ARE THE TWO BLACK HOLES OBSERVED BY LIGO PRODUCED FROM THE COLLAPSE OF A SINGLE STAR?

Image: Simulation of two colliding black holes. Animation created by SXS, the Simulating eXtreme Spacetimes (SXS) project (http://www.black-holes.org) - Caltech LIGO

If the GW signal observed by LIGO is due to the merger of two isolated black holes (BHs) in vacuum, no electromagnetic counterparts are expected. However, Fermi observed a signal 0.4 s after LIGO in a region of space compatible with the GW source.

A recent paper (Loeb 2016) suggests that the two black holes could be the result of the collapse of a single massive and rapidly rotating star. In this scenario the GRB is produced from a jet generated in the accretion disk of residual debris around the black hole or from an outflow generating by the BHs' merging.

The detection of a GRB afterglow in the future could be used to determine the precise localization of the electromagnetic source and eventually confirm the association to the GW source.

Loeb 2016 (accepted for publication in ApJ Letters) - Electromagnetic Counterparts to Black Hole Mergers Detected by LIGO (arXiv)

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NO CORRELATION BETWEEN FERMI GBM SIGNAL AND GW150914

Image: Merging black holes. Credit: NASA Recently it has been suggested that electromagnetic signals detected by Fermi GBM could be associated with the merger of the two black holes detected by LIGO ( GW150914 ).

Astrophysics News (March 22)

Scientists detect comets outside our solar system

An artist’s conception of a view from within the Exocomet system KIC 3542116. Credit: Danielle Futselaar Team of professional and citizen scientists identifies tails of comets streaking past a distant star Jennifer Chu | MIT News Office Scientists from MIT and other institutions, working closely with amateur astronomers, have spotted the dusty tails of six exocomets — comets outside our solar system — orbiting a faint star 800 light years from Earth. These cosmic balls of ice and dust, which were about the size of Halley’s Comet and traveled about 100,000 miles per hour before they ultimately vaporized, are some of the smallest objects yet found outside our own solar system. The discovery marks the first time that an object as small as a comet has been detected using transit photometry, a technique by which astronomers observe a star’s light for telltale dips in intensity. Such dips signal potential transits, or crossings of planets or other objects in front of a star, ...

SpaceTime

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