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.


April 2015

1.04.15 (Wednesday)
16:00
"A search for hyperluminous X-ray sources in the XMM-Newton source catalog"
Ivan ZOLOTUKHIN (IRAP, Toulouse, France & SAI MSU, Moscow, Russia)
Abstract
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"A search for hyperluminous X-ray sources in the XMM-Newton source catalog"

Ivan ZOLOTUKHIN (IRAP, Toulouse, France & SAI MSU, Moscow, Russia)

Abstract

We present a method to search for off-nuclear X-ray sources in the XMM-Newton source catalog by cross-matching it with large spectroscopic galaxy catalogs (e.g. SDSS) using special non-central match condition. Known distances to expected host galaxies then allow to select X-ray sources from their outskirts within specific luminosity range, 10^41 < L_X < 10^44 erg s^-1. We attempt to discard various possible contaminating foreground and background object classes such as AGN, BL Lacs, Galactic stars and compact objects by analyzing broadband radio-to-X-ray spectral energy distribution properties of selected sources available from other public wide area surveys. As an early result of our method we present several candidates to hyperluminous X-ray sources with high X-ray-to-optical flux ratios that can hardly be explained by invoking any conventional object type.

2.04.15 (Thursday)
12:00
"Clues about massive star evolution from Wolf-Rayet stars in the Milky Way field and the unique Westerlund 1 cluster"
Christopher K. ROSSLOWE (University of Sheffield)
Abstract
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"Clues about massive star evolution from Wolf-Rayet stars in the Milky Way field and the unique Westerlund 1 cluster"

Christopher K. ROSSLOWE (University of Sheffield)

Abstract

The Westerlund 1 Galactic cluster hosts an eclectic mix of coeval massive stars. At a modest distance of 4-5kpc, it offers a unique opportunity to study the resolved stellar content of a young (~5Myr) high mass (5x10^4 Msun) star cluster. With the aim of testing single-star evolutionary predictions, and revealing any signatures of binary evolution, I shall discuss analyses of NTT/SOFI near-IR spectroscopy of massive Wolf-Rayet (WR) stars in Westerlund 1. We find that Nitrogen-type WR stars are H-poor compared to their counterparts in the Milky Way field, and nearly all are less luminous than predicted by single-star isochrones at the age of Westerlund 1. I will also present a spatial analysis of the whole Galactic WR population - mapped using stars in clusters such as Westerlund 1 to calibrate IR absolute magnitudes. This has been used to test models of metallicity-dependent stellar evolution, and to make predictions regarding the complete Galactic WR star population that are of interest to spectroscopic surveys.

2.04.15 (Thursday)
14:00
"Isolated compact elliptical galaxies: stellar systems that ran away "
Igor CHILINGARIAN (CfA, USA)
Abstract
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"Isolated compact elliptical galaxies: stellar systems that ran away "

Igor CHILINGARIAN (CfA, USA)

Abstract

Compact elliptical galaxies form a rare class of stellar system (?30 presently known) characterized by high stellar densities, small sizes and often harboring metal-rich stars. They were thought to form through tidal stripping of massive progenitors until two isolated objects were discovered where massive galaxies performing the stripping could not be identified. By mining astronomical survey data, we have now found 195 compact elliptical galaxies in all types of environment. They all share similar dynamical and stellar population properties. Dynamical analysis for non-isolated galaxies demonstrates the feasibility of their ejection from host clusters and groups by three-body encounters, in agreement with numerical simulations. Hence, isolated compact elliptical galaxies and likely quiescent dwarfs are tidally stripped systems that ran away from their hosts.

7.04.15 (Tuesday)
12:00
"Exoplanet atmospheric studies through transmission spectroscopy with VLT+FORS2"
Elyar SEDAGHATI (ESO, Chile)
Abstract
Close
"Exoplanet atmospheric studies through transmission spectroscopy with VLT+FORS2"

Elyar SEDAGHATI (ESO, Chile)

Abstract

In the past few years, the study of exoplanets has evolved from being pure discovery, then being more exploratory in nature and finally becoming very quantitative. In particular, transmission spectroscopy now allows the study of exoplanetary atmospheres. Such studies rely heavily on space-based or large ground-based facilities, because one needs to perform time-resolved, high signal-to-noise spectroscopy. The very recent exchange of the prisms of the FORS2 atmospheric diffraction corrector on ESO's Very Large Telescope should allow us to reach higher data quality than was ever possible before. With FORS2, we have obtained the first optical ground-based transmission spectrum of WASP-19b, with 20 nm resolution in the 550--830 nm range. For this planet, the data set represents the highest resolution transmission spectrum obtained to date. I will present our results, which show large unexplained deviations from planetary atmospheric models in the transmission spectrum redwards of 790 nm, indicating either additional sources of opacity not included in the current atmospheric models for WASP-19b or additional, unexplored sources of systematics. I will highlight our detailed analysis of the systematics present in the data and the careful estimation of planetary parameter estimation.

8.04.15 (Wednesday)
15:30
"Black hole dynamics in globular clusters, nuclear star clusters and ultra-compact dwarfs"
Andreas KUEPPER (Columbia University)
Abstract
Close
"Black hole dynamics in globular clusters, nuclear star clusters and ultra-compact dwarfs"

Andreas KUEPPER (Columbia University)

Abstract

Stellar-mass black holes are by far the most massive objects in old stellar systems like globular clusters, nuclear star clusters and ultra-compact dwarfs. As such they quickly segregate to the center of a system and interact dynamically with each other and with the stars. Using direct N-body simulations and a hybrid approach, I study the dynamics of black holes and the consequences for the stellar systems. In low-mass systems such as globular clusters, the segregation causes strong expansion of the cluster, leading to the extended clusters we observe in the outer halo, e.g., the Palomar clusters and NGC 2419. In the center of the low-mass systems, the black holes interact and eject each other until one or none is left. In dense, high-mass systems, the black holes grow through tidal captures and tidal disruptions of stars while orbiting in the center of the systems and slowly ejecting each other. However, in case the stellar system is dense enough, the stellar mass black holes can grow to intermediate mass to supermassive sizes before they can eject each other. I will present simulation results and discuss observational evidence for these findings.


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