Multiwavelength interferometric observations and modeling of circumstellar disks

We investigate the structure of the innermost region of three circumstellar disks around pre-main sequence stars HD 142666, AS 205 N, and AS 205 S. We determine the inner radii of the dust disks and, in particular, search for transition objects where dust has been depleted and inner disk gaps have formed at radii of a few tenths of AU up to several AU. We performed interferometric observations with IOTA, AMBER, and MIDI in the infrared wavelength ranges 1.6-2.5um and 8-13um with projected baseline lengths between 25m and 102m. The data analysis was based on radiative transfer simulations in 3D models of young stellar objects (YSOs) to reproduce the spectral energy distribution and the interferometric visibilities simultaneously. Accretion effects and disk gaps could be considered in the modeling approach. Results from previous studies restricted the parameter space. The objects of this study were spatially resolved in the infrared wavelength range using the interferometers. Based on these observations, a disk gap could be found for the source HD 142666 that classifies it as transition object. There is a disk hole up to a radius of R_in=0.30AU and a (dust-free) ring between 0.35AU and 0.80AU in the disk of HD 142666. The classification of AS 205 as a system of classical T Tauri stars could be confirmed using the canonical model approach, i. e., there are no hints of disk gaps in our observations.Comment: accepted by Astronomy & Astrophysic

Halvány égi rádióforrások szerkezetének nagy felbontású térképezése = High resolution imaging of weak celestial radio sources

Nagyon hosszú bázisvonalú rádió-interferométeres (VLBI) csillagászati méréseket végeztünk nemzetközi antennahálózatokkal. A halvány extragalaktikus rádióforrások felmérését céló DEVOS programunkat beindítottuk. A kvazárok szerkezetét néhány ezred-ívmásodperces (mas) szöfelbontással tanulmányoztuk 5 GHz frekvencián, égi pozícióikat ~1 mas pontossággal határoztuk meg. A létrejövő minta kozmológiai, galaxisfejlődési, asztrometria célokra használható. A DEVOS-hoz újszerű VLBI megfigyelési módszert alkalmaztunk, s célpontjaink előzetes kiválasztására olyan eljárást dolgoztunk ki, amelynek alapján igen kedvező (közel 90%-os) detektálási arányt biztosíthatunk. Foglalkoztunk a DEVOS adatbázis, és a megfigyelési technika egyes alkalmazásaival. Bekapcsolódtunk egy nemzetközi programba, amelynek célja a közeljövő hatalmas optikai teleszkópjai pontos asztrometriai kalibrációjának megoldása VLBI mérések segítségével. A világegyetem legtávolabbi (z=5,77) ismert rádiókvazárját mas skálán feltérképeztük. Publikáltuk az AO 0235+164 blazárra vonatkozó űr-VLBI észleléssorozatunk eredményeit. Különösen nagy vöröseltolódású (z>3) kvazárokat kutattunk űr-VLBI technikával. Részt vettünk a nagyszámú aktív galaxismag űr-VLBI felmérését célzó programban. Foglalkoztunk a közepes tömegű fekete lyukak VLBI technikával való detektálhatóságával. Mosoni L. a futamidő alatt védte meg a DEVOS programban végzett kutatómunkájával kapcsolatban készített PhD értekezését. | We conducted radio interferometric astronomical experiments with Very Long Baseline Interferometry (VLBI), using international telescope networks. Our Deep Extragalactic VLBI?Optical Survey (DEVOS) aims at constructing a large sample of faint compact radio-emitting active galactic nuclei (AGNs). We imaged the radio structures of AGNs at a few milli-arcsecond (mas) angular resolution at 5 GHz. The positions of the sources are determined with mas accuracy. The sample will be invaluable for cosmological, astrophysical and astrometric studies. For DEVOS, we applied a novel observing technique and developed a target selection method thet provides nearly 90% VLBI detection rate. We studied some applications of the DEVOS data and the observing technique itself. We joined an international endeavour to prepare for the sufficiently precise astrometric calibration of next-generation large-aperture optical telescopes, with the help of VLBI. We imaged the most distant (z=5.77) radio-loud quasar known in the Universe. We published the results of our space VLBI monitoring observations of the blazar AO 0235+164. We studied quasars at extremly high redshifts (z>3) with space VLBI. We took part in the 5-GHz VSOP Survey Program. We investigated the possibility of detecting intermediate-mass black holes with the current VLBI networks. One of the participants, L. Mosoni obtained his PhD degree for his work with the DEVOS pilot study during the reported period

A phallikus tárgyak értelmezésének sokszínűsége

The diversity of interpretation phallic objects: The phallus or the male genitalia was the most popular sexual symbol in the Roman era. The phallic objects occur in a wide geographical and temporal region: from the Paleolithic to nowadays the phallic culture has always been revered and has a special meaning from the Mediterranean region to Japan. The veneration of phallus was global in nature, it was present in the lives of the wealty and the poor alike. With the help of the apotropaic force of the phallus they wanted to protect themselves, their children, their animals and their homes. The representations of the phallus appear widely in art and literature, so they can be interpreted in various ways based on their portrayal, material or region they have been found. They can be put into different groups based on their function. There are apotropaic and good-luck objects, objects that symbolize strength and dominion, and they even appear in black magic as votive phallic objects. This paper examines the variety of the forms and interpretation of phallic portrayal, making use of Pannonian and imperial artefacts. The artefacts that have been researched so far are not unique, their equivalents can be found across the whole Roman Empire. Based on these artefacts it can be said that in Pannonia, similarly to other provinces, the veneration of phallus is observable. However, because of the small number of known artefacts, local characteristics have not yet been identified

Analysis of the relationships between eye tracking information and text comprehension levels in healthcare

Health information can be found more easily than ever through a variety of digital texts: from health forums online, informative websites, or phone apps that monitor your health. It is important that the patients are able to comprehend this information correctly as it can lead to important decisions regarding their health. However, the average patient will have difficulties understanding digital texts as they contain medical terminology. Reading such content requires multiple cognitive processes and memory to fully grasp the communicated information. The data used in this project comes from an eye tracking experiment involving human subjects reading health related texts and answering questions about these texts. The eye tracking data includes information about the number of eye fixations, fixations’ durations and positions in different areas of interest of the screen. The read paragraph also had different complexities and there were different types of questions. First, a quantitative analysis involving multiple ANOVAs was performed to uncover the effect of different chosen factors. After some feature engineering guided by the previous analysis, machine learning was used to classify whether a participant would answer correctly or not using eye tracking data and variables relative to the text and questions. The initial analysis showed that increasing levels of complexity of the digital text resulted in more eye fixations and longer reading times and that different questions provoked different reading behaviors. More importantly, the random forest classification model was successful with a 96% accuracy thanks to the engineered features, showing that human decisions can almost be predicted using only our eyes’ behaviors

Radio structure of the most distant radio-detected quasar at the ten milli- arcsecond scale

We present a high resolution radio image of SDSS 0836+0054 identified recently as the most distant radio-detected quasar at a redshift of z=5.82. The observation was carried out with ten antennas of the European VLBI Network, spread from Europe to China and South Africa, at 1.6 GHz frequency on 2002 June 8. The source is detected with a total flux density of 1.1 mJy, equal to its flux density measured in the VLA FIRST survey. We found no indication of multiple images produced by gravitational lensing. The radio structure of the quasar at ~10-mas angular resolution appears somewhat resolved. It resembles the radio structure typical for lower redshift radio-loud active galactic nuclei. We obtained so far the best astrometric position of the source with an accuracy better than 8 mas, limited mainly by the structural effects in the phase-reference calibrator source.Comment: 5 pages, 2 figures, accepted for publication in MNRAS (Letters

Rumen cellulosomics : divergent fiber-degrading strategies revealed by comparative genome-wide analysis of six ruminococcal strains

Peer reviewedPublisher PD

Mid-infrared interferometric variability of DG Tau: implications for the inner-disk structure

Context. DG Tau is a low-mass pre-main sequence star, whose strongly accreting protoplanetary disk exhibits a so-far enigmatic behavior: its mid-infrared thermal emission is strongly time-variable, even turning the 10 $\mu$m silicate feature from emission to absorption temporarily. Aims. We look for the reason for the spectral variability at high spatial resolution and at multiple epochs. Methods. We study the temporal variability of the mid-infrared interferometric signal, observed with the VLTI/MIDI instrument at six epochs between 2011 and 2014. We fit a geometric disk model to the observed interferometric signal to obtain spatial information about the disk. We also model the mid-infrared spectra by template fitting to characterize the profile and time dependence of the silicate emission. We use physically motivated radiative transfer modeling to interpret the mid-infrared interferometric spectra. Results. The inner disk (r<1-3 au) spectra exhibit a 10 $\mu$m absorption feature related to amorphous silicate grains. The outer disk (r>1-3 au) spectra show a crystalline silicate feature in emission, similar to the spectra of comet Hale-Bopp. The striking difference between the inner and outer disk spectral feature is highly unusual among T Tauri stars. The mid-infrared variability is dominated by the outer disk. The strength of the silicate feature changed by more than a factor of two. Between 2011 and 2014 the half-light radius of the mid-infrared-emitting region decreased from 1.15 to 0.7 au. Conclusions. For the origin of the absorption we discuss four possible explanations: a cold obscuring envelope, an accretion heated inner disk, a temperature inversion on the disk surface and a misaligned inner geometry. The silicate emission in the outer disk can be explained by dusty material high above the disk plane, whose mass can change with time, possibly due to turbulence in the disk.Comment: 16 pages, 13 figure