A very-high-energy component deep in the γ-ray burst afterglow.

Gamma-ray bursts (GRBs) are brief flashes of γ-rays and are considered to be the most energetic explosive phenomena in the Universe1. The emission from GRBs comprises a short (typically tens of seconds) and bright prompt emission, followed by a much longer afterglow phase. During the afterglow phase, the shocked outflow-produced by the interaction between the ejected matter and the circumburst medium-slows down, and a gradual decrease in brightness is observed2. GRBs typically emit most of their energy via γ-rays with energies in the kiloelectronvolt-to-megaelectronvolt range, but a few photons with energies of tens of gigaelectronvolts have been detected by space-based instruments3. However, the origins of such high-energy (above one gigaelectronvolt) photons and the presence of very-high-energy (more than 100 gigaelectronvolts) emission have remained elusive4. Here we report observations of very-high-energy emission in the bright GRB 180720B deep in the GRB afterglow-ten hours after the end of the prompt emission phase, when the X-ray flux had already decayed by four orders of magnitude. Two possible explanations exist for the observed radiation: inverse Compton emission and synchrotron emission of ultrarelativistic electrons. Our observations show that the energy fluxes in the X-ray and γ-ray range and their photon indices remain comparable to each other throughout the afterglow. This discovery places distinct constraints on the GRB environment for both emission mechanisms, with the inverse Compton explanation alleviating the particle energy requirements for the emission observed at late times. The late timing of this detection has consequences for the future observations of GRBs at the highest energies.

Search for Dark Matter Annihilation Signals in the H.E.S.S. Inner Galaxy Survey.

The central region of the Milky Way is one of the foremost locations to look for dark matter (DM) signatures. We report the first results on a search for DM particle annihilation signals using new observations from an unprecedented γ-ray survey of the Galactic Center (GC) region, i.e., the Inner Galaxy Survey, at very high energies (≳100 GeV) performed with the H.E.S.S. array of five ground-based Cherenkov telescopes. No significant γ-ray excess is found in the search region of the 2014-2020 dataset and a profile likelihood ratio analysis is carried out to set exclusion limits on the annihilation cross section ⟨σv⟩. Assuming Einasto and Navarro-Frenk-White (NFW) DM density profiles at the GC, these constraints are the strongest obtained so far in the TeV DM mass range. For the Einasto profile, the constraints reach ⟨σv⟩ values of 3.7×10^{-26} cm^{3} s^{-1} for 1.5 TeV DM mass in the W^{+}W^{-} annihilation channel, and 1.2×10^{-26} cm^{3} s^{-1} for 0.7 TeV DM mass in the τ^{+}τ^{-} annihilation channel. With the H.E.S.S. Inner Galaxy Survey, ground-based γ-ray observations thus probe ⟨σv⟩ values expected from thermal-relic annihilating TeV DM particles.

The utilization of pre-implantation genetic testing in the absence of governance: a real-time experience.

To create a diagnostic document describing the utilization of pre-implantation genetic testing (PGT) in the absence of monitoring and regulation. Retrospective cohort study of couples undergoing PGT between 2004 and 2007 in Lebanon. The clinical indications for 192 PGT cycles performed during the study period were gender selection (96.3%), chromosomal aneuploidy (3.1%), and balanced translocation (0.5%). When gender selection was sought, the selection of a son was desired in 94.1% of cases. Of couples undergoing PGT for sex selection, 16.2% were childless, 8.6% had one child of the opposite gender, 28.1% had two same-gender children, 29.7% had three same-gender children, and 11.9% had four or more. Our findings demonstrate the morally questionable consequences of self-regulated systems in which physicians are the sole gatekeepers of norms and ethics.

Acceleration and transport of relativistic electrons in the jets of the microquasar SS 433.

SS 433 is a microquasar, a stellar binary system that launches collimated relativistic jets. We observed SS 433 in gamma rays using the High Energy Stereoscopic System (H.E.S.S.) and found an energy-dependent shift in the apparent position of the gamma-ray emission from the parsec-scale jets. These observations trace the energetic electron population and indicate that inverse Compton scattering is the emission mechanism of the gamma rays. Our modeling of the energy-dependent gamma-ray morphology constrains the location of particle acceleration and requires an abrupt deceleration of the jet flow. We infer the presence of shocks on either side of the binary system, at distances of 25 to 30 parsecs, and that self-collimation of the precessing jets forms the shocks, which then efficiently accelerate electrons.

Analysis of postural balance between two aquatic sports using vertical vs. horizontal body position.

OBJECTIVE: This study aims to analyze and compare the postural balance between two aquatic sports where vertical vs. horizontal body positions (i.e., windsurfing vs. swimming) are key techniques for both sports. SUBJECTS AND METHODS: Eight volunteer windsurfers and eight swimmers agreed to participate in this study. Each of the assessments was a 2D kinematic analysis of frontal and/or sagittal balance (i.e., in bipedal and/or unipedal stance) of the center of mass velocity on wobble board (Single Plane Balance Board) on hard and/or soft surface. Kinematic analysis was performed in 2D using two action-cams. Data were digitized using the video-based data analysis system SkillSpector. RESULTS: The results showed that the ANOVA, with repeated measures on 1 factor, showed a significant difference (p<0.001) between groups (i.e., swimmers and windsurfers) in all variables and in the interaction between ground (i.e., hard and foam) and group (p<0.01) in all tests in sagittal plane. Furthermore, for the ground*group interaction, a study (i.e., paired t-test) of the difference between balance (i.e., in frontal and/or sagittal plane) on hard and soft ground for each group showed that windsurfers had no difference in body sway in frontal and/or sagittal plane between hard and soft surface in bipedal stance. CONCLUSIONS: We concluded that the windsurfers showed better postural balance performances compared to swimmers in the bipedal posture on hard and soft ground. Also, the windsurfers presented a better stability level compared with the swimmers.

Time-resolved hadronic particle acceleration in the recurrent nova RS Ophiuchi.

Recurrent novae are repeating thermonuclear explosions in the outer layers of white dwarfs, due to the accretion of fresh material from a binary companion. The shock generated when ejected material slams into the companion star's wind can accelerate particles. We report very-high-energy (VHE; [Formula: see text]) gamma rays from the recurrent nova RS Ophiuchi, up to 1 month after its 2021 outburst, observed using the High Energy Stereoscopic System (H.E.S.S.). The temporal profile of VHE emission is similar to that of lower-energy giga-electron volt emission, indicating a common origin, with a 2-day delay in peak flux. These observations constrain models of time-dependent particle energization, favoring a hadronic emission scenario over the leptonic alternative. Shocks in dense winds provide favorable environments for efficient acceleration of cosmic rays to very high energies.

Revealing x-ray and gamma ray temporal and spectral similarities in the GRB 190829A afterglow.

Gamma-ray bursts (GRBs), which are bright flashes of gamma rays from extragalactic sources followed by fading afterglow emission, are associated with stellar core collapse events. We report the detection of very-high-energy (VHE) gamma rays from the afterglow of GRB 190829A, between 4 and 56 hours after the trigger, using the High Energy Stereoscopic System (H.E.S.S.). The low luminosity and redshift of GRB 190829A reduce both internal and external absorption, allowing determination of its intrinsic energy spectrum. Between energies of 0.18 and 3.3 tera-electron volts, this spectrum is described by a power law with photon index of 2.07 ± 0.09, similar to the x-ray spectrum. The x-ray and VHE gamma-ray light curves also show similar decay profiles. These similar characteristics in the x-ray and gamma-ray bands challenge GRB afterglow emission scenarios.

Genetics of autoimmune thyroid disease in the Lebanese population.

This study aims to investigate the association of human leukocyte antigen (HLA) class II genes and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) with autoimmune thyroid diseases in the Lebanese population. A total of 128 patients with autoimmune thyroid disease (55 with Graves' disease (GD) and 73 with Hashimoto's thyroiditis (HT)) were typed for HLA DQA1 (0301 and 0501) and DQB1 (0201, 0302, and 0303) and for 49A/G CTLA-4 using PCR-based sequence-specific priming methods. A total of 186 matched controls were typed for the same alleles and compared to the diseased population. Results showed no significant differences in HLA DQB1*0201 or DQB1*0301 allelic frequencies or CTLA-4 polymorphisms between patients and controls. For GD, there was a weak association with HLA DQB1*0302 [34.6% (19 of 55) vs. 21.5% (40 of 186), P = 0.048, odds ratio (OR) = 1.926, confidence interval (CI) = 0.999-3.715] and HLA DQB1*0302-DQA1*0501 haplotype [56.36% (31 of 55) vs. 40.8% (76 of 186), P = 0.042, OR = 1.870, CI = 1.018-3.433]. For HT, the frequencies of DQB1*0302-DQA1*0501 haplotype [28.8% (21of 73) vs. 14.5% (27 of 186), P = 0.008, OR = 2.378, CI = 1.241-4.558] and DQB1*0302-DQA1*0301 haplotype [60.2% (44 of 73) vs. 38.7% (72 of 186), P = 0.002, OR = 2.402, CI = 1.381-4.180] were significantly higher in patients. On the other hand, weak association was found between HT and DQA1*0301 allele [32.9% (24 of 73) vs. 20.9% (39 of 186), P = 0.044, OR = 1.846, CI = 1.011-3.373]. Findings show that DQB1*0302-DQA1*0501 and DQB1*0302-DQA1*0301 haplotypes may play a role in the pathogenesis of HT in the Lebanese population. For the 49A/G CTLA-4 polymorphism, no significant difference was found between patients and controls.