The 2-nd international Workshop

The UX Ori type stars and related topics

St. Petersburg, 30 September - 4 October 2019

The UX Ori type stars (or UXORs) are the photometrically most active young objects, predominantly Herbig Ae stars. They demonstrate aperiodic algol-like minima with amplitudes up to ∆V ∼ 2-3 mag and duration from a few days to a few weeks. The brightness variations are accompanied by changes in color, linear polarization and spectra. The most natural explanation of the observed phenomena is a model of variable circumstellar (CS) extinction taking into account scattered radiation from the CS disks. The source of the variable CS extinction is the perturbations in the innermost regions of the CS disks. Therefore the photometric behavior of UXORs is an important, and in some respects unique source of information about the dynamical state of these regions. In recent years extinction events on different timescales have been observed in several T Tauri stars. An important step in the study of such objects was made with the help of photometric observations from space: the CoRoT and Kepler missions. They have shown that the small-amplitude extinction events (dips) of different types (periodic or aperiodic) have been frequently observed in T Tauri stars. In this case the main source of the variable extinction are the dusty disk wind and the region of interaction of CS disk with the stellar magnetosphere. The goal of our workshop is to discuss the observational properties of UXORs and related objects in the light of new theoretical models.

Conference key topics:

  • Photometry, polarimetry and spectroscopy of UXORs
  • Infrared activity of UXORs and related objects
  • The circumstellar disks, disk winds and the nearest environment of young stars
  • Shadows on the disks, the disks in polarized light
  • Hydrodynamic processes in protoplanetary disks, periodic perturbations and protoplanet formation
  • The UXOR phenomena in T Tauri stars, connection with the AA Tau variables and dippers
  • The evolutionary trends of the UXORs activity

Scientific Organizing Committee:

Silvia Alencar
Jerome Bouvier
Vladimir Grinin (co-chair)
Sergej Lamzin
Geoffroy Lesur
Agnes Kospal
Antonella Natta
Rene Oudmaijer
Alla Rostopchina-Shakhovskaya (co-chair)
Evgeni Semkov

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