Stan Stefl

Basic parameters and properties of the rapidly rotating magnetic helium-strong B star HR 7355

The spectral and magnetic properties and variability of the B2Vnp emission-line magnetosphere star HR 7355 were analysed. The object rotates at almost 90 per cent of the critical value, meaning it ...

The Very Large Telescope Interferometer: 2010 edition

The ESO Very Large Telescope Interferometer (VLTI) offers access to the four 8-m Unit Telescopes (UT) and the four 1.8-m Auxiliary Telescopes (AT) of the Paranal Observatory located in the Atacama Desert in northern Chile. The two VLTI instruments, MIDI and AMBER deliver regular scientific results. In parallel to the operation, the instruments developments are pursued, and new modes are studied and commissioned to offer a wider range of scientific possibilities to the community. New configurations of the ATs array are discussed with the science users of the VLTI and implemented to optimize the scientific return. The monitoring and improvement of the different systems of the VLTI is a continuous work. The PRIMA instrument, bringing astrometry capability to the VLTI and phase referencing to the instruments has been successfully installed and the commissioning is ongoing. The possibility for visiting instruments has been opened to the VLTI facility.

Experiences from the first AMBER open time observations

The VLTI has been operating for about 5 years using the VINCI instrument first, and later MIDI. In October 2005 (Period 76) the first Science Operations with the AMBER instrument started, with 14 Open Time proposals in the observing queues submitted by the astronomical community. AMBER, the near-infrared/red focal instrument of the VLTI, operates in the bands J, H, and, K (i.e. 1.0 to 2.5 micrometers) with three beams, thus enabling the use of closure phase techniques. Light was fed from the 8m Unit Telescopes (UT). The Instrument was offered with the Low Resolution Mode (JHK) and the Medium Resolution Mode in K-band on the UTs. We will present how the AMBER VLTI Science Operations currently are performed and integrated into the general Paranal Science Operations, using the extensive experience of Service Mode operations performed by the Paranal Science operations and in particular applying the know-how learned from the two years of MIDI Science Operations. We will also be presenting the operational statistics from these first ever Open Time observations with AMBER.

Perspectives for the AMBER Beam Combiner

The Astronomical Multi-BEam Recombiner (AMBER), has been operational at the Very Large Telescope Interferometer (VLTI) for many years. We present here some of the constant improvements we have been providing while still operating the instrument, with a heavy load of visitor and service observing programs, most of the nights of the year. In particular, we present here improvements regarding the spectral calibration and correction of the atmospheric loss in squared visibility due to path difference jitter, allowing the instrument to achieve greater precision.

The 2008+ outburst of the Be star 28 CMa - a multi-instrument study

Resumen en: The precursor phase of the outburst started in October 2008 was intensively monitored by photometry, highresolution optical and near-IR spectroscopy and ...

PUCHEROS: a low-cost fiber-fed Echelle Spectrograph for the visible spectral range

PUCHEROS is a high resolution optical Echelle spectrograph designed for the 50 cm telescope located at the Pontificia Universidad Cat´olica de Chile (PUC) observatory of Santa Martina. With a resolution about 20,000, PUCHEROS is an ideal instrument to study bright and variable objects, our driving science case is the study of bright early type stars. Using a fiber optic to bring the light from the telescope to the instrument, it can be located in a gravity invariant, temperature stabilized location, allowing precise long-term stability. PUCHEROS will be a valuable tool both for research and didactics at the graduate and undergraduate level. In this work we present the optical and mechanical design of the spectrograph as well as the first laboratory tests.

Inter-Division IV/V WG on Active OB Stars

Our group studies active early-type (OB) stars, with historical focus on classical Be stars, but extending in recent years to include Slowly Pulsating B-stars (SPB), Beta-Cephei stars, the strongly magnetic Bp stars, Luminous Blue Vairiable (LBV) stars, and B[e] stars. An overall goal is to understand the nature, origin, and consequences of this activity, in terms of both the stellar structure and evolution, as well as the distribution and dynamics of circumstellar material and mass outflows.