792 research outputs found

    Localizations of Fast Radio Bursts on milliarcsecond scales

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    Fast Radio Bursts (FRBs) are transient sources that emit a single radio pulse with a duration of only a few milliseconds. Since the discovery of the first FRB in 2007, tens of similar events have been detected. However, their physical origin remains unclear, and a number of scenarios even larger than the number of known FRBs has been proposed during these years. The presence of repeating bursts in FRB 121102 allowed us to perform a precise localization of the source with the Very Large Array and the European VLBI Network (EVN). Optical observations with Keck, Gemini and HST unveiled the host to be a low-metallicity star-forming dwarf galaxy located at a redshift of 0.193. The EVN results showed that the bursts are co-located (within a projected separation of <40< 40 pc) to a compact and persistent radio source with a size of <0.7< 0.7 pc inside a star-forming region. This environment resembles the ones where superluminous supernovae (SLSNe) or long gamma-ray bursts are produced. Although the nature of this persistent source and the origin of the bursts remain unknown, scenarios considering a pulsar/magnetar energizing a young SLSN, or a system with a pulsar/magnetar in the vicinity of a massive black hole are the most plausible ones to date. More recent observations have shown that the bursts from FRB 121102 are almost 100% linearly polarized at an unexpectedly high and variable Faraday rotation measure, that has been observed to date only in vicinities of massive black holes. The bursts are thus likely produced from a neutron star in such environment, although the system can still be explained by a young neutron star embedded in a highly magnetized nebula. Upcoming interferometric searches are expected to report tens of these localizations in the coming years, unveil if this source is representative of the whole population or a particular case, and dramatically boosting the field of FRBs.Comment: 11 pages, 3 figures, proceedings of the 14th European VLBI Network Symposium & Users Meeting, held on 8-11 October 2018 in Granada, Spai

    4C 02.27: what is inside a double-double radio quasar?

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    Recently Jamrozy et al. (2009) identified 4C 02.27 (J0935+0204) as the first possible example of a double-double radio source which is optically identified with a quasar (i.e. not a galaxy), at the redshift of z=0.649. The overall projected angular size of the radio source reaches about 1.5', with a prominent "core" component in the centre. The two opposite pairs of radio lobes might indicate two periods of episodic activity. We report on our short exploratory 1.6-GHz Very Long Baseline Interferometry (VLBI) observations of the innermost radio structure of the quasar, conducted with the electronic European VLBI Network (e-EVN) on 2009 September 30. These revealed a milliarcsecond-scale compact source which is the base of the approaching one of the two symmetric relativistic jets currently supplying the hot spots in the inner pair of the arcsecond-scale radio lobes in 4C 02.27.Comment: 4 pages, 2 figures, to appear in the proceedings of the 10th European VLBI Network Symposium (September 20-24, 2010, Manchester, UK). Proceedings of Science (http://pos.sissa.it), PoS(10th EVN Symposium)07

    Swift J1910.1-0546/MAXI J1910-057: e-EVN non-detection at 1.6 GHz

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    We observed the new transient Swift J1910.1-0546/MAXI J1910-057 with the European VLBI Network (EVN) in real-time mode on 12 June 2012. The observations were at 1.6 GHz and lasted for 4 hours

    EVN detection of the newly-discovered black hold candidate MAXI J1836-194

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    The X-ray transient MAXI J1836-194 is most likely a Galactic stellar-mass black hole. It has been shown to harden in the X-rays and brighten in the infrared. Here, we report on the detection of MAXI J1836-194 at 5 GHz with the European VLBI Network, in real-time e-VLBI observations on 2011 October 17. The transient source was detected with a flux density of 5.4 +- 0.3 mJy at RA 18h35m43.44555s, Dec. -19d19'10.4921" (J2000, 1 sigma formal uncertainty ~0.5 mas, note that the systematic error may be much larger due to the low elevation.)

    The compact radio structure of the high-redshift blazar J1430+4204 before and after a major outburst

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    The high-redshift (z=4.72) blazar J1430+4204 produced an exceptional radio outburst in 2006. We analyzed 15-GHz radio interferometric images obtained with the Very Long Baseline Array (VLBA) before and after the outburst, to search for possible structural changes on milli-arcsecond angular scales and to determine physical parameters of the source.Comment: Proceedings of the 5th Workshop of Young Researchers in Astronomy and Astrophysics, Budapest, 2009; to be published in J. Phys.: Conf. Series (JPCS); 4 pages, 3 figure
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