Fermi and multifrequency observations of blazars

Journal Article · Fri Mar 26 00:00:00 EDT 2010 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3395998· OSTI ID:21367048

Monte, C ^[1]; Cavazzuti, E; Cutini, S; Giommi, P ^[2]; Mazziotta, M N ^[3]

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1. Dipartimento Interateneo di Fisica 'M.Merlin', Universita e Politecnico di Bari, Bari (Italy)
2. Agenzia Spaziale Italiana (ASI) Science Data center Frascati (Roma) (Italy)
3. Istituto Nazionale di Fisica Nucleare, Sezione di Bari, Bari (Italy)

The Fermi Gamma-ray Space Telescope was successfully launched on June 11, 2008 and has already opened a new era for gamma-ray astronomy. The Large Area Telescope(LAT), the main instrument on board Fermi, with its large field of view and effective area, combined with its excellent timing capabilities, presents a significant improvement in sensitivity over its predecessor EGRET. The preliminary results of the Spectral Energy Distribution Analysis performed on a sample of bright blazars are presented. We have studied the quasi-simultaneous Spectral Energy Distributions (SED) of 48 blazars, detected within the three months of the Fermi LAT Bright AGN Sample (LBAS) data taking period, combining Fermi and Swift data with radio NIR-Optical and hard-X/gamma-ray data. We have used these SEDs to characterize the peak position and intensity of both the low and the high-energy features of blazar spectra. The results have been used to derive empirical relationships that estimate the position of the two peaks from the broad-band colors, i.e. the radio to optical (alpha{sub ro}) and optical to X-ray (alpha{sub ox}) spectral slopes, and from the gamma-ray spectral index. Our data show that the synchrotron peak frequency is positioned between 10{sup 12.5} and 10{sup 14.5} Hz in FSRQs and between 10{sup 13} and 10{sup 17} Hz in BL Lacertae objects. We find that the gamma-ray spectral slope is strongly correlated with the synchrotron peak energy, as expected at first order in synchrotron--inverse Compton scenarios. However, simple homogeneous, one-zone, Synchrotron Self Compton (SSC) models cannot explain most of our SEDs, especially in the case of FSRQs and low energy peaked (LBL) BL Lacs. More complex models involving External Compton Radiation or multiple SSC components are required to reproduce the overall SEDs and the observed spectral variability.

• OSTI ID: 21367048
• Journal Information: AIP Conference Proceedings, Vol. 1223, Issue 1; Conference: 7. workshop on gamma-ray physics in the LHC era, Assisi (Italy), 7-9 Oct 2009; Other Information: DOI: 10.1063/1.3395998; (c) 2010 American Institute of Physics; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
BL LACERTAE OBJECTS
COSMIC GAMMA SOURCES
COSMIC PHOTONS
ENERGY SPECTRA
GALAXY NUCLEI
GAMMA ASTRONOMY
GAMMA DETECTION
GAMMA RADIATION
GAMMA SPECTRA
QUASARS
SENSITIVITY
TELESCOPE COUNTERS
X RADIATION
ASTRONOMY
BOSONS
COSMIC RADIATION
COSMIC RADIO SOURCES
COSMIC RAY SOURCES
DETECTION
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
IONIZING RADIATIONS
MASSLESS PARTICLES
PHOTONS
RADIATION DETECTION
RADIATIONS
SPECTRA