LIVIVO - Das Suchportal für Lebenswissenschaften

switch to English language
Erweiterte Suche

Suchergebnis

Treffer 1 - 6 von insgesamt 6

Suchoptionen

  1. Artikel ; Online: The optical-gamma correlation in BL Lacertae

    Raiteri Claudia M. / Villata Massimo / D’Ammando Filippo / Larionov Valeri M. / Gurwell Mark A. / Mirzaqulov Davron O. / Smith Paul S. / Carnerero Maria Isabel

    EPJ Web of Conferences, Vol 61, p

    2013  Band 04014

    Abstract: We present multifrequency light curves of BL Lacertae from February 2008 to October 2012. Lowenergy data (optical and millimetre) were acquired in the framework of a GASP-WEBT project. High-energy data (ultraviolet, X-ray, and γ-ray) come from ... ...

    Abstract We present multifrequency light curves of BL Lacertae from February 2008 to October 2012. Lowenergy data (optical and millimetre) were acquired in the framework of a GASP-WEBT project. High-energy data (ultraviolet, X-ray, and γ-ray) come from observations of the Swift, RXTE, and Fermi satellites. After a period of moderate activity, in May 2011 the source suddenly started to flare at γ and optical-UV frequencies. Activity at millimetre wavelengths and X rays began 3-4 months later. This behaviour offered a good opportunity to study the correlation among flux variability in different bands, in particular between the best-sampled optical and γ-ray light curves. However, even in this fortuitous case, we can only define a general correlation with likely no time lag, but with a lag uncertainty of ±1 day. Indeed, the data reveal a complex relationship between the γ and optical fluxes, which cannot be unveiled because of the small gaps in the sampling of this extremely variable source.
    Schlagwörter Physics ; QC1-999 ; Science ; Q ; DOAJ:Physics (General) ; DOAJ:Physics and Astronomy
    Thema/Rubrik (Code) 535
    Sprache Englisch
    Erscheinungsdatum 2013-12-01T00:00:00Z
    Verlag EDP Sciences
    Dokumenttyp Artikel ; Online
    Datenquelle BASE - Bielefeld Academic Search Engine (Lebenswissenschaftliche Auswahl)

    Volltext online

    Zusatzmaterialien

    Kategorien

    Fernleihe an ZB MED

    Sie können sich den gewünschten Titel als lokale Nutzerin oder lokaler Nutzer von ZB MED direkt an den Standort Köln schicken lassen.

  2. Artikel ; Online: The Gamma-ray Activity of the high-z Quasar 0836+71

    Jorstad Svetlana / Marscher Alan / Larionov Valeri / Gómez José L. / Agudo Iván / Angelakis Emmanouil / Casadio Carolina / Gurwell Mark / Hovatta Talvikki / Joshi Manasvita / Fuhrmann Lars / Karamanavis Vassilis / Lähteenmäki Anne / Molina Sol / Morozova Daria / Myserlis Ioannis / Troitsky Ivan / Ungerechts Hans / Anton Zensus J.

    EPJ Web of Conferences, Vol 61, p

    2013  Band 04003

    Abstract: The Fermi LAT detected an increase in γ-ray activity of the quasar 0836+710 (z=2.17) in Spring 2011 that culminated in a sharp γ-ray flare at the end of 2011 when the source reached a flux of 2.9×10−6 phot s−1cm−2 at 0.1-200 GeV. We monitor the quasar at ...

    Abstract The Fermi LAT detected an increase in γ-ray activity of the quasar 0836+710 (z=2.17) in Spring 2011 that culminated in a sharp γ-ray flare at the end of 2011 when the source reached a flux of 2.9×10−6 phot s−1cm−2 at 0.1-200 GeV. We monitor the quasar at optical wavelengths in photometric and polarimetric modes, at millimeter and centimeter wavelengths, and with the VLBA at 43 GHz. The optical brightness of the quasar increased by ~0.5 mag in R band and the degree of polarization oscillated between ~1% and ~6% during the highest γ-ray state, while the position angle of polarization rotated by ~300°. We have identified in the VLBA images a strong, highly polarized component that moves with an apparent speed of ~20 c. The component emerged from the core in the beginning of the γ-ray event and reached a flux maximum at the peak of the γ-ray outburst. We present the results of a correlative analysis of variations at different wavelengths along with the kinematic parameters of the parsec scale jet. We discuss the location of the high γ-ray emission in the relativistic jet, as well as the emission mechanisms responsible for γ-ray production.
    Schlagwörter Physics ; QC1-999 ; Science ; Q ; DOAJ:Physics (General) ; DOAJ:Physics and Astronomy
    Thema/Rubrik (Code) 520
    Sprache Englisch
    Erscheinungsdatum 2013-12-01T00:00:00Z
    Verlag EDP Sciences
    Dokumenttyp Artikel ; Online
    Datenquelle BASE - Bielefeld Academic Search Engine (Lebenswissenschaftliche Auswahl)

    Volltext online

    Zusatzmaterialien

    Kategorien

    Fernleihe an ZB MED

    Sie können sich den gewünschten Titel als lokale Nutzerin oder lokaler Nutzer von ZB MED direkt an den Standort Köln schicken lassen.

  3. Artikel ; Online: Jet-launching structure resolved near the supermassive black hole in M87.

    Doeleman, Sheperd S / Fish, Vincent L / Schenck, David E / Beaudoin, Christopher / Blundell, Ray / Bower, Geoffrey C / Broderick, Avery E / Chamberlin, Richard / Freund, Robert / Friberg, Per / Gurwell, Mark A / Ho, Paul T P / Honma, Mareki / Inoue, Makoto / Krichbaum, Thomas P / Lamb, James / Loeb, Abraham / Lonsdale, Colin / Marrone, Daniel P /
    Moran, James M / Oyama, Tomoaki / Plambeck, Richard / Primiani, Rurik A / Rogers, Alan E E / Smythe, Daniel L / SooHoo, Jason / Strittmatter, Peter / Tilanus, Remo P J / Titus, Michael / Weintroub, Jonathan / Wright, Melvyn / Young, Ken H / Ziurys, Lucy M

    Science (New York, N.Y.)

    2012  Band 338, Heft 6105, Seite(n) 355–358

    Abstract: Approximately 10% of active galactic nuclei exhibit relativistic jets, which are powered by the accretion of matter onto supermassive black holes. Although the measured width profiles of such jets on large scales agree with theories of magnetic ... ...

    Abstract Approximately 10% of active galactic nuclei exhibit relativistic jets, which are powered by the accretion of matter onto supermassive black holes. Although the measured width profiles of such jets on large scales agree with theories of magnetic collimation, the predicted structure on accretion disk scales at the jet launch point has not been detected. We report radio interferometry observations, at a wavelength of 1.3 millimeters, of the elliptical galaxy M87 that spatially resolve the base of the jet in this source. The derived size of 5.5 ± 0.4 Schwarzschild radii is significantly smaller than the innermost edge of a retrograde accretion disk, suggesting that the M87 jet is powered by an accretion disk in a prograde orbit around a spinning black hole.
    Sprache Englisch
    Erscheinungsdatum 2012-10-19
    Erscheinungsland United States
    Dokumenttyp Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 128410-1
    ISSN 1095-9203 ; 0036-8075
    ISSN (online) 1095-9203
    ISSN 0036-8075
    DOI 10.1126/science.1224768
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

    Zusatzmaterialien

    Kategorien

    Verfügbar in ZB MED Köln/Königswinter

    Zs.A 27: Hefte anzeigen Standort:
    Je nach Verfügbarkeit (siehe Angabe bei Bestand)
    bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular
    Jg. 1995 - 2021: Lesesall (1.OG)
    ab Jg. 2022: Lesesaal (EG)
    Zs.MG 77: Hefte anzeigen

    Über subito bestellen

    Dieser Service ist kostenpflichtig (siehe Lieferbedingungen von subito). Bestellungen, die einen Artikel nebst Supplementary Material umfassen, werden grundsätzlich wie mehrfache Bestellungen bearbeitet. Gebühren fallen in diesen Fällen für jede einzelne Bestellung an.

  4. Artikel ; Online: Resolved magnetic-field structure and variability near the event horizon of Sagittarius A.

    Johnson, Michael D / Fish, Vincent L / Doeleman, Sheperd S / Marrone, Daniel P / Plambeck, Richard L / Wardle, John F C / Akiyama, Kazunori / Asada, Keiichi / Beaudoin, Christopher / Blackburn, Lindy / Blundell, Ray / Bower, Geoffrey C / Brinkerink, Christiaan / Broderick, Avery E / Cappallo, Roger / Chael, Andrew A / Crew, Geoffrey B / Dexter, Jason / Dexter, Matt /
    Freund, Robert / Friberg, Per / Gold, Roman / Gurwell, Mark A / Ho, Paul T P / Honma, Mareki / Inoue, Makoto / Kosowsky, Michael / Krichbaum, Thomas P / Lamb, James / Loeb, Abraham / Lu, Ru-Sen / MacMahon, David / McKinney, Jonathan C / Moran, James M / Narayan, Ramesh / Primiani, Rurik A / Psaltis, Dimitrios / Rogers, Alan E E / Rosenfeld, Katherine / SooHoo, Jason / Tilanus, Remo P J / Titus, Michael / Vertatschitsch, Laura / Weintroub, Jonathan / Wright, Melvyn / Young, Ken H / Zensus, J Anton / Ziurys, Lucy M

    Science (New York, N.Y.)

    2015  Band 350, Heft 6265, Seite(n) 1242–1245

    Abstract: Near a black hole, differential rotation of a magnetized accretion disk is thought to produce an instability that amplifies weak magnetic fields, driving accretion and outflow. These magnetic fields would naturally give rise to the observed synchrotron ... ...

    Abstract Near a black hole, differential rotation of a magnetized accretion disk is thought to produce an instability that amplifies weak magnetic fields, driving accretion and outflow. These magnetic fields would naturally give rise to the observed synchrotron emission in galaxy cores and to the formation of relativistic jets, but no observations to date have been able to resolve the expected horizon-scale magnetic-field structure. We report interferometric observations at 1.3-millimeter wavelength that spatially resolve the linearly polarized emission from the Galactic Center supermassive black hole, Sagittarius A*. We have found evidence for partially ordered magnetic fields near the event horizon, on scales of ~6 Schwarzschild radii, and we have detected and localized the intrahour variability associated with these fields.
    Sprache Englisch
    Erscheinungsdatum 2015-12-04
    Erscheinungsland United States
    Dokumenttyp Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 128410-1
    ISSN 1095-9203 ; 0036-8075
    ISSN (online) 1095-9203
    ISSN 0036-8075
    DOI 10.1126/science.aac7087
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

    Zusatzmaterialien

    Kategorien

    Verfügbar in ZB MED Köln/Königswinter

    Zs.A 27: Hefte anzeigen Standort:
    Je nach Verfügbarkeit (siehe Angabe bei Bestand)
    bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular
    Jg. 1995 - 2021: Lesesall (1.OG)
    ab Jg. 2022: Lesesaal (EG)
    Zs.MG 77: Hefte anzeigen

    Über subito bestellen

    Dieser Service ist kostenpflichtig (siehe Lieferbedingungen von subito). Bestellungen, die einen Artikel nebst Supplementary Material umfassen, werden grundsätzlich wie mehrfache Bestellungen bearbeitet. Gebühren fallen in diesen Fällen für jede einzelne Bestellung an.

  5. Artikel ; Online: Bright radio emission from an ultraluminous stellar-mass microquasar in M 31.

    Middleton, Matthew J / Miller-Jones, James C A / Markoff, Sera / Fender, Rob / Henze, Martin / Hurley-Walker, Natasha / Scaife, Anna M M / Roberts, Timothy P / Walton, Dominic / Carpenter, John / Macquart, Jean-Pierre / Bower, Geoffrey C / Gurwell, Mark / Pietsch, Wolfgang / Haberl, Frank / Harris, Jonathan / Daniel, Michael / Miah, Junayd / Done, Chris /
    Morgan, John S / Dickinson, Hugh / Charles, Phil / Burwitz, Vadim / Della Valle, Massimo / Freyberg, Michael / Greiner, Jochen / Hernanz, Margarita / Hartmann, Dieter H / Hatzidimitriou, Despina / Riffeser, Arno / Sala, Gloria / Seitz, Stella / Reig, Pablo / Rau, Arne / Orio, Marina / Titterington, David / Grainge, Keith

    Nature

    2013  Band 493, Heft 7431, Seite(n) 187–190

    Abstract: A subset of ultraluminous X-ray sources (those with luminosities of less than 10(40) erg s(-1); ref. 1) are thought to be powered by the accretion of gas onto black holes with masses of ∼5-20M cicled dot, probably by means of an accretion disk. The X-ray ...

    Abstract A subset of ultraluminous X-ray sources (those with luminosities of less than 10(40) erg s(-1); ref. 1) are thought to be powered by the accretion of gas onto black holes with masses of ∼5-20M cicled dot, probably by means of an accretion disk. The X-ray and radio emission are coupled in such Galactic sources; the radio emission originates in a relativistic jet thought to be launched from the innermost regions near the black hole, with the most powerful emission occurring when the rate of infalling matter approaches a theoretical maximum (the Eddington limit). Only four such maximal sources are known in the Milky Way, and the absorption of soft X-rays in the interstellar medium hinders the determination of the causal sequence of events that leads to the ejection of the jet. Here we report radio and X-ray observations of a bright new X-ray source in the nearby galaxy M 31, whose peak luminosity exceeded 10(39) erg s(-1). The radio luminosity is extremely high and shows variability on a timescale of tens of minutes, arguing that the source is highly compact and powered by accretion close to the Eddington limit onto a black hole of stellar mass. Continued radio and X-ray monitoring of such sources should reveal the causal relationship between the accretion flow and the powerful jet emission.
    Sprache Englisch
    Erscheinungsdatum 2013-01-10
    Erscheinungsland England
    Dokumenttyp Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 120714-3
    ISSN 1476-4687 ; 0028-0836
    ISSN (online) 1476-4687
    ISSN 0028-0836
    DOI 10.1038/nature11697
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

    Zusatzmaterialien

    Kategorien

    Verfügbar in ZB MED Köln/Königswinter

    Zs.A 26: Hefte anzeigen Standort:
    Je nach Verfügbarkeit (siehe Angabe bei Bestand)
    bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular
    Jg. 1995 - 2021: Lesesall (1.OG)
    ab Jg. 2022: Lesesaal (EG)
    Zs.MG 9: Hefte anzeigen
    Zs.MO 244: Hefte anzeigen

    Über subito bestellen

    Dieser Service ist kostenpflichtig (siehe Lieferbedingungen von subito). Bestellungen, die einen Artikel nebst Supplementary Material umfassen, werden grundsätzlich wie mehrfache Bestellungen bearbeitet. Gebühren fallen in diesen Fällen für jede einzelne Bestellung an.

  6. Artikel ; Online: Gravitational Test beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole.

    Psaltis, Dimitrios / Medeiros, Lia / Christian, Pierre / Özel, Feryal / Akiyama, Kazunori / Alberdi, Antxon / Alef, Walter / Asada, Keiichi / Azulay, Rebecca / Ball, David / Baloković, Mislav / Barrett, John / Bintley, Dan / Blackburn, Lindy / Boland, Wilfred / Bower, Geoffrey C / Bremer, Michael / Brinkerink, Christiaan D / Brissenden, Roger /
    Britzen, Silke / Broguiere, Dominique / Bronzwaer, Thomas / Byun, Do-Young / Carlstrom, John E / Chael, Andrew / Chan, Chi-Kwan / Chatterjee, Shami / Chatterjee, Koushik / Chen, Ming-Tang / Chen, Yongjun / Cho, Ilje / Conway, John E / Cordes, James M / Crew, Geoffrey B / Cui, Yuzhu / Davelaar, Jordy / De Laurentis, Mariafelicia / Deane, Roger / Dempsey, Jessica / Desvignes, Gregory / Dexter, Jason / Eatough, Ralph P / Falcke, Heino / Fish, Vincent L / Fomalont, Ed / Fraga-Encinas, Raquel / Friberg, Per / Fromm, Christian M / Gammie, Charles F / García, Roberto / Gentaz, Olivier / Goddi, Ciriaco / Gómez, José L / Gu, Minfeng / Gurwell, Mark / Hada, Kazuhiro / Hesper, Ronald / Ho, Luis C / Ho, Paul / Honma, Mareki / Huang, Chih-Wei L / Huang, Lei / Hughes, David H / Inoue, Makoto / Issaoun, Sara / James, David J / Jannuzi, Buell T / Janssen, Michael / Jiang, Wu / Jimenez-Rosales, Alejandra / Johnson, Michael D / Jorstad, Svetlana / Jung, Taehyun / Karami, Mansour / Karuppusamy, Ramesh / Kawashima, Tomohisa / Keating, Garrett K / Kettenis, Mark / Kim, Jae-Young / Kim, Junhan / Kim, Jongsoo / Kino, Motoki / Koay, Jun Yi / Koch, Patrick M / Koyama, Shoko / Kramer, Michael / Kramer, Carsten / Krichbaum, Thomas P / Kuo, Cheng-Yu / Lauer, Tod R / Lee, Sang-Sung / Li, Yan-Rong / Li, Zhiyuan / Lindqvist, Michael / Lico, Rocco / Liu, Jun / Liu, Kuo / Liuzzo, Elisabetta / Lo, Wen-Ping / Lobanov, Andrei P / Lonsdale, Colin / Lu, Ru-Sen / Mao, Jirong / Markoff, Sera / Marrone, Daniel P / Marscher, Alan P / Martí-Vidal, Iván / Matsushita, Satoki / Mizuno, Yosuke / Mizuno, Izumi / Moran, James M / Moriyama, Kotaro / Moscibrodzka, Monika / Müller, Cornelia / Musoke, Gibwa / Mus Mejías, Alejandro / Nagai, Hiroshi / Nagar, Neil M / Narayan, Ramesh / Narayanan, Gopal / Natarajan, Iniyan / Neri, Roberto / Noutsos, Aristeidis / Okino, Hiroki / Olivares, Héctor / Oyama, Tomoaki / Palumbo, Daniel C M / Park, Jongho / Patel, Nimesh / Pen, Ue-Li / Piétu, Vincent / Plambeck, Richard / PopStefanija, Aleksandar / Prather, Ben / Preciado-López, Jorge A / Ramakrishnan, Venkatessh / Rao, Ramprasad / Rawlings, Mark G / Raymond, Alexander W / Ripperda, Bart / Roelofs, Freek / Rogers, Alan / Ros, Eduardo / Rose, Mel / Roshanineshat, Arash / Rottmann, Helge / Roy, Alan L / Ruszczyk, Chet / Ryan, Benjamin R / Rygl, Kazi L J / Sánchez, Salvador / Sánchez-Arguelles, David / Sasada, Mahito / Savolainen, Tuomas / Schloerb, F Peter / Schuster, Karl-Friedrich / Shao, Lijing / Shen, Zhiqiang / Small, Des / Sohn, Bong Won / SooHoo, Jason / Tazaki, Fumie / Tilanus, Remo P J / Titus, Michael / Torne, Pablo / Trent, Tyler / Traianou, Efthalia / Trippe, Sascha / van Bemmel, Ilse / van Langevelde, Huib Jan / van Rossum, Daniel R / Wagner, Jan / Wardle, John / Ward-Thompson, Derek / Weintroub, Jonathan / Wex, Norbert / Wharton, Robert / Wielgus, Maciek / Wong, George N / Wu, Qingwen / Yoon, Doosoo / Young, André / Young, Ken / Younsi, Ziri / Yuan, Feng / Yuan, Ye-Fei / Zhao, Shan-Shan

    Physical review letters

    2020  Band 125, Heft 14, Seite(n) 141104

    Abstract: The 2017 Event Horizon Telescope (EHT) observations of the central source in M87 have led to the first measurement of the size of a black-hole shadow. This observation offers a new and clean gravitational test of the black-hole metric in the strong-field ...

    Abstract The 2017 Event Horizon Telescope (EHT) observations of the central source in M87 have led to the first measurement of the size of a black-hole shadow. This observation offers a new and clean gravitational test of the black-hole metric in the strong-field regime. We show analytically that spacetimes that deviate from the Kerr metric but satisfy weak-field tests can lead to large deviations in the predicted black-hole shadows that are inconsistent with even the current EHT measurements. We use numerical calculations of regular, parametric, non-Kerr metrics to identify the common characteristic among these different parametrizations that control the predicted shadow size. We show that the shadow-size measurements place significant constraints on deviation parameters that control the second post-Newtonian and higher orders of each metric and are, therefore, inaccessible to weak-field tests. The new constraints are complementary to those imposed by observations of gravitational waves from stellar-mass sources.
    Sprache Englisch
    Erscheinungsdatum 2020-10-08
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.125.141104
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

    Zusatzmaterialien

    Kategorien

    Verfügbar in ZB MED Bonn

    Z 4' 58/153: Hefte anzeigen

    Über subito bestellen

    Dieser Service ist kostenpflichtig (siehe Lieferbedingungen von subito). Bestellungen, die einen Artikel nebst Supplementary Material umfassen, werden grundsätzlich wie mehrfache Bestellungen bearbeitet. Gebühren fallen in diesen Fällen für jede einzelne Bestellung an.

    Fernleihe an ZB MED

    Sie können sich den gewünschten Titel als lokale Nutzerin oder lokaler Nutzer von ZB MED direkt an den Standort Köln schicken lassen.

Zum Seitenanfang