When a Standard Candle Flickers

Publication: Research - peer-reviewJournal article – Annual report year: 2011

  • Author: Wilson-Hodge, Colleen A

    Marshall Space Flight Center

  • Author: Cherry, Michael L

    Louisiana State University, Dept. of Phys. & Astron

  • Author: Case, Gary L

    Louisiana State University, Dept. of Phys. & Astron

  • Author: Baumgartner, Wayne H

    Goddard Space Flight Center

  • Author: Beklen, Elif

    Middle East Tech. University

  • Author: Bhat, P Narayana

    University of Alabama in Huntsville

  • Author: Briggs, Michael S

    University of Alabama in Huntsville

  • Author: Camero-Arranz, Ascension

    Nat. Space Sci. & Technol. Center

  • Author: Chaplin, Vandiver

    University of Alabama in Huntsville

  • Author: Connaughton, Valerie

    University of Alabama in Huntsville

  • Author: Finger, Mark H

    Universities Space Res. Assoc.

  • Author: Gehrels, Neil

    Goddard Space Flight Center

  • Author: Greiner, Jochen

    Max Planck Institute

  • Author: Jahoda, Keith

    Goddard Space Flight Center

  • Author: Jenke, Peter

    Marshall Space Flight Center

  • Author: Kippen, R Marc

    Los Alamos Nat. Lab.

  • Author: Kouveliotou, Chryssa

    Marshall Space Flight Center

  • Author: Krimm, Hans A

    Goddard Space Flight Center

  • Author: Kuulkers, Erik

    Eur. Space Astron. Centre (ESAC)

  • Author: Lund, Niels

    Astrophysics, National Space Institute, Technical University of Denmark, Elektrovej, 2800, Kgs. Lyngby, Denmark

  • Author: Meegan, Charles A

    Universities Space Res. Assoc.

  • Author: Natalucci, Lorenzo

    INAF

  • Author: Paciesas, William S

    University of Alabama in Huntsville

  • Author: Preece, Robert

    University of Alabama in Huntsville

  • Author: Rodi, James C

    Louisiana State University

  • Author: Shaposhnikov, Nikolai

    Goddard Space Flight Center

  • Author: Skinner, Gerald K

    Goddard Space Flight Center

  • Author: Swartz, Doug

    Universities Space Res. Assoc.

  • Author: von Kienlin, Andreas

    Max Planck Institute

  • Author: Diehl, Roland

    Max Planck Institute

  • Author: Zhang, Xiao-Ling

    Max Planck Institute

View graph of relations

The Crab Nebula is the only hard X-ray source in the sky that is both bright enough and steady enough to be easily used as a standard candle. As a result, it has been used as a normalization standard by most X-ray/gamma-ray telescopes. Although small-scale variations in the nebula are well known, since the start of science operations of the Fermi Gamma-ray Burst Monitor (GBM) in 2008 August, a ~ 7% (70 mCrab) decline has been observed in the overall Crab Nebula flux in the 15-50 keV band, measured with the Earth occultation technique. This decline is independently confirmed in the ~ 15-50 keV band with three other instruments: the Swift Burst Alert Telescope ( Swift /BAT), the Rossi X-ray Timing Explorer Proportional Counter Array (RXTE /PCA), and the Imager on-Board the INTEGRAL Satellite (IBIS). A similar decline is also observed in the ~ 3-15 keV data from the RXTE /PCA and in the 50-100 keV band with GBM, Swift /BAT, and INTEGRAL /IBIS. The pulsed flux measured with RXTE /PCA since 1999 is consistent with the pulsar spin-down, indicating that the observed changes are nebular. Correlated variations in the Crab Nebula flux on a ~ 3 year timescale are also seen independently with the PCA, BAT, and IBIS from 2005 to 2008, with a flux minimum in 2007 April. As of 2010 August, the current flux has declined below the 2007 minimum.
Original languageEnglish
JournalAstrophysical Journal Letters
Publication date2011
Volume727
Issue2
PagesL40
ISSN2041-8213
DOIs
StatePublished
CitationsWeb of Science® Times Cited: 33

Keywords

  • X-rays: individual (Crab Nebula), Pulsars: individual (Crab Pulsar)
Download as:
Download as PDF
Select render style:
APAAuthorCBEHarvardMLAStandardVancouverShortLong
PDF
Download as HTML
Select render style:
APAAuthorCBEHarvardMLAStandardVancouverShortLong
HTML
Download as Word
Select render style:
APAAuthorCBEHarvardMLAStandardVancouverShortLong
Word

ID: 5251379