| 1. |
- Glasbey, JC, et al.
(författare)
-
- 2021
-
swepub:Mat__t
|
|
| 2. |
|
|
| 3. |
- Ajello, M., et al.
(författare)
-
High-energy emission from a magnetar giant flare in the Sculptor galaxy
- 2021
-
Ingår i: Nature Astronomy. - : Springer Nature. - 2397-3366. ; 5:4, s. 385-391
-
Tidskriftsartikel (refereegranskat)abstract
- Magnetars are the most highly magnetized neutron stars in the cosmos (with magnetic field 1013–1015 G). Giant flares from magnetars are rare, short-duration (about 0.1 s) bursts of hard X-rays and soft γ rays1,2. Owing to the limited sensitivity and energy coverage of previous telescopes, no magnetar giant flare has been detected at gigaelectronvolt (GeV) energies. Here, we report the discovery of GeV emission from a magnetar giant flare on 15 April 2020 (refs. 3,4 and A. J. Castro-Tirado et al., manuscript in preparation). The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope detected GeV γ rays from 19 s until 284 s after the initial detection of a signal in the megaelectronvolt (MeV) band. Our analysis shows that these γ rays are spatially associated with the nearby (3.5 megaparsecs) Sculptor galaxy and are unlikely to originate from a cosmological γ-ray burst. Thus, we infer that the γ rays originated with the magnetar giant flare in Sculptor. We suggest that the GeV signal is generated by an ultra-relativistic outflow that first radiates the prompt MeV-band photons, and then deposits its energy far from the stellar magnetosphere. After a propagation delay, the outflow interacts with environmental gas and produces shock waves that accelerate electrons to very high energies; these electrons then emit GeV γ rays as optically thin synchrotron radiation. This observation implies that a relativistic outflow is associated with the magnetar giant flare, and suggests the possibility that magnetars can power some short γ-ray bursts.
|
|
| 4. |
- Ajello, M., et al.
(författare)
-
Gamma Rays from Fast Black-hole Winds
- 2021
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 921:2
-
Tidskriftsartikel (refereegranskat)abstract
- Massive black holes at the centers of galaxies can launch powerful wide-angle winds that, if sustained over time, can unbind the gas from the stellar bulges of galaxies. These winds may be responsible for the observed scaling relation between the masses of the central black holes and the velocity dispersion of stars in galactic bulges. Propagating through the galaxy, the wind should interact with the interstellar medium creating a strong shock, similar to those observed in supernovae explosions, which is able to accelerate charged particles to high energies. In this work we use data from the Fermi Large Area Telescope to search for the gamma-ray emission from galaxies with an ultrafast outflow (UFO): a fast (v similar to 0.1 c), highly ionized outflow, detected in absorption at hard X-rays in several nearby active galactic nuclei (AGN). Adopting a sensitive stacking analysis we are able to detect the average gamma-ray emission from these galaxies and exclude that it is due to processes other than UFOs. Moreover, our analysis shows that the gamma-ray luminosity scales with the AGN bolometric luminosity and that these outflows transfer similar to 0.04% of their mechanical power to gamma-rays. Interpreting the observed gamma-ray emission as produced by cosmic rays (CRs) accelerated at the shock front, we find that the gamma-ray emission may attest to the onset of the wind-host interaction and that these outflows can energize charged particles up to the transition region between galactic and extragalactic CRs.
|
|
| 5. |
- Ajello, M., et al.
(författare)
-
First Fermi-LAT Solar Flare Catalog
- 2021
-
Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 252:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present the first Fermi-Large Area Telescope (LAT) solar flare catalog covering the 24th solar cycle. This catalog contains 45 Fermi-LAT solar flares (FLSFs) with emission in the gamma-ray energy band (30 MeV-10 GeV) detected with a significance of >= 5 sigma over the years 2010-2018. A subsample containing 37 of these flares exhibits delayed emission beyond the prompt-impulsive hard X-ray phase, with 21 flares showing delayed emission lasting more than two hours. No prompt-impulsive emission is detected in four of these flares. We also present in this catalog observations of GeV emission from three flares originating from active regions located behind the limb of the visible solar disk. We report the lightcurves, spectra, best proton index, and localization (when possible) for all FLSFs. The gamma-ray spectra are consistent with the decay of pions produced by >300 MeV protons. This work contains the largest sample of high-energy gamma-ray flares ever reported and provides a unique opportunity to perform population studies on the different phases of the flare and thus allowing a new window in solar physics to be opened.
|
|
| 6. |
- Lanner, M, et al.
(författare)
-
Subspecialty training in Europe: a report by the European Network of Young Gynaecological Oncologists
- 2021
-
Ingår i: International journal of gynecological cancer : official journal of the International Gynecological Cancer Society. - : BMJ. - 1525-1438. ; 31:4, s. 575-584
-
Tidskriftsartikel (refereegranskat)abstract
- ESGO (European Society of Gynaecological Oncology) and partners are continually improving the developmental opportunities for gynaecological oncology fellows. The objectives of this survey were to evaluate the progress in the infrastructure of the training systems in Europe over the past decade. We also evaluated training and assessment techniques, the perceived relevance of ENYGO (European Network of Young Gynaecological Oncologists) initiatives, and unmet needs of trainees.MethodologyNational representatives of ENYGO from 39 countries were contacted with an electronic survey. A graduation in well/moderately/loosely-structured training systems was performed. Descriptive statistical analysis and frequency tables, as well as two-sided Fisher’s exact test, were used.ResultsNational representatives from 33 countries answered our survey questionnaire, yielding a response rate of 85%. A national fellowship is offered in 22 countries (66.7%). A logbook to document progress during training is mandatory in 24 (72.7%) countries. A logbook of experience is only utilized in a minority of nations (18%) for assessment purposes. In 42.4% of countries, objective assessments are recognized. Trainees in most countries (22 (66.7%)) requested additional training in advanced laparoscopic surgery. 13 (39.4%) countries have a loosely-structured training system, 11 (33.3%) a moderately-structured training system, and 9 (27.3%) a well-structured training system.ConclusionSince the last publication in 2011, ENYGO was able to implement new activities, workshops, and online education to support training of gynaecological oncology fellows, which were all rated by the respondents as highly useful. This survey also reveals the limitations in establishing more accredited centers, centralized cancer care, and the lack of laparoscopic training.
|
|
