Multiband GPI imaging of the HR 4796A debris disk

Stars and planetary system

GPI Spectra of HR 8799 c, d, and e from 1.5 to 2.4 μm with KLIP Forward Modeling

Stars and planetary system

Revised astrometric calibration of the Gemini Planet Imager

Instrumentatio

GPI Spectra of HR 8799 c, d, and e from 1.5 to 2.4 μm with KLIP Forward Modeling

Stars and planetary system

An Updated Visual Orbit of the Directly Imaged Exoplanet 51 Eridani b and Prospects for a Dynamical Mass Measurement with Gaia

Stars and planetary system

Performance of the Gemini Planet Imager Non-redundant Mask and Spectroscopy of Two Close-separation Binaries: HR 2690 and HD 142527

Instrumentatio

High resolution interferometry of the QSO 1422+202

We present VLA A-array observations at 8.4 and 15GHz and European VLBI Network (EVN) observations at 1.6GHz of the radio source 1422+202. It is suggested that 1422+202 is a Medium-size Object in the evolutionary sequence from Compact Steep-spectrum Sources to larger sized radio sources. The VLBI data were analysed with the phase referencing technique and we show that the EVN can work as a phase stable instrument for separations between the calibrator source and the target source up to ~ 10 degrees. With the VLA and VLBI observations we investigate some of the issues about the nucleus of 1422+202 and we discuss the possible cause for the low frequency variability detected while monitoring the source

VLBI observations of the puzzling BL Lacertae object 0235+164

For over 20 years, many models have been proposed to explain the variability of AO0235+164. Among them, the most favorable has been micro-lensing. We have made a series of VLBI observations on this source in order to better understand its nature. The resultant maps indicate dramatic changes in the position angle of the jet between observations as well as a correlation between the intensity of the VLBI core and flux outbursts which occurred between the observing sessions. These characteristics, in conjunction with other arguments, suggest that the source variability is intrinsic, i.e. microlensing is of minor importance. We suggest two models: 1) a model in which the jet starts at a very small angle to the line of sight and then curves away to become about 6deg at about 1 mas from the core; and 2) a CME (Coronal Mass Ejection) model that also may explain the violent variability in intensity, polarization position angle, and jet direction in AO0235+164

Multifrequency interferometer and radio continuum monitoring observations of CTA 102

This paper represents the work of several years of observation of CTA 102 with both single dish telescopes and interferometric arrays, covering wavelengths from 1.2 cm to 1.3 mm. The resolution of the maps covers an order of magnitude from 0.5 mas to 50 μas. The images presented demonstrate the rapid structural changes in this source. These rapid structural changes correlates with the outbursts seen in the total flux, turnover frequency and in the spectral index. We have calculated the Brightness Temperatures of the components (TB ) directly from the determined component sizes and also using the logarithmic variability amplitudes and timescales to calculate the TB s. Both the methods yielded measurements of source frame T Bs no higher than ∼a few × 10 12 K. We find that the observed average proper motion is 0.4 0.07 mas/yr, which corresponds to an apparent transverse velocity of 11 ± 2 c.Copyright © 2003 EDP Sciences. This material is posted here with permission of EDP Sciences. Such permission of EDP Sciences does not in any way imply EDP Sciences endorsement of any of the University of Halmstads's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from EDP Sciences. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.</p

Consortium AMBER, VLTI-AMBER observations of Eta Carinae with high spatial resolution and spectral resolutions of 1,500 and 10,000

Advances in Stellar Interferometry, eds. J. D. Monnier, M. Schoeller and W. C. Danchi, SPIE 6268, (2006)International audienc