1+0.3, the Crab nebula, and develop a model for N157B in the Large Magellanic Cloud (LMC). We conclude that further observations of N158A could lead to its detection at VHE. According to our model, a FIR energy density of 5 eV cm$^{-3}$ could already lead to a detection in H.E.S.S. (assuming no other IC target field) within 50 hours of exposure and just the CMB inverse Compton contribution would produce VHE photons at the CTA sensitivity. We also propose models for G76.9+1.0, G310.6--1.6 and G292.0+1.8 which suggest their TeV detection in a moderate exposure for the latter two with the current generation of Cherenkov telescopes. We analyze the possibility that these PWNe are highly magnetized, where the low number of particles explains the residual detection in X-rays and their lack of detection at TeV energies.Comment: Accepted for publication in MNRA

Integral Inequalities and their Applications to the Calculus of Variations on Time Scales

We discuss the use of inequalities to obtain the solution of certain variational problems on time scales.Comment: To appear in Mathematical Inequalities & Applications (http://mia.ele-math.com). Accepted: 14.01.201

Exploring the effects of magnetar bursts in pulsar wind nebulae

We explore possible effects of a magnetar burst on the radio, X-ray, and gamma-ray flux of a pulsar wind nebula (PWN). We assume that the burst injects electron-positron pairs or powers the magnetic field and explore the total energy at injection and the spectral index needed in order to increase the X-ray flux by about one order of magnitude, as well as its decay time until reaching quiescence. We also explore magnetically powered phenomenology that could explain a temporary increase of the PWN synchrotron emitted flux and perhaps the relatively common lack of PWNe surrounding magnetars. This phenomenological study is of interest for fast radio bursts (FRBs) as well, given that the connection between magnetars and this kind of systems have been recently established observationally.Comment: 10 pages, 5 figures, accepted for publication in JHEA

Reverberation of pulsar wind nebulae (I): Impact of the medium properties and other parameters upon the extent of the compression

The standard approach to the long term evolution of pulsar wind nebulae (PWNe) is based on one-zone models treating the nebula as a uniform system. In particular for the late phase of evolved systems, many of the generally used prescriptions are based on educated guesses for which a proper assessment lacks. Using an advanced radiative code we evaluate the systematic impact of various parameters, like the properties of the supernova ejecta, of the inner pulsar, as well of the ambient medium, upon the extent of the reverberation phase of PWNe. We investigate how different prescriptions shift the starting time of the reverberation phase, how this affects the amount of the compression, and how much of this can be ascribable to the radiation processes. Some critical aspects are the description of the reverse shock evolution, the efficiency by which at later times material from the ejecta accretes onto the swept-up shell around the PWN, and finally the density, velocity and pressure profiles in the surrounding supernova remnant. We have explicitly treated the cases of the Crab Nebula, and of J1834.9--0846, taken to be representatives of the more and the less energetic pulsars, respectively. Especially for the latter object the prediction of large compression factors is confirmed, even larger in the presence of radiative losses, also confirming our former prediction of periods of super-efficiency during the reverberation phase of some PWNe.Comment: 12 pages, 7 figures, accepted for publication in MNRA

Application of Genetic Algorithms to the Manufacturing of Large Planar Array Antennas on RADAR Applications

A genetic algorithm (GA) is presented to obtain the best arrangement for the linear arrays (previously measured) used for the construction of a large planar array for radar applications. The designed algorithm allows the selection of the frequency and the pointing, furthermore the given weight of the different parameters of the radiation pattern (SLL, directivity…). Finally, some results are showed

HIFI Spectroscopy of H2O{\rm H_2O} submm Lines in Nuclei of Actively Star Forming Galaxies

We present a systematic survey of multiple velocity-resolved H$_2$O spectra using Herschel/HIFI towards nine nearby actively star forming galaxies. The ground-state and low-excitation lines (E$_{\rm up}\,\le 130\,{\rm K}$) show profiles with emission and absorption blended together, while absorption-free medium-excitation lines ($130\,{\rm K}\, \le\, E_{\rm up}\,\le\,350\,{\rm K}$) typically display line shapes similar to CO. We analyze the HIFI observation together with archival SPIRE/PACS H$_2$O data using a state-of-the-art 3D radiative transfer code which includes the interaction between continuum and line emission. The water excitation models are combined with information on the dust- and CO spectral line energy distribution to determine the physical structure of the interstellar medium (ISM). We identify two ISM components that are common to all galaxies: A warm ($T_{\rm dust}\,\sim\,40-70\,{\rm K}$), dense ($n({\rm H})\,\sim\,10^5-10^6\,{\rm cm^{-3}}$) phase which dominates the emission of medium-excitation H$_2$O lines. This gas phase also dominates the FIR emission and the CO intensities for $J_{\rm up} > 8$. In addition a cold ($T_{\rm dust}\,\sim\,20-30\,{\rm K}$), dense ($n({\rm H})\sim\,10^4- 10^5\,{\rm cm^{-3}}$) more extended phase is present. It outputs the emission in the low-excitation H$_2$O lines and typically also produces the prominent line absorption features. For the two ULIRGs in our sample (Arp 220 and Mrk 231) an even hotter and more compact (R$_s\,\le\,100$ pc) region is present which is possibly linked to AGN activity. We find that collisions dominate the water excitation in the cold gas and for lines with $E_{\rm up}\le300\,{\rm K}$ and $E_{\rm up}\le800\,{\rm K}$ in the warm and hot component, respectively. Higher energy levels are mainly excited by IR pumping.Comment: Accepted by ApJ, in pres

Dynamical Masses for Pre-Main Sequence Stars: A Preliminary Physical Orbit for V773 Tau A

We report on interferometric and radial-velocity observations of the double-lined 51-d period binary (A) component of the quadruple pre-main sequence (PMS) system V773 Tau. With these observations we have estimated preliminary visual and physical orbits of the V773 Tau A subsystem. Among other parameters, our orbit model includes an inclination of 66.0 $\pm$ 2.4 deg, and allows us to infer the component dynamical masses and system distance. In particular we find component masses of 1.54 $\pm$ 0.14 and 1.332 $\pm$ 0.097 M_{\sun} for the Aa (primary) and Ab (secondary) components respectively. Our modeling of the subsystem component spectral energy distributions finds temperatures and luminosities consistent with previous studies, and coupled with the component mass estimates allows for comparison with PMS stellar models in the intermediate-mass range. We compare V773 Tau A component properties with several popular solar-composition models for intermediate-mass PMS stars. All models predict masses consistent to within 2-sigma of the dynamically determined values, though some models predict values that are more consistent than others.Comment: ApJ in press; 25 pages, 6 figures; data tables available in journal versio

Reticulocyte Maturation Parameters Are Reliable Early Predictors of Hematopoietic Engraftment after Allogeneic Stem Cell Transplantation

AbstractEarly detection of donor-derived hematopoietic restoration after allogeneic stem cell transplantation (allo-SCT) is a crucial issue in the management of heavily immunocompromised patients. The aim of this prospective study was to validate our previously defined cutoff values for reticulocyte maturation parameters as early predictors of hematopoietic engraftment. Importantly, the effect of clinical variables in reticulocyte engraftment was also sought. For this purpose, we prospectively studied 136 consecutive patients undergoing allo-SCT from related (n = 89) or unrelated (n = 47) donors. High fluorescence reticulocytes (RETH), immature reticulocyte fraction (IRF), mean fluorescence index (MFI), and mean reticulocyte volume (MRV) were automatically measured in peripheral blood samples drawn on a daily basis. We previously defined reticulocyte engraftment when MFI ≥10, RETH ≥3%, IRF ≥10%, and MRV ≥110 fL. Median neutrophil engraftment was 18 days (range, 10-35 days); for reticulocyte parameters, the values were 14 days for IRF (range, 7-45 days), 14 days for MFI (range, 7-43 days), 15 days for RETH (range, 7-43 days), and 21 days for MRV (range, 9-74 days). These differences reached statistical significance for MFI and IRF when compared with standard neutrophil recovery, even when analyzing siblings or unrelated donors separately. In univariate analysis, donor-recipient ABO disparity adversely influenced erythroid engraftment (P = .04 for IRF, P = .03 for MFI), but the infusion of >2.9 × 106/kg of CD34+ cells was associated with a shorter time to reach erythroid engraftment (P = .02 for IRF and MFI). In Cox regression analysis, ≥100/μL neutrophils and IRF ≥10% were predictive parameters for standard neutrophil engraftment. Based on these findings, we suggest that serial measurement of IRF or MFI should be routinely used to trace hematopoietic restoration after allo-SCT because these preceded standard neutrophil recovery by a median of 4 days and are therefore very useful to make clinical decisions