44 research outputs found
A close look into the carbon disk at the core of the planetary nebula CPD-568032
We present high spatial resolution observations of the dusty core of the
Planetary Nebula with Wolf-Rayet central star CPD-568032. These observations
were taken with the mid-infrared interferometer VLTI/MIDI in imaging mode
providing a typical 300 mas resolution and in interferometric mode using
UT2-UT3 47m baseline providing a typical spatial resolution of 20 mas. The
visible HST images exhibit a complex multilobal geometry dominated by faint
lobes. The farthest structures are located at 7" from the star. The mid-IR
environment of CPD-568032 is dominated by a compact source, barely resolved by
a single UT telescope in a 8.7 micron filter. The infrared core is almost fully
resolved with the three 40-45m projected baselines ranging from -5 to 51 degree
but smooth oscillating fringes at low level have been detected in spectrally
dispersed visibilities. This clear signal is interpreted in terms of a ring
structure which would define the bright inner rim of the equatorial disk.
Geometric models allowed us to derive the main geometrical parameters of the
disk. For instance, a reasonably good fit is reached with an achromatic and
elliptical truncated Gaussian with a radius of 97+/-11 AU, an inclination of
28+/-7 degree and a PA for the major axis at 345+/-7 degree. Furthermore, we
performed some radiative transfer modeling aimed at further constraining the
geometry and mass content of the disk, by taking into account the MIDI
dispersed visibilities, spectra, and the large aperture SED of the source.
These models show that the disk is mostly optically thin in the N band and
highly flared.Comment: Paper accepted in A&
Characterisation of Long Baseline Calibrators at 2.3 GHz
We present a detailed multi-epoch analysis of 31 potential southern
hemisphere radio calibrators that were originally observed as part of a program
to maintain the International Celestial Reference Frame (ICRF). At radio
wavelengths, the primary calibrators are Active Galactic Nuclei (AGN), powerful
radio emitters which exist at the centre of most galaxies. These are known to
vary at all wavelengths at which they have been observed. By determining the
amount of radio source structure and variability of these AGN, we determine
their suitability as phase calibrators for long baseline radio interferometry
at 2.3 GHz. For this purpose, we have used a set of complementary metrics to
classify these 31 southern sources into five categories pertaining to their
suitability as VLBI calibrators. We find that all of the sources in our sample
would be good interferometric calibrators and almost ninety per cent would be
very good calibrators.Comment: 9 pages, 7 Figures, accepted MNRA
Real-time data streams from e-RemoteCtrl to central VLBI network status monitoring services like IVS Live
International audienc
Proceedings of the 11th European VLBI Network Symposium & Users Meeting, 9-12 October 2012, Bordeaux - France
International audienceThe conference highlighted the latest scientific results and technical developments from VLBI, space VLBI and e-VLBI. All fields of astrophysics were concerned - stellar, galactic and extragalactic - as well as astrometry and planetary science. Presentations addressing synergy between (e-)VLBI and other new or planned radio facilities (ALMA, LOFAR, e-MERLIN,...) or instruments at other wavelengths (Fermi, CTA, Gaia,...) were also an integral part of the program. The scientific program was organized in 11 sessions including 71 oral presentations, with an additional 43 posters available for viewing during the entire length of the conference. An EVN Users Meeting was also held during one of the evening to foster interaction between the EVN users and the EVN organization. The symposium was attended by a total of 122 delegates originating from 47 institutes world-wide, sharing new VLBI science and innovations while also building links with other communities
sand : an automated VLBI imaging and analysing pipeline – I. Stripping component trajectories
International audienc