Synchrotron outbursts in Galactic and extragalactic jets, any difference?

We discuss differences and similarities between jets powered by super-massive black holes in quasars and by stellar-mass black holes in microquasars. The comparison is based on multi-wavelength radio-to-infrared observations of the two active galactic nuclei 3C 273 and 3C 279, as well as the two galactic binaries GRS 1915+105 and Cyg X-3. The physical properties of the jet are derived by fitting the parameters of a shock-in-jet model simultaneously to all available observations. We show that the variable jet emission of galactic sources is, at least during some epochs, very similar to that of extragalactic jets. As for quasars, their observed variability pattern can be well reproduced by the emission of a series of self-similar shock waves propagating down the jet and producing synchrotron outbursts. This suggests that the physical properties of relativistic jets is independent of the mass of the black hol

Observation of the BL Lac objects 1ES 1215+303 and 1ES 1218+304 with the MAGIC telescopes

The two BL Lac objects 1ES 1215+303 and 1ES 1218+304, separated by 0.8 deg, were observed with the MAGIC telescopes in 2010 and 2011. The 20 hours of data registered in January 2011 resulted in the first detection at Very High Energy (>100 GeV) of 1ES 1215+303 (also known as ON-325). This observation was triggered by a high optical state of the source reported by the Tuorla blazar monitoring program. Comparison with the 25 hours of data carried out from January to May 2010 suggests that 1ES 1215+303 was flaring also in VHE gamma-rays in 2011. In addition, the Swift ToO observations in X-rays showed that the flux was almost doubled respect to previous observations (December 2009). Instead, 1ES 1218+304 is a well known VHE gamma-ray emitter lying in the same field of view, which was then simultaneously observed with the MAGIC telescopes. The overall observation time of nearly 45 hours has permitted to measure the spectrum of this source with a much higher precision than previously reported by MAGIC. Here, we present the results of the MAGIC and the multi-wavelength observations of these two VHE gamma-ray emitting AGNs.Comment: 4 pages, 5 figures, Proceedings of the 32nd ICRC (2011) Beijin

Quasi-periodicities of BL Lac Objects

We review the reports of possible year-long quasi-periodicities of BL Lac objects in the $\gamma$-ray and optical bands, and present a homogeneous time analysis of the light curves of PKS2155$-$304, PG1553+113, and BL Lac. Based on results from a survey covering the entire Fermi $\gamma$-ray sky we have estimated the fraction of possible quasi-periodic BL Lac objects. We compared the cyclical behaviour in BL Lac objects with that derived from the search of possible optical periodicities in quasars, and find that at z$\lesssim$1 the cosmic density of quasi-periodic BL Lac objects is larger than that of quasi-periodic quasars. If the BL Lac quasi-periodicities were due to a supermassive binary black hole (SBBH) scenario, there could be a tension with the upper limits on the gravitational wave background measured by the pulsar timing array. The argument clearly indicates the difficulties of generally associating quasi-periodicities of BL Lac objects with SBBHs.Comment: In publication on A&A, 6 pages, 4 figure (11 plots). Minor corrections adde

Synchrotron Outbursts in Galactic and Extra-galactic Jets, Any Difference?

We discuss differences and similarities between jets powered by super-massive black holes in quasars and by stellar-mass black holes in microquasars. The comparison is based on multi-wavelength radio-to-infrared observations of the two active galactic nuclei 3C 273 and 3C 279, as well as the two galactic binaries GRS 1915+105 and Cyg X-3. The physical properties of the jet are derived by fitting the parameters of a shock-in-jet model simultaneously to all available observations. We show that the variable jet emission of galactic sources is, at least during some epochs, very similar to that of extra-galactic jets. As for quasars, their observed variability pattern can be well reproduced by the emission of a series of self-similar shock waves propagating down the jet and producing synchrotron outbursts. This suggests that the physical properties of relativistic jets is independent of the mass of the black hole.Comment: 4 pages, 1 figure, Proceedings IAU Symposium No. 238. Black Holes: from Stars to Galaxies - across the Range of Masse

Microquasar Cyg X-3 -- a unique jet-wind neutrino factory?

The origin of astrophysical neutrinos is one of the most debated topics today. Perhaps the most robust evidence of neutrino counterpart comes from supermassive black holes in active galactic nuclei associated with strongly collimated outflows, or jets, that can accelerate particles to relativistic energies and produce neutrinos through hadronic interactions. Similar outflows can also be found from X-ray binaries, or `microquasars', that consist of a neutron star or a stellar-mass black hole accreting matter from a non-degenerate companion star. In some cases, these systems can accelerate particles up to GeV energies implying an efficient acceleration mechanism in their jets. Neutrino production in microquasar jets can be expected with suitable conditions and a hadronic particle population. Microquasar Cyg X-3 is a unique, short orbital period X-ray binary hosting a Wolf-Rayet companion star with a strong stellar wind. The interaction of the dense stellar wind with a relativistic jet leads to particle collisions followed by high-energy gamma-ray and potentially neutrino emission. Here, using the 10-year neutrino candidate sample of the IceCube neutrino observatory, we find that the events with the highest spatial association with Cyg X-3 occur during short-lived high-energy gamma-ray flaring periods indicating the possible astrophysical nature of these events.Comment: 5 pages, 2 figures, 1 table. This article has been accepted for publication in MNRAS published by Oxford University Press on behalf of the Royal Astronomical Societ