Periodic Emission from the Gamma-ray Binary 1FGL J1018.6-5856

Gamma-ray binaries are stellar systems containing a neutron star or black hole with gamma-ray emission produced by an interaction between the components. These systems are rare, even though binary evolution models predict dozens in our Galaxy. A search for gamma-ray binaries with the Fermi Large Area Telescope (LAT) shows that IFGL JI018.6-5856 exhibits intensity and spectral modulation with a 16.6 day period. We identified a variable X-ray counterpart, which shows a sharp maximum coinciding with maximum gamma-ray emission, as well as an 06V f) star optical counterpart and a radio counterpart that is also apparently modulated on the orbital period. IFGL J1018.6-5856 is thus a gamma-ray binary, and its detection suggests the presence of other fainter binaries in the Galaxy

Leg strength in peripheral arterial disease: associations with disease severity and lower-extremity performance

AbstractObjectiveThe purpose of this study was to determine relationships between lower-extremity arterial obstruction, leg strength, and lower-extremity functioning.DesignThe study design was cross-sectional. A total of 514 outpatients (269 with ankle-brachial index [ABI] <0.90), aged 55 and older, were identified from three Chicago-area hospitals. Individuals with history of lower-extremity revascularization were excluded.Main outcome measuresStrength in each leg, 6-minute walk, 4-meter walking velocity, accelerometer-measured physical activity, and a summary performance score were measured. The summary performance score is a composite measure of lower-extremity functioning, ranging from 0 to 12 (12 = best). The leg with the lower ABI was defined as the “index” leg, and the leg with higher ABI was defined as the “contralateral” leg.ResultsIndex leg ABI levels were associated linearly and significantly with strength for hip extension (P < .001), hip flexion (P < .001), knee extension (P = .066), and knee flexion (P = .003), adjusting for known and potential confounders. In adjusted analyses, the index ABI was also associated linearly and significantly with strength in the contralateral leg. Adjusting for confounders, including ABI, knee extension strength, was associated independently with functional measures.ConclusionAmong patients without prior leg revascularization, strength in each leg is highly correlated with the lower-leg ABI. Leg strength is associated independently with functional performance. Further study is needed to determine whether lower-extremity resistance training improves functioning in patients with peripheral arterial disease

Detection of the Characteristic Pion-Decay Signature in Supernova Remnants

Cosmic rays are particles (mostly protons) accelerated to relativistic speeds. Despite wide agreement that supernova remnants (SNRs) are the sources of galactic cosmic rays, unequivocal evidence for the acceleration of protons in these objects is still lacking. When accelerated protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma rays. This offers a compelling way to detect the acceleration sites of protons. The identification of pion-decay gamma rays has been difficult because high-energy electrons also produce gamma rays via bremsstrahlung and inverse Compton scattering. We detected the characteristic pion-decay feature in the gamma-ray spectra of two SNRs, IC 443 and W44, with the Fermi Large Area Telescope. This detection provides direct evidence that cosmic-ray protons are accelerated in SNRs.Fil: Ackerman, M.. Deutsches Elektronen Synchrotron DESY; AlemaniaFil: Ajello, M.. University of California; Estados UnidosFil: Allafort, A.. University Of Stanford; Estados UnidosFil: Baldini, L.. Universita Degli Studi Di Pisa; ItaliaFil: Ballet, J.. Universit´e Paris Diderot; FranciaFil: Garbiellini, G.. Universit`a di Trieste; ItaliaFil: Baring, M. G.. Rice University; Estados UnidosFil: Bastieri, D.. Universita Di Padova; ItaliaFil: Bechtol, K.. University Of Stanford; Estados UnidosFil: Bellazzini, R.. Istituto Nazionale di Fisica Nucleare; ItaliaFil: Blandford, R. D.. University Of Stanford; Estados UnidosFil: Bloom, E. D.. University Of Stanford; Estados UnidosFil: Bonamente, E.. Universita degli Studi di Perugia; ItaliaFil: Borgland, A. W.. University of Stanford; Estados UnidosFil: Bottaccini, E.. University Of Stanford; Estados UnidosFil: Brandt, T. J.. National Aeronautics And Space Administration. Goddart Institute For Space Studies; Estados UnidosFil: Bregeon, J.. Istituto Nazionale di Fisica Nucleare; ItaliaFil: Brigida, M.. Universit`a e del Politecnico di Bari; ItaliaFil: Bruel, P.. Ecole polytechnique, CNRS; FranciaFil: Buehler, R.. University Of Stanford; Estados UnidosFil: Busetto, G.. Universita di Padova; ItaliaFil: Buson, S..Fil: Caliandro, G. A.. Institut de Ciencies de l’Espai (IEEE-CSIC); EspañaFil: Cameron, R. A.. University Of Stanford; Estados UnidosFil: Caraveo, P. A.. INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica; ItaliaFil: Casandjian, J. M.. Universite Paris Diderot; FranciaFil: Cecchi, C.. Universita degli Studi di Perugia; ItaliaFil: Celic, O.. National Aeronautics And Space Administration. Goddart Institute For Space Studies; Estados UnidosFil: Charles, E.. University Of Stanford; Estados UnidosFil: Cillis, Analia Nilda. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

Histone H3 Serine 57 and Lysine 56 Interplay in Transcription Elongation and Recovery from S-Phase Stress

Contains fulltext : 84400.pdf (publisher's version ) (Open Access

The Vanishing of the Primary Emission Region in PKS 1510-089

In 2021 July, PKS 1510-089 exhibited a significant flux drop in the high-energy γ-ray (by a factor 10) and optical (by a factor 5) bands and remained in this low state throughout 2022. Similarly, the optical polarization in the source vanished, resulting in the optical spectrum being fully explained through the steady flux of the accretion disk and the broad-line region. Unlike the aforementioned bands, the very-high-energy γ-ray and X-ray fluxes did not exhibit a significant flux drop from year to year. This suggests that the steady-state very-high-energy γ-ray and X-ray fluxes originate from a different emission region than the vanished parts of the high-energy γ-ray and optical jet fluxes. The latter component has disappeared through either a swing of the jet away from the line of sight or a significant drop in the photon production efficiency of the jet close to the black hole. Either change could become visible in high-resolution radio images

The Elg1 Clamp Loader Plays a Role in Sister Chromatid Cohesion

Mutations in the ELG1 gene of yeast lead to genomic instability, manifested in high levels of genetic recombination, chromosome loss, and gross chromosomal rearrangements. Elg1 shows similarity to the large subunit of the Replication Factor C clamp loader, and forms a RFC-like (RLC) complex in conjunction with the 4 small RFC subunits. Two additional RLCs exist in yeast: in one of them the large subunit is Ctf18, and in the other, Rad24. Ctf18 has been characterized as the RLC that functions in sister chromatid cohesion. Here we present evidence that the Elg1 RLC (but not Rad24) also plays an important role in this process. A genetic screen identified the cohesin subunit Mcd1/Scc1 and its loader Scc2 as suppressors of the synthetic lethality between elg1 and ctf4. We describe genetic interactions between ELG1 and genes encoding cohesin subunits and their accessory proteins. We also show that defects in Elg1 lead to higher precocious sister chromatid separation, and that Ctf18 and Elg1 affect cohesion via a joint pathway. Finally, we localize both Ctf18 and Elg1 to chromatin and show that Elg1 plays a role in the recruitment of Ctf18. Our results suggest that Elg1, Ctf4, and Ctf18 may coordinate the relative movement of the replication fork with respect to the cohesin ring

Constraints on the intergalactic magnetic field using Fermi-LAT and H.E.S.S. blazar observations

Magnetic fields in galaxies and galaxy clusters are believed to be the result of the amplification of intergalactic seed fields during the formation of large-scale structures in the universe. However, the origin, strength, and morphology of this intergalactic magnetic field (IGMF) remain unknown. Lower limits on (or indirect detection of) the IGMF can be obtained from observations of high-energy gamma rays from distant blazars. Gamma rays interact with the extragalactic background light to produce electron-positron pairs, which can subsequently initiate electromagnetic cascades. The $\gamma$-ray signature of the cascade depends on the IGMF since it deflects the pairs. Here we report on a new search for this cascade emission using a combined data set from the Fermi Large Area Telescope and the High Energy Stereoscopic System. Using state-of-the-art Monte Carlo predictions for the cascade signal, our results place a lower limit on the IGMF of $B > 7.1\times10^{-16}$ G for a coherence length of 1 Mpc even when blazar duty cycles as short as 10 yr are assumed. This improves on previous lower limits by a factor of 2. For longer duty cycles of $10^4$ ($10^7$) yr, IGMF strengths below $1.8\times10^{-14}$ G ($3.9\times10^{-14}$ G) are excluded, which rules out specific models for IGMF generation in the early universe.Comment: 20 pages, 7 figures, 4 tables. Accepted for publication in ApJ Letters. Auxiliary data is provided in electronic format at https://zenodo.org/record/801431

HESS J1809−-193: a halo of escaped electrons around a pulsar wind nebula?

Context. HESS J1809$-$193 is an unassociated very-high-energy $\gamma$-ray source located on the Galactic plane. While it has been connected to the nebula of the energetic pulsar PSR J1809$-$1917, supernova remnants and molecular clouds present in the vicinity also constitute possible associations. Recently, the detection of $\gamma$-ray emission up to energies of $\sim$100 TeV with the HAWC observatory has led to renewed interest in HESS J1809$-$193. Aims. We aim to understand the origin of the $\gamma$-ray emission of HESS J1809$-$193. Methods. We analysed 93.2 h of data taken on HESS J1809$-$193 above 0.27 TeV with the High Energy Stereoscopic System (H.E.S.S.), using a multi-component, three-dimensional likelihood analysis. In addition, we provide a new analysis of 12.5 yr of Fermi-LAT data above 1 GeV within the region of HESS J1809$-$193. The obtained results are interpreted in a time-dependent modelling framework. Results. For the first time, we were able to resolve the emission detected with H.E.S.S. into two components: an extended component that exhibits a spectral cut-off at $\sim$13 TeV, and a compact component that is located close to PSR J1809$-$1917 and shows no clear spectral cut-off. The Fermi-LAT analysis also revealed extended $\gamma$-ray emission, on scales similar to that of the extended H.E.S.S. component. Conclusions. Our modelling indicates that based on its spectrum and spatial extent, the extended H.E.S.S. component is likely caused by inverse Compton emission from old electrons that form a halo around the pulsar wind nebula. The compact component could be connected to either the pulsar wind nebula or the supernova remnant and molecular clouds. Due to its comparatively steep spectrum, modelling the Fermi-LAT emission together with the H.E.S.S. components is not straightforward. (abridged)Comment: 14 pages, 10 figures. Accepted for publication in A&A. Corresponding authors: Vikas Joshi, Lars Mohrman

H.E.S.S. follow-up observations of GRB221009A

GRB221009A is the brightest gamma-ray burst ever detected. To probe the very-high-energy (VHE, $>$\!100 GeV) emission, the High Energy Stereoscopic System (H.E.S.S.) began observations 53 hours after the triggering event, when the brightness of the moonlight no longer precluded observations. We derive differential and integral upper limits using H.E.S.S. data from the third, fourth, and ninth nights after the initial GRB detection, after applying atmospheric corrections. The combined observations yield an integral energy flux upper limit of $\Phi_\mathrm{UL}^{95\%} = 9.7 \times 10^{-12}~\mathrm{erg\,cm^{-2}\,s^{-1}}$ above $E_\mathrm{thr} = 650$ GeV. The constraints derived from the H.E.S.S. observations complement the available multiwavelength data. The radio to X-ray data are consistent with synchrotron emission from a single electron population, with the peak in the SED occurring above the X-ray band. Compared to the VHE-bright GRB190829A, the upper limits for GRB221009A imply a smaller gamma-ray to X-ray flux ratio in the afterglow. Even in the absence of a detection, the H.E.S.S. upper limits thus contribute to the multiwavelength picture of GRB221009A, effectively ruling out an IC dominated scenario.Comment: 10 pages, 4 figures. Accepted for publication in APJL. Corresponding authors: J. Damascene Mbarubucyeye, H. Ashkar, S. J. Zhu, B. Reville, F. Sch\"ussle