ESA: Monster Black Hole Wakes Up After 26 Years

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ESA: Monster Black Hole Wakes Up After 26 Years

Post by bystander » Thu Jun 25, 2015 7:32 pm

Monster Black Hole Wakes Up After 26 Years
ESA Space Science | Integral | 2015 Jun 25
Over the past week, ESA's Integral satellite has been observing an exceptional outburst of high-energy light produced by a black hole that is devouring material from its stellar companion.

X-rays and gamma rays point to some of the most extreme phenomena in the Universe, such as stellar explosions, powerful outbursts and black holes feasting on their surroundings.

In contrast to the peaceful view of the night sky we see with our eyes, the high-energy sky is a dynamic light show, from flickering sources that change their brightness dramatically in a few minutes to others that vary on timescales spanning years or even decades.

On 15 June 2015, a long-time acquaintance of X-ray and gamma ray astronomers made its comeback to the cosmic stage: V404 Cygni, a system comprising a black hole and a star orbiting one another. It is located in our Milky Way galaxy, almost 8000 light-years away in the constellation Cygnus, the Swan. ...
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GSFC: NASA Missions Monitor a Waking Black Hole

Post by bystander » Tue Jun 30, 2015 5:52 pm

NASA Missions Monitor a Waking Black Hole
NASA | GSFC | Swift | 2015 Jun 30
Click to play embedded YouTube video.
NASA's Swift satellite detected a rising tide of high-energy X-rays from the constellation Cygnus on June 15, just before 2:32 p.m. EDT. About 10 minutes later, the Japanese experiment on the International Space Station called the Monitor of All-sky X-ray Image (MAXI) also picked up the flare.

The outburst came from V404 Cygni, a binary system located about 8,000 light-years away that contains a black hole. Every couple of decades the black hole fires up in an outburst of high-energy light, becoming an X-ray nova. Until the Swift detection, it had been slumbering since 1989.

An X-ray nova is a bright, short-lived X-ray source that reaches peak intensity in a few days and then fades out over a period of weeks or months. The outburst occurs when stored gas abruptly rushes toward a neutron star or black hole. By studying the patterns of the X-rays produced, astronomers can determine the kind of object at the heart of the eruption. ...

Astronomers classify this type of system as a low-mass X-ray binary. In V404 Cygni, a star slightly smaller than the sun orbits a black hole 10 times its mass in only 6.5 days. The close orbit and strong gravity of the black hole produce tidal forces that pull a stream of gas from its partner. The gas travels to a storage disk around the black hole and heats up to millions of degrees, producing a steady stream of X-rays as it falls inward.

But the disk flips between two dramatically different conditions. In its cooler state, the gas resists inward flow and just collects in the outer part of the disk like water behind a dam. Inevitably the build-up of gas overwhelms the dam, and a tsunami of hot bright gas rushes toward the black hole. ...

Black hole, quiet since 1989, now caught burping a rare X-ray flare
Penn State University | 2015 Jun 30

Alert Notice 520: X-ray nova and LMXB V404 Cyg in rare outburst
American Association of Variable Star Observers (AAVSO) | 2015 Jun 18
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GSFC: Swift Reveals a Black Hole Bull's-eye

Post by bystander » Fri Jul 10, 2015 1:14 pm

Swift Reveals a Black Hole Bull's-eye
NASA | GSFC | Swift | 2015 July 09
What looks like a shooting target is actually an image of nested rings of X-ray light centered on an erupting black hole. On June 15, NASA's Swift satellite detected the start of a new outburst from V404 Cygni, where a black hole and a sun-like star orbit each other. Since then, astronomers around the world have been monitoring the ongoing light show.

On June 30, a team led by Andrew Beardmore at the University of Leicester, U.K., imaged the system using the X-ray Telescope aboard Swift, revealing a series concentric rings extending about one-third the apparent size of a full moon. A movie made by combining additional observations acquired on July 2 and 4 shows the expansion and gradual fading of the rings.

Astronomers say the rings result from an "echo" of X-ray light. The black hole's flares emit X-rays in all directions. Dust layers reflect some of these X-rays back to us, but the light travels a longer distance and reaches us slightly later than light traveling a more direct path. The time delay creates the light echo, forming rings that expand with time.

Detailed analysis of the expanding rings shows that they all originate from a large flare that occurred on June 26 at 1:40 p.m. EDT. There are multiple rings because there are multiple reflecting dust layers between 4,000 and 7,000 light-years away from us. Regular monitoring of the rings and how they change as the eruption continues will allow astronomers to better understand their nature. ...

V404 Cygni is located about 8,000 light-years away. Every couple of decades the black hole fires up in an outburst of high-energy light. Its previous eruption ended in 1989. ...
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AAVSO: Understanding the Black Hole Binary V404 Cygni

Post by bystander » Fri Jan 08, 2016 6:08 pm

AAVSO Observers Contribute to Understanding the Black Hole Binary V404 Cygni
American Association of Variable Star Observers | 2016 Jan 07

V404 Cygni has been known as a variable star residing in the constellation Cygnus since the 18th century. It was believed to be a nova, a compact binary system containing a white dwarf primary and a sun-like secondary star, that undergoes unpredictable episodes of dramatic brightening - or 'outbursts' - before settling back down to quiescence for decades, until the next outburst.

The last outburst occurred in 1989. At that time, V404 Cyg released enormous amounts of energy in the x-ray, optical and radio wavelengths for several months before quieting back down again. The 1989 outburst offered the first chance for astronomers of the space age to observe V404 Cyg with satellites and ground based telescopes. From what they learned, V404 Cygni was reclassified as one of a new class of X-ray transient sources called low mass X-ray binaries (LMXBs), x-ray emitting binary systems where one of the components is either a black hole or neutron star.

On June 15th, 2015- after a 26 year wait- V404 Cygni woke up again. The first signs of renewed activity were spotted by the Burst Alert Telescope on NASA's Swift satellite, when it detected a sudden burst of gamma rays. This then triggered observations with its own X-ray telescope. Soon after, MAXI (Monitor of All-sky X-ray Image), part of the Japanese Experiment Module on the International Space Station, observed an X-ray flare from the same patch of the sky.

These observations triggered alerts throughout networks of professional and amateur astronomers around the world, causing hundreds of instruments to point towards the latest outburst. Analysis of this unprecedented amount of data has begun to bear fruit.

One international research team found that observations of black hole binary outbursts in visible light could reveal important phenomena, such as the flickering light emerging from gases surrounding the black hole. The team's results, published in Nature, indicate that optical rays and not just X-rays provide reliable observational data for black hole activity. ...

Repetitive patterns in rapid optical variations in the nearby black-hole binary V404 Cygni - Mariko Kimura et al
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Southhampton: Astronomers See Black Hole Raging Red

Post by bystander » Wed Mar 16, 2016 5:15 pm

Astronomers See Black Hole Raging Red
University of Southhampton, UK | STFC | 2016 Mar 16
Violent red flashes, lasting just fractions of a second, have been observed during one of the brightest black hole outbursts in recent years.

In June 2015, a black hole called V404 Cygni underwent dramatic brightening for about two weeks, as it devoured material that it had stripped off an orbiting companion star.

V404 Cygni, which is about 7,800 light years from Earth, was the first definitive black hole to be identified in our Galaxy and can appear extremely bright when it is actively devouring material.

In a new study, published in the journal Monthly Notices of the Royal Astronomical Society, an international team of astronomers, led by the University of Southampton, report that the black hole emitted dazzling red flashes lasting just fractions of a second, as it blasted out material that it could not swallow.

The astronomers associated the red colour with fast-moving jets of matter that were ejected from close to the black hole. These observations provide new insights into the formation of such jets and extreme black hole phenomena. ...

Furiously Fast and Red: Sub-second Optical Flaring in V404 Cyg during the 2015 Outburst Peak - P. Gandhi et al
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Southampton: Intense Wind Found ian Neighborhood of Black Hole

Post by bystander » Wed May 11, 2016 2:46 am

Intense Wind Found in the Neighborhood of a Black Hole
University of Southampton | 2016 May 09

An international team of astrophysicists, including Professor Phil Charles from the University of Southampton, have detected an intense wind from one of the closest known black holes to the Earth.

During observations of V404 Cygni, which went into a bright and violent outburst in June 2015 after more than 25 years of quiescence, the team began taking optical measurements of the black hole’s accretion disc using the 10.4-meter Gran Telescopio Canarias (GTC) -- the biggest optical-infrared telescope in the world, situated at the Roque de los Muchachos Observatory (Garafía, La Palma) in the Canary Islands.

The results, which are published today in Nature, show the presence of a wind of neutral material (un-ionized hydrogen and helium), which is formed in the outer layers of the accretion disc, regulating the accretion of material by the black hole. This wind, detected for the first time in a system of this type, has a very high velocity (3,000 kilometers per second) so that it can escape from the gravitational field around the black hole. ...

Regulation of Black-Hole Accretion by a Disk Wind During a Violent Outburst of V404 Cygni - T. Muñoz-Darias et al
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