The inset shows a still image showing one of the frames, only 1/40th
of a second in exposure time, with a red flash, as observed by the
ULTRACAM fast imager on the WHT
in the early morning hours of June 26, 2015. Click on the image above to
see a movie of fast red flashes from V404 Cygni. A ~6 second segment of
the ULTRACAM movie is repeated continuously.
The flashes are incredibly short and last less than one second, with
some of them being even faster than 1/40th of a second. The flashes are
equivalent to a luminosity of about 1000 times the Sun's power.
The background image shows a region of the sky in the Cygnus
constellation, with the Cygnus Loop supernova remnant on the bottom left
[ animated GIF | PNG ].
In a paper published in the journal Monthly Notices of the Royal Astronomical Society, astronomers report catching V404 Cygni black hole
while it was shimmering and
emitting red flashes, some of which were shorter than a timespan of only 1/40th of a second.
In June 2015, V404 Cygni abruptly started emitting a huge amount of
power, becoming one of the brightest objects in the Milky Way Galaxy as
seen in
X-rays. Telescopes worldwide, including the William Herschel and Isaac
Newton Telescopes, followed its ascent in brightness for about two
weeks,
leading up to June 26, after which the black hole gradually faded away.
Imagine an object 9 times larger in mass than the Sun, which is
radiating 1000 times more energy than our Sun gives off every second.
This is the power
that was seen to be emitted. As if this weren’t extreme enough, on June
26, the black hole appeared to be agitated and flickering red at high
speed.
The astronomers speculate that while the black hole was being force-fed
with material that it had stripped off a neighbouring star, it reacted
furiously
by blasting away some of the material in the form of a fast-moving
‘jet’. Lead author of the study Dr Poshak Gandhi, Associate Professor
and STFC Ernest Rutherford Fellow in the University of Southampton’s
Astronomy Group, said: "The duration of these flashing episodes could be
related to the switching on and off of a steady jet,
seen for the first time in detail.”
Gandhi also comments: “The very high speed tells us that the region
where this red light is being emitted must be very compact.
Piecing together clues about the colour, speed, and the power of these
flashes, we conclude that this light is being emitted from the base of
the black hole jet.
The origin of these jets is still unknown, although strong magnetic
fields are suspected to play a role."
Due to the unpredictable nature and rarity of these bright black hole
‘outbursts’, astronomers have very little time to react.
For example, V404 Cygni last erupted back in 1989. V404 Cygni was
exceptionally bright in June 2015 and provided an excellent opportunity
for such work. In fact, this was one of the brightest black hole
outbursts in recent years. But most outbursts are far dimmer, making
them difficult to study.
At a distance of 7800 light years from Earth, the black hole is too far
away to image its jet in fine detail.
But the speedy red flashes were important clues telling the astronomers
that such a jet had formed.
These observations are state-of-the-art, and could only be carried out
with the fast ULTRACAM imager, which happened to be mounted on the
WHT in June 2015 for about one week, just in time to catch the flurry of
activity.
Liam Hardy, PhD student at the University of Sheffield, and an ex-ING
student support astronomer, said: "It was difficult to catch these
signals from V404 Cygni in the small
gaps in our scheduled observing, but when we finally spotted the fast
flaring activity on our last night, it was tremendously exciting. We
knew immediately that these observations would be
of great interest to the community."
The nature of V404 Cygni system was unveiled in 1992, when observations
made using the telescopes of the Isaac Newton Group provided the
strongest observational evidence for the existence of a stellar-size black hole in our Galaxy.
More Information
- P. Gandhi et al., 2016, "Furiously Fast and Red: Sub-second Optical Flaring in V404 Cyg during the 2015 Outburst Peak", accepted for publication in MNRAS, 10.1093/mnras/stw571. Paper.
- "Astronomers see black hole raging red", movie and image.
- "Astronomers see black hole raging red", Southampton University press release, 16th March 2016.
- "Astronomers see black hole raging red", RAS press release, 16th Mar 2016.
- ULTRACAM web site.
Contact:
Javier Méndez (Public Relations Officer)
Source: Isaac Newton Group of Telescopes
