L. Viktor Tóth

Searching for electromagnetic counterpart of LIGO gravitational waves in the Fermi GBM data with ADWO

Aims. The Fermi collaboration identified a possible electromagnetic counterpart of the gravitational wave event of September 14, 2015. Our goal is to provide an unsupervised data analysis algorithm to identify similar events in Fermi ’s Gamma-ray Burst Monitor CTTE data stream. Methods. We are looking for signals that are typically weak. Therefore, they can only be found by a careful analysis of count rates of all detectors and energy channels simultaneously. Our Automatized Detector Weight Optimization (ADWO) method consists of a search for the signal, and a test of its significance. Results. We developed ADWO, a virtual detector analysis tool for multi-channel multi-detector signals, and performed successful searches for short transients in the data-streams. We have identified GRB150522B, as well as possible electromagnetic candidates of the transients GW150914 and LVT151012. Conclusions. ADWO is an independently developed, unsupervised data analysis tool that only relies on the raw data of the Fermi satellite. It can therefore provide a strong, independent test to any electromagnetic signal accompanying future gravitational wave observations.

A Catalog of Active Galactic Nuclei from the First 1.5 Gyr of the Universe

Active galactic nuclei (AGN) are prominent astrophysical objects that can be observed throughout the whole Universe. To understand the underlying physical processes and the different appearance of AGN types, extensive samples are needed. Nowadays, various AGN catalogues are available at different wavebands. However, at the highest redshifts data are still relatively sparse. These data are required for examining AGN properties in the early Universe. This way we can compare the earliest AGN with those seen at lower redshifts, and can study their cosmological evolution. Additionally, because of their high luminosity, AGN may also be used as probes to test cosmological models. With the aim of constructing a complete sample of all known AGN at z≥ 4, we are currently compiling a photometric catalogue from literature sources. We cross-match catalogues particularly at optical and radio wavebands, to build up a sample for detailed high-resolution radio interferometric studies. The continuously updated list now contains nearly 2600 objects with known spectroscopic redshifts, optical magnitudes, and auxiliary information about observations at other wavebands. About 170 of them are known radio sources for which we collect existing radio interferometric data from the literature.

Follow-Up Observations Toward Planck Cold Clumps with Ground-Based Radio Telescopes

The physical and chemical properties of prestellar cores, especially massive ones, are still far from being well understood due to the lack of a large sample. The low dust temperature ( ows, indicating that not all PCCs are in a prestellar phase. We have identified hundreds of starless dense clumps from a mapping survey with the Purple Mountain Observatory (PMO) 13.7-m telescope. Follow-up observations suggest that these dense clumps are ideal targets to search for prestellar objects.

Statistical properties of Fermi GBM GRBs' spectra

Statistical studies of gamma-ray burst (GRB) spectra may result in important information on the physics of GRBs. The Fermi GBM catalog contains GRB parameters (peak energy, spectral indices, intensity) estimated fitting the gamma-ray SED of the total emission (fluence, flnc), and during the time of the peak flux pflx. Using contingency tables we studied the relationship of the models best fitting pflx and flnc time intervals. Our analysis revealed an ordering of the spectra into a power law - Comptonized - smoothly broken power law - Band series. This result was further supported by a correspondence analysis (CA) of the pflx and flnc spectra categorical variables. We performed a linear discriminant analysis (LDA) to find a relationship between categorical (spectral) and model independent physical data. LDA resulted in highly significant physical differences among the spectral types, that is more pronounced in the case of the pflx spectra, than for the flnc spectra. We interpreted this difference as caused by the temporal variation of the spectrum during the outburst. This spectral variability is confirmed by the differences in the low energy spectral index and peak energy, between the pflx and flnc spectra. We found that the synchrotron radiation is significant in GBM spectra. The mean low energy spectral index is close to the canonical value of {\alpha} = -2/3 during the peak flux. However,

Chamaeleon’s Cold Cloud Cores

\alpha

The Properties of Planck Galactic Cold Clumps in the L1495 Dark Cloud

is ~ -0.9 for the spectra of the fluences. We interpret this difference as showing that the effect of cooling is important only for the fluence spectra.

Relationship between the large scale structure of the universe and spatial distribution of GRBs

ISOPHOT Serendipity Survey (ISOSS) observations of the nearby interstellar medium towards Chamaeleon have revealeda number of cold cloud cores. Far-infraredcolours have been studiedusing ISOSS and IRAS data. 10 very cold cores with colour temperatures Tdust≲13 K have been foundin an 11° x 8° sized region. Comparing the FIR data with radio measurements, all of the very cold cores have high gas column densities, N(H2) > 1021 cm-2, and 7 out of 10 have low gas temperatures as indicated by Tex(C18O) ≈ 8 K.

YSO Clusters on Galactic Infrared Loops

Planck Galactic Cold Clumps (PGCCs) possibly represent the early stages of star formation. To understand better the properties of PGCCs, we studied 16 PGCCs in the L1495 cloud with molecular lines and continuum data from Herschel, JCMT/SCUBA-2 and the PMO 13.7 m telescope. Thirty dense cores were identified in 16 PGCCs from 2-D Gaussian fitting. The dense cores have dust temperatures of

ISOPHOT 170 μm Serendipity Sky Survey: The First Galaxy Catalogue

T_{\rm d}

FOREGROUND OF GAMMA-RAY BURSTS (GRBS) FROM AKARI FIS DATA

= 11-14 K, and H