Seminars and Colloquia at ESO/Santiago

For ESO and ESO-related Conferences and Workshops in Europe and Chile please check the main Conferences and Workshops page.


Broadcast of the ESO talks is available upon request.  If anyone is interested, kindly contact us via email
at least 60 min prior  to the beginning of the talk.


January 2015

19.01.15 (Monday)
12:00
"The Atacama Surface Solar Maximum"
Roberto RONDANELLI (Universidad de Chile)
Abstract
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"The Atacama Surface Solar Maximum"

Roberto RONDANELLI (Universidad de Chile)

Abstract

Solar radiation reaching the earth's surface is one of the major drivers of climate dynamics. By setting the surface energy balance, downwelling solar radiation indirectly heats the atmosphere and controls the hydrological cycle. Besides its critical importance as a physical mechanism for driving climate and weather, solar radiation has attracted interest as a potentially major source of energy for human activities.
For a given latitude, solar radiation at the earth's surface depends mostly on the composition along the atmospheric path. Since the early 20th century major astronomical observatories have led the search for the best places for observation from the earth, which presents a similar problem to the one of finding the maximum of solar radiation at the surface. In particular, Mount Montezuma in the Atacama desert, Chile, was identified by the pioneers of solar observation as an ideal place to conduct the search for variations of the solar constant estimated from the earth's surface.
By using available global datasets, a semi-empirical model for the surface solar radiation over Northern Chile and a network of surface stations, we confirm Atacama as the place where the highest mean surface solar radiation is found. The most likely location of the maximum downwelling solar radiation over the surface of the planet is on the pre-Andean Domeyko cordillera (3500 to 5000 m above the mean sea level, between 24 to 25 °S, along 69 °W) with a value of about 310 ± 15 W/m2. We discuss the main regional and local features of this region that conspire to produce the solar maximum.
I will also discuss some elements of future trends in atmospheric opacity on the basis of climate scenarios from the CMIP-5 latest IPCC report.
Article for reference: http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-13-00175.1

20.01.15 (Tuesday)
12:00
"Status of VISIR and the water vapour radiometer on Paranal"
Florian KERBER (ESO)
Abstract
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"Status of VISIR and the water vapour radiometer on Paranal"

Florian KERBER (ESO)

Abstract

The VISIR mid-IR instrument is undergoing commissioning following an upgrade and will re-enter operations in April 2015. I’ll briefly summarise the status following commissioning 2. One important new aspect of VISIR operations is the introduction of a new constraint parameter: precipitable water vapour. Water vapour has a strong impact on atmospheric transmission in particular in the infrared. A Low Humidity and Temperature Profiling (LHATPRO) microwave radiometer, manufactured by Radiometer Physics GmbH (RPG), is used to monitor sky conditions over ESO’s Paranal observatory in support of VLT science operations. The unit which has been in operations for more than two years, measures several channels across the strong water vapour emission line at 183 GHz, necessary for resolving the low levels of precipitable water vapour (PWV) that are prevalent on Paranal (median ~2.4 mm). The instrument consists of a humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared camera (~10 μm) for cloud detection. I will present a statistical analysis of the homogeneity of all-sky PWV using 21 months of periodic (every 6 hours) all-sky scans from the radiometer. These data provide unique insight into the spatial and temporal variation of atmospheric conditions relevant for astronomical observations. I will provide a summary of the experience gathered and give some examples of the lessons learned with respect to supporting science observations.

22.01.15 (Thursday)
12:00
"Exocomets in the disk of young A type stars: the case of Beta Pictoris and HD172555"
Flavien KIEFER (IAP, France)
Abstract
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"Exocomets in the disk of young A type stars: the case of Beta Pictoris and HD172555"

Flavien KIEFER (IAP, France)

Abstract

The young planetary system surrounding Beta Pictoris harbors active minor bodies. Spectroscopic observations of Beta Pictoris reveal a high rate of transits of small evaporating bodies, i.e. exo-comets (Kiefer et al. 2014). I will report the analysis of more than thousand spectra collected with HARPS between 2003 and 2011, providing a sample of about 6000 variable absorption signatures due to transiting exocomets. Statistical analysis of the observed properties of these exocomets reveals that they belong to two distinct populations with highly different physical properties. A first family, producing shallow absorption lines, can be attributed to old exhausted comets, possibly trapped in a mean motion resonance with a massive planet; while a second family, producing deep absorption lines, is possibly related to the recent fragmentation of a few parent bodies. Our results strengthen the analogy of nature of the evaporating bodies observed for decades transiting Beta Pictoris with the bodies so-called comets in the Solar System. Recently, we discovered that the Beta Pic-like system of HD172555 also harbors exocomets (Kiefer et al. 2014). The analysis of the Ca II doublet of about a hundred HARPS spectra of HD172555 collected between 2004 and 2011 revealed typical variable absorption signatures of exocomets transiting the star. It is the second example after Beta Pictoris of a young A-type star harboring a debris disk in which exocomets are detected and characterized thanks to the simultaneous observation of the Ca II-K and Ca II-H lines.

28.01.15 (Wednesday)
15:30
"Stellar Spectroscopy during Exoplanet Transits: Dissecting fine structure across stellar surfaces"
Dainis DRAVINS (Lund Observatory & ESO Visiting Scientist)
Abstract
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"Stellar Spectroscopy during Exoplanet Transits: Dissecting fine structure across stellar surfaces"

Dainis DRAVINS (Lund Observatory & ESO Visiting Scientist)

Abstract

Differential spectroscopy during exoplanet transits permits to reconstruct spectra of small stellar surface portions that successively become hidden behind the planet. The center-to-limb behavior of stellar line shapes, asymmetries and wavelength shifts will enable detailed tests of 3-dimensional hydrodynamic models of stellar atmospheres, such that are required for any precise determination of abundances or seismic properties. Although very high quality spectra are required, already current data permit reconstructions of line profiles in the brightest transit host stars; http://arxiv.org/abs/1408.1402.


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