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Theoretical and observational work show that jets from AGN can trigger star formation. However, in the Milky Way the first -and so far- only clear case of relativistic jets inducing star formation has been found in the surroundings of the microquasar GRS 1915+105. Here we summarize the multiwavelength observations of two compact star formation IRAS sources axisymmetrically located and aligned with the position angle of the sub-arcsec relativistic jets from the stellar black hole binary GRS 1915+105 (Mirabel & Rodriguez 1994). The observations of these two star forming regions at centimeter (Rodriguez & Mirabel 1998), millimeter and infrared (Chaty et al. 2001) wavelengths had suggested -despite the large uncertainties in the distances a decade ago- that the jets from GRS 1915+105 are triggering along the radio jet axis the formation of massive stars in a radio lobe of bow shock structure. Recently, Reid et al.(2014) found that the jet source and the IRAS sources are at the same distance, enhancing the evidence for the physical association between the jets from GRS 1915+105 and star formation in the IRAS sources. We conclude that as jets from AGN, jets from microquasars can trigger the formation of massive stars, but at distances of a few tens of parsecs. Although star formation induced by microquasar jets may not be statistically significant in the Milky Way, jets from stellar black holes may have been important to trigger star formation during the re-ionization epoch of the universe (Mirabel et al. 2011). Because of the relative proximity of GRS 1915+105 and the associated star forming regions, they may serve as a nearby laboratory to gain insight into the physics of jet-trigger star formation elsewhere in the universe.
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We present a multi-frequency, dense radio monitoring program of the blazar OJ287 using the 100m Effelsberg radio telescope. We analyze the evolution in total flux density, linear and circular polarization to study the jet structure and its magnetic field geometry. The total flux density is measured at nine bands from 2.64 GHz to 43 GHz, the linear polarization parameters between 2.64 GHz and 10.45 GHz, and the circular polarization at 4.85 GHz and 8.35 GHz. The mean cadence is 10 days. Between MJD 57370 and 57785, OJ287 showed flaring activity and complex linear and circular polarization behavior. The radio EVPA showed a large clockwise (CW) rotation by ~340$^{circ}$ with a mean rate of -1.04 $^{circ}$/day. Based on concurrent VLBI data, the rotation seems to originate within the jet core at 43 GHz (projected size $le$ 0.15 mas or 0.67 pc). Moreover, optical data show a similar monotonic CW EVPA rotation with a rate of about -1.1 $^{circ}$/day which is superposed with shorter and faster rotations of about 7.8 $^{circ}$/day. The observed variability is consistent with a polarized emission component propagating on a helical trajectory within a bent jet. We constrained the helix arc length to 0.26 pc and radius to $le$ 0.04 pc as well as the jet bending arc length projected on the plane of the sky to $le$ 1.9-7.6 pc. A similar bending is observed in high angular resolution VLBI images at the innermost jet regions. Our results indicate also the presence of a stable polarized emission component with EVPA (-10$^{circ}$) perpendicular to the large scale jet, suggesting dominance of the poloidal magnetic field component. Finally, the EVPA rotation begins simultaneously with an optical flare and hence the two might be physically connected. That optical flare has been linked to the interaction of a secondary SMBH with the inner accretion disk or originating in the jet of the primary.
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We report our intensive radio monitoring observations of the jet in M87 with the VLBI Exploration of Radio Astrometry (VERA) and the European VLBI Network (EVN) from February 2011 to October 2012, together with contemporaneous high-energy gamma-ray light curves obtained by the Fermi-LAT. During this period, an elevated level of the M87 flux is reported at VHE gamma rays. We detected a remarkable increase of the radio flux density from the unresolved jet base (radio core) with VERA at 22 and 43GHz coincident with the VHE activity. Meanwhile, we confirmed with EVN at 5GHz that HST-1 (an alternative gamma-ray production candidate site) remained quiescent in terms of its flux density and structure. These results in the radio bands strongly suggest that the VHE gamma-ray activity in 2012 originates in the jet base within 0.03pc or 56 Schwarzschild radii from the central supermassive black hole. We further conducted VERA astrometry for the M87 core during the flaring period, and detected core shifts between 22 and 43GHz. We also discovered a clear frequency-dependent evolution of the radio core flare at 43, 22 and 5GHz; the radio flux density increased more rapidly at higher frequencies with a larger amplitude, and the light curves clearly showed a time-lag between the peaks at 22 and 43GHz. This indicates that a new radio-emitting component was created near the black hole in the period of the VHE event, and then propagated outward with progressively decreasing synchrotron opacity. By combining these results, we estimated an apparent speed of the newborn component, and derived a sub-luminal speed of less than ~0.2c. This value is significantly slower than the super-luminal (~1.1c) features that appeared from the core during the prominent VHE flaring event in 2008, suggesting that the stronger VHE activity can be associated with the production of the higher Lorentz factor jet.
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