MTA CSFK Konkoly Observatory

Budapest, Hungary

MTA CSFK Konkoly Observatory

Budapest, Hungary
Time filter
Source Type

Racz I.I.,Eötvös Loránd University | Balazs L.G.,Eötvös Loránd University | Balazs L.G.,MTA CSFK Konkoly Observatory | Bagoly Z.,Eötvös Loránd University | And 2 more authors.
AIP Conference Proceedings | Year: 2017

We studied the distribution of star-forming galaxies in the classical Millenium Simulation Springer et al. [1] and the Horizon Runs Kim et al. [2] databases. DeLucia and Blaizot [3] used a semi-analytical model for the galaxy genesis in Millenium I. We found a relationship between the distribution of the star-forming galaxies and the dark matter (DM), which we used as a transformation factor from the Millenium I to Millenium XXL. We simulated a star-forming galaxy sample with Markov Chain Monte Carlo (MCMC) method, and checked the relation between structures and the distribution of star-forming groups on a various scales. We concluded that above the BAO-scale we need a much more numerous sample than that of the current 407 GRBs to reveal the DM distribution. We got similar results applying our method to the Horizon Runs data. © 2017 Author(s).

Marton G.,MTA CSFK Konkoly Observatory | Toth L.V.,Eötvös Loránd University | Balazs L.G.,MTA CSFK Konkoly Observatory | Balazs L.G.,Eötvös Loránd University | And 6 more authors.
Proceedings of the International Astronomical Union | Year: 2015

The point sources in the Bright Source Catalogue (BSC) of the AKARI Far-Infrared Surveyor (FIS) were classified based on their far-IR and mid-IR fluxes and colours using Quadratic Discriminant Analysis method (QDA) and Support Vector Machines (SVM). The reliability of our results show that we can successfully separate galactic and extragalactic AKARI point sources in the multidimensional space of fluxes and colours. However, differentiating among the extragalactic sub-types needs further information. © 2016 International Astronomical Union.

Gutierrez P.J.,Institute Astrofisica Of Andalucia Csic | Jorda L.,Aix - Marseille University | Gaskell R.W.,Planetary Science Institute | Davidsson B.J.R.,Uppsala University | And 54 more authors.
Astronomy and Astrophysics | Year: 2016

Context. Data derived from the reconstruction of the nucleus shape of comet 67P/Churyumov-Gerasimenko (67P) from images of the OSIRIS camera onboard ROSETTA show evidence that the nucleus rotates in complex mode. First, the orientation of the spin axis is not fixed in an inertial reference frame, which suggests a precessing motion around the angular momentum vector with a periodicity of approximately 257 h ± 12 h.Second, periodograms of the right ascension and declination (RA/Dec) coordinates of the body-frame Z axis show a very significant (higher than 99.99%) periodicity at 276 h ± 12 h, different from the rotational period of 12.40 h as previously determined from light-curve analysis. Aims. The main goal is to interpret the data and associated periodicities of the spin axis orientation in space. Methods. We analyzed the spin axis orientation in space and associated periodicities and compared them with solutions of Euler equations under the assumption that the body rotates in torque-free conditions. Statistical tests comparing the observationally derived spin axis orientation with the outcome from simulations were applied to determine the most likely inertia moments, excitation level, and periods. Results. Under the assumption that the body is solid-rigid and rotates in torque-free conditions, the most likely interpretation is that 67P is spinning around the principal axis with the highest inertia moment with a period of about 13 h. At the same time, the comet precesses around the angular momentum vector with a period of about 6.35 h. While the rotating period of such a body would be about 12.4 h, RA/Dec coordinates of the spin axis would have a periodicity of about 270 h as a result of the combination of the two aforementioned motions. Conclusions. The most direct and simple interpretation of the complex rotation of 67P requires a ratio of inertia moments significantly higher than that of a homogeneous body. © ESO, 2016.

PubMed | MTA CSFK Konkoly Observatory, University of Padua, University of Maryland University College, National Central University and 14 more.
Type: | Journal: Science (New York, N.Y.) | Year: 2016

The Rosetta spacecraft has investigated comet 67P/Churyumov-Gerasimenko from large heliocentric distances to its perihelion passage and beyond. We trace the seasonal and diurnal evolution of the colors of the 67P nucleus, finding changes driven by sublimation and recondensation of water ice. The whole nucleus became relatively bluer near perihelion, as increasing activity removed the surface dust, implying that water ice is widespread underneath the surface. We identified large (1500 m

Toth L.V.,Eötvös Loránd University | Toth L.V.,Max Planck Institute for Astronomy | Marton G.,Eötvös Loránd University | Marton G.,MTA CSFK Konkoly Observatory | And 10 more authors.
Publications of the Astronomical Society of Japan | Year: 2014

We demonstrate the use of the AKARI all-sky survey photometric data in the study of galactic star formation. Our aim was to select young stellar objects (YSOs) in the AKARI Far-Infrared Surveyor (FIS) Bright Source Catalogue. We used AKARI/FIS and Wide-field Infrared Survey Explorer (WISE) data to derive mid- and far-infrared colors of YSOs. Classification schemes based on quadratic discriminant analysis (QDA) have been given for YSOs and the training catalog for QDA was the whole-sky selection of previously known YSOs (i.e., listed in the SIMBAD database). A new catalog of AKARI FIS YSO candidates including 44001 sources has been prepared; the reliability of the classification is over 90%, as tested in comparison to known YSOs. As much as 76% of our YSO candidates are from previously uncatalogued types. The vast majority of these sources are Class I and II types according to the Lada classification. The distribution of AKARI FIS YSOs is well correlated with that of the galactic ISM; local over-densities were found on infrared loops and towards the cold clumps detected by Planck. © The Author 2014. Published by Oxford University Press on behalf of the Astronomical Society of Japan. All rights reserved.

Kollath Z.,University of West Hungary | Kollath Z.,MTA CSFK Konkoly Observatory | Kranicz B.,University of Pannonia
Journal of Quantitative Spectroscopy and Radiative Transfer | Year: 2014

Multi-wavelength imaging luminance photometry of sky glow provides a huge amount of information on light pollution. However, the understanding of the measured data involves the combination of different processes and data of radiation transfer, atmospheric physics and atmospheric constitution. State-of-the-art numerical radiation transfer models provide the possibility to define an inverse problem to obtain information on the emission intensity distribution of a city and perhaps the physical properties of the atmosphere. We provide numerical tests on the solvability and feasibility of such procedures. © 2014 Elsevier Ltd.

Balazs L.G.,MTA CSFK Konkoly Observatory | Balazs L.G.,Eötvös Loránd University | Bagoly Z.,Eötvös Loránd University | Bagoly Z.,National Public Service University | And 5 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2015

According to the cosmological principle (CP), Universal large-scale structure is homogeneous and isotropic. The observable Universe, however, shows complex structures even on very large scales. The recent discoveries of structures significantly exceeding the transition scale of 370 Mpc pose a challenge to the CP. We report here the discovery of the largest regular formation in the observable Universe; a ring with a diameter of 1720 Mpc, displayed by 9 gamma-ray bursts (GRBs), exceeding by a factor of 5 the transition scale to the homogeneous and isotropic distribution. The ring has a major diameter of 43° and a minor diameter of 30° at a distance of 2770 Mpc in the 0.78 < z < 0.86 redshift range, with a probability of 2 × 10-6 of being the result of a random fluctuation in the GRB count rate. Evidence suggests that this feature is the projection of a shell on to the plane of the sky. Voids and string-like formations are common outcomes of large-scale structure. However, these structures have maximum sizes of 150 Mpc, which are an order of magnitude smaller than the observed GRB ring diameter. Evidence in support of the shell interpretation requires that temporal information of the transient GRBs be included in the analysis. This ring-shaped feature is large enough to contradict the CP. The physical mechanism responsible for causing it is unknown. © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Kobori J.,Eötvös Loránd University | Bagoly Z.,Eötvös Loránd University | Balazs L.G.,MTA CSFK Konkoly Observatory | Balazs L.G.,Eötvös Loránd University | Horvath I.,National Public Service University
Astronomische Nachrichten | Year: 2013

Gamma-ray bursts (GRBs) can be divided into three groups: short-, intermediate- and long-duration bursts. While the progenitors of the short and long ones are relatively known, the progenitors of the intermediate-duration bursts (IBs) are generally unknown. However, recent statistical studies suggest that they can be related to the long-duration bursts. Another types of GRBs are the so-called X-ray flashes (XRFs) and X-ray rich GRBs (XRRs). The former ones radiate more intensively in the X-ray bands than common GRBs, but in the cases of XRFs the main component of the emission is produced entirely at X-ray wavelengths. Also, the XRFs and IBs show some similarities regarding their prompt- and afterglow properties. In this work we investigate whether there is a difference between the global parameters of the X-ray flashes and intermediate-duration group of gamma-ray bursts. The statistical tests do not show any significant discrepancy regarding most of the parameters, except the BAT photon index, which is only a consequence of the definition of the XRFs. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Loading MTA CSFK Konkoly Observatory collaborators
Loading MTA CSFK Konkoly Observatory collaborators