Research :: PhD Topics for 2014 :: Instrumentation

Topics under the thematic line Space and Ground Systems and Technologiesavailable for the 2014 Call (2 PhD Topics):

  • 2014/501 – Towards exoplanetary atmospheres: new data reduction methods for the nIR
  • 2014/502 - Impact of the Wolf effect in ESPRESSO: Effects of propagation of partially coherent light on very high resolution spectra of stars

For further details please see the listing below with the abstract and advisors.

2014/501 – Towards exoplanetary atmospheres: new data reduction methods for the nIR

Advisors: Nuno C. Santos (CAUP), Cláudio Melo (ESO), Pedro Figueira (CAUP)

The search for extrasolar planets has as one of its crowns the study of exo-atmospheres. This goal has been shaping Science and scientific instrumentation for the last decade. In this project we provide a gradual approach to developing and perfecting of methodologies required for the detection and characterization of exo-atmospheres.

Building up on current in-house knowledge, we propose to develop the methodologies required for the extraction of the maximum of information, and in particular the minute signals of exoplanets from nIR spectra. The risk of this ambitions program will be minimized by a thorough and gradual pathway to this objective. The intermediary tasks and objectives have been laid out and a significant amount of observational data has already been acquired and is fully available to be explored from day one.

The expertise gained through this project will give the PhD the ability to efficiently reduce and explore nIR spectroscopic data, an emerging field in astronomy, in particular in the domain of extrasolar planets. The results of this project will be used for the science verification of two upgraded infrared instruments: CRIRES+ and VISIR (both at the VLT-ESO).

Notes: This topic requires a mixed fellowship (up to one year in ESO-Chile). This topic is also offered as topic 2014/106, under the thematic line on Planets.

2014/502 - Impact of the Wolf effect in ESPRESSO: Effects of propagation of partially coherent light on very high resolution spectra of stars

Advisors: José Rebordão (CAAUL)

The Wolf Effect (or Wolf shift) is a frequency shift in the electromagnetic spectrum, that has been described as a new redshift mechanism. The phenomenon occurs in several closely related phenomena in radiation physics, with analogous effects occurring in the scattering of light. It was first predicted by Emil Wolf in 1987 and subsequently confirmed in the laboratory by Dean Faklis and George Morris in 1988. Wolf and others have suggested that the Wolf effect as a possible non-cosmological redshift and also relevant to gravitational lensing. In optics, two non-Lambertian sources that emit beamed energy can interact in a way that causes a shift in the spectral lines. It is analogous to a pair of tuning forks with similar frequencies (pitches), connected together mechanically with a sounding board; there is a strong coupling that results in the resonant frequencies getting “dragged down” in pitch. The Wolf Effect requires that the waves from the sources are partially coherent.

ESPRESSO (Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations), is a super-stable optical high resolution spectrograph for the combined Coude’ focus of the VLT. It can be operated by either one of the UTs or collecting the light from up to 4 UTs simultaneously. In this last configuration, light from 4 UT’s is incoherently combined, in order to increase the flux delivered to the spectrograph. One of the most important goals of ESPRESSO is the detection of exo-planets through spectral changes induced by their orbiting velocity..

Given the spatial separation between the UT’s (~80 m), the length of partial optical paths in the Coudé train (~100 m) and the sensitivity of the spectrograph (<10 cm.s-1), all minute possible modifications to the spectra stemming from changes in the partial coherence of the light, should be analyzed in detail.

This PhD proposal will therefore address to what extent the Wolf effect should or should not be totally discarded in ESPRESSO, in spite of the split of the star beam by 4 UT’s having the potential to create a kind of cross-correlation equivalent to source partial coherence or other forms of source correlations required by the Wolf Effect.

This program will take place simultaneously with the actual implementation of ESPRESSO at ESO – Paranal and the candidate is expected to participate in that implementation and tests.