Although Kepler doesn't look in UV (where Cao's team saw iPTF14atg's ejecta shock), Oiling says that the telescope's sensitivity is so tremendous that, had there been a signal from material colliding with a companion star
, his team would have seen it in visible light.
The companion star
is about 125 times the volume of our sun, and towers over the tiny white dwarf, which is about the size of the Earth -- this is similar to comparing a hot air balloon and a marble.
Its outer hydrogen envelope becomes more loosely bound and vulnerable to gravitational stripping, or a type of stellar cannibalism, by the nearby companion star
. In that process, the more compact star winds up gaining mass, and the original massive star loses its hydrogen envelope, exposing its helium core to become a Wolf-Rayet star.
Team member Jennifer Sokoloski, also of Columbia University and co-investigator on the project, suggests these data indicate the companion star
plays an important role in shaping how material is ejected, presumably along the system's orbital plane, creating the pancake-shaped disk.
When van Staden observed the MSP over a 15-month period, he noticed an unexpected rise and fall in the companion star
's brightness - one that wasn't in sync with its orbital period.
But in the near future, as the supernova continues to fade, the relatively faint companion star
can be recovered.
Sahai and his colleagues used data gathered by Hubble to create a model that invokes the presence of a companion star
with an accretion disk to explain the ejection process.
Now, Maria Diaz Trigo (ESO) and colleagues report in the December 12th Nature that they have detected ionized iron and nickel in the jet from a stellar-mass black hole gobbling material from its companion star
. The evidence for atoms strongly favors the idea that the jet material comes from the black hole's accretion disk and is funneled out along magnetic strands that the disk itself has threaded through the black hole.
The researchers feel this is especially true for the system called HD 168443, where their ability to detect a companion star
was very strong.
The black hole in this compact pairing, known as MAXI J1659-152, is at least three times more massive than the Sun, while its red dwarf companion star
has a mass only 20 percent that of the Sun.
He and his collaborators used the Arecibo radio telescope, as well as the Greenbank radio telescope in West Virginia, to study millisecond pulsars, radio wave--emitting neutron stars that rotate hundreds of times a second and orbit a normal-density companion star
. The team restricted its 18-year study to those pulsars that reside in Milky Way globular clusters--crowded concentrations of several hundred thousand stars.
Millisecond pulsars generally form in binary systems, in which a neutron star spins itself up by siphoning material off its companion star
. But in Freire and Tauris's hypothesis, the spun-up stellar corpse is initially a white dwarf.