ALBERT

Description: Current models suggest gamma-ray bursts could be used as a way of probing Population-III stars – the first stars in the early Universe. In this paper, we use numerical simulations to demonstrate that late-time radio observations of gamma-ray burst afterglows could provide a means of identifying bursts that originate from Population-III stars, if these were highly massive, independently from their redshift. We then present the results from a pilot study using the Australia Telescope Compact Array at 17 GHz, designed to test the hypothesis that there may be Population-III gamma-ray bursts amongst the current sample of known events. We observed three candidates plus a control gamma-ray burst, and make no detections with upper limits of 20–40 μJy at 500–1300 d post-explosion.

Description: Gamma-ray bursts (GRBs) are produced by rare types of massive stellar explosion. Their rapidly fading afterglows are often bright enough at optical wavelengths that they are detectable at cosmological distances. Hitherto, the highest known redshift for a GRB was z = 6.7 (ref. 1), for GRB 080913, and for a galaxy was z = 6.96 (ref. 2). Here we report observations of GRB 090423 and the near-infrared spectroscopic measurement of its redshift, z = 8.1(-0.3)(+0.1). This burst happened when the Universe was only about 4 per cent of its current age. Its properties are similar to those of GRBs observed at low/intermediate redshifts, suggesting that the mechanisms and progenitors that gave rise to this burst about 600,000,000 years after the Big Bang are not markedly different from those producing GRBs about 10,000,000,000 years later.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Salvaterra, R -- Valle, M Della -- Campana, S -- Chincarini, G -- Covino, S -- D'Avanzo, P -- Fernandez-Soto, A -- Guidorzi, C -- Mannucci, F -- Margutti, R -- Thone, C C -- Antonelli, L A -- Barthelmy, S D -- De Pasquale, M -- D'Elia, V -- Fiore, F -- Fugazza, D -- Hunt, L K -- Maiorano, E -- Marinoni, S -- Marshall, F E -- Molinari, E -- Nousek, J -- Pian, E -- Racusin, J L -- Stella, L -- Amati, L -- Andreuzzi, G -- Cusumano, G -- Fenimore, E E -- Ferrero, P -- Giommi, P -- Guetta, D -- Holland, S T -- Hurley, K -- Israel, G L -- Mao, J -- Markwardt, C B -- Masetti, N -- Pagani, C -- Palazzi, E -- Palmer, D M -- Piranomonte, S -- Tagliaferri, G -- Testa, V -- England -- Nature. 2009 Oct 29;461(7268):1258-60. doi: 10.1038/nature08445.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉INAF, Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate (LC), Italy. salvaterra@mib.infn.it〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19865166" target="_blank"〉PubMed〈/a〉

Description: The tidal disruption of a solar-mass star around a supermassive black hole has been extensively studied analytically and numerically. In these events, the star develops into an elongated banana-shaped structure. After completing an eccentric orbit, the bound debris falls into the black hole, forming an accretion disk and emitting radiation. The same process may occur on planetary scales if a minor body passes too close to its star. In the Solar System, comets fall directly into our Sun or onto planets. If the star is a compact object, the minor body can become tidally disrupted. Indeed, one of the first mechanisms invoked to produce strong gamma-ray emission involved accretion of comets onto neutron stars in our Galaxy. Here we report that the peculiarities of the 'Christmas' gamma-ray burst (GRB 101225A) can be explained by a tidal disruption event of a minor body around an isolated Galactic neutron star. This would indicate either that minor bodies can be captured by compact stellar remnants more frequently than occurs in the Solar System or that minor-body formation is relatively easy around millisecond radio pulsars. A peculiar supernova associated with a gamma-ray burst provides an alternative explanation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Campana, S -- Lodato, G -- D'Avanzo, P -- Panagia, N -- Rossi, E M -- Della Valle, M -- Tagliaferri, G -- Antonelli, L A -- Covino, S -- Ghirlanda, G -- Ghisellini, G -- Melandri, A -- Pian, E -- Salvaterra, R -- Cusumano, G -- D'Elia, V -- Fugazza, D -- Palazzi, E -- Sbarufatti, B -- Vergani, S D -- England -- Nature. 2011 Nov 30;480(7375):69-71. doi: 10.1038/nature10592.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉INAF - Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate, Italy. sergio.campana@brera.inaf.it〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22129725" target="_blank"〉PubMed〈/a〉

Description: Gamma-ray bursts (GRBs) are most probably powered by collimated relativistic outflows (jets) from accreting black holes at cosmological distances. Bright afterglows are produced when the outflow collides with the ambient medium. Afterglow polarization directly probes the magnetic properties of the jet when measured minutes after the burst, and it probes the geometric properties of the jet and the ambient medium when measured hours to days after the burst. High values of optical polarization detected minutes after the burst of GRB 120308A indicate the presence of large-scale ordered magnetic fields originating from the central engine (the power source of the GRB). Theoretical models predict low degrees of linear polarization and no circular polarization at late times, when the energy in the original ejecta is quickly transferred to the ambient medium and propagates farther into the medium as a blast wave. Here we report the detection of circularly polarized light in the afterglow of GRB 121024A, measured 0.15 days after the burst. We show that the circular polarization is intrinsic to the afterglow and unlikely to be produced by dust scattering or plasma propagation effects. A possible explanation is to invoke anisotropic (rather than the commonly assumed isotropic) electron pitch-angle distributions, and we suggest that new models are required to produce the complex microphysics of realistic shocks in relativistic jets.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wiersema, K -- Covino, S -- Toma, K -- van der Horst, A J -- Varela, K -- Min, M -- Greiner, J -- Starling, R L C -- Tanvir, N R -- Wijers, R A M J -- Campana, S -- Curran, P A -- Fan, Y -- Fynbo, J P U -- Gorosabel, J -- Gomboc, A -- Gotz, D -- Hjorth, J -- Jin, Z P -- Kobayashi, S -- Kouveliotou, C -- Mundell, C -- O'Brien, P T -- Pian, E -- Rowlinson, A -- Russell, D M -- Salvaterra, R -- di Serego Alighieri, S -- Tagliaferri, G -- Vergani, S D -- Elliott, J -- Farina, C -- Hartoog, O E -- Karjalainen, R -- Klose, S -- Knust, F -- Levan, A J -- Schady, P -- Sudilovsky, V -- Willingale, R -- England -- Nature. 2014 May 8;509(7499):201-4. doi: 10.1038/nature13237. Epub 2014 Apr 30.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK. ; INAF/Brera Astronomical Observatory, via Bianchi 46, I-23807 Merate (LC), Italy. ; 1] Department of Earth and Space Science, Osaka University, Toyonaka 560-0043, Japan [2] Astronomical Institute, Tohoku University, Sendai 980-8578, Japan [3] Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai 980-8578, Japan. ; Astronomical Institute 'Anton Pannekoek', University of Amsterdam, PO Box 94248, 1090 SJ Amsterdam, The Netherlands. ; Max-Planck-Institut fur extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching, Germany. ; International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia. ; Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Science, Nanjing 210008, China. ; Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK 2100 Copenhagen, Denmark. ; 1] Instituto de Astrofisica de Andalucia (IAA-CSIC), Glorieta de la Astronomia s/n, E-18008 Granada, Spain [2] Unidad Asociada Grupo Ciencia Planetarias UPV/EHU-IAA/CSIC, Departamento de Fisica Aplicada I, ETS Ingenieria, Universidad del Pais Vasco UPV/EHU, Alameda de Urquijo s/n, E-48013 Bilbao, Spain [3] Ikerbasque, Basque Foundation for Science, Alameda de Urquijo 36-5, E-48008 Bilbao, Spain. ; Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia. ; AIM (UMR 7158 CEA/DSM-CNRS-Universite Paris Diderot) Irfu/Service d'Astrophysique, Saclay, F-91191 Gif-sur-Yvette Cedex, France. ; Astrophysics Research Institute, Liverpool John Moores University, Liverpool Science Park, IC2 Building, 146 Brownlow Hill, Liverpool L3 5RF, UK. ; Space Science Office, ZP12, NASA/Marshall Space Flight Center, Huntsville, Alabama 35812, USA. ; 1] Scuola Normale Superiore, 7, I-56126 Pisa, Italy [2] INAF/IASF Bologna, via Gobetti 101, I-40129 Bologna, Italy. ; 1] Instituto de Astrofisica de Canarias (IAC), E-38200 La Laguna, Tenerife, Spain [2] Departamento de Astrofisica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain [3] New York University Abu Dhabi, PO Box 129188, Abu Dhabi, United Arab Emirates. ; INAF/IASF Milano, via E. Bassini 15, 20133 Milano, Italy. ; INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy. ; Isaac Newton Group of Telescopes, Apartado de Correos 321, E-38700 Santa Cruz de la Palma, Canary Islands, Spain. ; Thuringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany. ; Department of Physics, University of Warwick, Coventry CV4 7AL, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24776800" target="_blank"〉PubMed〈/a〉

Description: Long-duration gamma-ray bursts (GRBs) are an extremely rare outcome of the collapse of massive stars and are typically found in the distant universe. Because of its intrinsic luminosity (L ~ 3 x 10(53) ergs per second) and its relative proximity (z = 0.34), GRB 130427A reached the highest fluence observed in the gamma-ray band. Here, we present a comprehensive multiwavelength view of GRB 130427A with Swift, the 2-meter Liverpool and Faulkes telescopes, and by other ground-based facilities, highlighting the evolution of the burst emission from the prompt to the afterglow phase. The properties of GRB 130427A are similar to those of the most luminous, high-redshift GRBs, suggesting that a common central engine is responsible for producing GRBs in both the contemporary and the early universe and over the full range of GRB isotropic energies.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Maselli, A -- Melandri, A -- Nava, L -- Mundell, C G -- Kawai, N -- Campana, S -- Covino, S -- Cummings, J R -- Cusumano, G -- Evans, P A -- Ghirlanda, G -- Ghisellini, G -- Guidorzi, C -- Kobayashi, S -- Kuin, P -- La Parola, V -- Mangano, V -- Oates, S -- Sakamoto, T -- Serino, M -- Virgili, F -- Zhang, B-B -- Barthelmy, S -- Beardmore, A -- Bernardini, M G -- Bersier, D -- Burrows, D -- Calderone, G -- Capalbi, M -- Chiang, J -- D'Avanzo, P -- D'Elia, V -- De Pasquale, M -- Fugazza, D -- Gehrels, N -- Gomboc, A -- Harrison, R -- Hanayama, H -- Japelj, J -- Kennea, J -- Kopac, D -- Kouveliotou, C -- Kuroda, D -- Levan, A -- Malesani, D -- Marshall, F -- Nousek, J -- O'Brien, P -- Osborne, J P -- Pagani, C -- Page, K L -- Page, M -- Perri, M -- Pritchard, T -- Romano, P -- Saito, Y -- Sbarufatti, B -- Salvaterra, R -- Steele, I -- Tanvir, N -- Vianello, G -- Wiegand, B -- Wiersema, K -- Yatsu, Y -- Yoshii, T -- Tagliaferri, G -- New York, N.Y. -- Science. 2014 Jan 3;343(6166):48-51. doi: 10.1126/science.1242279. Epub 2013 Nov 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Istituto Nazionale di Astrofisica (INAF)-Istituto di Astrofisica Spaziale e Fisica Cosmica (IASF) Palermo, Via Ugo La Malfa 153 I-90146 Palermo, Italy.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24263134" target="_blank"〉PubMed〈/a〉

Description: Several independent measurements have confirmed the existence of fluctuations ( F obs  ~ 0.1 nW m –2 sr –1 at 3.6 μm) up to degree angular scales in the source-subtracted near-infrared background (NIRB), but their origin is unknown. By combining high-resolution cosmological N -body/hydrodynamical simulations with an analytical model, and by matching galaxy luminosity functions (LFs) and the constraints on reionization simultaneously, we predict the NIRB absolute flux and fluctuation amplitude produced by high-redshift ( z  〉 5) galaxies (some of which harbour Population III stars, shown to provide a negligible contribution). This strategy also allows us to make an empirical determination of the evolution of the ionizing photon escape fraction: we find f esc  = 1 at z  ≥ 11, decreasing to ~0.05 at z  = 5. In the wavelength range 1.0–4.5 μm, the predicted cumulative flux is F  = 0.2–0.04 nW m –2 sr –1 . However, we find that the radiation from high-redshift galaxies (including those undetected by current surveys) is insufficient to explain the amplitude of the observed fluctuations: at l  = 2000, the fluctuation level attributable to z  〉 5 galaxies is F  = 0.01–0.002 nW m –2 sr –1 , with a wavelength-independent relative amplitude F / F  = 4 per cent. The source of the missing power remains unknown. This might indicate that an unknown component/foreground, with a clustering signal very similar to that of high-redshift galaxies, dominates the source-subtracted NIRB fluctuation signal.

Description: We investigate signatures of Population III (PopIII) stars in the metal-enriched environment of gamma-ray bursts (GRBs) originating from Population II-I (PopII/I) stars by using abundance ratios derived from numerical simulations that follow stellar evolution and chemical enrichment. We find that at z  〉 10 more than 10 per cent of PopII/I GRBs explode in a medium previously enriched by PopIII stars (we refer to them as GRBII-〉III). Although the formation of GRBII-〉III is more frequent than that of pristine PopIII GRBs (GRBIIIs), we find that the expected GRBII-〉III observed rate is comparable to that of GRBIIIs, due to the usually larger luminosities of the latter. GRBII-〉III events take place preferentially in small protogalaxies with stellar masses M * ~ 10 4.5 -10 7 M , star formation rates $\rm SFR \sim 10^{-3}{\rm -}10^{-1}\,\rm M_{\odot }\,yr^{-1}$ and metallicities Z ~ 10 – 4 -10 – 2 Z . On the other hand, galaxies with Z 〈 10 – 2.8 Z are dominated by metal enrichment from PopIII stars and should preferentially host GRBII-〉III. Hence, measured GRB metal content below this limit could represent a strong evidence of enrichment by pristine stellar populations. We discuss how to discriminate PopIII metal enrichment on the basis of various abundance ratios observable in the spectra of GRBs’ afterglows. By employing such analysis, we conclude that the currently known candidates at redshift z ~= 6 – i.e. GRB 050904 and GRB 130606A – are likely not originated in environments pre-enriched by PopIII stars. Abundance measurements for GRBs at z ~= 5 – such as GRB 100219A and GRB 111008A – are still poor to draw definitive conclusions, although their hosts seem to be dominated by PopII/I pollution and do not show evident signatures of massive PopIII pre-enrichment.

Description: We compare the prompt intrinsic spectral properties of a sample of short gamma-ray bursts (GRBs) with the first 0.3 s (rest frame) of long GRBs observed by Fermi /GBM (Gamma Burst Monitor). We find that short GRBs and the first part of long GRBs lie on the same E p – E iso correlation, that is parallel to the relation for the time-averaged spectra of long GRBs. Moreover, they are indistinguishable in the E p – L iso plane. This suggests that the emission mechanism is the same for short and for the beginning of long events, and both short and long GRBs are very similar phenomena, occurring on different time-scales. If the central engine of a long GRB would stop after ~0.3 x (1 + z ) s, the resulting event would be spectrally indistinguishable from a short GRB.

Description: Radio observations of Gamma-Ray Bursts (GRBs) afterglows are fundamental in providing insights into their physics and environment, and in constraining the true energetics of these sources. Nonetheless, radio observations of GRB afterglows are presently sparse in the time/frequency domain. Starting from a complete sample of 58 bright Swift long bursts (BAT6), we constructed a homogeneous sub-sample of 38 radio detections/upper limits which preserves all the properties of the parent sample. One half of the bursts have detections between 1 and 5 d after the explosion with typical fluxes F 100 μJy at 8.4 GHz. Through a Population SYnthesis Code coupled with the standard afterglow Hydrodynamical Emission model, we reproduce the radio flux distribution of the radio sub-sample. Based on these results, we study the detectability in the time/frequency domain of the entire long GRB population by present and future radio facilities. We find that the GRBs that typically trigger Swift can be detected at 8.4 GHz by Jansky Very Large Array within few days with modest exposures even at high redshifts. The final Square Kilometre Array (SKA) can potentially observe the whole GRB population provided that there will be a dedicated GRB gamma-ray detector more sensitive than Swift . For a sizeable fraction (50 per cent) of these bursts, SKA will allow us to perform radio calorimetry, after the trans-relativistic transition (occurring ~100 d), providing an estimate of the true (collimation corrected) energetics of GRBs.