Soft-gamma-ray repeaters (SGRs) are galactic X-ray stars that emit numerous short-duration (about 0.1 s) bursts of hard X-rays during sporadic active periods. They are thought to be magnetars: ...strongly magnetized neutron stars with emissions powered by the dissipation of magnetic energy. Here we report the detection of a long (380 s) giant flare from SGR 1806-20, which was much more luminous than any previous transient event observed in our Galaxy. (In the first 0.2 s, the flare released as much energy as the Sun radiates in a quarter of a million years.) Its power can be explained by a catastrophic instability involving global crust failure and magnetic reconnection on a magnetar, with possible large-scale untwisting of magnetic field lines outside the star. From a great distance this event would appear to be a short-duration, hard-spectrum cosmic gamma-ray burst. At least a significant fraction of the mysterious short-duration gamma-ray bursts may therefore come from extragalactic magnetars.
Aims. We study a sample of 427 gamma-ray bursts (GRBs), measured by the RHESSI satellite, statistically with respect to duration and hardness ratio. Methods. Standard statistical tests were used, ...such as $\chi^2$, F-test, and the maximum likelihood ratio test, to compare the number of GRB groups in the RHESSI database with that of the BATSE database. Results. Previous studies based on the BATSE Catalog claim the existence of an intermediate GRB group, besides the long and short groups. Using only the GRB duration T90 as information and $\chi^2$ or F-test, we do not find any statistically significant intermediate group in the RHESSI data. However, maximum likelihood ratio test reveals a significant intermediate group. Using the 2-dimensional hardness/T90 plane, the maximum likelihood analysis also reveals a significant intermediate group. In contrast to the BATSE database, the intermediate group in the RHESSI data set is harder than the long one. Conclusions. The existence of an intermediate group follows not only from the BATSE data set, but also from the RHESSI one.
The design and the simulated performances of a compact detector dedicated to the measurement of GRB photon polarization is presented. Such a detector would permit to answer the question “are most of ...the GRB strongly polarized?” in a mission of one year in space.
Using the RHESSI satellite as a Compton polarimeter, a recent study claimed that the prompt emission of GRB 021206 was almost fully linearly polarized. This was challenged by a subsequent reanalysis. ...We present a novel approach, applying our method to the same data. We identify Compton scattering candidates by carefully filtering events in energy, time, and scattering geometry. Our polarization search is based on time-dependent scattering rates in perpendicular directions, thus optimally excluding systematic errors. We perform simulations to obtain the instrument's polarimetric sensitivity, and these simulations include photon polarization. For GRB 021206, we formally find a linear polarization degree of capital pi sub(GRB) = 41 super(+) sub(-) super(5) sub(4) super(7) sub(4%), concluding that the data quality is insufficient to constrain the polarization degree in this case. We further applied our analysis to GRB 030519B and again found a null result.
GRB 051103 is considered to be a candidate soft gamma repeater (SGR) extragalactic giant magnetar flare by virtue of its proximity on the sky to M81/M82, as well as its time history, localization and ...energy spectrum. We have derived a refined interplanetary network localization for this burst which reduces the size of the error box by over a factor of 2. We examine its time history for evidence of a periodic component, which would be one signature of an SGR giant flare, and conclude that this component is neither detected nor detectable under reasonable assumptions. We analyse the time-resolved energy spectra of this event with improved time and energy resolution, and conclude that although the spectrum is very hard its temporal evolution at late times cannot be determined, which further complicates the giant flare association. We also present new optical observations reaching limiting magnitudes of R > 24.5, about 4-mag deeper than previously reported. In tandem with serendipitous observations of M81 taken immediately before and 1 month after the burst, these place strong constraints on any rapidly variable sources in the region of the refined error ellipse proximate to M81. We do not find any convincing afterglow candidates from either background galaxies or sources in M81, although within the refined error region we do locate two UV bright star-forming regions which may host SGRs. A supernova remnant (SNR) within the error ellipse could provide further support for an SGR giant flare association, but we were unable to identify any SNR within the error ellipse. These data still do not allow strong constraints on the nature of the GRB 051103 progenitor, and suggest that candidate extragalactic SGR giant flares will be difficult, although not impossible, to confirm.
GRB 021206 is one of the brightest GRBs ever observed. Its prompt emission, as measured by RHESSI, shows an unexpected spectral feature. The spectrum has a peak energy of about 700 keV and can be ...described by a Band function up to 4.5 MeV. Above 4.5 MeV, the spectrum hardens again, so the Band function fails to fit the whole RHESSI energy range up to 17 MeV. Nor does the sum of a blackbody function plus a power law, even though such a function can describe a spectral hardening. The cannonball model, on the other hand, predicts such a hardening, and we found that it fits the spectrum of GRB 021206 perfectly. We also analyzed other strong GRBs observed by RHESSI, namely, GRBs 020715, 021008, 030329, 030406, 030519B, 031027, and 031111. We found that all their spectra can be fit by the cannonball model, as well as by a Band function.
Abstract
Auditory synaptopathy/neuropathy (AS/AN) is a distinct type of sensorineural hearing loss in which the cochlear sensitivity to sound (i.e. active cochlear amplification by outer hair cells) ...is preserved whereas sound encoding by inner hair cells and/or auditory nerve fibers is disrupted owing to genetic or environmental factors. Autosomal-dominant auditory neuropathy type 2 (AUNA2) was linked either to chromosomal bands 12q24 or 13q34 in a large German family in 2017. By whole-genome sequencing, we now detected a 5500 bp deletion in ATP11A on chromosome 13q34 segregating with the phenotype in this family. ATP11A encodes a P-type ATPase that translocates phospholipids from the exoplasmic to the cytoplasmic leaflet of the plasma membrane. The deletion affects both isoforms of ATP11A and activates a cryptic splice site leading to the formation of an alternative last exon. ATP11A carrying the altered C-terminus loses its flippase activity for phosphatidylserine. Atp11a is expressed in fibers and synaptic contacts of the auditory nerve and in the cochlear nucleus in mice, and conditional Atp11a knockout mice show a progressive reduction of the spiral ganglion neuron compound action potential, recapitulating the human phenotype of AN. By combining whole-genome sequencing, immunohistochemistry, in vitro functional assays and generation of a mouse model, we could thus identify a partial deletion of ATP11A as the genetic cause of AUNA2.
The giant flare of 2004 December 27 from SGR 1806-20 represents one of the most extraordinary events captured in over three decades of monitoring the unk-ray sky. One measure of the intensity of the ...main peak is its effect on X- and unk-ray instruments. RHESSI, an instrument designed to study the brightest solar flares, was completely saturated for similar to 0.5 s following the start of the main peak. A fortuitous alignment of SGR 1806-20 near the Sun at the time of the giant flare, however, allowed RHESSI a unique view of the giant flare event, including the precursor, the main-peak decay, and the pulsed tail. Since RHESSI was saturated during the main peak, we augment these observations with Wind and RHESSI particle detector data in order to reconstruct the main peak as well. Here we present detailed spectral analysis and evolution of the giant flare. We report the identification of a relatively soft fast peak just milliseconds before the main peak, whose timescale and size scale indicate a magnetospheric origin. We present the novel detection of emission extending up to 17 MeV immediately following the main peak, perhaps revealing a highly extended corona driven by the hyper-Eddington luminosities. The spectral evolution and pulse evolution during the tail are presented, demonstrating significant magnetospheric twist during this phase, but no apparent magnetospheric evolution. Blackbody radii are derived for every stage of the flare, which show remarkable agreement despite the range of luminosities and temperatures covered. Finally, we confirm the existence of a hard afterglow emission extending up to 2.5 MeV in the hundreds of seconds following the giant flare.
We recently showed that blunt chest trauma reduced the expression of the myocardial oxytocin receptor (Oxtr), which was further aggravated by genetic deletion of the H2S-producing enzyme ...cystathionine γ-lyase (CSE). Exogenous H2S supplementation restored myocardial Oxtr expression under these conditions. Early life stress (ELS) is a risk factor for cardiovascular disease by affecting vascular and heart structures. Therefore, we tested the hypotheses that (i) ELS affects cardiac Oxtr and CSE expressions and (ii) Oxtr and CSE expression patterns depend on the duration of stress exposure. Thus, two stress paradigms were compared: long- and short-term separation stress (LTSS and STSS, respectively). Cardiac Oxtr expression was differentially affected by the two stress paradigms with a significant reduction after LTSS and a significant increase after STSS. CSE expression, which was significantly reduced in Oxtr-/- knockout hearts, was downregulated and directly related to Oxtr expression in LTSS hearts (r=0.657, p=0.012). In contrast, CSE expression was not related to Oxtr upregulation in STSS. Plasma Oxt levels were not affected by either ELS paradigm. The coincidence of LTSS-induced reduction of cardiac Oxtr and reduced CSE expression may suggest a novel pathophysiological link between early life adversities and increased risk for the development of cardiovascular disorders in adulthood.
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