1. |
- Algaba, Juan-Carlos, et al.
(author)
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Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign
- 2021
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In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 911:1
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Research review (peer-reviewed)abstract
- In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109 M o˙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87's spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded.
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2. |
- Abe, H., et al.
(author)
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Gamma-ray observations of MAXI J1820+070 during the 2018 outburst
- 2022
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 517:4, s. 4736-4751
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Journal article (peer-reviewed)abstract
- MAXIJ1820+070 is a low-mass X-ray binary with a black hole (BH) as a compact object. This binary underwent an exceptionally bright X-ray outburst from 2018 March to October, showing evidence of a non-thermal particle population through its radio emission during this whole period. The combined results of 59.5 h of observations of the MAXI J1820+070 outburst with the H.E.S.S., MAGIC and VERITAS experiments at energies above 200 GeV are presented, together with Fermi-LAT data between 0.1 and 500 GeV, and multiwavelength observations from radio to X-rays. Gamma-ray emission is not detected from MAXI J1820+070, but the obtained upper limits and the multiwavelength data allow us to put meaningful constraints on the source properties under reasonable assumptions regarding the non-thermal particle population and the jet synchrotron spectrum. In particular, it is possible to show that, if a high-energy (HE) gamma-ray emitting region is present during the hard state of the source, its predicted flux should be at most a factor of 20 below the obtained Fermi-LAT upper limits, and closer to them for magnetic fields significantly below equipartition. During the state transitions, under the plausible assumption that electrons are accelerated up to similar to 500 GeV, the multiwavelength data and the gamma-ray upper limits lead consistently to the conclusion that a potential HE and very-HE gamma-ray emitting region should be located at a distance from the BH ranging between 10(11) and 10(13) cm. Similar outbursts from low-mass X-ray binaries might be detectable in the near future with upcoming instruments such as CTA.
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3. |
- Adams, C. B., et al.
(author)
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Observation of the Gamma-Ray Binary HESS J0632+057 with the HESS, MAGIC, and VERITAS Telescopes
- 2021
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In: Astrophysical Journal. - : Institute of Physics Publishing (IOPP). - 0004-637X .- 1538-4357. ; 923:2
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Journal article (peer-reviewed)abstract
- The results of gamma-ray observations of the binary system HESS J0632 + 057 collected during 450 hr over 15 yr, between 2004 and 2019, are presented. Data taken with the atmospheric Cherenkov telescopes H.E.S.S., MAGIC, and VERITAS at energies above 350 GeV were used together with observations at X-ray energies obtained with Swift-XRT, Chandra, XMM-Newton, NuSTAR, and Suzaku. Some of these observations were accompanied by measurements of the H alpha emission line. A significant detection of the modulation of the very high-energy gamma-ray fluxes with a period of 316.7 +/- 4.4 days is reported, consistent with the period of 317.3 +/- 0.7 days obtained with a refined analysis of X-ray data. The analysis of data from four orbital cycles with dense observational coverage reveals short-timescale variability, with flux-decay timescales of less than 20 days at very high energies. Flux variations observed over a timescale of several years indicate orbit-to-orbit variability. The analysis confirms the previously reported correlation of X-ray and gamma-ray emission from the system at very high significance, but cannot find any correlation of optical H alpha parameters with fluxes at X-ray or gamma-ray energies in simultaneous observations. The key finding is that the emission of HESS J0632 + 057 in the X-ray and gamma-ray energy bands is highly variable on different timescales. The ratio of gamma-ray to X-ray flux shows the equality or even dominance of the gamma-ray energy range. This wealth of new data is interpreted taking into account the insufficient knowledge of the ephemeris of the system, and discussed in the context of results reported on other gamma-ray binary systems.
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4. |
- Veres, P., et al.
(author)
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Observation of inverse Compton emission from a long gamma-ray burst
- 2019
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In: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 575:7783, s. 459-
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Journal article (peer-reviewed)abstract
- Long-duration gamma-ray bursts (GRBs) originate from ultra-relativistic jets launched from the collapsing cores of dying massive stars. They are characterized by an initial phase of bright and highly variable radiation in the kiloelectron volt-to-mega electronvoltband, which is probably produced within the jet and lasts from milliseconds to minutes, known as the prompt emission(1,2). Subsequently, the interaction of the jet with the surrounding medium generates shock waves that are responsible for the afterglow emission, which lasts from days to months and occurs over a broad energy range from the radio to the gigaelectronvolt bands(1-6). The afterglow emission is generally well explained as synchrotron radiation emitted by electrons accelerated by the external shock(7-9). Recently, intense long-lasting emission between 0.2 and 1 teraelectronvolts was observed from GRB 190114C(10,11). Here we report multifrequency observations of GRB 190114C, and study the evolution in time of the GRB emission across 17 orders of magnitude in energy, from 5 x 10(-6) to 10(12) electronvolts. We find that the broadband spectral energy distribution is double-peaked, with the teraelectronvolt emission constituting a distinct spectral component with power comparable to the synchrotron component. This component is associated with the afterglow and is satisfactorily explained by inverse Compton up-scattering of synchrotron photons by high-energy electrons. We find that the conditions required to account for the observed teraelectronvolt component are typical for GRBs, supporting the possibility that inverse Compton emission is commonly produced in GRBs.
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5. |
- Abdalla, H., et al.
(author)
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HESS and MAGIC observations of a sudden cessation of a very-high-energy gamma-ray flare in PKS 1510-089 in May 2016
- 2021
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 648
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Journal article (peer-reviewed)abstract
- The flat spectrum radio quasar (FSRQ) PKS 1510-089 is known for its complex multiwavelength behaviour and it is one of only a few FSRQs detected in very-high-energy (VHE, E>100 GeV) gamma rays. The VHE gamma -ray observations with H.E.S.S. and MAGIC in late May and early June 2016 resulted in the detection of an unprecedented flare, which revealed, for the first time, VHE gamma -ray intranight variability for this source. While a common variability timescale of 1.5 h has been found, there is a significant deviation near the end of the flare, with a timescale of similar to 20 min marking the cessation of the event. The peak flux is nearly two orders of magnitude above the low-level emission. For the first time, a curvature was detected in the VHE gamma -ray spectrum of PKS 1510-089, which can be fully explained by the absorption on the part of the extragalactic background light. Optical R-band observations with ATOM revealed a counterpart of the gamma -ray flare, even though the detailed flux evolution differs from the VHE gamma -ray light curve. Interestingly, a steep flux decrease was observed at the same time as the cessation of the VHE gamma -ray flare. In the high-energy (HE, E> 100 MeV) gamma -ray band, only a moderate flux increase was observed with Fermi-LAT, while the HE gamma -ray spectrum significantly hardens up to a photon index of 1.6. A search for broad-line region (BLR) absorption features in the gamma -ray spectrum indicates that the emission region is located outside of the BLR. Radio very-long-baseline interferometry observations reveal a fast-moving knot interacting with a standing jet feature around the time of the flare. As the standing feature is located similar to 50 pc from the black hole, the emission region of the flare may have been located at a significant distance from the black hole. If this is indeed a true correlation, the VHE gamma rays must have been produced far down in the jet, where turbulent plasma crosses a standing shock.
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6. |
- Sen, P, et al.
(author)
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Vaccine hesitancy decreases in rheumatic diseases, long-term concerns remain in myositis: a comparative analysis of the COVAD surveys
- 2023
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In: Rheumatology (Oxford, England). - : Oxford University Press (OUP). - 1462-0332 .- 1462-0324. ; 62:10, s. 3291-3301
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Journal article (peer-reviewed)abstract
- ObjectiveCOVID-19 vaccines have a favorable safety profile in patients with autoimmune rheumatic diseases (AIRDs) such as idiopathic inflammatory myopathies (IIMs); however, hesitancy continues to persist among these patients. Therefore, we studied the prevalence, predictors and reasons for hesitancy in patients with IIMs, other AIRDs, non-rheumatic autoimmune diseases (nrAIDs) and healthy controls (HCs), using data from the two international COVID-19 Vaccination in Autoimmune Diseases (COVAD) e-surveys.MethodsThe first and second COVAD patient self-reported e-surveys were circulated from March to December 2021, and February to June 2022 (ongoing). We collected data on demographics, comorbidities, COVID-19 infection and vaccination history, reasons for hesitancy, and patient reported outcomes. Predictors of hesitancy were analysed using regression models in different groups.ResultsWe analysed data from 18 882 (COVAD-1) and 7666 (COVAD-2) respondents. Reassuringly, hesitancy decreased from 2021 (16.5%) to 2022 (5.1%) (OR: 0.26; 95% CI: 0.24, 0.30, P < 0.001). However, concerns/fear over long-term safety had increased (OR: 3.6; 95% CI: 2.9, 4.6, P < 0.01). We noted with concern greater skepticism over vaccine science among patients with IIMs than AIRDs (OR: 1.8; 95% CI: 1.08, 3.2, P = 0.023) and HCs (OR: 4; 95% CI: 1.9, 8.1, P < 0.001), as well as more long-term safety concerns/fear (IIMs vs AIRDs – OR: 1.9; 95% CI: 1.2, 2.9, P = 0.001; IIMs vs HCs – OR: 5.4 95% CI: 3, 9.6, P < 0.001). Caucasians [OR 4.2 (1.7–10.3)] were likely to be more hesitant, while those with better PROMIS physical health score were less hesitant [OR 0.9 (0.8–0.97)].ConclusionVaccine hesitancy has decreased from 2021 to 2022, long-term safety concerns remain among patients with IIMs, particularly in Caucasians and those with poor physical function.
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7. |
- Acciari, V.A., et al.
(author)
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Monitoring the magnetar SGR 1935+2154 with the MAGIC telescopes
- 2022
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In: Proceedings of Science. - 1824-8039. ; 395
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Conference paper (peer-reviewed)abstract
- The Galactic magnetar SGR 1935+2154 was associated with a bright, millisecond-timescale fast radio burst (FRB) which occured in April 2020, during a flaring episode. This was the first time an FRB was unequivocally associated with a Galactic source, and the first FRB for which the nature of the emitting source was identified. Moreover, it was the first FRB with a counterpart at another wavelength correlated in time, an atypical, hard X-ray burst, which provides clear evidence for accompanying non-thermal processes. The MAGIC Telescopes are Imaging Air Cherenkov Telescopes (IACTs) sensitive to very-high-energy (VHE, E>100 GeV) gamma rays. Located at the center of the camera lies the MAGIC Central pixel, a single fully-modified photosensor-toreadout chain to measure millisecond-duration optical signals, displaying a maximum sensitivity at a wavelength of 350 nm. This allows MAGIC to operate simultaneously both as a VHE gammaray and a fast optical telescope. The MAGIC telescopes have monitored SGR 1935+2154 in a multiwavelength campaign involving X-ray, radio and optical facilities. In this contribution, we will show the results on the search for the VHE counterpart of the first SGR-FRB source in this multiwavelength context, as well as the search for fast optical bursts with the MAGIC Central Pixel.
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8. |
- Krat, S., et al.
(author)
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Comparison of erosion and deposition in JET divertor during the first three ITER-like wall campaigns
- 2020
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In: Physica Scripta. - : IOP PUBLISHING LTD. - 0031-8949 .- 1402-4896. ; T171:1
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Journal article (peer-reviewed)abstract
- The manuscript presents an overview of the erosion and deposition data in the inner and outer JET divertor observed during the first three ITER-like wall campaigns (JET-ILW1, JET-ILW2, JET-ILW3). Erosion and deposition were studied using core samples cut out from divertor tiles. For the studied samples a similar general deposition pattern was observed in all three campaigns: More than 60% of the total deposition occurred in the upper region of the inner divertor on tiles 0 and 1, where Be was transported and deposited from the scrape-off layer. High erosion was observed only on tile 5. In JET-ILW2 and 3, erosion together with high power fluxes was observed in the outer divertor at the bottom of tile 7. Additionally, deposition peaks were observed on the sloping parts of tiles 4 and 6, which were more pronounced in JET-ILW2 and 3 due to placing the strike point more often on these tiles. The deposits consisted primarily of Be, with some additional D and C. Deposition rates were observed to decrease from campaign to campaign, with the C deposition rate decreasing the most, more than 2 times from JET-ILW1 to JET-ILW3. D retention up to levels of similar to 1 at% was observed up to large depths in the W protective coatings in all campaigns.
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9. |
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10. |
- Mayer, M., et al.
(author)
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Erosion and deposition in the JET divertor during the first ILW campaign
- 2016
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In: Physica Scripta. - : Institute of Physics Publishing (IOPP). - 0031-8949 .- 1402-4896. ; T167
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Journal article (peer-reviewed)abstract
- Erosion and deposition were studied in the JET divertor during the first JET ITER-like wall campaign 2011 to 2012 using marker tiles. An almost complete poloidal section consisting of tiles 0, 1, 3, 4, 6, 7, 8 was studied. The data from divertor tile surfaces were completed by the analysis of samples from remote divertor areas and from the inner wall cladding. The total mass of material deposited in the divertor decreased by a factor of 4-9 compared to the deposition of carbon during all-carbon JET operation before 2010. Deposits in 2011 to 2012 consist mainly of beryllium with 5-20 at.% of carbon and oxygen, respectively, and small amounts of Ni, Cr, Fe and W. This decrease of material deposition in the divertor is accompanied by a decrease of total deuterium retention inside the JET vessel by a factor of 10 to 20. The detailed erosion/deposition pattern in the divertor with the ITER-like wall configuration shows rigorous changes compared to the pattern with the all-carbon JET configuration.
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