Precise Measurements of Self-absorbed Rising Reverse Shock Emission from Gamma-ray Burst 221009A

The deaths of massive stars are sometimes accompanied by the launch of highly relativistic and collimated jets. If the jet is pointed towards Earth, we observe a "prompt" gamma-ray burst due to internal shocks or magnetic reconnection events within the jet, followed by a long-lived broadband synchrotron afterglow as the jet interacts with the circum-burst material. While there is solid observational evidence that emission from multiple shocks contributes to the afterglow signature, detailed studies of the reverse shock, which travels back into the explosion ejecta, are hampered by a lack of early-time observations, particularly in the radio band. We present rapid follow-up radio observations of the exceptionally bright gamma-ray burst GRB 221009A which reveal an optically thick rising component from the reverse shock in unprecedented detail both temporally and in frequency space. From this, we are able to constrain the size, Lorentz factor, and internal energy of the outflow while providing accurate predictions for the location of the peak frequency of the reverse shock in the first few hours after the burst.Comment: 11 figures, 4 table

Verification of R-matrix calculations for charged-particle reactions in the resolved resonance region for the 7^{7}Be system

International audienceR-matrix theory is used to describe nuclear reactions in the resolved resonance region. It uses information on bound states and low energy resonances to accurately parametrize cross sections on the resonances as well as the non-resonant background. Since the seminal work of Lane and Thomas (1958), the approach has been widely used to analyze experimental cross-section data in a broad range of fields spanning nuclear reaction dynamics, nuclear astrophysics, ion beam analysis and their applications. Different R-matrix codes have been developed and used in these different applications with very little communication among the developers or practitioners on the capabilities, achievements or limitations of the codes. A limited comparison among three R-matrix codes on neutron-induced reactions was performed by the International Atomic Energy Agency (IAEA) International Evaluation of Neutron Cross Section Standards project (2007). Since then, significant progress has been made in their implementation of the R-matrix algorithms, and R-matrix codes have enhanced capabilities. In this paper we present, for the first time, the results of a comprehensive effort to verify the most widely used R-matrix codes in the various fields of nuclear science and applications: AMUR, AZURE2, CONRAD, EDA, FRESCO, GECCCOS, and SAMMY. In addition to the description of the capabilities of the codes and their specifications, we discuss the results of a joint exercise which was coordinated by the International Atomic Energy Agency. The aim of the exercise was to compare calculations of charged-particle reaction cross sections for the light composite system$^{7}$Be. The calculations were performed by the codes using identical input R-matrix parameters and other specifications and were limited to charged-particle channels

Circulating vitamin D metabolites and kidney disease in type 1 diabetes

CONTEXT: Impaired vitamin D metabolism may contribute to the development and progression of diabetic kidney disease. OBJECTIVE: The aim of the study was to test associations of circulating vitamin D metabolites with risks of incident microalbuminuria, impaired glomerular filtration rate (GFR), and hypertension in type 1 diabetes. DESIGN: We performed a cohort study of 1193 participants in the Diabetes Control and Complications Trial (DCCT), a randomized clinical trial of intensive diabetes therapy, and its observational follow-up, the Epidemiology of Diabetes Interventions and Complications (EDIC) Study. We measured plasma concentrations of 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D, and 24,25-dihydroxyvitamin D by mass spectrometry at the end of the DCCT and tested associations with incident microalbuminuria, impaired GFR, and hypertension over up to 16 yr of EDIC follow-up. RESULTS: At the time metabolites were measured, mean age was 32.4 yr; mean duration of diabetes, 7.5 yr; mean iothalamate GFR, 132.9 ml/min/1.73 m(2); and geometric mean albumin excretion rate, 11.8 mg/24 h. Over follow-up, 166 cases of microalbuminuria, 54 cases of impaired GFR, and 541 cases of hypertension were observed. Compared with 25(OH)D of at least 30 ng/ml, 25(OH)D below 20 ng/ml was associated with a 65% higher risk of microalbuminuria (95% confidence interval, 7 to 154%) in adjusted analyses. Low concentrations of 24,25-dihydroxyvitamin D, but not 1,25-dihydroxyvitamin D, were also associated with increased risk of microalbuminuria. No circulating vitamin D metabolite was associated with risk of impaired GFR or hypertension. CONCLUSIONS: Low plasma concentrations of 25(OH)D and 24,25-dihydroxyvitamin D are associated with increased risk of microalbuminuria in type 1 diabetes. In contrast, we did not find evidence linking impaired vitamin D metabolism to early GFR loss or the development of hypertension

Precise measurements of self-absorbed rising reverse shock emission from gamma-ray burst 221009A

The deaths of massive stars are sometimes accompanied by the launch of highly relativistic and collimated jets. If the jet is pointed towards Earth, we observe a ‘prompt’ gamma-ray burst due to internal shocks or magnetic reconnection events within the jet, followed by a long-lived broadband synchrotron afterglow as the jet interacts with the circumburst material. While there is solid observational evidence that emission from multiple shocks contributes to the afterglow signature, detailed studies of the reverse shock, which travels back into the explosion ejecta, are hampered by a lack of early-time observations, particularly in the radio band. We present rapid follow-up radio observations of the exceptionally bright gamma-ray burst GRB 221009A that reveal in detail, both temporally and in frequency space, an optically thick rising component from the reverse shock. From this, we are able to constrain the size, Lorentz factor and internal energy of the outflow while providing accurate predictions for the location of the peak frequency of the reverse shock in the first few hours after the burst. These observations challenge standard gamma-ray burst models describing reverse shock emission