English  |  正體中文  |  简体中文  |  Items with full text/Total items : 66984/66984 (100%)
Visitors : 22915783      Online Users : 918
RC Version 7.0 © Powered By DSPACE, MIT. Enhanced by NTU Library IR team.
Scope Tips:
  • please add "double quotation mark" for query phrases to get precise results
  • please goto advance search for comprehansive author search
  • Adv. Search
    HomeLoginUploadHelpAboutAdminister Goto mobile version


    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/27894


    Title: WEBT multiwavelength monitoring and XMM-Newton observations of BL Lacertae in 2007-2008 Unveiling different emission components
    Authors: Raiteri,CM;Villata,M;Capetti,A;Aller,MF;Bach,U;Calcidese,P;Gurwell,MA;Larionov,VM;Ohlert,J;Nilsson,K;Strigachev,A;Agudo,I;Aller,HD;Bachev,R;Benitez,E;Berdyugin,A;Bottcher,M;Buemi,CS;Buttiglione,S;Carosati,D;Charlot,P;Chen,WP;Dultzin,D;Forne,E;Fuhrmann,L;Gomez,JL;Gupta,AC;Heidt,J;Hiriart,D;Hsiao,WS;Jelinek,M;Jorstad,SG;Kimeridze,GN;Konstantinova,TS;Kopatskaya,EN;Kostov,A;Kurtanidze,OM;Lahteenmaki,A;Lanteri,L;Larionova,LV;Leto,P;Latev,G;Le Campion,JF;Lee,CU;Ligustri,R;Lindfors,E;Marscher,AP;Mihov,B;Nikolashvili,MG;Nikolov,Y;Ovcharov,E;Principe,D;Pursimo,T;Ragozzine,B;Robb,RM;Ros,JA;Sadun,AC;Sagar,R;Semkov,E;Sigua,LA;Smart,RL;Sorcia,M;Takalo,LO;Tornikoski,M;Trigilio,C;Uckert,K;Umana,G;Valcheva,A;Volvach,A
    Contributors: 天文研究所
    Keywords: EXTRAGALACTIC RADIO-SOURCES;ACTIVE GALACTIC NUCLEI;PHOTON IMAGING CAMERA;GAMMA-RAY EMISSION;MULTIFREQUENCY OBSERVATIONS;SPECTRAL VARIABILITY;COMPLETE SAMPLE;AGILE DETECTION;LIGHT CURVES;HELICAL JETS
    Date: 2009
    Issue Date: 2010-06-29 19:35:37 (UTC+8)
    Publisher: 中央大學
    Abstract: Context. BL Lacertae is the prototype of the blazar subclass named after it. Yet, it has occasionally shown a peculiar behaviour that has questioned a simple interpretation of its broad-band emission in terms of synchrotron plus synchrotron self-Compton (SSC) radiation. Aims. In the 2007-2008 observing season we carried out a new multiwavelength campaign of the Whole Earth Blazar Telescope (WEBT) on BL Lacertae, involving three pointings by the XMM-Newton satellite in July and December 2007, and January 2008, to study its emission properties, particularly in the optical-X-ray energy range. Methods. The source was monitored in the optical-to-radio bands by 37 telescopes. The brightness level was relatively low. Some episodes of very fast variability were detected in the optical bands. Flux changes had larger amplitude at the higher radio frequencies than at longer wavelengths. Results. The X-ray spectra acquired by the EPIC instrument onboard XMM-Newton are well fitted by a power law with photon index Gamma similar to 2 and photoelectric absorption exceeding the Galactic value. However, when taking into account the presence of a molecular cloud on the line of sight, the EPIC data are best fitted by a double power law, implying a concave X-ray spectrum. The spectral energy distributions (SEDs) built with simultaneous radio-to-X-ray data at the epochs of the XMM-Newton observations suggest that the peak of the synchrotron emission lies in the near-IR band, and show a prominent UV excess, besides a slight soft-X-ray excess. A comparison with the SEDs corresponding to previous observations with X-ray satellites shows that the X-ray spectrum is very variable, since it can change from extremely steep to extremely hard, and can be more or less curved in intermediate states. We ascribe the UV excess to thermal emission from the accretion disc, and the other broad-band spectral features to the presence of two synchrotron components, with their related SSC emission. We fit the thermal emission with a black body law and the non-thermal components by means of a helical jet model. The fit indicates a disc temperature greater than or similar to 20 000 K and a luminosity greater than or similar to 6 x 10(44) erg s(-1).
    Relation: ASTRONOMY & ASTROPHYSICS
    Appears in Collections:[天文研究所] 期刊論文

    Files in This Item:

    File Description SizeFormat
    index.html0KbHTML430View/Open


    All items in NCUIR are protected by copyright, with all rights reserved.

    社群 sharing

    ::: Copyright National Central University. | 國立中央大學圖書館版權所有 | 收藏本站 | 設為首頁 | 最佳瀏覽畫面: 1024*768 | 建站日期:8-24-2009 :::
    DSpace Software Copyright © 2002-2004  MIT &  Hewlett-Packard  /   Enhanced by   NTU Library IR team Copyright ©   - Feedback  - 隱私權政策聲明