اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThe flaring blazars of the first 1.5 years of the AGILE mission
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We report the AGILE gamma-ray observations and the results of the multiwavelength campaigns on seven flaring blazars detected by the mission: During two multiwavelength campaigns, we observed gamma-ray activity from two Flat Spectrum Radio Quasars of the Virgo region, e.g. 3C 279 and 3C 273 (the latter being the first extragalactic source simultaneously observed with the gamma-ray telescope and the hard X ray imager of the mission). Due to the large FOV of the AGILE/GRID instrument, we achieved an almost continuous coverage of the FSRQ 3C 454.3. The source showed flux above 10E-6 photons/cm2/s (E > 100 MeV) and showed day by day variability during all the AGILE observing periods. In the EGRET era, the source was found in high gamma-ray activity only once. An other blazar, PKS 1510-089 was frequently found in high gamma-ray activity. S5 0716+71, an intermediate BL Lac object, exhibited a very high gamma-ray activity and fast gamma-ray variability during a period of intense optical activity. We observed high gamma-ray activity from W Comae, a BL Lac object, and Mrk 421, an high energy peaked BL Lac object. For this source, a multiwavelength campaign from optical to TeV has been performed.
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Since its launch in April 2007, the AGILE satellite detected with its Gamma-Ray Imaging Detector (GRID) several blazars at high significance: 3C 279, 3C 454.3, PKS 1510-089, S5 0716+714, 3C 273, W Comae, Mrk 421 and PKS 0537-441. Moreover, AGILE was
able both to rapidly respond to sudden changes in blazar activity state at other wavelengths and to alert other telescopes quickly in response to changes in the gamma-ray fluxes. Thus, we were able to obtain multiwavelength data from other observatories such as Spitzer, Swift, RXTE, Suzaku, INTEGRAL, MAGIC, VERITAS, as well as radio-to-optical coverage by means of the GASP Project of the WEBT and REM. This large multifrequency coverage gave us the opportunity to study the Spectral Energy Distribution of these sources from radio to gamma-rays energy bands and to investigate the different mechanisms responsible for their emission. We present an overview of the AGILE results on these gamma-ray blazars and the relative multifrequency data.
The AGILE gamma-ray satellite accumulated data over two years on several blazars. Moreover, for all of the sources detected by AGILE, we exploited multiwavelength observations involving both space and ground based telescopes and consortia, obtaining
in several cases broad-band spectral energy distributions (SEDs) which span from the radio wavelengths up to the TeV energy band. I will review both published and yet unpublished AGILE results on gamma-ray blazars, discussing their time variability, their gamma-ray flare durations and the theoretical modeling of the SEDs. I will also highlight the GASP-WEBT and Swift fundamental contributions to the simultaneous and long-term studies of gamma-ray blazars.
During the first 3 years of operation the Gamma-Ray Imaging Detector onboard the AGILE satellite detected several blazars in a high gamma-ray activity: 3C 279, 3C 454.3, PKS 1510-089, S5 0716+714, 3C 273, W Comae, Mrk 421, PKS 0537-441 and 4C +21.35.
Thanks to the rapid dissemination of our alerts, we were able to obtain multiwavelength data from other observatories such as Spitzer, Swift, RXTE, Suzaku, INTEGRAL, MAGIC, VERITAS, and ARGO as well as radio-to-optical coverage by means of the GASP Project of the WEBT and the REM Telescope. This large multifrequency coverage gave us the opportunity to study the variability correlations between the emission at different frequencies and to obtain simultaneous spectral energy distributions of these sources from radio to gamma-ray energy bands, investigating the different mechanisms responsible for their emission and uncovering in some cases a more complex behaviour with respect to the standard models. We present a review of the most interesting AGILE results on these gamma-ray blazars and their multifrequency data.
The ANTARES telescope is well-suited for detecting astrophysical transient neutrino sources as it can observe a full hemisphere of the sky at all times with a high duty cycle. The background due to atmospheric particles can be drastically reduced, an
d the point-source sensitivity improved, by selecting a narrow time window around possible neutrino production periods. Blazars, being radio-loud active galactic nuclei with their jets pointing almost directly towards the observer, are particularly attractive potential neutrino point sources, since they are among the most likely sources of the very high-energy cosmic rays. Neutrinos and gamma rays may be produced in hadronic interactions with the surrounding medium. Moreover, blazars generally show high time variability in their light curves at different wavelengths and on various time scales. This paper presents a time-dependent analysis applied to a selection of flaring gamma-ray blazars observed by the FERMI/LAT experiment and by TeV Cherenkov telescopes using five years of ANTARES data taken from 2008 to 2012. The results are compatible with fluctuations of the background. Upper limits on the neutrino fluence have been produced and compared to the measured gamma-ray spectral energy distribution.
The Galactic bulge region is a rich host of variable high-energy point sources. Since 2005, February 17 we are monitoring the source activity in this region about every three days with INTEGRAL. Thanks to the large field of view, the imaging capabili
ties and the sensitivity at hard X-rays, we are able to present for the first time a detailed homogeneous (hard) X-ray view of a sample of 76 sources in the Galactic bulge region. We describe the successful monitoring program and show the first results for a period of about one and a half year. We focus on the short (hour), medium (month) and long-term (year) variability in the 20-60 keV and 60-150 keV bands. When available, we discuss the simultaneous observations in the 3-10 keV and 10-25 keV bands. Per visibility season we detect 32/33 sources in the 20-60 keV band and 8/9 sources in the 60-150 keV band. On average, we find per visibility season one active bright (>~100 mCrab, 20-60 keV) black-hole candidate X-ray transient and three active weaker (<~25 mCrab, 20-60 keV) neutron star X-ray transients. Most of the time a clear anti-correlation can be seen between the soft and hard X-ray emission in some of the X-ray bursters. Hard X-ray flares or outbursts in X-ray bursters, which have a duration of the order of weeks, are accompanied by soft X-ray drops. On the other hand, hard X-ray drops can be accompanied by soft X-ray flares/outbursts. We found a number of new sources, IGR J17354-3255, IGR 17453-2853, IGR J17454-2703, IGR J17456-2901b, IGR J17536-2339, and IGR J17541-2252. We report here on some of the high-energy properties of these sources. The high-energy light curves of all the sources in the field of view, and the high-energy images of the region, are made available through the WWW at http://isdc.unige.ch/Science/BULGE/.
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