792 research outputs found
Localizations of Fast Radio Bursts on milliarcsecond scales
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 pc) to a compact and persistent radio source with a size
of 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?
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
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
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
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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