arXiv subjects

Z. Abraham

Publications and source records attributed to Z. Abraham.

21 records · Page 2Linked to original sources

arXiv2003

Microvariability in the optical polarization of 3C279

We present results of a microvariability polarization study in the violently variable quasar 3C279. We have resolved the polarization curves in the V band for this object down to timescales of minutes. We found two main components in the evolution of the degree of linear polarization, one consisting of a flicker with timescales of several tens of minutes and other component with far more significant variations on timescales of a few days. The linear polarization descended from $\sim 17$ % down to $\sim 8$ % in three nights. The polarization angle underwent a sudden change of more that 10 degrees in a few hours, perhaps indicating the injection of a new shock in the jet. The amplitude of the intranight flickering in the degree of polarization is at the level of $\sim 1$%. These are probably the best sampled polarization data ever obtained for this object. We also performed IR observations and we provide a follow-up of the evolution of this source at such energies after the main polarization outburst.

astro-ph↗

arXiv2002

Dust Formation Events in Colliding Winds: an application to eta Car

Recent IR observations indicate that many massive binary systems present dust formation episodes, in regions close to the stars, during the periastron passage. These systems are known to be high-energy sources, and it is believed that wind collisions are the origin of the emission. In this work we show that wind collisions not only increase the X-ray emission but also allow dust formation. As an application we study eta Car, which presents, near periastron, an increase in the X-ray emission followed by a sudden decrease that lasts for about a month. We reproduce this feature calculating the optical depth due to dust formation along the orbital period.

astro-ph↗

arXiv2002

Grain Formation in Post-Shocked Wind Collisions of Massive Binary Systems

Massive binary star systems are not uncommon, and neither the supersonic collision of their winds. In the present work we study these shocks and the further consequences on wind structure. The post-shock gas is a warm and high-density environment, which allows dust to form and grow. We show that this growth is fast, of just a few hours. An application for etaCarinae shows that, probably, the decline of X-rays fluxes observed in its light curve is the consequence of its high absorption in periodic dust formation events, on the periastron passage.

astro-ph↗