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[en] We present multi-epoch optical spectroscopy of seven southern Fermi-monitored blazars from 2008 to 2013 using the Small and Medium Aperture Research Telescope System (SMARTS), with supplemental spectroscopy and polarization data from the Steward Observatory. We find that the emission lines are much less variable than the continuum; four of seven blazars had no detectable emission line variability over the 5 yr observation period. This is consistent with photoionization primarily by an accretion disk, allowing us to use the lines as a probe of disk activity. Comparing optical emission line flux with Fermi γ-ray flux and optical polarized flux, we investigate whether relativistic jet variability is related to the accretion flow. In general, we see no such dependence, suggesting that the jet variability is likely caused by internal processes like turbulence or shock acceleration rather than a variable accretion rate. However, three sources showed statistically significant emission line flares in close temporal proximity to very large Fermi γ-ray flares. While we do not have sufficient emission line data to quantitatively assess their correlation with the γ-ray flux, it appears that in some cases the jet might provide additional photoionizing flux to the broad-line region (BLR), which implies that some γ-rays are produced within the BLR, at least for these large flares
[en] We have obtained a full suite of Spitzer observations to characterize the debris disk around HR 8799 and to explore how its properties are related to the recently discovered set of three massive planets orbiting the star. We distinguish three components to the debris system: (1) warm dust (T ∼ 150 K) orbiting within the innermost planet; (2) a broad zone of cold dust (T ∼ 45 K) with a sharp inner edge orbiting just outside the outermost planet and presumably sculpted by it; and (3) a dramatic halo of small grains originating in the cold dust component. The high level of dynamical activity implied by this halo may arise due to enhanced gravitational stirring by the massive planets. The relatively young age of HR 8799 places it in an important early stage of development and may provide some help in understanding the interaction of planets and planetary debris, an important process in the evolution of our own solar system.
[en] We report on the location of the γ-ray emission region in flares of the BL Lacertae object OJ287 at > 14 pc from the central supermassive black hole. We employ data from multi-spectral range (total flux and linear polarization) monitoring programs combined with sequences of ultra-high-resolution 7 mm VLBA images. The correlation between the brightest γ-ray and mm flares is found to be statistically significant. The two γ-ray peaks, detected by Fermi-LAT, that we report here happened at the rising phase of two exceptionally bright mm flares accompanied by sharp linear polarization peaks. The VLBA images show that these mm flares in total flux and polarization degree occurred in a jet region at > 14 pc from the innermost jet region. The time coincidence of the brighter γ-ray flare and its corresponding mm linear polarization peak evidences that both the γ-ray and mm outbursts occur > 14 pc from the central black hole. We find two sharp optical flares occurring at the peak times of the two reported γ-ray flares. This is interpreted as the γ-ray flares being produced by synchrotron self-Compton scattering of optical photons from the flares triggered by the interaction of moving knots with a stationary conical shock in the jet.