Posted on by Tammy Plotner

Chandra Captures Enticing Evidence Of Black Hole’s Bondi Radius

The galaxy NGC 3115 is shown here in a composite image of data from NASA's Chandra X-ray Observatory and the European Southern Observatory's Very Large Telescope (VLT). Credit: X-ray: NASA/CXC/Univ. of Alabama/K.Wong et al, Optical: ESO/VLT

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Those who are interested in black holes are familiar with the event horizon, but the Chandra X-Ray Observatory is giving us an even more detailed look into the structure surrounding these enigmas by imaging the inflowing hot gases. Galaxy NGC 3115 contains a supermassive black hole at its heart and for the first time astronomers have evidence of a critical threshold known as the “Bondi radius”.

Located approximately 32 million light years from the Solar System in the constellation of Sextans, NGC 3115 is a prime candidate for study. Contained in its nucleus is a billion-solar-mass black hole which is stripping away hot gases from nearby stars which can be imaged in X-ray. “The Chandra data are shown in blue and the optical data from the VLT are colored gold. The point sources in the X-ray image are mostly binary stars containing gas that is being pulled from a star to a stellar-mass black hole or a neutron star. The inset features the central portion of the Chandra image, with the black hole located in the middle.” says the team. “No point source is seen at the position of the black hole, but instead a plateau of X-ray emission coming from both hot gas and the combined X-ray emission from unresolved binary stars is found.”

In order to see the machination of the black hole at work, the Chandra team eradicated the signal given off by the binary stars, separating it from the super-heated gas flow. By observing the gas at varying distances the team could then pinpoint a threshold where the gas first becomes impacted by the supermassive black hole’s gravity and begins moving towards the center. This point is known as the Bondi radius.

“As gas flows toward a black hole it becomes squeezed, making it hotter and brighter, a signature now confirmed by the X-ray observations. The researchers found the rise in gas temperature begins at about 700 light years from the black hole, giving the location of the Bondi radius.” says the Chandra team. “This suggests that the black hole in the center of NGC 3115 has a mass of about two billion times that of the Sun, supporting previous results from optical observations. This would make NGC 3115 the nearest billion-solar-mass black hole to Earth.”

Original Story Source: Chandra News Further Reading: Resolving the Bondi Accretion Flow toward the Supermassive Black Hole of NGC 3115 with Chandra.

Posted on by Tammy Plotner

Catch A Pulsar By The Tail

A pulsar located about 1,600 light years from Earth.

Originally discovered by the Fermi Gamma Ray Space Telescope in 2009, Pulsar PSR J0357 had a bit of a surprise for astronomers when NASA’s Chandra X-ray Observatory turned an eye its way. Even though it might be 1,600 light years from Earth and half a million years old, it would appear this object has a cosmic sense of humor. Stretching across 4.2 light years is an enormous tail…

Viewable only at X-ray wavelengths, this incredible cosmic contrail is the longest ever associated with a so-called “rotation- powered” pulsar. Unlike other pulsars, J0357 gets its power from energy depletion as the spin rate decreases. But where did the plumage come from? According to the Chandra data, it may be an emission from energetic particles in the pulsar wind produced while turning around magnetic field lines. While artifacts of this type have been noted before, they’re classed as bow-shocks generated by the supersonic motion of pulsars through space. From there, the wind pulls the particles along behind it as the pulsar passes through interstellar gas.

But Pulsar PSR J0357 isn’t exactly fitting into a neat a tidy category…

According to data taken from Fermi, J0357 is only losing a small amount of energy as its spin rate slows. This means it shouldn’t be producing a particle wind of such proportions. Another anachronism is the placement of the bright portions of the tail – not anywhere near where bow-shocks are associated with pulsars.

“Further observations with Chandra could help test this bow-shock interpretation.” says the Chandra team. “If the pulsar is seen moving in the opposite direction from that of the tail, this would support the bow-shock idea.”

Original News Source: Chandra News.

Posted on by Tammy Plotner

Turning On A Supermassive Black Hole

A new study combining data from ESO’s Very Large Telescope and ESA’s XMM-Newton X-ray space observatory has turned up a surprise. Most of the huge black holes in the centres of galaxies in the past 11 billion years were not turned on by mergers between galaxies, as had been previously thought. Credit: CFHT/IAP/Terapix/CNRS/ESO

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ESO’s Very Large Telescope and ESA’s XMM-Newton X-ray Space Observatory has just opened our eyes once again. While we thought that the massive black holes that lurk at the center of large galaxies (and they always lurk, don’t they? they never just lay about, lallygag, or loiter…) for the last 11 billion years were turned on by mergers, we’re finding out it just might not be so.

For all astronomers, we’re aware that galactic structure involves a mostly quiescent central black hole. But as we reach further out into the Universe, we’re finding that early, brighter galaxies have a middle monster – one which appears to be noshing on a material that emits intense radiation. So if a galaxy merger isn’t responsible, then where does the material originate to ignite a quiet black hole into an active galactic nucleus? Maybe the omni-present dark matter…

Viola Allevato (Max-Planck-Institut für Plasmaphysik; Excellence Cluster Universe, Garching, Germany) and an international team of scientists from the COSMOS collaboration have studied 600 active galaxies in an intensively mapped region called the COSMOS field. Spanning an area consisting of about five degrees of celestial real estate in the constellation of Sextans, the COSMOS field has been richly observed by multiple telescopes at multiple wavelengths. This gives astronomers a great “picture” from which to draw data.

What they found was pretty much what they had expected – most of the active galaxies in the past 11 billion years were only moderately bright. But what they weren’t prepared to understand is why the majority of these more common, less bright active galaxies weren’t triggered by mergers. It’s a problematic situation that had previously been tackled by the Hubble Space Telescope, but COSMOS is looking back even further in time and with greater detail – a three-dimensional map showing where the active galaxies reside. “It took more than five years, but we were able to provide one of the largest and most complete inventories of active galaxies in the X-ray sky,” said Marcella Brusa, one of the authors of the study.

These new charts could help further our understanding of distribution as the universe aged and further refine modeling techniques. The new information also points to active galactic nuclei being hosted in large galaxies with abundances of dark matter… against popular theory. “These new results give us a new insight into how supermassive black holes start their meals,” said Viola Allevato, who is lead author on the new paper. “They indicate that black holes are usually fed by processes within the galaxy itself, such as disc instabilities and starbursts, as opposed to galaxy collisions.”

Alexis Finoguenov, who supervised the work, concludes: “Even in the distant past, up to almost 11 billion years ago, galaxy collisions can only account for a small percentage of the moderately bright active galaxies. At that time galaxies were closer together so mergers were expected to be more frequent than in the more recent past, so the new results are all the more surprising.”

Original News Source: ESO Press Release.

Posted on by Tammy Plotner

MAXI Peers Into Black Hole Binaries

X-ray all-sky image obtained by MAXI's first 10-month observation Bright X-ray sources (mainly binaries comprising neutron stars and black holes) exist in large numbers around the Galactic Center (in the direction of Sagittarius) and along the Galactic Plane (Milky Way) and change from day to day. Colors indicate the "hardness" of X-ray spectrum. More than 200 X-ray sources including weak ones have been identified. Credit: JAXA

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The Monitor of All-sky X-ray Image, or MAXI for short, spends its time aboard the ISS conducting a full sky survey every 92 minutes. Its sole purpose is to monitor X-ray source activity and report. Unlike stars seen in visible light, X-ray sources aren’t evenly distributed and can exhibit some highly unusual behavior. What causes these erratic moments? Read on…

“Most visible stars shine with energies generated by nuclear fusion in their cores. In these stars, if the energy generated in their core increases more than usual, the whole object expands and eventually lowers the core temperature. In this way, negative feedback is activated to stabilize the nuclear reaction. For this reason, these stars shine very stably for most of their lifetime.” says Nobuyuki Kawai of the Tokoyo Institute of Technology. “On the other hand, the energy source of most intense X-ray sources is gravitational energy released when the gas surrounding extremely compact bodies like black holes and neutron stars is accreted onto them. The normal stars’ stabilizing mechanism does not work in this process, and accordingly, X-ray intensity fluctuates in response to changes in the supply of gas from the surrounding area.”

This means MAXI needs to keep a close watch on both known and unknown X-ray sources for activity. Catching it as it happens allows an alert to be posted to other observatories for monitoring and study. Right now the focus has been on MAXI’s 18 month study of black hole binaries – the most famous of which is Cygnus X-1. It is well-known this famous source shines brilliantly in the X-ray spectrum, but it switches between a “hard” and “soft” state. These periods of high and low energy may be directly related to the density of gas which surrounds it.

“We can get a clue to estimate the mass of a black hole by examining the X-ray intensity and radiation spectrum in the soft state. As a result of analysis of the motion of the companion star rotating the center of gravity of the binary system, we found that Cygnus X-1 is a remarkably smaller object than normal stars, with an X-ray source mass about 10 times the solar mass but which emits hardly any visible light.” says Professor Kawai. “If applying star theory, such an object must be a black hole.”

Right now astronomers are studying gas properties and estimate there are about 20 binary X-ray sources other than Cygnus X-1. Most of these black hole binaries are considered to be “X-ray nova” – showing activity anywhere from every few years to only once in the four decades we’ve been studying them in this light. With the help of MAXI’s sensitive all-sky monitoring, researchers now stand a chance of being able to monitor activity from beginning to end. Has it been successful? You bet. When black hole binary, XTE J1752-223, was discovered by the routine patrol of RXTE, MAXI also detected the emergence of this new X-ray nova and was able to observe all the activities until it disappeared in April 2010. On September 25, 2010 MAXI and the Swift satellite discovered black hole binary MAXI J1659-152 almost simultaneously allowing it to be observed by researchers and amateur astronomers around the world.

“In addition to these black hole binaries, MAXI has achieved many interesting observations including: detection of the largest flare from active galactic nuclei in X-ray observation history; discovery of a new binary X-ray pulsar, MAXI J1409-619; and detection of a number of intense star flares.” says Kawai. “As long as the ISS is operating, we will use MAXI to monitor the X-ray sky, which changes restlessly and violently.”

Original Story Source: Japan Aerospace Exploration Agency.

Posted on by Tammy Plotner

Eccentric Binary Creates Dual Gamma-Ray Flares

This diagram, which illustrates the view from Earth, shows the binary's anatomy as well as key events in the pulsar's recent close approach. Credit: NASA/Goddard Space Flight Center/Francis Reddy

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It’s a gamma-ray flare – the most extreme form of light so far known. So, what could top it? Try a pair of gamma-ray flares. Way off in the southern constellation of Crux, an extreme team of stars gave a real show to NASA’s Fermi Gamma-ray Space Telescope. In December 2010, they blew past each other at about the distance Venus orbits our Sun. Why was this encounter so unique? Because one member was hot and blue/white… and the other a pulsar.

“Even though we were waiting for this event, it still surprised us,” said Aous Abdo, a Research Assistant Professor at George Mason University in Fairfax, Va., and a leader of the research team.

Astronomers were aware that PSR B1259-63 and LS 2883 made a close pass to each other about every 3 to 4 years and were eagerly anticipating the action. Residing at about 8,000 light years away, the signature signal from PSR B1259-63 was discovered in 1989 by the Parkes radio telescope in Australia. It is suspected to be quite small – about the size of Washington, DC and weighs about twice as much as Sol. What’s cool is it rotates at a dizzying 21 times per second… shooting of a powerful beam of electromagnetic energy that sweeps around like a search light. Next door the blue/white companion star lay embedded in gas, measuring in about 9 times larger size and weighing in at about 24 solar masses. Of these “odd couples” only four are known to produce gamma-rays and only this particular system is known to contain a pulsar… one that punches through the gas disk both coming and going during orbit.

“During these disk passages, energetic particles emitted by the pulsar can interact with the disk, and this can lead to processes that accelerate particles and produce radiation at different energies,” said study co-author Simon Johnston of the Australia Telescope National Facility in Epping, New South Wales. “The frustrating thing for astronomers is that the pulsar follows such an eccentric orbit that these events only happen every 3.4 years.”

On December 15, 2010, all “eyes” and “ears” were turned the system’s way in anticipation of the dual gamma-ray burst. The observatories included Fermi and NASA’s Swift spacecraft; the European space telescopes XMM-Newton and INTEGRAL; the Japan-U.S. Suzaku satellite; the Australia Telescope Compact Array; optical and infrared telescopes in Chile and South Africa; and the High Energy Stereoscopic System (H.E.S.S.), a ground-based observatory in Namibia that can detect gamma rays with energies of trillions of electron volts, beyond Fermi’s range.

“When you know you have a chance of observing this system only once every few years, you try to arrange for as much coverage as you can,” said Abdo, the principal investigator of the NASA-funded international campaign. “Understanding this system, where we know the nature of the compact object, may help us understand the nature of the compact objects in other, similar systems”.

While the EGRET telescope aboard NASA’s Compton Gamma-Ray Observatory had been observing this rare pair since the 1990s, no gamma-ray emission in the billion-electron-volt (GeV) energy range had ever been recorded. But, as the time of passage approached, the Large Area Telescope (LAT) aboard Fermi began to pick up faint gamma-ray emission. “During the first disk passage, which lasted from mid-November to mid-December, the LAT recorded faint yet detectable emission from the binary. We assumed that the second passage would be similar, but in mid-January 2011, as the pulsar began its second passage through the disk, we started seeing surprising flares that were many times stronger than those we saw before,” Abdo said.

To make this strange scenario even more unusual, radio and x-ray readings were nominal as the gamma-rays flared. “The most intense days of the flare were Jan. 20 and 21 and Feb. 2, 2011,” said Abdo. “What really surprised us is that on any of these days, the source was more than 15 times brighter than it was during the entire month-and-a-half-long first passage.”

It won’t happen again until May, 2014… But you can bet astronomers will be tuned in to catch the action!

Original Story Source: NASA / Fermi News.

Posted on by Tammy Plotner

Neutron Star Burps Up Stellar Gas

This animated sequence of images illustrates the partial ingestion of a clump of matter by the neutron star hosted in the Supergiant Fast X-Ray Transient, IGR J18410-0535. The ingestion of the clump material produced a dramatic increase in the X-rays released by the neutron star, which was detected with XMM-Newton. The peak in the X-ray luminosity corresponds to the period when the accretion rate was at its maximum. Credits: ESA/AOES Medialab

During a routine twelve and a half hour observation of star system IGR J18410-0535, the XMM-Newton caught an event that would make Emily Post proud… a not-so-discreet burp from a neutron star. Continue reading “Neutron Star Burps Up Stellar Gas”

Posted on by Tammy Plotner

Cygnus X-1: Blue Supergiant Pairs With Black Hole

This X-ray image of Cygnus X-1 was taken by a balloon-borne telescope, the High Energy Replicated Optics (HERO) project. NASA image.

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Discovered in 1964 during a rocket flight, Cygnus X-1 holds the record for being the strongest X-ray source seen from Earth. The blue supergiant star designated as HDE 226868 is just part of this high-mass X-ray binary system… the other is a black hole.

“We present a detailed study of the X-ray dust scattering halo of the black hole candidate based on two Chandra HETGS observations. Using 18 different dust models, including one modified by us (dubbed XLNW), we probe the interstellar medium between us and this source.” says Jingen Xiang, et al. “A consistent description of the cloud properties along the line of sight that describes at the same time the halo radial profile, the halo lightcurves, and the column density from source spectroscopy is best achieved with a small subset of these models… The remainder of the dust along the line of sight is close to the black hole binary.”

Located about 6,000 light years from Earth as measured by the Hipparcos satellite (but this value has a relatively high degree of uncertainty), Cygnus X-1 has been the topic for a huge amount of astronomical studies for nearly 50 years. We’re aware the blue supergiant variable star orbits its unseen companion at roughly 1/5 the distance of the Sun to the Earth (0.2 AU), and we surmised that stellar wind accounted for the accretion disk around the X-ray source. We are also aware of a pair of jets spewing material into interstellar space. Deep inside, superheated materials are sending out copious amounts of X-rays, but what else lay beyond? Can we separate star from event horizon with accuracy?

“We report a direct and accurate measurement of the distance to the X-ray binary Cygnus X-1, which contains the first black hole to be discovered. The distance of 1.86(-0.11,+0.12) kpc was obtained from a trigonometric parallax measurement using the Very Long Baseline Array. The position measurements are also sensitive to the 5.6 d binary orbit and we determine the orbit to be clockwise on the sky.” says Mark J. Reid, et al. “We also measured the proper motion of Cygnus X-1 which, when coupled to the distance and Doppler shift, gives the three-dimensional space motion of the system. When corrected for differential Galactic rotation, the non-circular (peculiar) motion of the binary is only about 21 km/s, indicating that the binary did not experience a large “kick” at formation.”

If you don’t think this is exciting news, then think again. “The compact primary in the X-ray binary Cygnus X-1 was the first black hole to be established via dynamical observations.” says Lijun Gou. “We have recently determined accurate values for its mass and distance, and for the orbital inclination angle of the binary. Building on these results, which are based on our favored (asynchronous) dynamical model, we have measured the radius of the inner edge of the black hole’s accretion disk by fitting its thermal continuum spectrum to a fully relativistic model of a thin accretion disk.”

Determining the spin rate has been high on the list of observations – and difficult because it changed states periodically. Only when it is in a soft spectral state can accurate measurements be taken. Oddly enough, for all the countless observations taken of Cygnus X-1 over the years, it has never been caught in a thermally dominant state. To that end, the black hole spin is measured by estimating the inner radius of the accretion disk.

“Our results take into account all significant sources of observational and model-parameter uncertainties, which are dominated by the uncertainties in black hole mass, orbital inclination angle and distance.” says the team. “The uncertainties introduced by the thin-disk model we employ are particularly small in this case, given the disk’s low luminosity.”

Heisenberg would be so proud….

Original Story Souce: Cornell University Library with facts from Wikipedia.

Posted on by Tammy Plotner

Black Hole Devours Star and Hurls Energy Across 3.8 Billion Light Years

What University of Warwick researchers think the star may have looked like at the start of its disruption by a black hole at the center of a galaxy 3.8 billion light years distant resulting in the outburst known as Sw 1644+57. Credit: University of Warwick / Mark A. Garlick

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Engaging the Hubble Space Telescope, Swift satellite and the Chandra X-ray Observatory, astronomers at the University of Warwick were quick to pick up a signal from Swift’s Burst Alert Telescope on March 28, 2011. In a classic line from Easy Rider, Jack Nicholson says: “It’s a UFO beaming back at you.” But this time it isn’t a UFO… it’s the death scream of a star being consumed by a black hole. The alert was just the beginning of a series of x-ray blasts that turned out to be the largest and most luminous event so far recorded in a distant galaxy.

Originating 3.8 billion light years from Earth in the direction of the constellation of Draco, the beam consisting of high energy X-rays and gamma-rays remained brilliant for a period of weeks after the initial event. As more and more material from the doomed star crossed over the event horizon, bright flares erupted signaling its demise. Says Dr. Andrew Levan, lead researcher on the paper from the University of Warwick; “Despite the power of this the cataclysmic event we still only happen to see this event because our solar system happened to be looking right down the barrel of this jet of energy”.

Dr Andrew Levan is a researcher at the University of Warwick.
Dr. Levan’s findings were published today in the Journal Science in a paper entitled “An Extremely Luminous Panchromatic Outburst from the Nucleus of a Distant Galaxy”. His findings leave no doubt as to the origin of the event and it has been cataloged as Sw 1644+57.

“The only explanation that so far fits the size, intensity, time scale, and level of fluctuation of the observed event, is that a massive black at the very centre of that galaxy has pulled in a large star and ripped it apart by tidal disruption.” says Levan. “The spinning black hole then created the two jets one of which pointed straight to Earth.”

And straight into our eager eyes…

Original Story Source: Eurekalert.

Posted on by Tammy Plotner

Baby Black Holes Grew Up Fast

This composite image from NASA's Chandra X-ray Observatory and Hubble Space Telescope (HST) combines the deepest X-ray, optical and infrared views of the sky. X-ray: NASA/CXC/U.Hawaii/E.Treister et al; Infrared: NASA/STScI/UC Santa Cruz/G.Illingworth et al; Optical: NASA/STScI/S.Beckwith et al

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For more than six weeks, the watchful eye of NASA’s Chandra X-ray Observatory kept track of a small portion of sky dubbed the Chandra Deep Field South (CDFS). Its object was to research 200 distant galaxies dating back to about 800 million to 950 million years old. What Chandra was looking for was evidence of massive black holes. The deepest evidence yet…

When combined with very deep optical and infrared images from NASA’s Hubble Space Telescope, the new Chandra data leads astronomers to speculate that young black holes may have evolved in unison with their young galaxies. “Until now, we had no idea what the black holes in these early galaxies were doing, or if they even existed,” said Ezequiel Treister of the University of Hawaii, lead author of the study appearing in the June 16 issue of the journal Nature. “Now we know they are there, and they are growing like gangbusters.”

What does this new information mean? The massive growth of the black holes in the CDFS are just shy of being a quasar – the super-luminous by-product of material slipping over the event horizon. “However, the sources in the CDFS are about a hundred times fainter and the black holes are about a thousand times less massive than the ones in quasars.” How often did it occur in the new data? Try between 30 and 100% of the case studies, resulting in a estimated 30 million supermassive black holes in the early Universe.

“It appears we’ve found a whole new population of baby black holes,” said co-author Kevin Schawinski of Yale University. “We think these babies will grow by a factor of about a hundred or a thousand, eventually becoming like the giant black holes we see today almost 13 billion years later.”

While the existence of these early black holes had been predicted, no observation had been made until now. Due to their natural “cloaking devices” of gas and dust, optical observation had been prohibited, but x-ray signatures don’t lie. The concept of tandem black hole / galaxy growth has been studied closer to home, but taking a look further back into time and space has revealed growth a hundred times more than estimated. These new Chandra results are teaching us that this connection begins at the beginning.

“Most astronomers think in the present-day universe, black holes and galaxies are somehow symbiotic in how they grow,” said Priya Natarajan, a co-author from Yale University. “We have shown that this codependent relationship has existed from very early times.”

Theories also abound which imply neophyte black holes may have played “an important role in clearing away the cosmic “fog” of neutral, or uncharged, hydrogen that pervaded the early universe when temperatures cooled down after the Big Bang”. But to the contrary, the new Chandra findings point towards the pervasive materials stopping ultraviolet radiation before the re-ionization process can occur. Resultant stars and dormant black holes are the most likely culprit to have cleared space for the cosmic dawn.

Although the Chandra X-ray Observatory is up to the task of picking up on uber-faint objects at incredible distances, these baby black holes are so veiled that only a few photons can slip through, making individual detection impossible. To gather this new data, the team employed Chandra’s directional abilities and tallied the hits near the positions of distant galaxies and found a statistically significant signal.

Original Story Source: Chandra News.

Posted on by Tammy Plotner

Australian Student Uncovers the Universe’s Missing Mass

Comic Microwave Background Courtesy of NASA / WMAP Science Team

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Not since the work of Fritz Zwicky has the astronomy world been so excited about the missing mass of the Universe. His evidence came from the orbital velocities of galaxies in clusters, rotational speeds, and gravitational lensing of background objects. Now there’s even more evidence that Zwicky was right as Australian student – Amelia Fraser-McKelvie – made another breakthrough in the world of astrophysics.

Working with a team at the Monash School of Physics, the 22-year-old undergraduate Aerospace Engineering/Science student conducted a targeted X-ray search for the hidden matter and within just three months made a very exciting discovery. Astrophysicists predicted the mass would be low in density, but high in temperature – approximately one million degrees Celsius. According to theory, the matter should have been observable at X-ray wavelengths and Amelia Fraser-McKelvie’s discovery has proved the prediction to be correct.

Dr Kevin Pimbblet from the School of Astrophysics explains: “It was thought from a theoretical viewpoint that there should be about double the amount of matter in the local Universe compared to what was observed. It was predicted that the majority of this missing mass should be located in large-scale cosmic structures called filaments – a bit like thick shoelaces.”

Up until this point in time, theories were based solely on numerical models, so Fraser-McKelvie’s observations represent a true break-through in determining just how much of this mass is caught in filamentary structure. “Most of the baryons in the Universe are thought to be contained within filaments of galaxies, but as yet, no single study has published the observed properties of a large sample of known filaments to determine typical physical characteristics such as temperature and electron density.” says Amelia. “We examine if a filament’s membership to a supercluster leads to an enhanced electron density as reported by Kull & Bohringer (1999). We suggest it remains unclear if supercluster membership causes such an enhancement.”

Still a year away from undertaking her Honors year (which she will complete under the supervision of Dr Pimbblet), Ms Fraser-McKelvie is being hailed as one of Australia’s most exciting young students… and we can see why!