Clumpy wind accretion in Cygnus X-1

Cygnus X-1 is one of the brightest X-ray sources observed and shows the X-ray intensity variations on time scales from milliseconds to months in both the soft and hard X-rays. In the recent work by Ishika Palit, Agnieszka Janiuk and Bożena Czerny, we aim to understand the physical mechanism responsible for the short timescale X-ray variability(<100 s) of the source in its Hard/Low state. The simulated GR Hydrodynamical model with shock solutions is in good agreement with the observed power density spectra of the source.
Article in print in ApJ is available on-line under this link.
Schematic

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Article about disappearing star accepted to ApJ Letters

Our article entitled “On the maximum stellar rotation to form a black hole without an accompanying luminous transient”, by Ariadna Murguia-Berthier, co-authored by Aldo Batta, Agnieszka Janiuk, Ilya Mandel, Enrico Ramirez-Ruiz and Rosa Wallace-Everson, has been accepted for publication in the Astrophysical Journal Letters.

In this work, we use the results of GR MHD simulations to constrain the maximal stellar rotation rates of the disappearing massive progenitors PHL293B-LBV and N6946-BH1, and to provide an estimate of the overall rate of disappearing massive stars. We find that about a few percent of single O-type stars with measured rotational velocities are expected to spin below the critical value before collapse and are thus predicted to vanish without a trace.

The ArXiv link to the text is here.


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