Suchergebnisse

This paper reports observations of a 22 GHz water maser 'superburst' in the G25.65+1.05 massive star-forming region, conducted in response to an alert from the Maser Monitoring Organisation (M2O). Very long baseline interferometry (VLBI) observations using the European VLBI Network (EVN) recorded a maser flux density of 1.2 × 104 Jy. The superburst was investipgated in the spectral, structural, and temporal domains and its cause was determined to be an increase in maser path length generated by the superposition of multiple maser emitting regions aligning in the line of sight to the observer. This conclusion was based on the location of the bursting maser in the context of the star-forming region, its complex structure, and its rapid onset and decay. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society ; RAB acknowledges support through the EACOA Fellowship from the East Asian Core Observatories Association. GO acknowledges support from the Australian Research Council Discovery project DP180101061 funded by the Australian Government, the CAS 'Light of West China' Program 2018-XBQNXZ-B-021, and the National Key R&D Program of China 2018YFA0404602. TH is financially supported by the MEXT/JSPS KAKENHI Grant Number 17K05398. BM acknowledges support from the Spanish Ministerio de Economía y Competitividad (MINECO) under grants AYA2016-76012-C3-1-P and MDM-2014-0369 of ICCUB (Unidad de Excelencia 'María de Maeztu'). NS acknowledges support from Russian Science Foundation grant 18-12-00193. AMS is supported by the Ministry of Science and High Education (the basic part of the State assignment, RK No. AAAA-A17-117030310283-7) and by the Act 211 Government of the Russian Federation, contract No.02.A03.21.0006. JOC acknowledges support by the Italian Ministry of Foreign Affairs and International .

The binary neutron star merger event GW170817 was detected through both electromagnetic radiation and gravitational waves. Its afterglow emission may have been produced by either a narrow relativistic jet or an isotropic outflow. High-spatial-resolution measurements of the source size and displacement can discriminate between these scenarios. We present very-long-baseline interferometry observations, performed 207.4 days after the merger by using a global network of 32 radio telescopes. The apparent source size is constrained to be smaller than 2.5 milli-arc seconds at the 90% confidence level. This excludes the isotropic outflow scenario, which would have produced a larger apparent size, indicating that GW170817 produced a structured relativistic jet. Our rate calculations show that at least 10% of neutron star mergers produce such a jet.© 2019 The Authors, some rights reserved. All rights reserved. ; The National Institute of Astrophysics is is acknowledged for PRIN-grant (2017) 1.05.01.88.06. The Italian Ministry for University and Research (MIUR) is acknowledged through the project >FIGARO> (Prin-MIUR) grant 1.05.06.13. ASI is acknowledged for grant I/004/11/3. The research leading to these results has received funding from the European Commission Horizon 2020 Research and Innovation Programme under grant agreement 730562 (RadioNet). The Spanish Ministerio de Economa y Competitividad (MINECO) is acknowledged for financial support under grants AYA201676012-C3-1-P, FPA2015-69210-C6-2-R, and MDM-2014-0369 of ICCUB (Unidad de Excelencia >Mara de Maeztu>). M.A.P.-T. acknowledges support from the Spanish MINECO through grants AYA2012-38491-C02-02 and AYA2015-63939-C2-1-P.T.A. is supported by the National Key R&D Programme of China (2018YFA0404603). E.C.-M. acknowledges support from the European Union's Horizon 2020 research and innovation program under grant agreement 653477. S.F. thanks the Hungarian National Research, Development and Innovation Office (OTKA NN110333) for support. The Long Baseline Array is part of the Australia Telescope National Facility, which is funded by the Australian Government for operation as a National Facility managed by CSIRO. ; Peer Reviewed