12 research outputs found
Changes in QTc and PR Intervals among Indian Type 2 Diabetes Patients with Respect to Prevailing Glycated Hemoglobin Level: a Retrospective Analysis
MAGIC upper limits to the VHE gamma-ray flux of 3C 454.3 in high emission state.
We report upper limits to the very high energy flux (E>100 GeV) of the flat
spectrum radio quasar 3C454.3 (z=0.859) derived by the Cherenkov telescope
MAGIC during the high states of July/August and November/December 2007. We
compare the upper limits derived in both time slots with the available
quasi-simultaneous MeV-GeV data from the AGILE gamma-ray satellite and
interpret the observational results in the context of leptonic emission models.
The source was observed with the MAGIC telescope during the active phases of
July-August 2007 and November-December 2007 and the data were analyzed with the
MAGIC standard analysis tools. For the periods around the ends of July and
November, characterized by the most complete multifrequency coverage, we
constructed the spectral energy distributions using our data together with
nearly simultaneous multifrequency (optical, UV, X-ray and GeV) data. Only
upper limits can be derived from the MAGIC data. The upper limits, once
corrected for the expected absorption by the extragalactic background light,
together with nearly simultaneous multifrequency data, allow us to constrain
the spectral energy distribution of 3C454.3. The data are consistent with the
model expectations based on the inverse Compton scattering of the ambient
photons from the broad line region by relativistic electrons, which robustly
predicts a sharp cut-off above 20-30 GeV.Comment: 5 pages, 1 figure, submitted to A&
Suzaku and Multi-wavelength Observations of OJ 287 during the Periodic Optical Outburst in 2007.
Suzaku observations of the blazar OJ 287 were performed in 2007 April 10--13
and November 7--9. They correspond to a quiescent and a flaring state,
respectively. The X-ray spectra can be well described with single power-law
models in both exposures. The derived X-ray photon index and the flux density
at 1 keV were found to be Gamma = 1.65 +- 0.02 and S_{1 keV} = 215 +- 5 nJy, in
the quiescent state. In the flaring state, the source exhibited a harder X-ray
spectrum (Gamma = 1.50 +- 0.01) with a nearly doubled X-ray flux density S_{1
keV} = 404^{+6}_{-5} nJy. Moreover, significant hard X-ray signals were
detected up to ~ 27 keV. In cooperation with the Suzaku, simultaneous radio,
optical, and very-high-energy gamma-ray observations were performed with the
Nobeyama Millimeter Array, the KANATA telescope, and the MAGIC telescope,
respectively. The radio and optical fluxes in the flaring state (3.04 +- 0.46
Jy and 8.93 +- 0.05 mJy at 86.75 Hz and in the V-band, respectively) were found
to be higher by a factor of 2--3 than those in the quiescent state (1.73 +-
0.26 Jy and 3.03 +- 0.01 mJy at 86.75 Hz and in the V-band, respectively). No
notable gamma-ray events were detected in either observation. The spectral
energy distribution indicated that the X-ray spectrum was dominated by inverse
Compton radiation in both observations, while synchrotron radiation exhibited a
spectral cutoff around the optical frequency. Furthermore, no significant
difference in the synchrotron cutoff frequency was found between the quiescent
and flaring states. According to a simple synchrotron self-Compton model, the
change of the spectral energy distribution is due to an increase in the energy
density of electrons with small changes of both the magnetic field strength and
the maximum Lorentz factor of electrons.Comment: 22 pages, 8 figures; accepted for publication in PAS
Simultaneous multi-frequency observation of the unknown redshift blazar PG 1553+113 in March-April 2008
The blazar PG 1553+113 is a well known TeV gamma-ray emitter. In this paper we determine its spectral energy distribution through simultaneous multi-frequency data to study its emission processes. An extensive campaign was carried out between March and April 2008, where optical, X-ray, high-energy (HE) gamma-ray, and very-high-energy (VHE) gamma-ray data were obtained with the KVA, Abastumani, REM, RossiXTE/ASM, AGILE and MAGIC telescopes, respectively. We combine the data to derive the source's spectral energy distribution and interpret its double-peaked shape within the framework of a synchrotron self-Compton model