Mykolayiv, Ukraine
Mykolayiv, Ukraine

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Zauderer B.A.,Harvard University | Berger E.,Harvard University | Margutti R.,Harvard University | Levan A.J.,University of Warwick | And 22 more authors.
Astrophysical Journal | Year: 2013

We present X-ray, optical, near-infrared (IR), and radio observations of gamma-ray bursts (GRBs) 110709B and 111215A, as well as optical and near-IR observations of their host galaxies. The combination of X-ray detections and deep optical/near-IR limits establish both bursts as "dark." Sub-arcsecond positions enabled by radio detections lead to robust host galaxy associations, with optical detections that indicate z ≲ 4 (110709B) and z 1.8-2.9 (111215A). We therefore conclude that both bursts are dark due to substantial rest-frame extinction. Using the radio and X-ray data for each burst we find that GRB 110709B requires mag and GRB 111215A requires mag (assuming z = 2). These are among the largest extinction values inferred for dark bursts to date. The two bursts also exhibit large neutral hydrogen column densities of NH, int ≳ 1022 cm-2 (z = 2) as inferred from their X-ray spectra, in agreement with the trend for dark GRBs. Moreover, the inferred values are in agreement with the Galactic AV -N H relation, unlike the bulk of the GRB population. Finally, we find that for both bursts the afterglow emission is best explained by a collimated outflow with a total beaming-corrected energy of E γ + E K (7-9) × 1051 erg (z = 2) expanding into a wind medium with a high density, Myr-1(n 100-350 cm -3 at 1017 cm). While the energy release is typical of long GRBs, the inferred density may be indicative of larger mass-loss rates for GRB progenitors in dusty (and hence metal rich) environments. This study establishes the critical role of radio observations in demonstrating the origin and properties of dark GRBs. Observations with the JVLA and ALMA will provide a sample with sub-arcsecond positions and robust host associations that will help to shed light on obscured star formation and the role of metallicity in GRB progenitors. © 2013. The American Astronomical Society. All rights reserved.

Tello J.C.,Institute Astrofisica Of Andalucia Iaa Csic | Castro-Tirado A.J.,Institute Astrofisica Of Andalucia Iaa Csic | Gorosabel J.,Institute Astrofisica Of Andalucia Iaa Csic | Gorosabel J.,University of the Basque Country | And 8 more authors.
EAS Publications Series | Year: 2013

Since the early 90s Gamma Ray Bursts have been accepted to be of extra-galactic origin thanks to the isotropic distribution observed by BATSE and the redshifts observed in some of their optical or infrared counterparts. Nevertheless, there have been a few cases that upon further examination have turned out to be of galactic origin. Several of these galactic sources have presented a Fast Rise, Exponential Decay structure which leads us to believe that there could be an underlying correlation. In this work we do several statistical analyses to determine the degree of contamination by galactic sources that certain subsample of known FREDs have. And find that certain subsamples have a most probable contamination between 27% and 34%. © EAS, EDP Sciences 2013.

Biernacka M.,Jan Kochanowski University | Panko E.,Nikolaev National University | Bajan K.,Pedagogical University of Cracow | Godlowski W.,University of Opole | Flin P.,Jan Kochanowski University
Astrophysical Journal | Year: 2015

We analyzed the orientation of the sample of ACO galaxy clusters. We examined the alignment in a subsample of 1056 galaxy structures taken from the Panko-Flin (2006) Catalog with known BM morphological types. We were looking for a correlation between the orientation of the cluster and the positions of neighboring clusters. The Binggeli effect (the excess of small values of the Δθ angles between the direction toward neighboring clusters and the cluster position angle) is observed, having a range up to about 45 h-1 Mpc. The strongest effect was found for elongated BM type I clusters. This is probably connected with the origins of the supergiant galaxy and with cluster formation along a long filament or plane in a supercluster. © 2015. The American Astronomical Society. All rights reserved.

Munoz-Darias T.,University of Southampton | De Ugarte Postigo A.,Institute Astrofisica Of Andalucia Iaa Csic | De Ugarte Postigo A.,Niels Bohr Institute | Russell D.M.,Institute of Astrophysics of Canarias | And 19 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

We present a 30-day monitoring campaign of the optical counterpart of the bright X-ray transient Swift J1745-26, starting only 19min after the discovery of the source.We observe the system peaking at i~17.6 on day six (MJD 561 92) to then decay at a rate of ~0.04 mag d-1. We show that the optical peak occurs at least 3 d later than the hard X-ray (15-50 keV) flux peak. Our measurements result in an outburst amplitude greater than 4.3 mag, which favours an orbital period ≲21 h and a companion star with a spectral type later than ~A0. Spectroscopic observations taken with the Gran Telescopio de Canarias 10.4 m telescope reveal a broad (full width at half-maximum ~1100 km s-1), double-peaked Ha emission line from which we constrain the radial velocity semi-amplitude of the donor to be K2 > 250 km s-1. The breadth of the line and the observed optical and X-ray fluxes suggest that Swift J1745-26 is a new black hole candidate located closer than ~7 kpc. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

van der Horst A.J.,University of Amsterdam | Curran P.A.,Curtin University Australia | Miller-Jones J.C.A.,Curtin University Australia | Linford J.D.,University of New Mexico | And 38 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

MAXI J1659-152 was discovered on 2010 September 25 as a new X-ray transient, initially identified as a gamma-ray burst, but was later shown to be a new X-ray binary with a black hole as the most likely compact object. Dips in the X-raylight curves have revealed that MAXI J1659-152 is the shortest period black hole candidate identified to date. Here we present the results of a large observing campaign at radio, submillimetre, near-infrared (nIR), optical and ultraviolet (UV) wavelengths. We have combined this very rich data set with the available X-ray observations to compile a broad-band picture of the evolution of this outburst. We have performed broad-band spectral modelling, demonstrating the presence of a spectral break at radio frequencies and a relationship between the radio spectrum and X-ray states. Also, we have determined physical parameters of the accretion disc and put them into context with respect to the other parameters of thebinary system. Finally, we have investigated the radio-X-ray and nIR/optical/UV-X-ray correlations up to ̃3 yr after the outburst onset to examine the link between the jet and the accretion disc, and found that there is no significant jet contribution to the nIR emission when the source is in the soft or intermediateX-ray spectral state, consistent withour detection of the jet break at radio frequencies during these states. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Perez-Ramirez D.,University of Jaén | Norris J.P.,Boise State University | Gorosabel J.,IAA CSIC | Gorosabel J.,Technical University of Madrid | And 8 more authors.
EAS Publications Series | Year: 2013

We present the results from an optical monitoring campaign aimed at studying the afterglow properties of the short GRB 100816A. We implemented a new way of processing the Swift-BAT data, and based on it we reclassified this burst as short, discarding the initial classification as long. Observations were carried out mainly with the GTC Telescope within the four following days after the burst to investigate the optical photometry of its afterglow, and a year later to localize the host. We completed the optical imaging with the 1.23 m and 3.5 m CAHA Telescopes. We built and fitted the nIR-optical SED for the characterization of the host. The best fit of the SED (χ2/d.o.f. = 1.656) obtained for assumed values of a solar metallicity, and an extinction of AV = 0.2mag is obtained for a starburst galaxy with a dominant stellar population aging about 360 Myr. © EAS, EDP Sciences 2013.

Flin P.,Jan Kochanowski University | Panko E.,Nikolaev National University
Baltic Astronomy | Year: 2011

Tadeusz Banachiewicz (1882-1954) was an outstanding Polish astronomer, mathematician and geodesist. He was a professor at the Jagiel-lonian University in Cracow and director of the Astronomical Observatory (1919-1954), and had a strong influence on Polish astronomy. His achievements led to honorary degrees at universities, fellowships in academies of sciences, and the prestige of high positions in international organizations, such as the International Astronomical Union and the Baltic Geodetic Commission. He is known from both his theoretical and observational studies, his famous motto being: "observo ergo sum". Here we recall three years of his activity in Tartu, where Tadeusz Banachiewicz made the most important steps in his career. He arrived at Yuryev in October of 1915, employed as a young assistant. In March 1918 he became the extraordinary professor and director of the Astronomical Observatory.

Tello J.C.,Institute Astrofisica Of Andalucia Iaa Csic | Castro-Tirado A.J.,Institute Astrofisica Of Andalucia Iaa Csic | Gorosabel J.,Institute Astrofisica Of Andalucia Iaa Csic | Perez-Ramirez D.,University of Jaén | And 6 more authors.
Astronomy and Astrophysics | Year: 2012

Context. Since the early 1990s, gamma ray bursts (GRB) have been accepted to be of extra-Galactic origin because of the isotropic distribution observed by BATSE and the redshifts observed via absorption line spectroscopy. Nevertheless, upon closer examination at least one case turned out to be of Galactic origin. This particular event presented a fast rise and exponential decay (FRED) structure, which leads us to believe that other FRED sources might also be Galactic. Aims. This study was set out to estimate the most probable degree of contamination by Galactic sources that certain samples of FREDs have. Methods. To quantify the degree of anisotropy, the average dipolar and quadripolar moments of each sample of GRBs with respect to the Galactic plane were calculated. This was then compared to the probability distribution of simulated samples comprising a combination of isotropically generated sources and Galactic sources. Results. We observe that the dipolar and quadripolar moments of the selected subsamples of FREDs are found more than two standard deviations outside those of random isotropically generated samples. The most probable degree of contamination by Galactic sources for the FRED GRBs of the Swift catalog detected until February 2011 that do not have a known redshift is about 21 out of 77 sources, which represents roughly 27%. Furthermore, we observe that by removing from this sample those bursts that have any type of indirect redshift indicator and multiple peaks, the most probable contamination increases to 34% (17 out of 49 sources). Conclusions. It is probable that a high degree of contamination by Galactic sources occurs among the single-peak FREDs observed by Swift. Accordingly, we encourage additional studies on these types of events to determine the nature of what could be an exotic type of Galactic source. © ESO, 2012.

Lysenkov E.A.,Nikolaev National University | Lysenkov E.A.,Ukrainian Academy of Sciences | Klepko V.V.,Ukrainian Academy of Sciences | Yakovlev Y.V.,Ukrainian Academy of Sciences
Surface Engineering and Applied Electrochemistry | Year: 2016

The electrical properties of the polyether/carbon nanotube (CNT) systems doped with LiClO4 inorganic salt are studied via impedance spectroscopy. The percolation thresholds are evaluated in the context of the standard percolation theory for the nanofilled systems based on polyethylene glycol and polypropylene glycol, being 0.45 and 0.5%, respectively. Two percolation thresholds are observed for the polyether–CNT–LiClO4 systems. A modified percolation model with consideration of two percolation transitions is proposed. © 2016, Allerton Press, Inc.

Panko E.,Nikolaev National University
Baltic Astronomy | Year: 2011

The Modified Catalog of Galaxy Clusters and Groups (Panko & Flin 2006, PF), covering an area of 5000 square degrees in the southern sky, was used as the input for the search of galaxy superclusters. Only the estimated redshifts could be used, since the PF catalog is a 2D catalog, with the calibration correlating the redshift of galaxy clusters with the magnitude of the tenth brightest cluster galaxy. Only galaxy clusters containing more than 50 galaxies were considered, and the FoF method was applied. The nearest neighbour distances for 1711 input clusters were calculated and analyzed, and 20 isolated clusters were found with the nearest neighbour at a distance greater than 68 h -1 Mpc. A distance of 24 h -1 Mpc between clusters was selected for the supercluster search, and 49 superclusters containing from 4 to 9 galaxy clusters were detected. Calculations for each supercluster include: its inferred center, RA, Dec, z est, the maximum distance between supercluster members and the estimated supercluster shapes. A typical size of superclusters identified here is about 55h -1 Mpc, and they appear mainly as elongated pancakes, with a weak correlation between the axes c/a and b/a, without a strong dependence on multiplicity.

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