Microvariability in the southern gamma-ray blazar PKS 0537-441

Romero, Gustavo E.; Combi, J. A.; Cellone, S. A.
April 2000
AIP Conference Proceedings;2000, Vol. 510 Issue 1, p333
Academic Journal
The southern blazar PKS 0537-441 is one of the most variable active galactic nuclei. It has displayed extreme forms of variability in its emission from radio to gamma-ray wavelengths. Here we present results of new optical microvariability observations of this blazar in the V and R bands, obtained with high-quality CCD photometry made with a 2.15-m telescope at CASLEO, Argentina. We have found variability with amplitudes of more than 100% over timescales of ∼2 days, similar to what has been observed in gamma-rays by EGRET. The spectral index, contrarily to what is expected from microlensing, showed changes of ∼27% during the observing period, with a trend to steepen with decreasing flux. This seems to reflect an intrinsic mechanism behind the variability and, consequently, suggests that optical and gamma-ray emitting regions in this source can be co-extensive. If the most extreme manifestations of radio variability are also intrinsic, they might involve coherent emission processes. We have used our observations, along with EGRET and ROSAT data, to constrain the central black hole mass, which seems to be ∼8×10[sup 7] M⊙ For such a mass the γ-ray variability is originated at ∼290 gravitational radii from the central source. © 2000 American Institute of Physics.


Related Articles

  • γ-ray spectral changes during blazar outbursts. Sreekumar, P.; Hartman, R. C.; Mukherjee, R.; Pohl, M. // AIP Conference Proceedings;2001, Vol. 587 Issue 1, p314 

    We examined the archival EGRET data on time-variable γ-ray blazars for systematic variations in the spectra during different intensity states (flare/quiet). Although the changes in the individual source spectra can be well measured in only a few cases, the collective results from the blazar...

  • Spectral properties of gamma-ray detected blazars from 5 to 37 GHz. Tera¨sranta, Harri // AIP Conference Proceedings;2000, Vol. 510 Issue 1, p352 

    Radio monitoring data from the Metsa¨hovi Radio Observatory and the University of Michigan Radio Astronomical Observatory are used to study if the spectral indexes of the mean flux between used frequencies are different between γ-ray detected and not detected AGN. The γ-ray detected AGN...

  • The Correlation between γ-Ray and Radio Emissions for the Fermi Blazars. Yang, J.; Fan, J. // Journal of Astrophysics & Astronomy;Mar-Jun2011, Vol. 32 Issue 1/2, p203 

    Based upon the Fermi blazars sample, the radio and γ-ray emissions are compiled for a sample of 74 γ-ray loud blazars to calculate the radio to γ-ray effective spectrum index α. The correlations between α and γ-ray luminosity, and between radio and γ-ray luminosity are also...

  • MICROQUASARS IN THE MILKY WAY. Mirabel, I. Félix; Rodríguez, Luis Felipe // Sky & Telescope;May2002, Vol. 103 Issue 5, p32 

    Explores microquasars in the Milky Way galaxy. Origin of quasars; Circumstances to the discovery of microquasars; Validation of the Einsteinian special theory of relativity; Comparison of microquasars and microblazars.

  • Hadronic blazar models and correlated X-ray/TeV flares. Rachen, Jo¨rg P. // AIP Conference Proceedings;2000, Vol. 515 Issue 1, p41 

    The hypothesis that AGN jets might be the sources of the ultra-high energy cosmic rays has originally motivated the venture of TeV gamma ray astronomy. Surprisingly, after the discovery of TeV emission from blazars the attention has shifted to more traditional explanations which do not involve...

  • Extragalactic background light absorption signal in the 0.26–10 TeV spectra of blazars. Vassiliev, Vladimir V. // AIP Conference Proceedings;2000, Vol. 515 Issue 1, p105 

    Recent observations of the TeV γ-ray spectra of the two closest active galactic nuclei (AGNs), Markarian 501 (Mrk 501) and Markarian 421 (Mrk 421), by the Whipple and HEGRA collaborations have stimulated efforts to estimate or limit the spectral energy density (SED) of extragalactic...

  • UBVRI photometry of southern sky BL Lacs. Sefako, R. R.; de Jager, O. C.; Winkler, H. // AIP Conference Proceedings;2001, Vol. 558 Issue 1, p732 

    Seventeen southern sky BL Lacs were observed in UBVRI using the CCD Camera on the 1.0m telescope at the South African Astronomical Observatory (SAAO) in Aug and Nov 1999. The analyses of all the seventeen sources are now complete, and are available via anonymous ftp...

  • Blue quasars and blazar unification. Georganopoulos, Markos // AIP Conference Proceedings;2001, Vol. 558 Issue 1, p712 

    Blue quasars (BQ) are sources with strong broad emission lines and flat hard X-ray spectra, properties that characterise classical flat spectrum radio quasars (FSRQs), and high peak frequencies and steep soft X-ray spectra, properties that characterise intermediate or high peak frequency BL...

  • Effect of adiabatic cooling on non-thermal spectra of blazars. Bhattacharyya, Subir; Sahayanathan, Sunder; Kaul, C. L.; Bhat, C. L. // AIP Conference Proceedings;2001, Vol. 558 Issue 1, p696 

    We investigate the effect on the radio to soft x-ray non-thermal emission from blazars due to the inclusion of the adiabatic loss mechanism, in addition to the usual synchrotron and particle escape losses of energetic electrons in the jets of blazars. We model the emission region as an expanding...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics