Seminars

I will briefly review the programme of the GA which contained 7 Symposia,15 Focus Meetings and many other activities. A few scientific results,

like relativistic motion of the star S2 around the Galactic Centre blackhole, news from Gaia, etc. will be treated in more detail. Overview of the

new members and officers of the IAU, as well as its centenary celebrationswill also be given.

Francois Bourrin will present his institute CEFREM and his last results on particles characterization using optics acoustics from glider moorings and potential of satellites.

The life of a pulsar born in a binary system has been studied in many ways. The recent proliferation of eclipsing millisecond pulsars, split into two classes called Redbacks and Black Widows, lets us study a variety of pulsars in short orbits around low-mass stars during a pause in the accreting phase and in the post-accreting phase. In addition to studying their evolution, these new systems also allow measurements of the upper range of neutron star masses and give us new ways of studying pulsar winds. But the observational and theoretical challenges are proliferating as fast as the spiders themselves. I will review where we are observationally with these systems, and discuss old and new theoretical challenges.

Europlanet brings together researchers active in planetary and space research from across Europe. Since 2005, Europlanet has provided Europe’s planetary science community with a platform to exchange ideas and personnel, share expertise, research tools, data and facilities, define key science goals for the future, and familiarise and engage stakeholders, policy makers and European citizens with planetary science. The Europlanet programme was founded through a €2 million Framework 6 coordination Action and subsequently developed through a €6 million Framework 7 Research Infrastructure Europlanet RI which, for the first time, provided a structure for transnational access to leading planetary science facilities. Today, Europlanet is a collegial organisation designed to support European planetary science with a sustainable, active community for decades to come.

To date Europlanet has a membership of over 60 institutions, linked by a Memorandum of Understanding (MoU), that have agreed to cooperate on an informal and mutually beneficial basis. Europlanet members include past beneficiaries of Europlanet as well as new partners. By the end of this decade, Europlanet aims to have more than 180 members signed up to the MoU – at least 90% of planetary science institutions in the European Research Area.

For Tartu Observatory, Estonia and other young EU countries, Europlanet helps to integrate in the planetary science community by applying its technology, telescopes and astronomical expertise. For example, for the upcoming call of Europlanet facilities and services Nigel Mason has invited Andris Slavinskis as a coordinator of the Baltic–Finnish Europlanet Hub and he is happy to help with further interest and questions.

The modelling of gas and other matter around stars is often described by hydrodynamics (HD) or multi-fluid hydrodynamics. Accretion and decretion phenomena, i.e. outflows from stars, are connected with nonlinear flows, today often treated with numerical methods. The classical representation of nonlinear flows has been done already by Lagrange and Stokes, later by Clebsch and Monge, using special potentials from which the flow fields can be derived. These potentials, inserted into the HD equations lead to nonlinear Poisson equations, and represent the vortices or the compressibility of the gas, in analogy to nonlinear Schroedinger-Eigenvalue equations or the equations of nonlinear magnetohydrostatics. Our aim is to extend these equations and involved methods as tools for investigating the circulation and outflow of circumstellar matter around massive stars.

Moorits Muru and Oskar Aava (both Tartu University) will present their master and bachelor theses.

Moorits Muru
Detection of WHIM structure candidates in the SDSS spectroscopic survey
A significant fraction of the local baryons as predicted by the LambdaCDM cosmology models are not detected in surveys. One proposed solution to the missing baryons problem is that it is in form of diffuse warm-hot intergalactic medium (WHIM). Studies on simulation data have shown a correlation between galaxy luminosity overdensity in the filamentary network and WHIM overdensity. In this work, the correlation is applied to SDSS spectroscopic survey data. Study of WHIM structures over a selection of line of sights is presented.

Oskar Aava
Kosmoloogilise keskkonna mõju galaktikate morfoloogiale
Enamik elliptilisi galaktikaid on punasemad ja heledamad. Töö uurib kas, kui fikseerides värvus ja heledus, on võimalik vaadelda morfoloogia muutumist, kui muuta keskkonda. Keskkonna kirjeldavaks parameetriks on galaktikate tihedus.

In this talk I will address the sensitivity analysis (SA) of mathematical models of physical objects and processes.  In a wide number of applications, it is of substantial interest to know the sensitivities of
output parameters of models to their input parameters – essentially, the partial or variational derivatives of the output parameters to, respectively, discrete or continuous input parameters.  In the nutshell, the sensitivity analysis of models can be likened to differential calculus of functions, or variational calculus of functionals, and for analytic models it is the case indeed.  But in the majority of practical cases one has to deal with numerical models, and in this talk I will address two alternative approaches – the linearization approach and adjoint approach to SA, which complement each other.  I will show a number of demo examples illustrating both approaches.

'The blazar OJ287 has a supermassive binary black hole system as its central engine. It is a highly relativistic system and we use post-Newtonian equitation of motion to solve the BBH orbit. This includes the effects of gravitational radiation from the system. We find that the observation of OJ287 demands inclusion of gravitational radiation reaction effects beyond the quadrupolar order. It turns out that even the effects of hereditary terms which depend on the history of the source are required to predict impact flare timings of OJ287 and we develop an approach to incorporate it into the binary black hole model for OJ287. We find an excellent agreement between the theoretical predictions and the best fit to the data that spans over 10 orbital cycles. Additionally, We show that the orbit-averaged gravitational wave flux deviates 6.5% from the flux calculated from the standard quadrupole formula.

There are several methods to estimate gap fraction of forest canopies, however none of them is perfect. Measurements over RAMI stands at Järvselja in several years using different methods are compared. Airborne laser scanner measurements by Estonian Land Board in summer 2017 are involved. The new ALS Riegl VQ-1560i has high point density, records several hits and full waveforms. Some other homogeneous stands are involved in the study.

Landsat-8 OLI and Sentinel-2 MSI images from years 2015 and 2016, 1:10,000 digital soil map and a large number of reference samples was used with a random forest machine learning implementation in GRASS GIS to construct tree species map for the entire territory of Estonia (42,755 km2). Class probabilities for seven main tree species, an extra class for other species and probability of the forest cover not confirming forest definition was imputed for each pixel. Validation of dominant species distribution by area sowed very strong correlation at county level both in state forests (R2=0.98) and in private forests (R2=0.93). Validation of tree species composition using harvester measurement data from 2,045 regeneration felling areas showed also very strong correlation (R2=0.75) with the measured values of the share of coniferous trees. There was some tendency to overestimate the share of more common species and underestimation was found for the species with smaller share. The accuracy for the share of deciduous species that were present in smaller number of reference observations, was substantially smaller. Validation of the results by using data from 659 large sample plots from the database of the Estonian Network of Forest Research and 3,002 small sample plots from the National Forest Inventory (NFI) data base confirmed the findings based on of harvester data. The NFI data revealed also a decrease of estimation error with the increase of forest age. Overall, the constructed map provides valuable data about tree species composition for the forests where no up to date inventory data are available or for the projects that require continuous cover of tree species data of known quality over the entire Estonia.

Networking of automated instruments on unmanned platforms, e.g. AERONET-OC and RADCALNET, has proved to be the most effective way to provide validation data for Copernicus optical missions. The re-use of data from each site for many optical missions (S2, S3, PROBA-V, MODIS, VIIRS, L8, Pléiades,ENMAP,PRISMA,SABIAMAR,etc.) gives a huge economy of scale. The existing AERONET-OC and RADCALNET networks are based on multispectral instruments, which are expensive to acquire and require modelling associated uncertainties to cover all spectral bands of all sensors. Recent advances in opto-electronics facilitate the use of miniaturized hyperspectral spectrometers, with reduced price. Industrial production of video surveillance cameras greatly reduces the price of pointing systems for scientific instruments. Improved LEDs can provide a stable light source for relative calibration and continuous autonomous monitoring of radiometers. Webcams (for remote inspection of instruments and maintenance support) and data transmission have become cheaper allowing reducing the running costs and improving the reliability of autonomous instrument systems. The objective of the HYPERNETS project is to develop a new lower cost hyperspectral radiometer and associated pointing system and embedded calibration device for automated measurement of water and land bidirectional reflectance. The instrument will be tested in a prototype network covering a wide range of water and land types and operating conditions. Quality controlled data with associated uncertainty estimates will be provided automatically for the validation of all optical satellite missions. Preparations will be made a) for the new instrument design (and associated calibration service) to be commercialized with an expected lifetime of at least 10 years and b) for the networks to be further expanded to become the main source of surface reflectance validation data for all spectral bands of all optical missions for at least the next 10 years.

We present a model where the observed dark matter abundance is produced via freeze-out before the electroweak phase transition. We show that in this case the dark matter annihilation channels determining its freeze-out are different from those producing indirect detection signal. We present a benchmark model where the indirect annihilation cross-section is significantly larger than the freeze-out one. The model also has a gravitational wave signature due to the first order electroweak phase transition.

Rein Ahas (Professor of Human Geography, University of Tartu) will make a presentation “Is big data useful for social research? A paradigm shift in geography.” (In Estonian)

Second Sentinel-2 Validation Team Meeting is taking place on the 29.-31. January in Italy. This presentation will be to rehearse for my first conference and for an oral presentation. In my presentation I will give an overview of comparison of  atmospheric correction methods for Sentinel-2 over Estonian lakes. For estimating water quality parameters from satellite data, it is important to use appropriate atmospheric correction to remove influence of atmosphere.

Specialists from the UT International Cooperation Unit will give an overview of the Erasmus+ programme. 

Professor Arvi Freiberg (Head of the Biophysics Laboratory, Institute of Physics, Tartu University) will give an overview of the research topics and methods in his lab including the latest scientific achievements.
(In Estonian)

Anu Reinart will make a presentation “Introduction to Interreg project BalticSatApps”.

The presentation bases on analysis of thermal radiation reaching to different altitudes for different standard atmospheres and arctic weather profiles, using radiative transfer model FUTBOLIN. Also hypothetical situations with carbon dioxide on the level of year 2000 or double are analysed.

We present some of the results from Cosmic Large-Scale Structurein X-rays (CLASSIX) Cluster Survey, which is currently the largestwell-defined X-ray galaxy cluster sample.

Our first result from the survey includes constraints on the intraclustermagnetic field and the large-scale distribution of dark matter througha new class of objects, called superstes-clusters.
By comparing observed properities of the clusters in the superstes-clusterswe show that the regions defined as superstes-clusters are small, butprovide a special place where clusters grow differently from the field.The second part of the talk is based on our cosmological constraintsand the discussions on the discrepancies found between the probes ofthe large-scale structure and the Planck. Possible sources of discrepancywill be discussed in terms of non-zero total mass of neutrinos, Hubbleparameterm cluster scaling relations and the effect of selection biasintroduced in a survey.

The goal of the project “Satikas” is setting up a processing chain that detects the cutting events using the Copernicus Sentinel-1 and Sentinel-2 data. The presentation aims to give an overview of the software architecture and problems encountered during its development.

I talk about the galaxy cluster A2142, a central cluster in a collapsing core of the supercluster, its structure and galaxy populations. I compare it with other rich galaxy groups and clusters from the Sloan Digital Sky Survey and show that in several aspects A2142 stands out among them.

To understand how galaxies and the large scale structure they inhabit, forms, it is important to complement observations with computational simulations. Tartu Observatory cosmologists and galaxy physicists have long used the results of the Sloan Digital Sky Survey (SDSS) as an observational basis for their work. Recently the Virgo consortium published their Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulation database. EAGLE is a combined dark and baryonic matter simulation, which studies structure and galaxy formation from redshift 20 to the present. In this talk I present some statistical properties of redshift ~ 0 SDSS and EAGLE galaxies and show how well they do (or do not) match up.

Experiments investigating spectral responses of plants' physiology have been carried out during last ~120 years but young herbaceous species or young tree seedlings growing in similar conditions have been used as test subjects. Light conditions vary vertically in canopies of trees; therefore leaves of upper and lower part of trees' canopy have acclimated differently in respect to light conditions. I present the results of an experiment where we tried to find out how physiology of leaves originated from upper and lower part of the forest growing trees' canopy responds to different spectra of light.

In the seminar we will present our biased view of the recent developments of dark matter physics in the context of astro-particle physicist. We are summing up some ideas on dark matter physics from the first gravitationally measured neutron star merge event. Next, we will comment the ideas and constraints related to 'primordial black hole dark matter'. Then we are proposing some ideas how one can exploit the Gaia experiment and some strong lensing data to resolve finer substructures of dark matter. Finally, we give a mini-review cosmic ray physics in the energy range from MeV to TeV. We will sum up the ‘anomalies' in this energy range: positron excess above 10 GeV, antiproton excess above 20 GeV, gamma ray excess at 2-5 GeV at the Galactic Centre and differences in the spectral indexes and the brakes in the “should-be similar and simple" power-law spectra of protons and heavier elements.

During the seminar, the Jaan Einasto International Scholarship for the year 2017 will be awarded.

J-PAS is a narrow band, very wide field Cosmological Survey to be carried out from the Javalambre Astrophysical Observatory in Spain with a dedicated 2.5m telescope and a 4.7deg^2 camera with 1.2Gpix. Starting in 2016, J-PAS will observe 8600 deg^2 of the Northern Sky and measure 0.003(1+z) precision photometric redshifts for nearly 1E08 LRG and ELG galaxies plus several million QSOs, sampling an effective volume of ~14 Gpc^3 up to z = 1.3. J-PAS will also detect and measure the mass of more than a hundred thousand galaxy clusters, setting constrains on Dark Energy which rival those obtained from BAO measurements.The key to the J-PAS potential is its innovative approach the combination of 54 145°A filters, placed 100°A apart, and a multi-degree field of view (FoV) which makes it a powerful "redshift machine", with the survey speed of a 4000 multiplexing low resolution spectrograph, but many times cheaper and much faster to build. Moreover, since the J-PAS camera is equivalent to a very large, 4.7deg^2 "IFU", it will produce a time-resolved, 3D image of the Northern Sky with a very wide range of Astrophysical applications in Galaxy Evolution, the nearby Universe and the study of resolved stellar populations. J-PAS will have a lasting legacy value in many areas of Astrophysics, serving as a fundamental dataset for future Cosmological projects.Here, I will talk about the overall description, status and scientific potential of the survey.

Spectral signatures of forests collected in helicopter measurements at Järvselja can be represented as the sum of five basis vectors. The procedure allows to compress spectral signatures of forests and makes these data better manageable.

One of the greatest challenges of modern theoretical physics is explanation of the accelerated expansion of the Universe. The usual approach is to introduce the Dark Energy, but recently another approach started to be increasingly popular, where the laws of gravity are reconsidered and modified. It turns out that it is possible to modify not just the standard general relativity, but also first find the equivalent formulation in the framework of teleparallel geometry and use it to construct new modified theories of gravity with number of interesting features. In this talk I will introduce this novel approach to modified gravity and present some recent results.

The most important greenhouse gases are water vapour (60%) and CO2 (26%), derived from the U.S. Standard Atmosphere from 1976. Carbon dioxide spatial and seasonal variation is quite small, while precipitable water variability exceeds in Estonia 40 and globally 100 times. Difference in absorption between humid and dry profile is still surprisingly small, as considerable difference is only in spectral regions where there is no complete absorption. The presentation bases on analysis of absorption of surface thermal radiation in three weather profiles conditions with different humidity content, using radiative transfer model FUTBOLIN. Also hypothetical situations with double amounts of carbon dioxide or methane will be presented.

Slides are in English, presentation will be also, if needed.

When a globular cluster (GC) moves in a gravitational field of a larger galaxy, GC looses its stars due to tidal forces and “evaporation”. Usually evaporation dominates. As a result of these processes a narrow stellar stream will form. When the second data release of the Gaia satellite measurements will be available in April next year, it is possible to start to analyse stellar coordinates and velocities in the whole 6D phase space. We hope that by using our filament finder and FoF algorithms, it would be possible to identify several tens of new stellar streams.

Cold dark matter (DM) theory predicts that a certain amount of DM exists in form of minihalos and have predicted mass spectrum of these minihalos. Due to interactions between minihalos and stellar streams, small disturbances will be created in structures of streams. Thus, after identifying streams and thereafter by studying the number and amplitude of density and velocity disturbances in these streams, it would be possible to constrain the mass spectrum of DM minihalos and to test the validity of CDM theory.

One direction in the search of observable imprints of quantum gravity studies is the study of modified dispersion relations for fundamental particles on spacetime. They model the pictorial idea that higher energetic particles interact stronger with the quantum nature of gravity then lower energetic ones.

Famous proposals how to implement this idea explicitly are so called Rainbow-Gravity, Doubly/Very/Deformed/DeSitter Special Relativity, kappa-Poincare Curved Momentum Spaces or Relative Locality. They all lead to a modified dispersion relation for particles propagating through flat spacetime.

However to link modified dispersion relations to a quantum gravity effect we need to study them on curved spacetimes. In order to do so we will identify dispersion relations with the Level sets of Hamilton functions which govern the motion of fundamental point particles. Considering homogeneous and isotropic as well as spherically symmetric Hamilton functions we can derive observables, like the time of arrival of photons which are emitted from the same source at the same time but with different four momenta and the innermost circular photon orbits around black holes.

As soon as deviations from the general relativistic dispersion relation are present new observable effects emerge. For the homogeneous and isotropic Hamiltonian I discuss the so called lateshift, for the spherically symmetric Hamiltonian we find that the innermost circular trajectories for photons around a black hole depend on the photon energy.

Presentation slides

Rotational speed is an important physical parameter of stars: knowing the distribution of stellar rotational velocities is essential for understanding stellar evolution. However, rotational speed cannot be measured directly and is instead the convolution between the rotational speed and the sine of the inclination angle -- v sin(α). The problem itself can be described via a Fredhoml integral of the first kind. A new method (Curé et al. 2014) to deconvolve this inverse problem and obtain the cumulative distribution function for stellar rotational velocities is based on the work of Chandrasekhar & Münch (1950). Another method to obtain the probability distribution function is Tikhonov regularization method (Christen et al. 2016). The proposed methods can be also applied to the mass ratio distribution of extrasolar planets and brown dwarfs (in binary systems, Curé et al. 2015).

For stars in a cluster, where all members are gravitationally bounded, the standard assumption that rotational axes are uniform distributed over the sphere is questionable. On the basis of the proposed techniques a simple approach to model this anisotropy of rotational axes has been developed with the possibility to “disentangling” simultaneously both the rotational speed distribution and the orientation of rotational axes.

Since Nicolaus Copernicus  proposed for the first time the model of the Solar System, it has taken nearly 450 yr to detect the first planet around stars other than the Sun (Wolszczan & Frail 1992; Mayor & Queloz 1995; Marcy & Butler 1996). The progress has been much faster since, and the first multiple planetary system orbiting a main-sequence (MS) star was found only a few years later by Butler et al. (1999).  Today, the focus of most planet searches is on MS stars with planets in stable habitable zones (HZ). From a list of almost 2000 exoplanet candidates, 20 are potentially habitable, including the first Earth-like planet (Gliese 581 d – Udry et al. 2007).
        Stars beyond the MS are frequently avoided in planet searches because they are known to exhibit various types of variability: RV variations of unknown origin were pointed out to be common in red giants (RGs) by Walker et al. (1989), and multiple pulsation modes are often present. In addition, the rotation of starspots across the stellar disk can affect the spectral line profiles of these stars (Vogt et al. 1987; Walker et al. 1992; Saar & Donahue 1997). However, soon after the first discovery (ι Dra b Frink et al. 2002), searches for planets around stars beyond the MS have become recognized as important in building a complete picture of planet formation and evolution for several reasons. First, they allow extending the reach of the most versatile RV technique, which is not applicable on the MS because of the high effective temperature of the stars and their fast rotation rates, to objects with masses significantly higher than solar (e.g., o UMa, a 3 M⊙ giant with a planet – Sato et al. 2012). Second, the planetary systems around evolved stars are much older than those around MS stars, and therefore they are suitable for long-term dynamical stability considerations. Planetary systems around giants are also subject to changes induced by stellar evolution, and therefore are suitable for studies of star – planet interactions, and last but not least, evolved planetary systems carry information on the initial population of planetary systems to be found around white dwarfs. It is no surprise then that several projects devoted to searches for RV planets that orbit RGs were launched.  One of the largest of them is the PennState – Toruń Centre for Astronomy Planet Search (PTPS, Niedzielski et al. 2007; Niedzielski & Wolszczan 2008a,b).
       In my talk I will present the sample of PTPS, current status of our planet search and the most recent discoveries. I will also  discuss some properties of the exoplanets around evolved stars from the PTPS perspective.

We present an analysis of star formation among galaxies in and around 30 massive clusters at z=0.15-0.30, combining Spitzer 24um and GALEX NUV imaging from the Local Cluster Substructure Survey (LoCuSS) with extensive spectroscopy from the Arizona Cluster Redshift Survey (ACReS), including >10,000 confirmed cluster members. We show that the specific-SFRs of star-forming cluster galaxies are systematically lower than their counterparts in the field at fixed stellar mass and redshift, and demonstrate that this requires most (if not all) massive star-forming galaxies accreted into clusters to have their star formation slowly quenched on 1-2 Gyr time-scales. We also present an XMM survey to search for X-ray groups in the vicinity of these same clusters, identifying 39 X-ray groups that are in the process of being accreted by the clusters. We discuss what these groups mean for the mass growth of clusters, and show that galaxies within these groups are being pre-processed before they arrive in the cluster.

The formation and evolution of massive stars is still an open question as many physical phenomena inside massive stars are poorly understood. The field of asteroseismology helps us explore these stellar interiors by observing the surface brightness variability of stars. Although, space missions have made asteroseismic observations of hundreds of solar-like stars, our knowledge of massive stars is relatively poor due to the small number of them observed from space. Ground-based observations can not achieve the precision for proper asteroseismic analysis but, for massive stars with suitably large brightness amplitudes, they can be used to expand on the known asteroseismic constraints. The availability of small-scale telescopes helps to study massive stars with good temporal coverage that is unachievable from space missions.

In order to study massive stars in different evolutionary phases, we monitored 22 star clusters for three years and obtained light curves for over 3000 stars using a telescope in New Mexico, USA. We identified 354 variable stars of which 60% were first discoveries of variability. We used frequency analysis along with the pulsation HR diagram to classify our variable stars and determine multi-periodic stars. Analysing the probability density function of variable stars, we found the upper limit of cluster membership fraction to be higher than predicted from other works.

Mass loss in massive stars determines the evolution of their temperature, luminosity, etc. Mass-loss rates in binary stellar systems can be measured from the change in their periods, indicating either a spin-up or slow-down of the system. To study mass-loss rates in eclipsing massive binaries, we used a Bayesian approach to determine the period change of seven selected binary systems. For this, we used archival data together with our own observations. For three stars, we reported the period change for the first time. In addition, we determined the origin and values of the mass-loss rates for all seven binaries as well as modelled their orbital and stellar parameters.

Summary

The presentation will be divided into 2 parts
Part 1: Academic and professional career (What I did): - The first master in Biomonitoring of marine ecosystems included a general presentation to my master thesis, entitled "Experimental study of the grazing of the herbivorous copepod Clausocalanus arcuicornis on the micro phytoplankton under natural conditions and contamination in the Bay of Bizerte_Tunisia".

                    - Technician (Geographic information system (GIS)) in French company
                   - My first semester in France

 Part2:  My Master thesis (what I am doing now)

                   - Global presentation for our topic and mention the research questions.
                  - Algorithms applied (Calibration and validation).

Presentation I Video
Abstract: Large scale chemical abundance gradients in the Galactic disks, small-scale abundance structures, and the mean chemical abundance values in the Solar vicinity, are important constraints to Galactic chemo-dynamical formation and evolution models. The formation and evolution of stars, and interstellar gas and dust depends on the distribution and evolution of matter in the Galaxy. Therefore, metallicity structures within the Milky Way can be mapped from the abundance analysis of its gas and stars. A sample of over 370 spectral type B main sequence stars within 1.5 kpc radius from the Sun, was observed with the MIKE high-resolution spectrograph on the Magellan 6.5-m telescope on Las Campanas observatory in Chile in 2007. The purpose of my Master’s project was to start mapping the present-day elemental abundance structure of the Solar neighbourhood, by determining the stellar atmospheric parameters, and Si and O abundances, with methods in stellar spectroscopy. The Master's project is a part of an international study aimed to determine the elemental abundances of B-type main sequence stars near the Solar vicinity and in the outer Galactic disk (Braganca et al. 2012, 2015; Garmany et al. 2015, Braganca et al. in prep.).

Gamma-ray bursts (GRBs) are the most energetic explosions in the Universe after the Big Bang. They are observed as sudden flashes of gamma rays from random directions in the sky, lasting from seconds to minutes. GRBs are thought to result from cataclysmic events associated with the birth of a compact object (neutron star or a black hole) either in the collapsing core of a massive star or in a NS-NS or NS-BH merger. Despite being discovered almost half a century ago, the mechanism of their emission is still a matter of active debate. I will review our current understanding of the processes at work and will discuss how detailed numerical modelling can place constraints on the physical conditions at the source as well as the GRB environments.

Presentation

In this talk I review recent work done at Metsähovi Radio Observatory on various classes of active galactic nuclei (AGN). By combining observations at several frequencies, from radio to gamma-rays, we can study the variability and spectral energy distributions, and therefore the processes governing the behaviour and properties of AGN. We use data not only from the Metsähovi radio telescope but also from a large number of other instruments, for example, the Planck and Fermi satellites to name a few. In my research I concentrate on two very different types of AGN; radio-loud blazar-type AGN such as flat spectrum radio quasars and BL Lac objects, and low-luminosity AGN, usually presumed radio-quiet or even radio-silent, such as Narrow-line Seyfert 1 galaxies. My goal is to study the formation and evolution of relativistic jets, and how particularly young sources fit in the evolutionary and unification scenarios of AGN.

Presentation

Cosmic rays are high energy charged particles originating from deep space. Although discovered now more than a century ago many questions of their origin are still unanswered. Even more remarkable are recent discoveries of their spectral behavior that differ noticeably from the predictions of standard models widely used to date. This indicates both the inadequateness of current models and the possibility for extra sources from astrophysics and the so called new physics. In this talk we discuss the newest results from AMS-02 experiment and their implications.

Video I Presentation

Video I Presentation

Presentation I Video

• Jaan Einasto (pdf)
• Peeter Tenjes (pdf)
• Rain Kipper (pdf)

Video

100 years ago, on April 8^th, 1917, the outstanding Estonian astronomer Grigori Kuzmin was born. We shall commemorate his legacy with a small thematic seminar on April 18^th 2017 at Tartu Observatory, summarising his life, research, and impact on the present-day research.

The seminar will start at 10.30 in the cafeteria with a free-form gathering, and will continue with presentations at 11.00-12.30 in the main auditorium. Talks will be given by Jaan Einasto, Peeter Tenjes, and Rain Kipper.

The scientific work of Kuzmin on galaxies and stellar dynamics was written with extraordinary clarity and brilliance. However, being published only in Russian and partly remaining unpublished, it never gained a worthy international recognition. Nevertheless, his scientific legacy lives on in the works on galaxies and dark matter carried out at Tartu Observatory, and is louder and louder echoing back from the broader astronomical community.

Tartu Observatory will soon release the English translations of the principal publications of Kuzmin.

Spatial and temporal patterns of forest background (understory) reflectance are crucial for retrieving biophysical parameters of forest canopies (overstory) and subsequently for ecosystem modeling. However, systematic reflectance data covering different site types are almost missing. This presentation will focus on the validation of background reflectance retrievals using MODIS bidirectional reflectance distribution function (BRDF) data against in-situ understory reflectance measurements covering a diverse set of long-term ecological research (LTER) sites distributed along a wide latitudinal and elevational gradient across Europe: protected coniferous blueberry forest in Sweden, karst forest system in Austria, floodplain broadleaf forest and coniferous forest in the Czech Republic, and Mediterranean agro-sylvo-pastoral woodlands in Portugal. The multi-angle remote sensing data-based methodology was originally developed for the forest background signal retrieval in a boreal region. Here its performance will be tested across diverse forest conditions and moments during the growing season, which is a necessary step before conducting extensive mapping over forested areas. The results can be also used as an input for improved modeling of local carbon and energy fluxes.

E-Science in astronomy develops infrastructure and methods to make new developments from information technologies and computing hardware available to a broad spectrum of astronomers. Its focus is on problems which are common between various scientific projects but can't usually be addressed within their scope. Central to this is access to the scientific data, either by collaborative environments for many scientists, or dealing with the data via thoroughly vetted software / pipelines, and with publishing data for free access, carefully curated and with as much provenance as possible.

Detecting and studying the magnetic fields of exoplanets will allow for the investigation of their interior structure, rotation period, atmospheric dynamics and escape, moons, star-planet interactions, and potential habitability. It was postulated that the magnetic fields of short-period exoplanets could be constrained if their near-UV light curves start earlier than in their optical light curves. This effect can be explained by the presence of a bow shock in front of the planet formed by interactions between the stellar coronal material and the planet's magnetosphere. Furthermore, if the shocked material in the magnetosheath is optically thick, it will absorb starlight and cause an early ingress in the near-UV light curve. We observed the transits of 19 short-period exoplanets from the ground in the near-UV. All of our observations resulted in non-detections of the desired effect but we can still put constraints on the planetary atmospheres with our data. To explain our non-detections we simulate the atomic physics, chemistry, radiation transport, and dynamics of the plasma characteristics in the vicinity of short-period exoplanets using the code CLOUDY. Using CLOUDY we have investigated whether there is an absorption species in the near-UV that can exist to cause an observable early ingress. We find that there isn't a species in any wavelength (including near-UV) that can cause an absorption. Therefore, we show though observations and theory that the near-UV transit method for detecting exoplanet magnetic fields needs to be updated. Additionally, we also simulate escaping planetary gas in ionization and thermal equilibrium with the stellar radiation field with CLOUDY. Promising sources of opacity from the X-ray to radio wavelengths are found, some of which are not yet observed.

Jaan Pelt will talk about frequency dependent correlations and total solar irradiance.

Abstract: Uncovering the nature of 'dark matter' -- a type of nearly undetectable matter, hypothesized to account for an observed excess of gravitational forces -- is one of the most profound and visible problems in current-day physical sciences. Although the problem can be traced back to the 1930s, it was not until the early 1970s that the issue of 'missing mass' was widely recognized. In this paper I explore why it was that the dark matter problem became prominent only after such a long period. I argue that it was not only the advancement of new evidence, like flat rotation curves, that gave rise to interest in dark matter.

Rather, to understand the establishment of dark matter we should take into account both the institutional developments in astronomy of the 1960s, and the rise of the discipline of physical cosmology. Only when regarding this broader context, I show, we can make sense of how dark matter came to matter.

Star formation in disc galaxies in often concentrated into more or less beautiful spiral structures. However, reasons why it is so are not clear yet. Long time the dominating theory was the density wave theory. And indeed, in case of several galaxies it was found that kinematic and photometric properties of the spirals in these galaxies are consistent with predictions of the theory. On the other hand, in case of several galaxies these predicted properties were not found. In recent years, other possible mechanisms to initiate density perturbations in galaxy discs were studied and were found to be promising to describe several observed properties of spirals. These mechanisms are interactions with dwarf galaxies or gas clouds. As the density waves are small perturbations their life cycle is related with the stability conditions in galaxy discs. In case of a nearby and well-observed Andromeda spiral galaxy (M31) we derived that the disc component of the galaxy is very stable leading us to a conclusion that possible density waves will vanish rather quickly and probably cannot trigger star formation.

Presentation will be in English to prepare for the defence of doctoral thesis. Martin Ligi will defend his doctoral thesis on 28 March 2017 at 10:15. Supervisors: Tiit Kutser and Anu Reinart.

Urmas Peterson will talk about coastal remote sensing applications “From the reeds in Estonia to the lakes in Europe”.

Aarne Männik will make a presentation “Modelling Estonian climate: experiences and future perspectives”

Many cosmological problems require three-dimensional all-sky galaxy catalogues reaching beyond the very local universe. As the currently deepest all-sky spectroscopic survey (2MRS) has mean z=0.03 only, such datasets at larger redshifts and covering more than 2pi sterad are available only from combining imaging surveys at different wavelengths and estimating photometric redshifts (photo-zs). I will present two such photo-z catalogues - 2MPZ and WISE x SuperCOSMOS - which are unique in terms of their combination of sky coverage (respectively ~4pi and ~3pi sterad) and depth (z<0.2 and z<0.4). They are continuously finding various cosmological uses, and I will discuss some of them, in particular those that I am involved in. These include detailed local cosmography (crucial in the recent discovery of the Vela Supercluster); universal isotropy and homogeneity tests; cross-correlations with other all-sky datasets, such as Planck CMB lensing or Fermi gamma-ray background; and even searches for electromagnetic counterparts of gravitational wave emitters.

The future of Estonian climate has been modeled several times since year 1996. Scenarios of the last climate prediction project will be shown and discussed.

Galaxy superclusters are visually one of the most dominant features of the large-scale of the universe. They are massive concentrations of galaxies, contrasting to the seemingly empty regions beside them. Superclusters can extend from tens to over hundred megaparsecs, they contain from hundreds to thousands of galaxies, and many galaxy groups and clusters. Unlike galaxy clusters, superclusters are clearly unrelaxed systems, not gravitationally bound as crossing times exceed the age of the universe, and show little to no radial symmetry.

In this study we used several galaxy samples to create catalogues of structures that, we think, correspond to what are generally considered galaxy superclusters. Superclusters were delineated as continuous over-dense regions in galaxy luminosity density fields. A number of parameters characterising the spatial position, size and shape of superclusters are calculated and analysed.

Presentation will be about doctoral thesis in English.

The possible application of the thermal bands of Landsat 8 and MODIS in the remote sensing of Estonian landscape, in particular of wetlands, is discussed. A more general discussion on the applications of thermal remote sensing is initiated.

Tartu Observatooriumi kauaaegse teaduri Olavi Kärneri 75. sünniaastapäevale pühendatud teadusseminar. 

Ettekanded:
1. Kaarin Riives-Kaagjärv. Olavi Kärneri õpinguaastad 
2. Sirje Keevallik. Kolleeg, kellega polnud võimalik tülli minna
3. Jaan Pelt. Solaarkonstandi muutlikkusest
4. Piia Post. Kliima tolerantsist 
5. Heino Mardiste. Eesti orienteerumise grand old man 

Seminari juhatab Piia Post.

AMUSE (Astrophysical Multipurpose Software Environment) is a software framework for astrophysical simulations, in which existing codes from different domains, such as stellar dynamics, stellar evolution, hydrodynamics and radiative transfer can be easily coupled. AMUSE uses Python to interface with existing numerical codes. The AMUSE interface handles unit conversions, provides consistent object oriented interfaces, manages the state of the underlying simulation codes and provides transparent distributed computing.

The basics of AMUSE will be demonstrated. Presenter would like everyone attending to install AMUSE on their computers so that it would be possible to code alongside me. The easiest way to install AMUSE is to download and unpack the binary release from http://www.amusecode.org/

In the talk a short overview will be given about the H2020 project EOMORES that just had its kick-off meeting. 

The easiest method for detecting life on an exoplanet in the near future is through biosignature gas concentrations in its atmosphere. Still, life is generally not the only source and sink of these gases. Due to this, we need to estimate how biosignature production rates depend on environmental conditions. This talk will be about experiments currently in progress in Massachusetts Institute of Technology (MIT), involving building of a bioreactor for growing bacteria in simulated exoplanet atmospheres and measuring bacterial gas production rates using it.

Results show that after a mowing event on grasslands, median VH (vertical transmit, horizontal receive) and VV (vertical transmit, vertical receive) polarisation values of 12-day Sentinel-1 coherence were statistically significantly higher than those from before the event.

Reet Adamsoo, Lawyer on intellecutal property rights in University of Tartu will give a presentation about intellectual property rights, copyright scope of scientific articles, agreements about IP between research institutions and entreprises etc.

Presentation will be in Estonian.

Most important greenhouse gases are water vapour (60%) and carbon dioxide (26%) (Kiehl and Trenberth, 1997). Are these proportions valid also in the Arctic with an order of magnitude less water vapour than at standard atmosphere or in double CO2 situation? These questions will be examined, using radiative transfer model FUTBOLIN.

Dr. Mikhail Medvedsky, Head of the Department for Astrometry and Space Geodynamics
Main astronomical observatory of National Academy of Sciences of Ukraine

• "Main astronomical observatory of NAS of Ukraine" (pdf)
• "Unified telescope control system" (pdf)

Dr. Vadym Naumov, Head of Photonics Lab, Senior Research Scientist, National Academy of Sciences of Ukraine

Dr. Fiodar Pliavaka, Head of fast-running processes department, Heat and Mass Transfer Institute of National Academy of Science of Belarus

• "Smart Polishing Technology" (pdf)
• Article about history of magnetorheological finishing (pdf)

Dr. Ilgmars Eglitis, Director of the Institute of Astronomy, University of Latvia
"Space Research at the Institute of Astronomy of University of Latvia" (pdf)

Mirjam Randla did her Master's thesis in the University of Perpignan in Southern France during MIDAS program (Managing Impacts of Deep-seA reSource exploitation). In the presentation she gives an overview of the characteristics of resuspended sediment plumes, particles and heavy metals.

Toomas Tõrra will talk about precision agriculture.

An overview of the data processing chain of the Estonian Environmental Observatory's spectroradiometer SkySpec will be given and the measurement results will be compared with the data from Tõravere actinometric station.

Kairi Raabe spent the spring semester of 2016 at the University of Toronto at professor J.M. Chen's biogeochemical cycle modelling lab, studying the model BEPS (Boral Ecosystem Productivity Simulator). The seminar will include an introduction of the model and an overview of the suitability of this model for Estonia.

We report on the discovery of a long stellar bar comprising the majority or totality of the stellar mass of the bulge in the Milky Way. Our program establishes that the Galaxy is a bulgeless system with the bar formed by secular evolution of the disk. We then explore the oldest component of the Galaxy with RR lyrae stars.

While much current research is focused on galaxy formation, a growing body of evidence suggests that countless galaxies have also been destroyed over the 14 billion year history of the universe, many of them cannibalized by neighbors or torn apart by gravitational forces. Globular clusters, ancient stellar systems that swarm around galaxies like bees around a hive, are providing valuable new insights into this cosmic carnage, revealing how the births and deaths of galaxies may be intertwined.

Students of environmental remote sensing will present their group work. Seminar will be in Estonian

Authors: Andres Kuusk and Joel Kuusk

Summary

Aerosol optical depth and columnar water vapor have been estimated using the inversion of the 6S atmospheric radiative transfer model on SkySpec spectra at Järvselja SMEAR-Estonia. Results of inversion are compared to AERONET data at Tartu Observatory (TO), Tõravere in 2013-2016 on days when SMEAR-Estonia and TO were in the same air mass. There are some systematic differences in estimated parameter values, but correlations are high. The modelled spectral irradiance using estimated atmosphere parameters matches the measured spectra with high accuracy.

I will talk about my experience working at the NOT for almost two years. I will also give an overview of the science being done with the NOT and how Tartu astronomers could get observing time at the NOT or other telescopes worldwide through OPTICON, The Optical Infrared Co-ordination.

Variations of the emission lines in the spectrum of the yellow symbiotic star AG Draconis have been studied for over 14 yr (1997-2011), using more than 500 spectra obtained with the 1.5-m telescope at Tartu Observatory, Estonia. The time interval covered includes the major (cool) outburst of AG Dra that started in 2006. Taking also into account photometric behaviour of AG Dra, the main findings can be summarized as follows. (i) The cool and hot outbursts of AG Dra can be distinguished from the variations of optical emission lines. (ii) The Raman scattered emission line of O VI at λ6825 almost disappeared during the cool outburst. (iii) The lower excitation emission lines did not change significantly during the cool outburst, but they do vary in hot outbursts and also follow orbital motion. (iv) The similarity of variations in AG Dra to those in the prototypical symbiotic star Z Andromedae allows us to suggest that a combination nova model proposed for the latter object might also be responsible for the outburst behaviour of AG Dra.

Evolution of the Cosmic Web

Presentation is about galaxy modelling: dynamical methods and applications.
Abstract: http://www.fi.ut.ee/en/events/rain-kipper-galaxy-modelling-dynamical-methods-and-applications

Andromeda, our dearest neighbour galaxy, has many different faces depending on the observed wavelength. We have combined data ranging from the ultra-violet to millimeter wavelengths. I will present a study linking the stellar emission in M31 with the dark shadows cast by interstellar dust. We have constructed a detailed 3D radiative transfer model of Andromeda, exposing the galaxy at all inclination angles. I will discuss the different dust heating sources and the internal energy balance of the galaxy. Finally, we look for possible probes to estimate the dominating heating sources in galaxies.

Krista Alikas will make a short presentation about her doctoral thesis titled "From research to applications: monitoring optically complex waters with MERIS/ENVISAT data". She will defend her doctoral thesis on 15 June 2016 at 10:15 at Physicum W. Ostwaldi 1 , room B103. 

http://www.ut.ee/en/events/krista-alikas-research-applications-monitoring-optically-complex-waters-merisenvisat-data

Massive stars affect strongly their environment through their intense stellar winds, which transfer momentum and energy to the interstellar medium and enrich it with chemically processed material as they evolve. This interaction becomes substantial in short-lived transition phases of massive stars (e.g. B[e] Supergiants, Luminous Blue Variables, Yellow Hypergiants) in which mass-loss is more enhanced and usually eruptive. However, these phases are not well-understood, such as the lack of B[e] Supergiants predicted from stellar evolution theory. In order to improve our knowledge for the particular class of B[e] Supergiants we have initiated a campaign to study them with high-resolution optical and near-infrared spectroscopy. This tool allow us to investigate their complex circumstellar environment, consisting of a combination of atomic, molecular and dust regions of different temperatures and densities. We use the strategic [OI] and [CaII] emission lines, and the CO bandheads to probe the structure and the kinematics of their formation regions. We find that these emission lines form either in a single or in multiple equatorial rings, a probable result of previous mass-loss events.

Seminar presentation I Video

In August 2013 terrestrial laser scanner measurements were carried out in the RAMI pine stand at Järvselja. The transparency of the crown layer (gap fraction) as a function of the zenith angle is estimated and compared to the similar estimates using digital hemispherical photos. An attempt is made to estimate the foliage area of the stand using the point quadrat analysis.

An overview of the problems detected by me in the first data release of the EBHIS. A brief description will be provided of the problems that have already been solved and the main attention will be devoted to the still open questions.

Seminar presentation

Olmekütmine on linnades meie kliimavöötmes oluline sissehingatavate osakeste ja heitgaaside tekitaja. Hinnanguliselt on Eestis ca 600 enneaegset surma aastas tingitud just sissehingatavatest osakestest. Hiljutised uuringud on näidanud et kütmisel kasutatakse laialt jäätmeid, mille põlemine pole madalate temperatuuride tõttu lõplik ja tekivad kahjulikud orgaanilised ühendid. Ettekanne tugineb 2l avaldatud uuringul: ACMS jt teiste seadmetega teostatud osakeste päritolu uuringule Tartus ning jäätmete ja küttepuude koospõletamisel kontrollitud tingimustes laboris.

An overview of the aims, technical setup, data reduction stages of the survey and comparison of the EBHIS with other similar surveys. The main attention will be focused on the problems that must be solved to get from raw telescope records clean HI data.

Seminar presentation

Video

Spatial and temporal patterns of forest background (understory) reflectance are crucial for retrieving biophysical parameters of forest canopies (overstory) and subsequently for ecosystem modeling. In this study we retrieved seasonal courses of understory normalized difference vegetation index (NDVI) from multiangular Moderate Resolution Imaging Spectroradiometer bidirectional reflectance distribution function (MODIS BRDF)/albedo data. We compared satellite-based seasonal courses of understory NDVI to understory NDVI values measured in different types of forests distributed along a wide latitudinal gradient (65.12°N–31.35°N).

Our results indicated that the retrieval method performs well particularly over open forests of different types. We also demonstrated the limitations of the method for closed canopies, where the understory signal retrieval is much attenuated.

I give a brief overview of the history of the Wall family, the richest supercluster complexes in the Universe, introduce a new member of the family, the BOSS Great Wall at redshift z = 0.47, and describe our study of the dynamical state and future evolution of the superclusters from the Sloan Great Wall.

Seminar presentation

Sloan Great Wall

Boss Great Wall

Emission-line stars are typically surrounded by dense circumstellar material, often in form of rings or disc-like structures. Line emission from forbidden transitions traces a diversity of density and temperature regimes. Of particular interest are the forbidden lines of [O I] λλ6300, 6364 and [Ca II] λλ7291, 7324. They arise in complementary, high-density environments, such as the inner-disc regions around B[e] supergiants. To study physical conditions traced by these lines and to investigate how common they are, we initiated a survey of emission-line stars. Here, we focus on a sample of nine B[e] stars in different evolutionary phases.

Seminar presentation

The problems of angular distribution of gap fraction in pine forests are tackeled. The forest gap fraction model is modified by improving the model for single crown transmittance. Can we assume that the pine shoots inside a crown envelope are randomly dispersed or clumped? In the examples data from a few Finnish sample plots are used.

B[e] supergiants are a group of evolved massive stars in a short-lived transition phase. During this phase, these objects eject large amounts of material, which accumulates in a circumstellar ring or disk-like structure, revolving around the star on Keplerian orbits. The mechanism responsible for the mass ejection is, however, yet unknown. In most objects, the disks seem to be stable over many decades. This guarantees these disks as ideal chemical laboratories to study molecule formation and dust condensation. Combining high-resolution optical and infrared spectroscopic data allows to search for emission features that trace the disk structure, kinematics, and chemical composition at different distances from the star. I will present an overview of the status of our knowledge about the structure and kinematics of B[e] supergiant stars' disks, based on currently available information from different observational tracers.

Presentation

Video

Identifying the nature of dark matter is the central problem of (particle) astrophysics. Even though the abundance of dark matter in the universe is about five times as large that of ordinary baryonic matter, very little is known about the properties of the particles that make up dark matter. One possibility is that not all of it is without self-interactions. This talk is exactly on this part of the dark sector. Both theory and simulation results of the interacting dark matter - the dark plasma is given. Talk is in English, unless all attendees understand Estonian.

Seminar presentation

Dr Jaan Liira will make a presentation “Will human impact always cause negative ecological consequences on woodland?”. Examples of structure and diversity of managed woodlands will be shown. Dr Jaan Liira is senior researcher of plant ecology at Tartu University.

Dr. Thomas Jagdhuber from DLR Microwaves and Radar Institute (DLR HR) is visiting Tartu Observatory and giving two presentations:

10:00 – 10:45 Soil moisture estimation with remote sensing

11:00 – 11:45 DLR Microwaves and Radar Institute and its research activities

DLR HR is one of the leading research centres of the world on radar remote sensing technology and physical interpretation of measurements.

DLR HR has given a major contribution to the success of satellite missions: SRTM, TerraSAR-X and TanDEM-X. In the coming years they are about to release the most accurate global Digital Elevation Model (DEM) with 12 m horizontal and 2 m vertical resolution. Tartu Observatory has cooperated with DLR HR since 2011.

Spectral and integral albedo of the Järvselja test-site is estimated using data of helicopter measurements in 2007-2015 and MODIS land products.

The overall aim of the GLaSS (Global Lakes Sentinel Service) project is to develop a system for using the upcoming data of Sentinel-2 and Sentinel-3 satellites for monitoring lakes and reservoirs. This project also includes case studies demostrating the applicability of Earth Observation (EO) data for different types of global lakes. Eutrophic shallow lakes represent a group of lakes situated in heavily populated areas where the presence of cyanobacterial blooms prevent periodically activities in or on a lake leading to socio-economic problems. Therefore it is important that the EO methods could provide the adequate monitoring of these environments. This study comprises eight representative European water bodies that were investigated by using MERIS (MEdium Resolution Imaging Spectrometer) and Landsat 8 data.

Agnieszka Bialek will give a short introduction to National Physical Laboratory followed by a description of Optical Radiometry measurement capabilities. Then she will talk about her recent projects including setting up a new radiometric calibration site at Namib Desert and collaboration with Tartu Observatory on Ocean Colour radiometers.

Agnieszka Bialek received MSc degree in Technical Physics from Wroclaw University of Technology, Poland in 2003. She works at National Physical Laboratory, UK since 2006. Her current research is focused on uncertainty reduction in Earth Observation by implementation of rigorous SI traceability. In 2012 she started part–time PhD study at the University of Surrey with aim to establish SI traceability for satellite derived optical images, Land and Ocean, using vicarious calibration methodologies. Her scientific experience is related to optical measurements including absolute radiometric calibration and instruments characterisation as well as the data modelling.

Ketlin Reis will talk about modeling forest fire smoke trajectory and validation of SILAM model based on data from Russian forest fires in year 2010.

In the first part of my talk I introduce the recent paper “The lopsided distribution of satellite galaxies”. The second part of my talk is dedicated to the Bisous model. I will introduce some recent studies where we used the Bisous model and I will give some prospects what are the planned developments of the model.

Maret will talk about the photos, and poet Riina Einasto will read some poems. After presentation we have a perzel of lights in the cafeteria. 

Open the photo of exhibition

Existing UV radiation measurement data of AvaSpec-256 and Bentham DMc150F-U will be presented. Due to gaps in measurements caused by technical reasons, previously developed models were used to calculate UV daily doses from 2008 to 2013. Both daily doses from measurements and model calculations are shown and compared. Also previously made time series of yearly doses from 1955 are extended with the results.

Andris Slavinskiswill present his PhD thesis "ESTCube-1 attitude determination". Dissertation defence will take place on November 26, 2015 at 14:15 in Physicum B103.

Abstract:
This thesis presents the ESTCube-1 attitude determination system (ADS). ESTCube-1 is a satellite build according to the one-unit CubeSat standard (≈ 10 × 10 × 10 cm). The satellite was launched in May 2013 and operated until May 2015. The main scientific mission of ESTCube-1 was to perform the first electric solar wind sail (E-sail) in-orbit demonstration. The E-sail is a propellantless propulsion technology concept. The sail consists of long, thin, centrifugally stretched and positively charged tethers that deflect charged particles in the solar wind, hence generate the spacecraft thrust.

The main requirement of the ESTCube-1 ADS is to determine the attitude with an accuracy better than 2° for the following purposes: high rate spin control (hundreds of degrees per second) for centrifugal tether deployment; monitoring of tether deployment; trigger the charging of the tether in synchronisation with the satellite spin; measure angular velocity changes caused by the Coulomb drag interaction between the charged tether and the surrounding ionospheric plasma.

The ADS has Sun sensors, magnetometers and gyroscopic sensors. Geomagnetic field model and Sun position model were used to reference the respective sensor measurements. An unscented Kalman filter was used to estimate the attitude. Before the launch, the system was characterised in the laboratory and by simulations. With in-orbit recalibration and validation, the system was significantly improved. For validation, an independent attitude determined from on-board images was used. The system fulfils the requirements set by the E-sail experiment — the expanded uncertainty of comparison is 1.75° (95% confidence level, k = 2). For all 15 samples, the difference is less than 1.44° which is well within the uncertainty budget.

Full text is available for download here: http://dspace.ut.ee/handle/10062/49230

Marina Haldna (Centre for Limnology of Estonian University of Life Sciences; MSc in mathematical statistics) will talk about “Estimation of the statistical relationships - based on the environmental monitoring data of the Estonian large lakes”. Subject of the presentation is environmental (survey) monitoring of the two Estonian large lakes, and how to use monitoring data in estimation of statistical relationships (not only correlations) between different water variables. Correlations between original data show good relationships but we do not differentiate thereby the effect of seasonality or location as well as weather conditions to observed variables or their associations. It is often unclear if studied variables influence each other directly, depend on the same third factors or have the same oscillation coincidentally. Examples of using SAS/STAT and R statistical software.

Dr Aveliina Helm will talk about "Plant diversity in grasslands, role of landscape structure and habitat history”. She will talk about large-scale and landscape-scale factors that drive plant diversity patterns in grassland ecosystems. Development of biodiversity is long-lasting process, influenced by not only local environmental conditions but also by management history, habitat spatial structure and size of species pools.

AG Dra is a well-known bright symbiotic binary with a white dwarf and a pulsating red giant. In the system of AG Dra, three periods of variability are detected. The longer one around 550 d is related to the orbital motion we discovered already in last millennium (1999), the shorter one around 355 d and interpreted as pulsations of the red giant. Finally in 2014 we understood that there is the third period in range from 359 to 375 days. The outbursts in the system are just repeated with this last period.

Intermediate polars represent a major fraction of all cataclysmic variables detected by INTEGRAL in hard X-ray. These object have been recently proposed to be the dominant X-ray source population detected near the Galactic centre and they also contribute significantly to the X-ray diffuse Galactic ridge emission. Nevertheless, only 25 % of all known intermediate polars was detected in hard X-ray so far. This fact can be related with activity state of these close interacting binaries. Multi-frequency (from optical to X-ray) investigation of intermediate polars is essential to understand physical mechanisms responsible for observed activity of these objects. 

Short rotation forestry (SRF) is a novel silvicultural method in Estonia, offering an alternative for re-use of abandoned agricultural lands. In Northern Europe hybrid aspen is considered as the most promising hardwood for SRF but also silver birch has shown fast growth on fertile previous agricultural lands. During the last 15 years research has been carried out on permanent sample plots in Estonian hybrid aspen and silver birch plantations concerning growth development and factors affecting it, the plantations’ effect on soil properties and biodiversity. Hybrid aspen and silver birch are also test species in the Free Air Humidity Manipulation (FAHM) experiment, where the impact of elevated air humidity (predicted consequence of climate change in northern latitudes) is studied on deciduous forests and the changes have been detected in trees’ growth rate, nutrient uptake, phenology, wood chemistry, etc.

In the era of integral field spectroscopy, there will be lot of observations which leads to possibility of modeling the kinematics of galaxy. We developed and tested a method to model galaxy dynamics with Jeans equations and third integral.

Lea Hallik will talk about H2020 project MULTIPLY (MULTIscale SENTINEL land surface information retrieval Platform).

Kaupo Voormansik will talk about the relationships between TerraSAR-X and Sentinel-1 polarimetric parameters and grassland structure with potential applicability for cutting/mowing detection.

Presentation is based on the UV spectra recorded by Bentham spectrometer and on the hourly data of broadband solar radiation. Two versions of wavelength split between UVB and UVA spectral ranges, 315 and 320 nm, are considered and the UVA/UVB ratios presented in usual energetic scale as well as in the erythema weighted effective energy.

Joel and Ilmar spent three weeks in NPL, the National Metrology Institute of UK. They studied the properties of spectral stray light and nonlinearity of several spectroradiometers. The presentation will give some background information and the first results.

Gas giants are believed to form far from their host stars. The existence of hot Jupiters means that they must have migrated to where they are today. The presentation will give a short overview of different planetary migration mechanisms and the role of migrating gas giants in the formation of our Solar System based on numerical simulations.

Jan Pisek will report on his joint endeavors with Branden McNeil (West Virginia University, USA) and Harald Lepisk how to best use UAV-mounted cameras to measure leaf angles in broadleaf canopies.

I will try to give a short overview of a few scientific topics (e.g. star-forming galaxies, structure of the Milky Way, massive stars, the Sun and other magnetically active stars). There will also be a few words on the IAU as organization. Finally, if there is time left, some more touristic impressions from the O'ahu island.

Andres Kuusk will talk about the role that reflected radiation plays in measurements conducted with the LAI-2000 plant canopy analyzer. Assumptions and systematic biases of optical LAI (leaf area index) estimations will be discussed.

Annual Nordic Ozone Group conference - NOG2015 took place in Denmark from 7- 8 May 2015. Presentation introduces Nordic Ozone Group and its participants. Also an overview of recent issues and problems on UV-radiation and ozone for different countries is presented.

AG Draconis is a symbiotic binary star with an early type (spectral class K) cool giant. Its hot component is a white dwarf whose high luminosity (about 1000 solar luminosities) is maintained due to thermonuclear shell burning of accreted matter. AG Dra undergoes frequent outbursts of 1-3 mag, they can be divided into hot and cool ones. Major cool outbursts occur at about 12-15 years intervals, while minor scale hot outbursts can repeat almost once a year. Spectroscopic observations of AG Dra have been performed on our 1.5-meter telescope since 1997. Together with colleagues from Slovakia we have analysed these observations as well as the available photometric observations. Some trends and regularities in the behaviour of the strongest emission lines (hydrogen Balmer series alpha and beta, He I at 6678 A, He II at 4686 A) will be discussed. Of special interest is the spectral line at 6825 A, encountered only in symbiotic stars and originating as Raman scattering of the O VI photons on the atoms of neutral hydrogen. Nature and physical mechanism of such frequent outbursts in so called classical symbiotic stars still remain a bit mysterious.

Roughly aerosols are divided into fine mode and coarse mode fractions. The first is related to biogenic and anthropogenic emissions, including fires. Almost each year episodes of large AOD are met but most time there is background aerosol. The aerosol influence on ground-level solar radiation depends on the availability of direct irradiance. The background and smoke aerosol are separated and studied. Smoke episodes have two peaks - in April-May and in July-August. In July-August the AOD of background aerosol and its fine mode fraction are the largest.

Seminar video

• Ann Alice Ehala "RAITS teleskoobi süvafotomeetria galaktika NGC 3448 näitel"
• Eero Vaher "Validation of SMART stellar atmosphere models"
• Kristiina Verro "Physical Properties of the Nova Remnant Nova Persei 1901"

The presentations will be in Estonian.

Dr Pille Mänd from University of Tartu Department of Botany Chair of Ecophysiology will talk about plant water use efficiency (WUE) from global perspective.

Dr Anu Sõber from University of Tartu will talk about leaf temperature measurements and environmental factors influencing leaf temperature.

Elar Asuküll will talk about coloured dissolved organic matter and its variability in Lake Peipsi through 2008-2011. He will also give a brief introduction to his doctoral studies which are related to CDOM and plans to estimate carbon fluxes from all of the lakes in the World.

Jan Pisek will make a short presentation on characterization, validation and intercomparison of clumping index maps from POLDER, MODIS, and MISR satellite data over reference sites.

Several active galactic nuclei show periodic variations of flux density in radio and optical. However, it is still unclear what is the cause of the periodic flux density variations in these sources. The variability can be explained by various phenomena, including a supermassive binary black hole in the centre, plasma instabilities in the relativistic jet, jet precession, and helical moving of blobs in the jet. In this talk, we will present the results of a detailed study of jet physics of several quasars and blazars using multi-frequency very long baseline interferometry which gives the highest possible in astronomy resolution. We also compared jet structural changes with single dish multi-frequency observations spanning more than 30 years together with optical and gamma-ray data. In particular, analysis of the long-term kinematics of two active galactic nuclei S5 1803+784 and 0605-085 shows evidence for jet precession. The jet is precessing with a timescale similar to a period in the total flux-density light curves. We also found four blazars and quasars (3C 454.3, 3C 446, CTA 102, 0133+476) which show clear periodical total flux-density radio variability. Moreover, in the case of 3C 454.3 and 3C 446 the predicted flares were meanwhile observed.

The magnetic field is considered to be the most important energy source and engine concerning the heating processes in the solar atmosphere. Magnetic reconnection and subsequently physical dissipation processes lead to plasma heating and acceleration of plasma and particles. It is often criticized that Ohmic dissipation in current sheets is not the only or main source of heating and acceleration processes in the corona or solar flares. Often compressional plasma motions and subsequently forming shocks also lead to heating and acceleration. We prove precisely that the formation of arbitrary, strong spatially fluctuating current sheets, so called fragmented or fractal currents, are not necessarily consequences of instabilities or collapse processes, but are generic in MHD theory, even for regular solutions. The occurrence of non-singular but strong and strongly localized current sheets can basically contribute to the problems of coronal heating and particle acceleration, and can trigger eruptive and dissipative events like, e.g. magnetic reconnection.

Structural changes in leaves due to the environmental condition will be shown using tremble (Populus tremula), silver birch (Betula pendula) and other species as examples.

Hannes Keernik will talk about his doctoral thesis "Methods for analysis of column water vapor in the Baltic Sea region and in the Arctic".

We will give a short overview about the methodology we use to do the inventories for the land use, land-use change and forestry (LULUCF) sector. Where the information is coming from and where it is going.

We talk about satellite images and archives from practical viewpoint.

Andromeda, our near neighbour and the largest spiral galaxy on the sky, offers us a unique possibility to study the link between the stellar populations and the interstellar medium on the smallest spatial scales, while maintaining the global view as well. We exploit a panchromatic (UV to sub-millimetre) dataset and model the spectral energy distribution of each 140x140 pc region in Andromeda. On these local scales, we find similar correlations between SFR, specific SFR, dust temperature and mass, stellar mass,... as for entire galaxies. This suggests that these relations are in situ correlations, driven by processes that must be local in nature. Our goal is to explore these interactions in a self-consistent way through state-of-the-art radiative transfer simulations. A challenging task with great potential.

Seminar presentation

Agu Laisk will talk about spectral measurements of plants from the point of view of plant physiology and remote sensing

Lea Hallik will give a short presentation about COST Action ES1309: Innovative optical Tools for proximal sensing of ecophysiological processes (OPTIMISE) and COST Action FA1306 “The quest for tolerant varieties: Phenotyping at plant and cellular level”.

Seminar will be in Estonian.

Wolf-Rayet stars are the descendants of over 20 solar mass O-type stars. Being evolved massive stars, they are still young in astronomical terms, so their location has likely not changed much since formation. Most of the O-type stars in the Galaxy are connected to a cluster and/or an OB-association, but some massive stars are found to be isolated, even when the runaway stars are excluded. This is not supported by the current star formation theory which states that massive stars need to be formed in clusters. This study tries to find methods to detect clusters of pre-main sequence stars around Wolf-Rayet stars from photometric data from public archives.

Climate change is faster and more severe in the Arctic than in the rest of the world. Changes in the Arctic may be related to climate changes in northern Europe and may partly explain them. Usually, the climate analyses are focusing on certain regions, without evaluation of influences from neighbouring regions. Still, it is known that at adjoin regions weather and climate are strongly related to each other. We used NCEP-CFSR and ERA-INT reanalyses monthly mean values for 1979 – 2009 of temperature and specific humidity vertical profiles up to 300 hPa, sea level pressure, precipitable water and total cloud content. There were some differences between NCEP-CFSR and ERA-INT reanalyses results, but no fundamental disagreements in trends or correlation patterns.

Slides are in english, talk will be also, if required.

We will take a look at the dependence of various galactic properties on the environment density and consider the causes of the dependences.

Forest ecosystems are a major part of the biosphere and control land surface-atmosphere interactions. They influence atmospheric composition and climate significantly being sources and sinks of trace gases and energy. Hemiboreal forests are located in the transitional zone between boreal and temperate forest biomes. Mixed stands of both coniferous and deciduous tree species are characterized by a greater seasonal variability of forest microclimate, canopy shape and density compared to boreal forests. A 20 m height scaffolding tower located in Järvselja (58°16'N 27°16'E) in a forest stand dominated by Norway spruce (Picea abies (L.) Karst.) with co-domination of Silver birch (Betula pendula Roth.) and Black alder (Alnus glutinosa L.) was used for the CO2 flux measurements. Two years of continuous eddy covariance measurements over a mixed hemiboreal forest at the SMEAR Estonia (Station for Measuring Ecosystem-Atmosphere Relations) were studied to assess annual and diurnal dynamics of CO2 fluxes and their main environmental drivers.

In this talk I shall present methods that need to be applied to digitized astronomical photographic plates, in order to extract valuable data for contemporary scientific research. Light curves extracted from tens of thousands of plates from the past century allow studies of astrophysical phenomena on time scales of decades.

Authors: Jan Pisek (presenter), Miina Rautiainen, Maris Nikopensius, Kairi Raabe

We study the clustering of galaxies as function of luminosity and redshift in the range 0.35 < z < 1.25 using data from the Advanced Large Homogeneous Area Medium Band Redshift Astronomical (ALHAMBRA) survey. The ALHAMBRA data used in this work covers 2.38deg^2 in 7 independent fields, after applying a detailed angular selection mask, with accurate photometric redshifts, \sigma_z < 0.014(1+z), down to I_AB < 24. Given the depth of the survey we select samples in B-band luminosity down to L^th = 0.16L* at z = 0.9. We mesure the real-space clustering using the projected correlation function, accounting for photometric redshift uncertainties. In addition, for galaxies with M^th_B < -18.6, we perform the clustering evolution with segregated populations using ALHAMBRA templates, separating in early and late type galaxies. The high quality of ALHAMBRA photometric redshift and its high density field allow us to extend the projected correlation function down to 0.03 h^-1 Mpc, below any other calculations before.

Seminar presentation

Seminar video

Alhambra video:

A methodology by Roman et al. (2009, RSE) for establishing the spatial representativeness of field sites for validation of satellite retrievals from global land surface albedo and reflectance anisotropy products is applied to Järvselja RAMI stands. Variogram functions extracted from Landsat Thematic Mapper retrievals of surface albedo using multiple spatial and temporal thresholds were used to assess the degree to which Järvselja RAMI stands are able to capture the intrinsic variability of the immediate landscape extending to a satellite pixel. This approach can  improve our understanding of product uncertainty both in terms of the representativeness of the field data we collect and their relationship to larger satellite pixels.

Video

Presentation

Remote sensing seminars 2014/2015 will start by Anu Reinart leading the discussion about the activities at Department of Remote Sensing.

Understanding the formation and evolution processes of galaxies remains among the most important unsolved problems in present-day astrophysics and cosmology. A reliable and detailed description of the mass-density profile and structural properties of galaxies through cosmic time is a much-needed step forward but – whereas nearby systems have been thoroughly analyzed – painfully little is known about more distant objects, since observational limitations make it difficult to employ the traditional diagnostic tools. In my talk I will describe how to overcome these difficulties by combining the information obtained from all the available constraints: strong gravitational lensing, extended/2D stellar kinematics and stellar population synthesis (SPS) modelling. This provides a robust way to conduct unprecedentedly detailed investigations of the dark and luminous structure of both elliptical and disk galaxies at redshift z = 0.1 and beyond. Finally, by complementing the results of the joint lensing and dynamics study with the inferences from spectroscopic SPS analysis of optical line-strength indices, we are in the position of putting strong constraints also on the steepness and (for the first time) the lower cut-off of the stellar initial mass function of massive ellipticals.

Matteo Barnabe presentation (pdf)

Stellar winds are obstacles for the interstellar medium which shows a relative movement with respect to the star, e.g. the Sun. Due to the interaction of both flows, namely that of the stellar wind and the interstellar medium flow, both flows are decelerated and contact surfaces form, so called astropauses or in the case of the Sun the heliopause. The solar wind cavity inside the heliopause is called the heliosphere (=general astrosphere). Usually these separating surfaces, the astropauses, are defined and determined by the distribution and location of the null points of the magnetic field and null point of the plasma flow, the so called stagnation points. We present and discuss simplified models of such astrospheres and especially their downflow regions, the astrotails, taking (ideal) field-aligned MHD flows into consideration. Almost certainly shear flows occur in these astrospheres or at the astropauses and a strong fragmentation of electric currents, magnetic field and vortices takes place. Even if for the calculation of these nonlinear steady-state MHD flows, well ordered magnetic field structures are used, fractal-like structures will be formed. The cascading down to very small structures can lead to instabilities, eruptive processes like reconnection and the occurence of strong localized electric fields. These processes may be also responsible for acceleration mechanisms, contributing to cosmic ray production.

Video of the seminar.

The infrared part of the radiation balance in Estonia will be described in this presentation. Separately have been analyzed the radiation of ground surface and the atmospheric counterradiation, also their dependence on meteorological parameters. The analysis is based on the measurements of long-wave radiation at the Tartu-Tõravere meteorological station.

Video of the seminar.

Using a sample of 140.000 Lyman-alpha quasars from BOSS, we obtain a 5 sigma detection of the baryon acoustic oscillations peak in the auto-correlation function of the Lyman-alpha forest. This detection can be used to measure the expansion rate of the Universe as well as the angular diameter distance at redshift 2.34 with respective precisions of 2.7% and 5.8% (1 sigma errors). The optimal combination of these measurements is determined with a 2% precision. During this talk I will present the details of this analysis and the cosmological implications of these measurements.
 
More details: arXiv:1404.1801

In this work the seasonal reflectance dynamics in hemi-boreal forests were studied. The data for this study was collected at Järvselja Training and Experimental Forestry District (Estonia, 27.26°E 58.30°N).

Measurements were taken in the RAMI (RAdiation Model Intercomparison) sites that represent different understory types of hemi-boreal forests: the silver birch stand (*Betula pendula Roth*): *herb-rich*, the Scots pine stand (*Pinus sylvestris L.*): *transitional bog *and the Norway spruce stand (*Picea abies (L.) Karst /Betula pendula Roth*): *mesic* and *sub-xeric*.

The field campaign lasted from May to September 2013. For each site the fractional cover of understory and understory spectra were estimated ten times i.e. every 2 to 3 weeks. The results confirm previous observations that the reflectance differences became more pronounced later on as the growing period proceeded. Also it is possible to distinguish the most fertile site with shortwave index PRI (photochemical reflectance index).

Collaborators: Indrek Kolka, Jaan Laur, Tõnis Eenmäe, Taavi Tuvikene

Language of the presentation will be decided on site.

Introduction of the results of phenologycal measurements of Laeva test site made from May to June 2013. We made measurements on 6 forest growth sample plots, processed gap fraction data with the program
HemiSPherical Project Manager (HSP) and used the processed data to assess plant area index of sample plots.

To gather the data from sample plots, two digital cameras equipped with fish-eye lens were used. Next step for gap fraction estimation was to use HSP program to restore above canopy hemispherical image from
the below canopy measurement. The simplest way to restore the above canopy image is to interpolate the sky pixel values taken from the canopy gaps (Lang et al., 2010). Plant area index was used to assess the results of 3 independent operators.

Language of the presentation will be decided on site.

Language of the presentation will be decided on site.

Language of the presentation will be decided on site.

Language of the presentation will be decided on site.

Language of the presentation will be decided on site.

Language of the presentation will be decided on site.

10.00 - Jan-Erik Ovaldsen (Norra): Photometry, time delay and microlensing for the 'classical' double quasar
11.00 - Rudy Schild (USA): A new picture of quasar structure
15.00 - Sjur Refsdal (Norra): Astrophysical applications of gravitational lensing