Optical afterglows from two-component jets under various configurations are investigated numerically. Generally, the light curve is characterized by a rapid rebrightening when the observer is off-axis with respect to the narrow component, with the amplitude and peak time depending on detailed parameters. We further show that the optical afterglow of XRF 030723, especially its notable and rapid ...

The energy release in gamma-ray bursts is one of the most useful clues on the nature of their “inner engines”. We show that, within the framework of the relativistic external shocks afterglow model, the narrowness of the observed X-ray luminosity of GRB afterglows, implies that the energy of the GRB jets after the early afterglow phase spans less than one order of magnitude. This result is not ...

We report the discovery of water maser emission in eight active galactic nuclei (AGN) with the 70-m NASA Deep Space Network (DSN) antennas at Tidbinbilla, Australia and Robledo, Spain. The positions of the newly discovered masers, measured with the VLA, are consistent with the optical positions of the host nuclei to within 1σ (0. 3 radio and 1. 3 optical) and most likely mark the locations of t...

Magnetically driven astrophysical jets are related to accretion and involve toroidal magnetic field pressure inflating poloidal magnetic field flux surfaces. Examination of particle motion in combined gravitational and magnetic fields shows that these astrophysical jet toroidal and poloidal magnetic fields can be powered by the gravitational energy liberated by accreting dust grains that have b...

Using the Submillimeter Array (SMA) we have imaged for the first time the 321.226 GHz, 1029−936 ortho-H2O maser emission. This is also the first detection of this line in the Cepheus A high-mass star-forming region. The 22.235 GHz, 616 − 523 water masers were also observed with the Very Large Array 43 days following the SMA observations. Three of the nine detected submillimeter maser spots are ...

We calculate gamma-ray burst (GRB) afterglow light curves from a relativistic jet as seen by observers at various viewing angles, vobs, relative to the jet axis. We describe three increasingly more realistic models and compare the resulting light curves. An observer at , where v0 is the initial jet opening angle, should see v ! v obs 0 a light curve very similar to that for an on-axis observer....

HST observations provided us with the spatial resolution required to explore in detail the properties of the Narrow Line Region of Seyfert galaxies. In Seyferts with extended radio structures the HST images revealed a very close connection between radio and optical line emission. We interpret this result as strong evidence that the line-emitting gas is compressed by the shocks created by the pa...

Jet driving and fragmentation process in collapsing primordial cloud are studied using three-dimensional MHD nested grid simulations. Starting from a rotating magnetized spherical cloud with the number density of nc ≃ 10 cm, we follow the evolution of the cloud up to the stellar density nc ≃ 10 cm. We calculate 36 models parameterizing the initial magnetic and rotational energies (γ0, β0). In t...

We present a study of outflow and feedback in the well-known Seyfert 2 galaxy Markarian 573 using high angular resolution long-slit spectrophotometry obtained with the Hubble Space Telescope Imaging Spectrograph (STIS). Through analysis of the kinematics and ionization state of a biconical outflow region emanating from the nucleus, we find that the outflow does not significantly accelerate the ...